Manual For Quality Seed Production in Wheat.: January 2014

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Wheat
Production
Manual
for
Quality Seed Production
Abebe Atlaw
Karta Kaske
Mekonnen Haile
የኢትዮጵያ የግብርና ምርምር ኢንስቲትዩት

Ethiopian Institute of Agricultural Research
Wheat
Production
Manual
for
Quality Seed Production
©EIAR, 2014
›=ÓU›=' 2007
Website: http://www.eiar.gov.et
Tel: +251-11-6462633
Fax: +251-11-6461294
P.O.Box: 2003
Addis Ababa, Ethiopia
ISBN: 978-99944-66-07-8
Copyediting and design: Abebe Kirub

Contents
Introduction ............................................................................................................... 4
Characteristics Quality Wheat Seed ......................................................................... 5
Principles of Wheat Seed Production ....................................................................... 6
Diseases of Lower Stem and Roots........................................................................ 22
Pest Management................................................................................................... 24
Harvesting............................................................................................................... 28
Seed Quality Control............................................................................................... 33
Seed Quality Assurance ......................................................................................... 35
Methods for Seed Quality Testing .......................................................................... 36
Genetic Purity Maintenance.................................................................................... 39
Maintenance Breeding and Breeder Seed Production............................................ 40
Generation System of Seed Multiplication .............................................................. 46
Types of Mechanical Dividers ................................................................................. 53
Determining Seed Moisture .................................................................................... 54
Purity Analysis ........................................................................................................ 56
Purity Components ................................................................................................. 57
Steps in Seed Germination Test ............................................................................. 59
Controlling Fungi in Germination Tests................................................................... 60
Seed Health Management ...................................................................................... 61
Examination by seed washing (washing test) ......................................................... 62
Seed Storage .......................................................................................................... 64
Seed Marketing....................................................................................................... 66
Distribution .............................................................................................................. 67
Product Option, Targeting Species and Quantities ................................................. 68
Inputs for Seed Production ..................................................................................... 70
Risks and Uncertainties in Defining Seed Demand ................................................ 71
Costs in Seed Production ....................................................................................... 72
3
Quality wheat seed production
Introduction
Wheat seed technology includes rapid multiplication, timely supply,
assurance of high seed quality, and supply with reasonable prices. The time
taken to avail the desired quantities of high quality seeds to farmers is a
measure of efficiency for a successful wheat seed industry. Good quality
wheat seed is a function of physical purity, viability and vigor, genetic
purity, and seed health. Physical purity refers that farmers should be able to
sow only pure wheat seed. Therefore, this calls for removing undesirable
contaminants and immature shriveled seeds and make sure to maintain the
physical purity of seed.
Genetically pure seed of a wheat variety possesses unique economic and

diagnostic characters of the variety. Isolation, rouging, using generation
system of seed multiplication, and taking proper cautions during harvesting
and processing ensure the genetic purity of wheat seeds.
Wheat seeds that are free from seed-borne diseases help in raising disease
free crop and checking further spread of the disease. Seeds infested with
pests lose viability very fast during storage and become unfit for planting
within a very short time. Proper seed storage and treatment with fungicides
also maintains the health of wheat seeds. Fumigation and seed treatment
control storage pests of wheat.
A true wheat seed has a matured ovule developed after sexual fertilization
that consists of embryo, stored food and protective coats. The important
events involved in seed development and maturation include pollination,
fertilization, and development of the fertilized ovule.
Seed structures in wheat determine cultivar identity, shelf life of the seeds,
and proper post –harvest operations such as drying, threshing, processing,
cleaning, and grading minimize mechanical damages. Key features of
wheat seeds used in cultivar identification include, seed weight, color, seed
size, shape, and hairs.
[4]
Characteristics Quality Wheat Seed
Repeated use of seeds from generation-to-generation without renovation
breaks variety identity, subsequently no more seed of that variety.
Therefore, cycle of renovation and multiplication of seeds by generation
system is more important to overcome the harmful effect of farmers' saved
seed. The difference between grain and seed is presented in Table 1.
Table 1. The difference between seed and grain

Seed Grain
It should be a viable one Need not be a viable one
It should have maximum seed certification Not so
standards
Should satisfy minimum seed certification No such requirements
standards
It should be completely treated with It should never be treated with any chemicals,
pesticide/fungicide to protect the seed against since used for consumption
storage pests and fungi
Respiration rate and other physiological and No such specifications
biological processes should be kept at low level
during storage
Should be compulsorily certified /truthfully labeled No such condition in grain production
Should never be converted into gain unless Can be converted as seed provided the
warranted situation warrants
It should satisfy all the quality norms Not considered
[5]
Principles of Wheat Seed Production
The production of high quality seed with high genetic and physical purity,
high germination, vigorous, large size, free from weeds and seed-borne
diseases, and low moisture content requires technical skill and knowledge.
Maintaining the genetic purity of the seed is important and enables growers
to exploit the full benefits of introducing improved varieties of wheat.
Thus, seed production involves skilled supervision and organized
conditions. The principles of seed production are genetic and agronomic.
Genetic principles
There are clear manifestations for the deterioration of the genetic potential
of a wheat variety due to phenomena number of reasons that could
occur during the production cycles. The most vivid explanation
(Table 2) for deterioration of varieties include
 Developmental variations;
 Mechanical mixtures;
 Mutations;
 Natural crossing;
 Minor genetic variations;
 Pest and diseases; and
 Technique of the plant breeder.
Table 2. Factors responsible for deterioration of wheat varieties
Factors Phenomena Corrective actions

Developmental variations Growing the seed crop under Grow varieties in the areas of
environments with differing soil their natural adaptation.
fertility, climate, photoperiod for
several consecutive years
Mechanical mixtures Sowing more than one variety Rouging the seed fields
with the same drill and/or in critically, proper rotation system
adjacent fields, volunteer plants and taking utmost care during
seed production and processing
Mutations Spontaneous changes Rouging
Natural crossing (not serious Growing two wheat varieties in Applying proper isolation
in wheat) very close proximity distance (3-5 meters)
[6]
Factors Phenomena Corrective actions
Minor genetic variations Insufficiently fixed traits Allowing sufficient time for yield
trials
Selected influence of pest Newer races of pests and Use of disease free seed and
and disease diseases seed production under strict
disease free conditions
The techniques of the plant Cytogenetic irregularities and Strict variety testing procedure
breeder premature release of varieties and DUS test
Agronomic principles
Wheat seed and grain production requires similar operations but different
strategies. However, seed production differs from grain production in terms
of land requirement, isolation, rouging, and prevention of contamination
and limitations of generations. Another difference is that seeds must meet
specific quality standards of the national seed regulations. The technical,
administrative and legislative control of the certification agency provides
guidelines for the production of good quality seed that meets the standards.
Climate and location

A wheat variety grown for seed production must be suitable to climatic and
photoperiodic conditions prevailing in specific location. Areas with
moderate rainfall, humidity and temperatures with sufficient dry sunny
period for seed harvesting are suitable for wheat seed production.
Extremely high temperature during anthesis causes desiccation of pollen

resulting in poor seed set. Excessive rainfall conditions normally result in a
higher incidence of pest and diseases making harvesting and other
operations of seed production extremely difficult. Rainfall after
physiological maturity may delay harvest maturity and cause pre-
germination of seed in standing crops. A mature wheat seed crop becomes
increasingly susceptible to shattering, strong winds, and heavy rainfall.
Sufficient sunshine, moderate rainfall, and absence of strong winds are
ideal for the production of high quality seed.
Land selected for the wheat seed should have the following characteristics.
 The seed plot should be prepared sufficiently and on time, have light and
well-drained soil texture with very good fertility characteristics;
[7]
 The plot should be free from volunteer plants and seeds of weeds and other
plants;
 The soil of the selected plot should be comparatively free from soil borne
diseases and pests;
 The plot must be well drained, leveled and feasible for isolation as per the
requirements of the certification standards;
 Soil neither acidic nor alkaline; and
 Field should be rotated for 1 to 3 seasons.
Field isolation
To ensure high quality seeds, isolation of fields is critical in seed
production schemes
 The seed crop must be sufficiently isolated from nearby fields of the same or
other contaminating crops as per the requirements of the certification
standards;
 The seed crop should be isolated by providing enough distance between seed
plots and contaminating fields;
 Maintain a minimum isolation distance of 3 to 5 meters as indicated in wheat
seed standards of Ethiopia for different generations. Note that the distances
indicated are the measurements from the edge of the seeds farm to the edge of
the nearest farm of a similar crop in all directions;
 During harvesting, machines should be cleaned sufficiently before harvesting
the other variety. Harvesting similar varieties at once is advisable to avoid
unnecessary time consumption during repeated cleaning of combines;
 Even after the seed crop is harvested, effective isolation of seed from
different varieties is essential to avoid mechanical contamination;
 Bags, stores, cleaning machines, and other equipment must be clean during
post-harvest seed handling; and
 Cleaned seed should always been packed in new bags and when necessary it
should be treated with appropriate seed dressing chemicals.
Land clearing and preparation

In Ethiopia, land clearing begins at about February-April in every year
before the onset of rainfall. The following practices include the common
practice in land preparation to produce wheat seeds
 Depending on the availability of rainfall and machinery , stubble cultivation
should be done immediately after harvest;
[8]
 Plow and harrow the field and then ridge where necessary to ensure a uniform
fine seed bed;
 Use ox-plow or ridger and plow across the slope;
 Make sure that the seed bed is free from weeds and remove volunteers of the
same crop (if any) before sowing;
 When irrigating wheat field, the deep plow the soil and make it fine. Pre-
sowing irrigation is necessary for uniform germination. Give a light shallow
disking after pre sowing irrigation; and
 Leveling of the seedbed is important provide uniform stands and facilitate
rouging.
Selection of variety
An ideal variety yields best under the local conditions and is resistant to locally
prevalent diseases and insects. The variety should be high yielding and disease
resistant. Similarly, the crop produces should have good quality and brings the best
price in the market. The seed should be of known purity and appropriate class.
Obtain the required breeder/pre basic/basic and certified seed of selected variety
from a source approved by the certification agency.
Planting the crop

 Sowing dates generally depend on location, soil type, on-set and distribution
of rainfall and variety. Untimely planting (early or late) is likely to result in
reduced yield. Late maturing varieties require early planting relative to early
varieties;
 Raised beds can be especially effective on heavy soils that hold moisture for a
long times. They improve drainage, keeping the root system and plant crown
aerated and reducing the chance of root rot, and they can reduce nitrogen loss
due to de-nitrification and leaching;
 Seeds of the selected improved variety should be planted on the
recommended time of sowing;
 Sow the seeds at the recommended time which in Ethiopia is usually when
rainfall is established and when good land preparation has been conducted;
 In higher and intermediate altitudes, in “meher” season, wheat can be planted
between mid-June and late August. However, in “belg” season, the crop can
be planted from mid-February to early April;
 In moisture stress areas, plant should be done as fast as possible; for instance
in Assasa area planting wheat resumes early June;
 In waterlogged Vertisols, planting is done late in the season. Poorly drained
plots are not advisable for wheat seed production.
[9]
In most Vertisols, with improved drainage, wheat can be planted in the first half of
July. However, delayed sowing can cause the crop not to mature well before the
end of the rainy season. It is important to remember that pest and disease attack is
severe on late-planted crops. Seeds from late-planted crops are shriveled and have
low vigor.
Sowing method
 Sowing in rows facilitates effective plant protection measures, rouging
operations, and field inspection;
 Spacing between rows can be 10 and 25 cm;
 Under optimum conditions, drill the seed with a depth of 3-5 cm for sowing.
Deeper sowing can be done in drier conditions and in sandy soils than in clay
soils; and
 The seed crop is sown in rows by mechanical drillers, which allows desired
quantity of seed to be planted at uniform depth.
Seed rates
The optimum seed rates for wheat depends on type of cultivar, tillering
ability, 1000 seed weight, germination percentage, method of planting, and
area of production. For seed production fields, use lower seed rate for
higher multiplication factors, but to lower yield per unit area. Higher
multiplication factors lead to rapid seed increase i.e., more seed harvested
per kilogram of seed planted, and farmers will benefit from the improved
variety earlier. Low seed rates do not only increase the multiplication
factor, but also often improve seed quality because a lower number of
plants per unit of land receive better nutrition, thus producing better quality
seed. Practically, , very lower seed rates may be used when planting early
generations when extensive agronomic practices are used, but certified seed
is planted at the normal or slightly lower seed rate.
Planting depth
 Sowing depth of wheat seed is with the range of 2-4 cm;
 Seed absorbs 35-45% of its own weight before germination; and
 The coleoptiles or second leaf penetrates the soil and results in emergence of
the seedling, usually within 5 to 7 days after planting under normal
conditions;
[10]
Crop Rotation
Rotation of wheat with non-cereal crops could provide several benefits to
the subsequent wheat crop. It improves soil-structure, add organic matter,
and reduce weed, disease and insect pest problems. Soil fertility enhanced
if the preceding crop legume. For example, a precursor mustard increases
wheat yield substantially with this crop also improves soil structure,
suppresses weed and breaks soil-borne disease cycle.
Weeding
Weeds compete with the crop plants, carry diseases and harbor insects.
Weeds can significantly lower the crop yield and seed quality. At harvest, s
weeds could be harvested along with the crop, so that wheat seed would be
contaminated with weed seed. Therefore, to produce high quality seed
thorough control of weeds on the wheat seed plots, i.e., essential.
Depending on the level of weed infestation, weeding a wheat seed farm
should begin 2 weeks after sowing or even earlier, , with a second weeding
at 4–5 weeks, and a third weeding at 7–8 weeks, depending on the duration
to maturity of the crop and the level of weed infestation.
When some weeds emerged after land preparation, but before sowing, mix
the pre-emergence herbicide and spray immediately after sowing. Planting
seed crops on clean, fallow land or following crop rotation is recommended
to keep weed problem at a minimum. Rotation crops such as Ethiopian
mustard are recommended in the wheat seed production systems to reduce
weed pressure on the subsequent seed crops. Integrated weed control has
paramount importance for complete management of weeds in wheat seed
crops. Grass weed species such as Avena fatua, Phalaris paradoxa, Lolium
temulentum, and Setaria pumila are becoming more troublesome in
wheat production.
Using herbicides requires some knowledge of the right product for a

particular crop, the right time to apply it using the correct sprayer
calibration. Seek advice from your extension agent on appropriate
herbicide types and rates if you are not conversant with their use
[11]
Fertilizer
Adequate amounts of nitrogen and phosphorous are crucial for the proper
growth and development of the wheat seed crop. Farmers should know the
location specific nutritional requirements of the seed crop and ensure
proper nutrition at all stages of wheat growth. A well-balanced supply of
nitrogen, phosphorus and potassium is essential for seed production by
influencing seed development and seed quality.
Role of Nitrogen
 Nitrogen is taken up by plants as - NO3 ; NH4;
 N is the building block for amino acids, proteins and nucleic acids. Therefore,
Nitrogen is responsible for grain yield;
 If seed is broadcasted apply 1/3 at planting mixed with DAP and the balance as
top dress at 30-35 days after germination and after weed control;
 Urea ideally should be incorporated in the soil by rain; or manually by spot
application every 30-40 cm between spots;
 When seed is row planted apply 100 % of urea as top dress at 30 – 35 days after
germination and after weed control; and
 When wheat is row planted, incorporate urea in the soil at 7-10 cm depth;
manually by spot application, every 30-40 cm between spots on same row and
skip one row as shown in the diagram below.
 However, higher rates of fertilizers may increase disease incidence. In Ethiopia,
both N and P increased the incidence of stripe rust, though the effect of P was
less pronounced (Tanner et al., 1992). In a similar study, the density of wild oat
panicles increased with N fertilizer, but decreased with P fertilizer; and
 Top dressing wheat crops with high levels of N will make the crop lodge,
which makes it difficult to be field inspected by the seed certification service.
Role of Phosphorus
 Phosphorus plays a vital role in virtually every plant process that involves
energy transfer;
 Phosphorous (DAP) contribute to overall plant health by regulating energy-
electron transfer in all plant processes. It is not directly responsible for grain
yield;
 High-energy phosphate, held as a part of the chemical structures of
Adenosine Di-phosphate (ADP) and ATP, is the source of energy that drives
the multitude of chemical reactions within the plant;
[12]
 Movement of nutrients within the plant depends largely upon transport
through cell membranes, which requires energy to oppose the forces of
osmosis;
 Phosphorus is essential for enhancing seed maturity and K for seed
development;
 On row planted wheat, DAP is drilled as band application near the seed, but
not in contact with the seed on same row, or band application on alternate
rows; during planting and incorporated in the soil; and
 On broadcasted wheat, DAP can also be broadcasted and incorporated in the
soil at same time as seeds.
Irrigation
 Wheat crop requires 40 cm of water to complete its life cycle. When growth
and yield factors are rated according to importance, the availability of
moisture always ranks near the top;
 Yields, up to a point are determined by availability and use of moisture.
Irrigation is a means by which an adequate moisture supply to the crop can be
better assured;
 This provides a potential for increased yields over dry land production and
the opportunity to stabilize annual fluctuations in yield and seed quality;
 First irrigation is done before sowing since the seeds should be sown in
irrigated wet soil.
 Crop should be irrigated at 10 - 20 days interval.
 Depending on the soil, 4-6 irrigation may suffice;
 Second at crown root initiation stage (30-35 days after sowing);
 Other irrigation should be at late tiller, late joining, flowering, milk and
dough stages; and
 Additional 2-3 irrigation may be needed on light soils
 Irrigation during tillering to flowering and panicle initiation stage to heading
are very critical. This determines the quality of the seeds.
Rouging and Field Inspection

Field inspection refers to the scrutiny of seed production plots by a team of
qualified persons. The primary objective of field inspection is to ensure that
the seeds are not contaminated beyond certain specified maximum limits.
Seed inspection also ensures that the steps necessary to minimize genetic
and physical contamination are properly and in time to make them
effective. Regular field inspections are critical to identify off-types and to
remove them before they pollute the seed farm.
[13]
Rouging follows a systematic procedure and should be carried out at the

time when rogues can be most easily identified, and before any
contamination occurs to the seed crop. Adequate and timely rouging
constitutes the single most important operation in seed production. The best
periods for rouging wheat are at heading and at maturity. This is because;
off-types and other varieties of the same species are most easily identified.
In wheat, all off-types, including those that appear due to residual

segregation, should be removed. Rouges are pulled out and discarded at the
earliest possible phases. They can be removed at heading and at maturity.
Plants obviously differing in height, color of vegetation, leaf size, shape,
and orientation, or any other morphological characteristics as well as
malfunctioned and diseased plants should be removed completely.
Undesirable plants not distinguishable earlier should be removed soon after
head emergence. While removing the plants with heads infested by seed
borne disease or loose smut, precautions must be taken to ensure that
spores are not spread to healthy plants. Rouging at maturity is also
necessary to remove off types not distinguishable earlier and contaminants
affecting physical purity.
The procedures in field inspections include

 After locating the field the inspector should check the boundaries of the field,
variety to be inspected, crop history of the field to be inspected, source of the
field, class of certification, area of the seed and adjacent fields within the
isolation distance to verify the contaminants;
 2-3 rouging may be necessary to bring the seed plot to seed certification
standards;
 First rouging just ahead of the flowering stage or during flowering, avoid all
and the entire off types and diseased plants from ground level; and
 5-6 rouging members with a leader must know the detailed characters of the
variety for seed.
It is very important to take data without bias. Record counts at random and
covers the maximum area in the field. Sampling locations in the fields
should be as representative and as many as possible. Make observations on
representative samples, as it is not possible to examine all plants in the
[14]
field. Five counts are taken for an area up to two hectares and an additional
count taken for each additional two hectares or part thereof.
The procedures for counting include the following

 Count the average number of heads in one step in five different locations;
 Start at random at any plant in any row and take enough steps to count too
heads;
 Count the number of off-type heads which have shed pollen or are shedding
pollen. Also count the number of diseased head and weed plants;
 Repeat the process ten places to make 1,000 heads and this will be one count;
 Repeat the entire process as many times as required for the field size under
inspection and;
 Remove all plants that are abnormal from the field;
Diseases and insect pest management

Fusarium, tilletia, drechslera, septoria, ustilago, corynebacterium,
pseudomonas and xanthomonas, and nematodes are the most important
seed-borne diseases.
Leaf rusts
The cereal rusts Puccinia graminis (causing stem rust, P. striiformis
(causing yellow or stripe rust), P. hordei (causing dwarfing or leaf rust) and
P. coronata (causing crown or leaf rust) regularly cause serious losses of
wheat, barley, oats and rye throughout the world. Owing to their prime role
in limiting the productivity of these cereal crops in almost every major
cereal-producing country, the rust diseases deserve special and detailed
attention.
Small, orange-brown lesions are key features of leaf rust infections. These
blister-like lesions are most common on leaves but can occur on the leaf
sheath, which extends from the base of the leaf blade to the stem node.
Lesions caused by leaf rust are normally smaller, more round, and cause
less tearing of the leaf tissue than those caused by stem rust. The
management of the disease includes using resistant varieties and
application of foliar fungicides.
[15]
Rusts caused by Puccinia tritina are late season diseases that are most
severe in the season with lower temperature and high humidity. The fungi
grow only on the living host plants and have very narrow host ranges.
Leaf rust
Stem rust
Stem rust causes blister-like lesions on leaves, leaf sheaths, and stems.
Infection of glumes and awns is also possible. The reddish-brown spores of
the fungus cause considerable tearing as they burst through the outer layers
of the plant tissues. Mature stem rust lesions are more elongated than those
of leaf rust. Disease management: genetic resistance, and using foliar
fungicides, sowing healthy seeds of high quality is a concern of farmers
and seed producers to improve crop productivity
Stem rust
Septoria tritici blotch
This fungal disease causes tan, elongated lesions on wheat leaves. Lesions
may have a yellow margin, but the degree of yellowing varies among
varieties. The dark, reproductive structures produced by the fungus are key
[16]
diagnostic features and can often be seen without magnification. This
disease is also known as speckled leaf blotch. Using resistant varieties,
foliar fungicides, and crop rotation are the common management
approaches to control the disease.
Septoria blotch
Stripe rust
Stripe rust causes yellow, blister-like lesions that are arranged in stripes.
The disease is most common on leaves, but head tissue also can develop
symptoms when disease is severe. This disease is sometimes referred to as
yellow rust. Using resistant varieties, foliar fungicides, and crop rotation
are the common management approaches to control the disease.
Stripe/yellow rust
[17]
Diseases of Heads and Seeds
Common bunt
Wheat kernels infected by common bunt have a gray-green color and are wider
than healthy kernels. Diseased kernels can be seen in developing wheat heads but
are often not detected until harvest. The outer layers of diseased kernels remain
intact initially but are easily broken during grain harvest, releasing masses of black,
powdery spores. The fungus produces chemicals with a fishy odor, which
sometimes causes this disease to be referred to as “stinking smut.” Using fungicide
seed treatment and varieties that are disease-free is the common and effective
solution to manage the disease.
Bunt of wheat. The kernels are filled with masses of black spores
Scab or fusarium head blight

Scab or head blight, is caused primarily by the fungus Fusarium
graminearum but other species F. culmorum and F. avenaceum can cause
the disease. These pathogens occur as soil inhabitants as well as
saprophytes on crop residues and are always present. In addition to causing
scab, they also cause seed decay, seedling blight, and crown root rot of
wheat. They cause stalk and ear rots of corn and sorghum. Wheat heads are
most susceptible to infection by airborne spores during anthesis; however,
infection can occur up to the soft dough stage. Symptoms of Fusarium head
blight include tan or light brown lesions encompassing one or more
spikelets. Some diseased spikelets may have a dark brown discoloration at
the base and an orange fungal mass along the lower portion of the glume.
Grain from plants infected by Fusarium head blight is often shriveled and
has a white chalky appearance. Some kernels may have a pink
discoloration.
[18]
Management of the disease include
 Avoiding the most susceptible varieties and planting into maize residue;
 Applying a fungicide at early flowering if wet weather prevails before and
during flowering;
 Using crop rotations in which wheat does not follow wheat, maize or
sorghum; and.
 Avoiding over irrigation during full heading and especially flowering
Fusarium head blight
Loose smut
The normal head tissue of plants infected by loose smut is replaced by
dark masses of fungal spores, giving the heads a black powdery
appearance. It is possible to see heads damaged by loose smut while much
of the head is still inside the boot. Only the central stem of the head is left
after the spores are released. Common bunt is a seedling-infecting
pathogen that has spores that are carried on the outside of the seed coat or
are present in the soil. Management of the disease include fungicide seed
treatment and using disease-free seeds
Loose smut
[19]
Sooty head molds
Sooty head molds are characterized by a dark green or black mold growth
on the surface of mature wheat heads. These molds are part of a naturally
occurring complex of organisms that help to decay dead plant debris. Sooty
molds are most common when mature wheat is subjected to repeated rains
and delayed harvest. This disease also may affect plants that have been
damaged by root rot. The sooty head mold growth is normally superficial.
Its effect on grain is minor, but it can make for dusty harvest operations.
Sooty molds can contribute to a discoloration of the grain called black
point. The management of the disease is generally impractical or not
needed.
Sooty head molds
Stagonospora nodorum
The disease causes dark brown or purple lesions on heads. Lesions are
often more intense at the top of the glume, with brown streaks or blotches
extending down toward the base of the spikelet. The presence of tiny fungal
reproductive structures embedded in the tissue can confirm the diagnosis
but will require significant magnification.
The management of the disease includes using genetic resistance, foliar

fungicides, crop rotation, and fungicide seed treatment. Effective control of
all pests, including diseases and insects, is essential to produce a healthy
seed crop. In addition to heavy reductions in seed yields, diseases and pests
damage the quality of the produce. Treating seeds with appropriate
fungicides effectively checks development of soil and seed borne diseases.
Applying the appropriate fungicides and insecticides in proper quantities
and at the tight time can effectively control rusts and Russian Wheat Aphid.
Adoption of appropriate schedules of plant protection and rouging of
[20]
diseased plants and ears from time to time will further check the spread of
diseases and insects; and Seed-borne pathogens may cause injury to the
seed itself, or to the plant, which emerges from that seed.
[21]
Diseases of Lower Stem and Roots
Common root rot
Common root rot causes premature death of wheat, resulting in patches of
white heads scattered throughout a field. Infected plants are dark at the
base and have poor root development. A key diagnostic feature of the
disease is dark-brown lesions on the thin stem extending from the base of
the plant to the remnant of the seed. Healthy sub-crown internodes should
be cream colored and firm. The management aspect of the disease include
crop rotation and control of grassy weeds.
Root rot
Fusarium root, crown, and foot rots

Fusarium root, crown, and foot rots cause patches of wheat to die
prematurely, resulting in areas of white heads within a field. Infected plants
are typically brown at the base and have poor root development. During
advanced stages of the disease, the Fusarium fungus often produces a pink,
cottony growth inside the lower portions of the stem. Often, the disease is
most severe after prolonged periods of dry weather. Managing the disease
include crop rotation, control grassy weeds.
Fusarium/crown/foot root
rot
Take-all
[22]
This fungal disease causes premature death of the plant, resulting in patches
of white heads in of wheat. Plants infected by take-all normally have a
black discoloration of the lower stem and roots. Frequently, the disease is
most severe in wet areas of a field and near field edges where the fungus
survives in association with grassy weeds. The disease can easily managed
by applying proper crop rotation and controlling grassy weeds.
Take-all
[23]
Pest Management
Pests like termites, armyworms; brown wheat mite, aphids, and jassids
commonly affect wheat at different growth stages. Some wheat pests have
the potential to spread to other similar agro-climatic zones where wheat is
grown. Many of these pests, or groups of pests, typically undergo annual
outbreaks in many countries and cause substantial crop losses. Most are not
easily controlled with conventional pest management strategies. The
description and control methods for these insects described hereafter may
have wide application in countries where they currently are considered
pests and in countries where they may yet become established.
Russian Aphids (Diuraphis noxia)

Russian wheat aphid (RWA) established as a major aphid pest of wheat in
Europe, Africa, Asia and North and South America, where it has caused
crop losses of up to 80 % in heavily infested areas. In Africa, its most
severe infestations have occurred on rain-fed wheat and barley in the
highlands of Ethiopia, These aphids feed on the upper leaf surfaces and roll
up the leaves to produce a protected microhabitat where they can feed
undisturbed. Infested leaves exhibit purple or white longitudinal streaks.
Heavily infested plants may appear flattened, with young tillers lying
almost prostrate on the ground. when plants become unsuitable or
overcrowded, winged aphids reproduce and migrate to other plants or
crops.
Aphids can damage the crop directly by feeding or indirectly through their
ability to vector/ transmitting Barley yellow Dwarf Virus (BYDV). BYDV
is a persistent virus that can be retained by the aphid for weeks and can be
transmitted in minutes to a few hours of aphid feeding.
Aphids exist in different stages like winged (alates), and wingless

(apterous) sexual and asexual forms. The rapid spread takes place through
asexual reproduction where females give rise directly to nymphs rather than
eggs.
[24]
Management
When feeding in sufficient numbers, they can cause considerable damage,
but under normal conditions, losses are not much. Using a tolerant or
resistant variety is an excellent management tactic. Chemical pesticides are
recommended for this pest in wheat if the level of aphids per tiller crosses
10 during vegetative phase and 5 during reproductive phase. However,
there is a need to keep watch on this pest. The spray of imidacloprid @ 20
g a.i. per ha initially on border rows and if infestation is severe then in
entire field will give good protection against this pest. Generally, natural
enemies present in the field help in controlling the population of this pest.
Aphids feeding on wheat Symptoms of BYDV on flag leaves in wheat
Hessian fly
The Hessian fly (Mayetiola destructor) has long been a wheat pest in
regions adjacent to the Mediterranean Sea in northern Africa, southern
Europe and western Asia. Hessian fly can be found in small numbers in
most wheat fields at harvest. If the wheat stubble is destroyed after harvest,
the fly dies and the life cycle is broken. Often Hessian flies begin
depositing eggs very soon after seedling emergence. Once the pest is
established on a new wheat plant, their eggs hatch within a few days and
the tiny maggots migrate into the whorl of small wheat plants, ultimately
locating below ground at the stem’s base, where they enter the pupa stage.
While feeding, the larvae injure the plants by rupturing leaf or stem cells.
They cause the plant to form an area of nutritive tissue around the base to
enhance their feeding, which can result in tiller stunting and dieback. A
heavy infestation on early-stage plants may greatly reduce plant stand. The
damage caused by the maggots of the pest are mainly on vegetative growth,
which might reduce the activity of photosynthesizing machinery resulting
to stunting growth. The maggots during feeding also inject toxic substances
resulting to inhibition of plant growth. These toxin acts as inhibitors to the
[25]
plants and overall hormonal action of plants disturbs resulting to poor
growth.
Management
Because the Hessian fly life cycle depends largely on the presence of wheat
stubble, rotations that prevent to plant new wheat into or near a previous
wheat crop’s stubble will be an effective way to prevent infestations. Since
the Hessian fly is a weak flier, putting distance between the location of new
wheat plantings and the previous season’s wheat fields can be a successful
method of preventing new infestations. Disking wheat stubble after harvest
effectively kills the Hessian fly. It is also possible to control the damage
caused by the pest using resistant and tolerant wheat varieties. Long-
residual foliar pyrethroid insecticides applied shortly after wheat emerges
at, or before, the two to three-leaf stages have been very effective in
controlling Hessian fly
Adult Hessian Fly
Termites (Odontotermis obesus, Microtermis obesi)

Termites attack the crop at various growth stages, from seedlings to
maturity. The severely damaged plants look wilted and dried. On partially
damaged roots,, the plants show yellowing.
Management
For effective management, recommended insecticides such as endosulfan,
chlorpyriphos and carbosulfan can be used both for seed treatment and for
broadcast of treated soil in standing crop.
Armyworm (Mythimna separate)

Armyworm infests small grains, usually wheat crop in the season. They can
cause serious defoliation, injury to the flag leaf, and cause head drop.
[26]
Armyworm populations fluctuate greatly from year to year and across areas
of the country. The larvae are found in the cracks of soil and hide during
the day but feed during night or early morning. In wet and humid weather,
they may feed during daytime also. Armyworm is the only caterpillar found
in large numbers in small grains. They are active at night, hiding under
plant litter such as old corn stalks and at the base of wheat plants during
daylight hours. After dark, they feed on foliage from the bottom of the
plant upward. As they eat the lower foliage or as it is destroyed by leaf
pathogens, the armyworm larvae feed higher, eventually reaching the flag
leaf. If populations are high, large caterpillars may also feed on the stem
just below the head.
Management
Management of armyworm is based on scouting, thresholds, and resulting
application of insecticides when necessary. Infestations of armyworms are
not easily detected by casual observation because caterpillars hide during
the day. Fortunately, several signs of armyworm infestation occur, and
caterpillars can be monitored if the correct technique is used. Any field
with significant bird activity should be scouted. Signs of armyworm leaf
feeding and caterpillar droppings can also be good indicators. Feeding is
sometimes inconspicuous because small caterpillars do not eat much and
feeding signs are often concentrated on the lower part of the plant.
. Armyworm on wheat leaf
[27]
Harvesting
After completion if essential cultural operations and approval of seed fields
for certification, the crop is ready for harvest. The appropriate time of
harvesting to ensure maximum seed yield and quality is of great
significance. Seed are physiologically mature, i.e., fully developed when
they still have high moisture content. This permits seed harvest earlier, if
you have good artificial drying facilities. When seed are harvested and
bulked together, they must be quite dry, or you will lose them. If seed
harvested with high moisture content and do not dry them immediately, the
high seed moisture will cause the seed to heat, molds will grow, and the
seed will die very quickly. If the seed are badly spoiled, they cannot even
be used for grain. Most seed crops are harvested when the seed are at
"harvest maturity. For most grain crops, this is around 12-14% moisture
content; for oily seed such as soybean, groundnut or cotton, this is around
8-10% moisture. However, for wheat the best moisture content varies from
14 to 17%. Harvesting of wheat seed crops at lower seed moisture contents
minimizes mechanical damage to the seed and helps in coping with seed
drying problems in the highlands of Ethiopia.
Combines do not operate well above 15% seed moisture. To know the
moisture content of seed you can bite a seed and if it is dry and hard
enough to crack pen, the seed are dry enough to harvest. When the seed
crop has turned brown and is drying out, be sure to check moisture content
of the seed every day. In hot dry weather, one or two days can make a big
difference is seed moisture. Fully matured seed is easily harvested and
cleaned with minimal harvest losses. While early harvest may make
combining difficult, with increased losses in combining and threshing,
harvesting at later stages may result in increased losses due to weather,
lodging, seed shattering and pest and diseases. Wheat seed crop may be
harvested manually or mechanically, taking care to avoid mechanical injury
to seeds during harvesting and threshing operations. Avoid any chance of
mechanical mixing of seeds and maintain lot identity. In combine
harvesting adjust combines carefully to avoid losses.
[28]
Harvest methods
Many methods of harvest are used. Any method can be used, just so long as
the seed is cleanly removed from the field. Harvest should be completed
before weather or moisture damages the seed or crop, so the seed crop is
kept pure, and the seed are not mechanically damaged. Cereals are often cut
and tied into bundles. Stack bundles with the seed heads up, so they do not
touch the ground and keep them in small groups so they will stand up until
they are dry enough to thresh. Plants are cut and bundled when they still
have moisture high enough to prevent loss of seed by shattering. The
bundles may be stacked in the field in small groups to dry, or may be
carried to a central place near the threshing operation for stacking there.
When the bundles are stacked, stack 6-10 bundles together; this is
necessary so the air can circulate around the bundles and dry out the seed.
If too many bundles are stacked together, the seed will not dry properly.
When they are properly dried, the bundles can be threshed to remove seed
from the plants. If combine harvesters are available, the combines can cut
different varieties separately to not mix them and thresh the plants in a
"combined" single operation in the field.
Seed drying
Cemented threshing floors or use of canvas is preferred for drying to
maintain the quality of seeds. Sun drying of seeds on threshing floors,
spreading the seeds in thin layers, may be necessary to reduce its moisture
content and improve the storage quality. Drying wheat seed to its safe
moisture limit preserve its viability and vigor. Mechanical drying systems
can also be used to speed up the drying process. When sun drying, care
must be taken at all stages to avoid mechanical mixing.
Drying methods
Many methods of drying seed are used. The method to use depends on how
much seed you have; how much you have in facilities, equipment and
operating expenses; and other cost and volume factors.
The important requirements for seed drying are:

 The seed must not be mixed or contaminated with other seed;
 Trash, dirt, etc., must not be mixed in with the seed;
[29]
 The seed must be protected from rain or other water, insects, pests (including
birds), and other damaging influences while it is drying; and
 All seed must dry uniformly; some spots cannot be over-dried, while other
spots are not fully dried.
Common drying methods used by informal growers include:
Drying Floor: This is probably the most common drying method. A smooth,
clean floor is made of either wood, concrete, dried mud, or other material.
Drying in bags on a rack: Small amounts of seed in loose-weave jute

(burlap) bags; filled the bags 1/3 to 1/2 full; then hang the bags on a rack so
that the seed in the bag is spread out in a thin layer.
Drying in kitchen: Small amounts of 2-4 bags (loosely woven jute or burlap
bags) are sometimes dried by hanging them in the family kitchen, in the
area where the cooking fire is located. Heat from cooking warms the air
around the seed bags. As the air gets warmer, its RH gets lower, so the air
can absorb more moisture from seed.
Artificial Drying: With Fans and Heaters: Many types and designs of
artificial dryers are used. They are quite good if you have the money to
purchase and operate them. They may dry seed in bulk, or in bags; their
capacity ranges from a few bags to many tons
Seed dressing
Breeders’ and foundation seeds are usually very costly; hence, considering
every effort is essential to ensure their survival in the field. Seeds to be
multiplied should be dressed properly with the recommended seed dressing
chemicals; Pre-harvest foliar application of chemicals can also reduce the
internally seed-borne fungi and can be combined with seed treatment to
produce healthy seed. Apart from disease control, seed treatment also has a
positive effect on crop growth and yield; and follows the instructions on the
sachet when dressing seeds.
[30]
Seed storage
Wheat seeds are stored from harvest to the next planting, which may be
used in the next season. Seed moisture and temperature are influencing the
storage of wheat seeds. To store wheat seed for a long time, it must be at
safe moisture content. High moisture contents allow insect and
microorganism activity, which cause heating. Maintenance of seed viability
depends on the conditions experienced before and during storage. Avoid
damage during harvesting, inadequate or improper drying, rough handling
and poor physical storage. Seed harvested at maturity, dried to safe
moisture content, stored under favorable conditions and protected from
damage and pests until it can be planted.
Conditions that cause the loss of seed viability in storage include:

 Immature or damaged seed cannot survive long storage periods;
 Mechanical injury to seed during harvest or handling makes it more
susceptible to deterioration in storage;
 Seed should be properly dried before going into storage and protected from
moisture and high relative humidity. Fungi cause damage to stored seed if
seed moisture is high;
 High storage temperature has a damaging effect on seed. Stores should be
designed so that low temperatures are maintained;
 some seed treatments cause seed to die if it is stored too long; therefore, seed
should only be treated when it is certain that it will be sold for planting;
 Rodents, mainly rats and mice, can be most destructive to seed. Effective
rodent control (traps and poison) is essential in all seed stores. A complete
program of exclusion, sanitation and control should be used; and
 insects should be controlled by a combination of insecticides and fumigants.
Use safest fumigants.
For wheat, high seed moisture, i.e., above 11 to 12 % is the most

damaging, and seed must be kept as dry as possible in storage. The
response of wheat seed to high atmospheric humidity (RH) in storage
varies with temperature. Research studies indicate that the critical
moisture content for wheat that increases the rate of respiration is
14.6 %. In general, stored wheat seed should be kept at moisture
content levels below 12 % and relative humidity should not exceed
50 to 60 %. About a dozen species of storage insects occur widely
[31]
and may cause serious damage to seed stored at 9% or higher
moisture content. Insects attack the endosperm and/or embryo, and
create high moisture, which leads to heating. Rodents and birds eat
seed, damage bags and scatter, mix and contaminate seed. Seed may
be stored in sacks or bags for short period. Label seeds properly and
stacked on wooden pellets. Storage facilities should be dry, cool, and
clean, disinfected with appropriate pesticides.
[32]
Seed Quality Control
Evaluating seed quality

Farmers have used aspects of seed quality to protect the next cropping
season’s investment for many years. The intention is not to raise doubts
about the supplier’s reputation but to ensure seed performance after
planting. The advent of laboratory research on seeds resulted in simple
testing and analytical techniques. However, due to movement of seeds
within and between countries, discrepancies in test results became evident
in seeds of the same lots when different interested parties tested them.
These discrepancies were due to differences in the definitions, methods,
equipment and materials employed.
Most are adequate for national seed testing requirements, although

currently skills and experience relate to food-crop seeds. Quality is a
relative term meaning a degree of excellence expressed as a rating when
compared with an acceptable standard. It may be better, equal or worse in
comparison depending on the criteria and wording used. There are 11 major
characteristics, which can be considered as measurements of seed quality.
Sometimes, these characteristics are referred to as attributes of seed quality.
They are
 analytical purity (physical);
 cultivar or genetic purity;
 germination;
 vigor;
 moisture content;
 health;
 seed density (weight per number);
 origin or provenance;
 incidence of noxious weed seed;
 homogeneity; and
 appearance
In most seed-testing laboratories, only three of them, namely analytical

purity, incidence of noxious weed seed and germination are evaluated. To
[33]
evaluate these characteristics many countries have established "official"
seed-testing stations recognized by law.
Components of seed quality

Seed quality is a function of genetic, physical, physiological and health.
These characteristics are clearly identified as follows:
 Genetic: Genetic purity (trueness to type) of a variety can be deteriorating due

to several factors during production cycles. The important factors are inherent
genetic information contained in the seed that provides the potential for
higher yield, better grain quality and greater tolerance to biotic or abiotic
stresses; and varietal identity, specifically the transfer of seed of desired
variety from the breeder to the farmer through successive generations of seed
multiplications.
 Physiological: the viability, germination and vigor of seed which determines
the germination and subsequent seedling emergence and crop establishment
in the field as well as the storage potential of the seed lot;
 Physical: analytical purity, freedom from other crop/weed seeds
contamination, seed size, seed weight and seed lot uniformity; and
 Health: absence of infection with seed-borne diseases or contamination with
noxious weeds
[34]
Seed Quality Assurance
The two common ways to introduce quality controls are at the various steps
leading up to the point of sale (pre-marketing control); and at the point of
sale (marketing control).
Pre-marketing control
This step concentrates on maintaining the identity of the variety through
production, procurement, conditioning and storage. In such a system, it is
necessary to ensure that the variety comes from approved sources. Such
control systems are referred to as certification and are often recommended
where reassurance is required as to the genetic identity and quality aspects
that are not easily verifiable by visually examining the seed. Seed
certification, therefore, helps to assure trueness-to-variety and satisfactory
quality of a selected portion of the seed that may be available in a country.
The system involves quality control system to determine eligibility of
varieties, verification of seed source, field inspection, sampling processed
seed, seed testing and evaluation against quality standards, producing and
fixing certified seed labels, conducting variety control tests and information
and education.
Marketing control
In the marketing control program, emphasis is often on seed sampling,
laboratory evaluation and appropriate follow-up that will minimize the
chance of inferior seed for sale. The adoption of the most appropriate level
of standards depends on the:
 ability and resources available;

 extent (range of) and type of seed activities;
 organizations involved and their responsibilities;
 cause and effect of reported seed quality abuse; and
 educational level of participants and benefactors; and government
agricultural policy
[35]
Seed Quality Testing
Seed purity standards for certified seeds

The acceptable standards of purity for certified seeds are indicated in Table
4. Seeds can be rejected as being impure when there are a higher
percentage of seeds of other varieties, a low germination percentage, high
moisture content, and a higher percentage of inert matter.
Wheat seeds should be free from seeds of cultivated crops in the seed field
and whose seed are so similar to wheat seeds that it is difficult to separate
them economically by mechanical means. Those seeds cause physical
admixture with the wheat seed only when the crop matures approximately
at the same time when the wheat seed crop matures.
Objectionable weed species are harmful in one or more of the following

ways
 the size and shape of their seeds are so similar to that of wheat seed that is
difficult to remove their seed economically by mechanical means;
 their growth habit is detrimental to the growing seed crop due to competing
effect;
 their plant parts are poisonous or injurious to human and animals; and
 they serve as alternate hosts for crop pests and diseases.
Seed health refers to those diseases and pests designated for the
certification of seeds and for certification must be met with. Seed borne
diseases of wheat for which certification must be met in Ethiopia are of
wheat include loose smut, and septoria. During seed production and
distribution, follow appropriate cautions to protect the seed supply system
from those diseases.
[36]
Table 4: Minimum requirements for wheat seed certification
Standards Breeder/ pre Basic Certified C2 C3 Commercial Emergency Method of test
basic
Field standards
Rotation (min. years) 3 2 2 1 1 1 1
Isolation (m) 5 5 3 3 3 3 3
Off types and other varieties (max %) 0.03 0.05 0.1 0.2 0.2 0.3 0.5
Laboratory standards
Pure seed (min %) 98 98 97 97 97 95 95 ES 472
Other crop seed (max. %) 0.03 0.05 0.1 0.2 0.2 0.3 0.5 ES 473
Weed seed (max %) N.S 0.02 0.03 0.05 0.05 0.05 0.1 ES 472
Infected/infested/seed (max %) N.S 0.02 0.03 0.05 0.05 0.05 0.1 ES 476
Inert matter (max %) 1 2 2 2 2 2 2 ES 472
Germination (min %) 90 90 85 85 85 85 80 ES 474 ES 475
Verification of species and cultivar ES 477
Moisture content (max %) 13 13 13 13 13 13 13 ES 478
37
Identifying seed quality
To identify the quality of seed, the following are used in the organized seed
industry:
 Seed analysis tag: Every bag of seed should have a tag, which describes the seed
quality factors required by law to be on the seed label.;
 Certification tag: Variety is the genetic ability to be certain things and do certain
things, such as is of a specific variety and yield more. Seed certification is a
special technical process which ensures genetic purity;
 Freedom from adulteration: Each seed bag should be unopened, and sealed as proof
that it has not been opened and mixed. Examine the bags, and look for the seals
and indications that the bag has not been tampered with;
 Proper treatment: The seed must be treated with proper dosages of the proper seed;
 Protectant chemicals: Each seed must be thoroughly covered with the protectant
treatment, which can usually be easily seen because the treatment includes a dye
which colors the seed; and
 The seed supplier: Not all seed sellers are reliable. Some sell low quality seed;
others will mix seed, or even re-use seed bags filled with low-quality seed instead
of the original high-quality seed;
To get good seed, always buy from a reliable dealer. If someone offers low-
price seed, it probably is not even worth that low price; and tags on bags may
carry the following information:
 Crop name;
 Variety name;
 Pure crop seed %;
 Other crop seed %;
 Weed seed %;
 Inert material %;
 Germination %;
 Germination %;
 Sometimes, moisture % of the seed;
 Lot number;
 Who produced the seed, and where; and
 Year the seed was grown.
[38]
Genetic Purity Maintenance
Seed producers should take appropriate measure to maintain genetic purity of
their wheat varieties. The common steps to achieve true to type seed in the
wheat seed are identified as follows
 Using seed of appropriate class from approved source to raise the seed crop;
 Fixing preceding crop requirements to avoid contamination due to volunteer
plants;
 Isolating seed crop from sources of contamination by natural crossing with other
varieties grown alongside and off-types present in the field by wind;
 Avoiding contamination due to mechanical mixtures at the time of sowing,
harvesting, threshing, processing and handling of seeds, and contamination due
to seed borne diseases;
 Rouging off-types differing in characteristics from those of the seed variety. The
off types may arise due to presence of the some recessive genes in heterozygous
conditions, arising from mutations. The heterozygous plants segregate for the
characters affected by the particular gene(s) in later production cycles to give rise
to off types. Volunteer plants may arise from accidentally planted seed or from
seed produced by earlier crops contributing to off types;
 Certifying the e genetic purity of seed under commercial seed production, which
require qualified and experienced personnel of seed certification agency should
inspect seed crops at all stages of growth and verify seed lots or purity and
quality.; and
 Periodic testing of genetic purity of seeds, by growing the crop to ensure
maintenance of quality.
[39]
Maintenance Breeding and Breeder
Seed Production
Access to genetically pure seed stock allows producers to achieve maximum
quality and performance of new and established varieties. Breeders’ seed
constitutes the basis for all further seed production. Unless the breeder’s seed
is of highest purity and quality the seed multiplied from it cannot be regarded
as satisfactory and therefore affect the performance of a variety. Reducing the
contamination and ensuring quality particularly varietal purity and identity is
of paramount importance. Therefore, new lots of breeder’s seed must be
regularly produced to initiate production of later generations through variety
maintenance. This call for defining variety maintenance as the perpetuation of
a small stock of parental material through repeated multiplication following a
precise procedure.
Objectives of maintenance breeding

 maintain genetic purity;
 maintain the identity of the crop/variety;
 maintain other good qualities of the seed; and
 maintain seed supply-use continuum.
Selection criteria
Selection should focus on the following issues
 Trueness to type;
 Uniformity;
 Diseases; and
 Off-types/segregation, i.e., stand performance.
Sources of seed contamination

The following are considered as the major sources for seed contamination
 Genetic Contamination:-this is the residual segregation, spontaneous mutations or

undesirable natural out-crossing due to inadequate isolation;
 Mechanical Contamination:- this results from very wide range but mainly due to
insufficient cleanliness of fields, equipment and inadequate measures to avoid
contamination; and
[40]
 Pathological Contamination:- occurs through infections particularly with seed-
borne diseases or from pathogens from same variety, other crops or weeds
Methods of seed maintenance

Due considerations should be given on the following methods while
maintaining seeds
o Purification. It is used in situations where there is no organized procedure
o Mass selection:-The individual best typical plants are selected. These individual
typical plants are bulk harvested and the rest are discarded. The resultant seed is
used for further multiplication.
o Ear to row:- considered to be the best method. Single plants typical of variety are
selected, harvested and kept separately. These seeds are planted in rows; during
production. Off-type rows and rows with off-type plants are discarded,
conforming rows are bulked for further multiplication.
Maintenance responsibility
Maintainer should maintain breeders’ seeds of released varieties of wheat. In
Ethiopia, the law allows the maintainer to delegate representative maintainer.
Large-scale commercialization of a variety is linked to effective maintenance
and seed production continuum. The varietal purity of subsequently
multiplied pre-basic, basic and certified seed largely depend upon the quality
of the nucleus/breeder’s seed. Unless the nucleus/ breeder’s seed is of highest
purity and quality the seed multiplied from it cannot be regarded as of
satisfactory genetic purity. Unsatisfactory genetic purity, especially in cross-
pollinated crops, could ultimately severely affect the performance of a variety.
It is therefore, of utmost importance that the nucleus/breeder’s seed is
produced in such a manner that satisfactory genetic purity, identity and the
other good qualities of seed are maintained.
Maintaining Nucleus Seed of Varieties

For maintaining nucleus seed of pre-released or newly released varieties the
following procedures should be followed
 Sampling of the variety to obtain nucleus seed. New numbers, lines or selection
that are highly promising, based on performance in breeding nurseries and yield
trials, should be sampled for seed purification. These samples provide a
beginning for purifying new varieties and for possible increase and distribution
[41]
to farmers. Not more than fifteen new varieties in any one crop at a station
should be sampled in one year,
 Table examination of samples: The two hundred plants of each sample should be
threshed separately and the seed should be examined in piles on the table.
Discard any pile appearing obviously off type, diseased or otherwise
unacceptable. The seeds of each two hundred-plant samples or less are now
ready to be sown in a variety purification nursery called as nucleus.
 Locating and seeding of nucleus: Each nucleus seed should be grown on clean
fertile land at an experiment station in the region or in area in which this new
variety could be grown, in the event of its release. The land must not have had a
crop of the same kind in the previous year.
 Inspecting nucleus two-row plots and removal of off types: Throughout the season
of growth, from the seedling stage until maturity, the nucleus plot should be
examined critically. Differences in the habit of early plant growth, leaf color, rate
of growth, time of heading, height head characteristics and diseases reactions
should be looked for. If a plot differs distinctly from the average in the pre-
heading stages of growth, it should be removed before heading.
 Harvesting and threshing of nucleus: Each remaining plot, of which there should
be at least 180 out of the original 200 should be harvested individually with a
sickle and tied in a bundle. The total bundles of each nucleus should be labeled
and stored until the current years yield rests for trials are obtained. The nucleus
bundles of any new variety should be discarded, if it is found unworthy of being
continued.
 Later the seed should be cleaned in a fanning mill or by hand methods, the grain
from each nucleus plot being placed in a pile on the seed table. The 180 or more
piles of seed of one nucleus must be examined for approximate uniformity of
seed appearance, and any pile, which appears to be off type discarded. All the
remaining piles of the seed should be masked together in one lot. This should
treated with fungicide and insecticide, bagged, labeled and stored as "Breeder’s
Stock Seed" for use in the next year. Breeder’s stock seed is the original purified
seed stock of a new variety in the hands of the plant breeder s.
The following steps are critical in maintaining breeder’s seed

 Breeder’s stock seed from the nucleus should be sown on the clean, fertile land,
which did not grow a crop of the same kind in the previous year. The space
required for the seeding the breeder’s stock is about 1.2 ha;
 The field should properly isolated;
 The best farm procedures should be used in the sowing, raising and harvesting of
breeder’s stock;
[42]
 It should be produced at the experimental station in the area in which the new
variety has been bred.
 The seeding should be done in such a way as to make the best use of the limited
amount of seed available and to facilitate rouging. The row spacing should be
sufficient to permit examination of plants in rows for possible mixture or off
types;
 All plants not typical of the variety should be pulled and removed. There should
be very few plants to rogue out if the previous year’s nucleus breeder’s stock
seed was well protected from natural crossing and careful rouging was done and
there were no impurities during cleaning etc. The rouging should be done before
flowering, as was done for the nucleus/breeder’s stock seed; and
 In the breeder’s stock is harvested and threshed, the equipment used must be
scrupulously clean and free from seeds of any other varieties. This cleanliness
should be extended to cards and bags as well as threshing machine itself. The
seed should now be 99.9 % pure as to variety. This breeder’s seed is ready now
for increase of foundation seed. A portion of this breeder’s seed should be
retained by the breeders to sown a continuation breeders seed of the variety.
Any one of the following methods could be used to maintain the breeder’s
seed of established wheat varieties
 The breeder’s seed of local varieties could be maintained by growing them in

isolated plots and by very rigorous rouging during various stages of crop growth,
where the various plant characters are observable. The method of handling the
breeder seed crop is the same as described earlier for breeder’s seed of newly
released varieties; and
 The genetic purity of established varieties could be satisfactorily improved by
bulk selection. In this method 2,000 to 2,500 plants typical of the variety are
selected, harvested, and threshed separately. The seeds from each plant are
examined and any pile which shows any obvious off-types, or otherwise appears
dissimilar, are discarded. The remaining piles of seed are bulked to constitute the
breeder’s seed. The other practices of handling remain the same.
Characters be used during inspection and their acceptance range of variation

are shown in Table 5.
Table 5.. Characters used for identification of wheat varieties and their expected variations
Character Stages Varieties
[43]
Initial growth habit 30-35 DAS* Spreading, semi-erect, erect
Auricle color 60-65 DAS Hyaline, purple
Waxy bloom on leaf 60-65 DAS Present, absent
Color of leaves 60-65 DAS Dark green, green, light green
Days of 50% flowering At the time of ear Early, mid late, late
emergence
Plant height 15 days after Tall, semi-dwarf, double dwarf, triple
flowering dwarf
Ear characters
Waxy bloom on ear AEE** Present, absent
Awning AEE** Present, absent
Density AEE** Lax, mid lax, normal, dense
Color At maturity Brown, light brown, pale yellow
Spikelets mid third, At maturity Broad, sloping, elevated, indented
glumes shoulder
Spikelets mid third, At maturity Short blunt, short sharp, long sharp
glume beak shape
Seed color After threshing Amber, red
Carry-over Seed
The breeder must carry-over at least enough seed to safeguard against the loss
of variety if there is a complete failure during foundation seed multiplication.
In addition, the breeder should further safeguard variety by arranging to have a
portion of the seed originally released stored under the ideal conditions.
Based on the above characters the ear rows, which are segregating for one or
several characters, are rejected. In wheat generally 3-4% off types are
expected. Ear rows with typical character of the variety and that show
uniformity with regard to the diagnostic characters are harvested and threshed
individually or separately. If about 10% rejection assumed, then about 430-
450 rows are left after selection. With the assumption of 300 g yield from
each ear row, about 80 to 100 kg of seed will be harvested from 450 ear rows.
This seed, when bulked, is normally called nucleus seed and will be used for
planting large breeder seed plot. If the breeder seed requirement is of a
particular variety is around 2.5-3.0 tons then this entire nucleus seed can be
planted in about one hectare area in order to produce the desired quantity of
breeder seed. However, if the breeder seed requirement is less than 2.5 to 3.0
tons per variety then only the required quantity of nucleus seed is used and
[44]
the remaining seed can be kept in the air-conditioned storage for the years to
come.
[45]
Generation System of Seed
Multiplication
Generation system of seed multiplication is the production of a particular class
of seed from specific class of seed up to certified seed stage. The choice of a
proper seed multiplication model is the key to further success of a seed
program, which depends on the rate of genetic deterioration, seed
multiplication ratio, and total seed demand.
Based on the above factors, different seed multiplication models may be

applied for wheat seed multiplication, and the national seed program should
decide how quickly the farmers can be supplied with the seed of newly
released varieties. In view of the basic factors, the chain of seed multiplication
model for wheat could be;
 Four-generation model: Breeder seed, Pre-basic seed, basic seed, Certified seed,
or
 Five-generation model: Breeder seed, Pre-basic seed, Basic seed, Certified seed
(I), Certified seed (II).
Breeder seed is a seed directly controlled by the originating or the sponsoring

breeder or institution, which is the basic seed for recurring increase of pre-
basic and basic seed. Pre-basic seed is the seed stock handled to maintain
specific identity and genetic purity, which may be designated or distributed
and produced under careful supervision of an agricultural experiment station.
This seed is the source of all other certified seed classes through basic seed.
Basic seed is the progeny of the pre-basic seed so handled as to maintain its
genetic identity and purity, approved, and certified by a certifying agency. It
should be of quality suitable to produce certified seed. Certified seed is the
progeny of basic seed. Its multiplication is so handled to maintain genetic
identity and physical purity according to standards specific for wheat.
Certified seed in wheat may be the progeny of certified seed provided this
production does not exceed two generations beyond basic seed and if the seed-
certifying agency determines the genetic and physical purity are not
significantly altered.
[46]
The seed multiplication ratio of wheat determines the amount of seed expected
in the next generation. Seed multiplication ration refers to the number of seeds
to be produced from a single seed when it is sown and harvested. It can be
calculated as the amount of seed sown divided by the amount harvested. The
seed multiplication ratio of wheat is 1:20.
Seed quality testing

Several techniques are available to evaluate the quality of seed. The International
Seed Testing Association (ISTA) has devised methodologies and techniques.
Definitions used in seed quality testing;
 Lot: This is a specified quantity of seed that is physically identifiable and for
which an International Analysis Certificate may be issued;
 Primary sample: A small portion taken from one location in the lot (also known
as an initial sample);
 Composite sample: A mixture of all the primary samples from the lot;
 Submitted sample: This is the sample submitted to the testing station, comprising
the composite sample reduced as necessary; and
 Working sample: A reduced sample taken from the submitted sample in the
laboratory, used in a given quality test.
Seed Processing
Seed processing is done to narrow down the level of heterogeneity of the seed
lot by using suitable processing techniques. The seed lot is heterogeneous
because of the following reasons:
 The soil is heterogeneous in availability of nutrients, and physical, chemical and

biological properties;
 The seed size variability occurs due to the position of seed on the head, time of
pollination over a period of time;
 Biotic factors such as pests and diseases; and
 Management practices such water, land preparation, leveling, staggered sowing,
and uneven distribution of fertilizer and irrigation water, uneven plant protection
sprays, and uneven maturity at harvest.
It is possible to upgrade germination ability and vigor of seed by grading seeds

according to size, specific gravity, length and density. Large size, a denser
seed, and optimum length exemplify germination ability and vigor. To obtain
[47]
particular range of size, shape, length and density of seeds, the quality of the
lot is upgraded by grading them appropriately.
The common assumption in seed processing include the following
 there should be complete separation;

 there should be minimum seed loss;
 upgrading should be possible for any particular quality; and
 processing should have more efficiency
The following physical characteristics are used to separate seeds:
 Size: Based on size it can be separated with air screen cleaner cum grader;
 Length: Disc or indented cylinder separator;
 Weight: Specific gravity separator;
 Shape: Spiral separator or draper seed dodder mill; and
 Color: Electronic color separator
 Electrical conductivity: Seed differing in their ability to conduct electrical charge
can be separated with electronic separator.
Seed Quality Determination

Maintenance of quality standards is important in wheat seed production. Seed
quality can be determined by the internal quality assurance system of the
producer company and/or seed certification laboratories. In any case, quality
components such as physical purity, moisture content, germination and vigor
have to be tested before distribution to the users. The genetic purity of the seed
is done through grow out tests.
Methods for seed quality testing

The following definitions devised ISTA are used in seed quality testing
 Seed Lot: This is a specified quantity of seed that is physically identifiable and
for which an International Analysis Certificate may be issued. The maximum
quantity of a seed lot in wheat is 20 tons;
 Primary sample: A small portion taken from one location in the lot;;
 Composite sample: A mixture of all the primary samples from the lot;
 Submitted sample: This is the sample submitted to the testing station, comprising
the composite sample reduced as necessary;;
[48]
 Working sample: A reduced sample taken from the submitted sample in the
laboratory, used in a given quality test. Seed sampling is drawing a portion of
seed lot that represents the entire seed lot; and
 Sealed container: A sealed container for both lots and samples is one that is
closed in such a way that it cannot be opened and closed again without either
destroying the seal or leaving evidence of tampering.
 Sampling intensity: The number of samples drawn depending on the
number of containers or the amount of bulk.
Since it is physically and financially impossible to examine large numbers of

seeds, a representative portion of the population is taken and examined; the
portion is called a sample. Collecting the sample is called sampling and
conclusions about the population are based on tests using the sample. The
more representative the sample, the more accurate the conclusion. The
objective of seed sampling, therefore, is to obtain a sample of a size that is
suitable for tests with the same constituents in the same proportions as in the
entire seed lot. If the population has a uniform distribution of characteristics
(homogeneous) then a sample from any point would be identical with others
from other points when analyzed. However, this homogeneity rarely occurs
because of variation between and within fields or plots, and position on the
inflorescence. Samples must therefore be taken from several locations in the
seed lot.
The basic technique is to sample randomly a quantity of seed using a method

where every seed in the population has the same chance of being chosen.
Where there are only a few containers or sacks, samples can be taken from the
top, middle and bottom of each sack. Samples are taken using special spears
designed to take seeds of different sizes from a specific area within the seed
mass. The following formula can be used to calculate how many bags should
be sampled if more than one is present:
The number of samples drawn, i.e., sampling intensity depending on the
number of containers or the amount of bulk is presented in Tables 6 and 7
Table 6. Sampling intensity for r seeds in bags
Number of bags Sampling intensity

Up to 5 containers Sample each container but never <5 primary samples
[49]
6-30 containers Sample at least one in every three containers but never <5 primary samples
31-400 Sample at least one in every five containers but never <10 primary samples
>400 Sample at least one in every 7 containers but never <80 primary samples.
Table 7 Sampling intensity for seeds in bulk

Number of bags Sampling intensity
Up to 500 kg At least five primary samples
501-3000 kg One primary sample for each 300 kg but not less than 5 primary samples
3001-20,00 0kg One primary sample at each 500 kg but not less than 10 primary samples
>20,000 kg One primary sample for each 700 kg but not less than 40 primary samples.
Where seed stocks are depleted by taking samples of recommended size, a

sequential sample is taken. This involves taking a smaller initial sample,
which is then compared to predetermined criteria for acceptance or rejection.
If the initial sample meets the criteria, it can be used for tests. If not, other
sequential samples are taken until the combined sample meets the criteria for
acceptance. When seeds are stored for a long time a further sample may be
required to determine the extent of deterioration of the seed. The frequency of
sampling is determined by environmental conditions and the age of the seed.
Sampling should be more frequent in hot humid areas or in seed lots stored for
long periods. It may also be a legal requirement based on national experience
as to how long seed remains viable, e.g. six months or one year. Sampling
may be done from the farmer, from cleaning equipment and from the various
stores in the distribution system.
Usually, samples from seed lots are collected by taking small proportion of
seeds randomly and combining them. From this sample, smaller samples are
obtained by one or more stages. In each stage thorough mixing and dividing is
necessary. Samples are taken from bags or from bulk using appropriate trier.
Bin sampler: Used for drawing samples from the lots stored in bins.
Nobbe Trier: The name was given after Fredrick Nobbe. This tries is made in
different dimensions to suit various kinds of seeds. It has pointed tube long
enough to reach the center of the bag with an oval slot near the pointed end.
The length is very small and it is suitable to sample seeds from bags but not in
bulk.
[50]
Sleeve type Trier: It is the most commonly used trier for seed sampling. There
are of two kinds: with and without compartments. It consists of a hallow brass
tube inside with a closely fitting outer sleeve or jacket which has a solid
pointed end. Both the inner as well as the outer tubes are provided with
openings or slots on their walls. When the inner tube is turned, the slots in the
tube and sleeve are in line. The inner tube may or may not have partitions.
This Trier can be used horizontally or vertically. It is inserted diagonally at an

angle of 300C in the closed position until it reaches the center of the bag. Then
the slots are opened by giving half turn in clockwise direction and gently
agitated with inward push and jerk so that the seeds will fill each compartment
through the opening from different layers of the bag, then it is again closed,
withdrawn, and emptied in a plastic bucket. This trier is used for drawing seed
samples from the seed lots packed in bags or in containers.
The minimum submitted sample sizes for various seed tests in wheat are as
follows:
 For moisture test 100 g;

 For grow out test 1000 g, i.e., for field and laboratory test; and
 For other tests such as purity, and germination 1000 g
Submitted samples should be packed, sealed, and marked for identification.

For moisture testing, samples should be packed separately in moisture proof
bag and kept in container along with submitted sample. The label on the
sample bags should bear the following notes
[51]
Date: --------------- Crop: ------------ Variety ------------
Class of seed: ----------------
Quantity of seed in lot (kg): ------------
Test(s) required: Purity Germination  Moisture
The submitted sample is subjected to thorough mixing and dividing to obtain

the representative homogenous seed sample for analysis by reducing it to the
desired working sample.
Working sample: It is the reduced sample with required weight with which the
seed quality tests are conducted in seed testing laboratory and obtained from
the submitted sample through subsequent mixing and dividing.
Mixing and dividing of seeds: Different methods can be applied to mix and
divide submitted samples to a working sample. In wheat the mechanical
dividing method is commonly applied in seed testing laboratories.
Objectives of mechanical dividing:

 To mix the seed sample and make homogenous as far as possible;
 To reduce the seed sample to the required size without any bias; and
 The sample is reduced to desired size by passing the seeds through the divider
repeatedly with one-half remain at each occasion.
[52]
Types of Mechanical Dividers
Boerner Divider
It consists of a hopper, a cone and series of baffles directing the seeds into two
spouts. The baffles are of equal size and equally spaced and every alternate
one leading to one spout. They are arranged in circle and are directed inward.
A valve at the base of the hopper retains the seed in the hopper. When the
valve is opened, the seeds fall by gravity over the cone where they are equally
distributed and approximately equal quantity of seeds will be collected in each
spout. A disadvantage of this divider is that it is difficult to check for
cleanliness.
Centrifugal Divider
The principle involved is the centrifugal force, which is used to mix and
divided seeds. The seeds fall on a shallow rubber spinner, which rotates, by an
electric motor throw out the seeds by centrifugal force. The circle or the area
where the seeds fall is equally divided.
Riffle Divider Method

A Riffle Divider consists of a hopper with attached channels or ducts, a frame
to hold the hopper, four receiving pans and a pouring pan. Alternating ducts or
channels lead from the hopper to the collecting pans on either side. This
divider is suitable for most kinds of seeds. Riffle dividers are available with a
range of channel sizes; large channels for large seeded crop kinds and smaller
channels for small-seeded crop kinds.
Soil Divider
A soil divider consists of a hopper with attached channels or ducts, two
receiving pans and a pouring pan. Alternating ducts or channels lead from the
hopper to the collecting pans on either side. The seeds fall on a tray and
directly divided in to two. Under the divider, two trays are found on which
seeds are thrown. The circle or the area where seeds fall is equally divided.
[53]
Determining Seed Moisture
Moisture content of a seed sample is the loss in weight when it is dried. It is
expresses as a percentage of the weight of the original sample. It is one of the
most important factors in maintenance of seed quality. Seed moisture in
wheat can be determined using methods such as air oven method, and
moisture meters.
In the air oven method, seed moisture is removed by drying the seed sample at
130 0C for 2 hours. The amount of sample submitted for moisture
determination of wheat seed using this method is 100 g. Fine grinding is
necessary before the moisture content is determined. In such cases, at least
50% of the ground material should pass through wire meshes of 0.5 mm and
not more than 10% remain on a wire sieve mesh of 1.0 mm.
If the moisture content of the submitted sample is more that 17%, pre-drying
is required. For this purpose, two 50 g portions are weighed and placed on
open trays at 130 0C for 5-10 min. The pre-dried samples should be kept in
closed desiccators for cooling before working samples are ground.
Steps in moisture determination

 Weigh empty container with its cover;
 Mix the submitted sample thoroughly and take two small portions of it to ground
finely;
 Fill the container with 5 gram of ground sample and weigh it;
 Remove the lead/cover of the container and open container should be kept in the
oven which has already been heated to 1300C, drying duration is for 2 hours;
 At the end of 2 hours, container should be closed with its cover;
 Transfer the container into a desiccator, close the desiccator and allow the
sample to cool for 30 min; and,
 Weigh the sample again and the moisture content can be calculated to one
decimal place using the following formula:
[54]
Where, m= seed moisture content, m1= weight of the container with its cover, m2= weight of the container
with its cover and seeds before drying, m3= weight of the container with its cover and seeds after drying.
The duplicate results of the determination may not differ by more than 0.2%
otherwise, the analysis should be repeated.
If pre-dried, the moisture content is calculated from the results obtained in the
first (pre-drying) and second stages of the procedure. If S1 is the moisture lost
in the first stage and S2 is the moisture lost in the second stage, each
calculated as above and expressed as a percentage, the original moisture
content of the sample is calculated as below:
m=moisture content, S1=moisture percentage lost in pre-drying, S2=moisture percentage lost in drying
stage.
[55]
Purity Analysis
The objectives of purity analysis are to determine the composition by weight
of the variety and contaminants in the sample. The analysis separates the
working sample into three components:
 Pure seed refers to the kind or kind and variety under consideration. It also refers
to the species stated by the sender or found to predominate in the test;.
 Other seed refers to other kinds of crop seed or varieties or weed seed; and
 Inert matter refers to seed-like structures, from both crop and weed plants, and
other matter that is not seed.
The purity analysis in wheat is done on the working sample of a prescribed
weight drawn from the submitted sample. The analysis may be made on one
working sample of the prescribed weight or on two sub-samples of at least half
this weight. The working sample for purity analysis is weighed as follows
(Table 8)
Table 8 Working sample for purity analysis

Weight of the working sample (g) The number of decimal Example
places required
<1 4 0.6542
1-9.999 3 6.542
10-99.99 2 65.42
100-999.9 1 654.2
1000 or more 0 6542
[56]
Purity Components
Pure seed
It includes all botanical varieties of wheat. Immature, undersized, shriveled,
diseased or germinated seeds are also pure seeds. In wheat pure seed also
includes broken seeds, if the size is >0.50 of the original size unlike in
legumes.
Other crop seed

It refers to the seeds of crops other than the wheat seed examined, for
example, barley, and field peas
Weed seed
It includes seeds of those species normally recognized as weed or specified
under seed regulations as noxious weeds in wheat; for example, wild oats
Inert matter
It includes seed like structures, stem pieces, leaves, sand particles, stone
particles, empty glumes, lemmas, chaff, awns, stalks longer than florets, and
spikelets.
Calculating purity components

All the four components must be weighed to the required number of decimal
places. The percentage of the components is determined as follows:
If the loss or gain between the weight of the original sample and the sum of all
the four components is in excess of one %, another analysis should be made.
[57]
Determining Germination Percentage

Germination in wheat refers the emergence and proper development from the
embryo of essential structures such as root and shoot. A germination test is
performed to determine what proportion of seeds in a lot will germinate under
favorable conditions and produce normal seedlings capable of development
into reproductively mature plants.
Basic requirements for seed germination are: water, oxygen, light and suitable
temperature. These conditions have to be maintained at optimum to insure
germination.
Germination tests are conducted with a pure seed fraction. A minimum of 400
seeds are required in four replicates of 100 seeds each or eight replicates of 50
seeds each depending on the size of the seed and size of container of substrate.
[58]
Steps in Seed Germination Test
Step 1: Preparation for germination testing

 Identify specific requirements for temperature, light and any other
treatments needed to test germination of wheat seed;
 Identify availability of equipment and appropriate environment to fulfill
those requirements. If not, the best possible should be found;
 Take a random sample of seeds from the submitted sample after mixing
thoroughly;
 Count out 400 seeds for each test. Return excess seeds back to the
container;
 Divide these seeds into at least four replicates; and
 If the seeds are very dry (with moisture content below 8%) and are likely
to suffer from imbibition damage, it may be necessary to raise the
moisture content (this process is called humidification) to 15–17% before
testing for germination.
Step 2: Setting up the germination test

Although several methods are available to test germination, the three methods
described below are suggested for wheat;
1. Top-of-paper method (TP)
2. Between-paper method (BP) Absorbent paper is used as
3. Germination in sand (S) substrate for germination
Paper substrate quality

 It is important that high-quality paper be used as a substrate in order to obtain
uniform germination and reproducible results; and
 If possible, the paper should meet the following specifications:
o The paper used as substrate should not be toxic to developing seedlings. Symptoms
of paper toxicity include shortened and discolored root tips
o It should be able to absorb and supply sufficient moisture for the seeds to germinate.
o It should be strong enough not to disintegrate when handled, and not to be
penetrated by the roots of developing seedlings.
o It should have a neutral pH of 6–7.
[59]
Controlling Fungi in Germination Tests
Fungal contamination is a common occurrence during germination testing. It

is usually associated with immature, damaged or old seeds. It can also arise
because of hygiene problems in the seed-testing area.
 Adopt the following laboratory practices to minimize the risk of fungal

contamination:
o Clean and disinfect (by surface sterilization with 70–95% alcohol or 20%
domestic bleach) the test area and incubators between batches to limit the spread
of fungal attack;
o Washing hands, benches and inside incubators with hot soapy water is a simple
but effective technique to reduce contamination.
 Space seeds properly to ensure that individual seeds do not touch each other.
Use greater numbers of replicates, if necessary;
 Provide an optimum environment for germination so that seeds germinate
quickly—the temperature regime should be suitable and the test environment
must be well aerated;
 Ensure cleanliness of germination test media and containers—make sure that
they are not sources of inoculums. Sterilize container surfaces by wiping
them with 70–95% alcohol or soaking them in 20% bleach or hot water at 55
°C for 10–15 minutes; and
 Avoid imbibition injury by humidifying seeds that could lead to leakage of
cell contents, which provide sources of nutrients to fungi.
 Promptly remove decaying seeds to prevent the spread of fungi to
neighboring seeds. If contamination is increasing, wash the seeds well in 1–
10% bleach and re-commence the test in a clean container on a new
substrate;
 Remove seed-covering structures such as glumes before tests when they are
found to be sources of infection;
 Remove seeds that have germinated before harvest and subsequently dried, as
they can be sources of infection;
 Seed dressing: add a pinch of fungicide to the container holding seeds
prepared for germination testing. Thoroughly shake the container so that
seeds receive a uniform coating of fungicide.; and
 Surface sterilization: soak seeds for ten minutes in a 1% solution of sodium
hypochlorite. The concentration of household bleach is usually 5% sodium
[60]
hypochlorite. Add 80 ml of distilled water to 20 ml of bleach to get a 1%
solution. Rinse the seeds thoroughly before testing for germination.
Reporting germination tests

The result of the germination test is calculated as the average of 4 x 100 seed
replicates. It is expressed as percentage by number of normal seedlings. The
percentage is calculated to the nearest whole number. The percentage of
abnormal seedlings, hard, fresh and dead seeds is calculated in the same way.
If the result is nil for any of these categories it shall be reported as '0'. The
reporting format for germination results is presented as follows.
Crop/Species: ------------------ Substrate: -------------
Variety: ------------------- Temperature: ---------
Lot number: ---------------- Light: --------
Date of storage: ---------------- Special treatments: ---------------
Date of testing: ----------------- Incubation time: -------------------
Replication Normal Seedlings Total Remarks
I II III IV
No of seeds tested
Date Days
Total germinated
Abnormal
Hard/Dormant
Dead
Germination (%)
Seed Health Management

Seed health refers to the health status of a seed. Sowing healthy seeds of high
quality is a concern of farmers and seed producers to improve crop
[61]
productivity. To avoid harmful organisms traveling from infected to non-
infected areas within a country or across international boundaries
The objectives of seed health tests include the following

 For quarantine;
 To evaluate planting value;
 For seed certification scheme;
 For advisability of seed treatment;
 To test seeds for storage quality or for feeding; and
 To test resistance of cultivars
 To inspect dry seeds
 To see physical abnormalities that include shriveling of the seed coat;,
reduction or increase in seed size, and discoloration or spots in the seed coat
Examination by seed washing (washing test)

This type of test is also called washing test. It involves testing surface-borne
fungi spores: Teliospores of smuts and bunts of wheat, and
Examination of seeds after incubation

Blotter method
 The seeds are plated on water soaked filter papers (three layers of well moistened
blotter papers ;
 Incubated usually for 7 days at 22 0C under 12 h alternating cycles of light and
darkness;
 Fungi developed on each seed are examined under different magnifications of a
stereomicroscope and identified; and
 The identification of the fungi is based on the way they grow on seeds, habit and
characters, and on the morphological characters of fruiting bodies, spores/conidia
observed under a compound microscope.
Agar plate method

 Generally surface-disinfected seeds are plated on an agar medium;
 Incubated for 5-7 days at 22-25 0C under 12 hr alternating cycles of light (Phillip
fluorescent tube 40W) and darkness;
 Fungi growing out from seeds on the medium are examined and identified; and
 Identification is based on colony characters and morphology of sporulating
structures
[62]
Seedling symptom test
Some of the seed-borne fungi are capable of attacking seeds, impair
germination by causing rotting of the sown seeds and in producing symptoms
on young seedlings or even killing the affected seedlings.
Managing seed-borne pathogens

 Physical: kill the pathogen not the seed
 Chemical: Protect the seed/seedling against pathogens
 Biological:
o Protect seed/seedling against pathogens
o Induce systemic resistance
o Improve plant growth
 Seed treatment…
o Hot water
o Chlorine
o Aerated steam
o Hot, dry air
o Fungicides
 Preemptive measures in the field

o Cultural (Rotation, sanitation and other agronomic practices)
o Host resistance
o Certified seed
o Integrated disease management
[63]
Seed Storage
The main objective of seed storage is to maintain seed quality from
harvesting to planting. While factors such as maternal environment, seed
maturity and harvesting, and seed processing have important role in achieving
maximum seed vigor maintaining it can only be successful through proper
storage. Seed storage conditions depend on the nature of the seed: orthodox or
recalcitrant. Wheat seeds can be dried well and stored for more than one year
under cool dry conditions.
The principle of seed storage is slowing down of seed deterioration through

application of appropriate techniques. Following are essentials in wheat seed
storage:
 Seed storage conditions should be dry and cool;

 Effective storage pest control;
 Proper sanitation in seed stores;
 Drying seeds to safe moisture content before placing in store; and
 Storing high quality seed, i.e., clean, treated and has high germination
Seed storage begins from physiological maturity and extends until seeds
germinate or they are rejected to be non-seed. Seed storage is segmented into
 post-maturation (seed in field from physiological maturity to harvest);

 bulk seed (seed in aeration drying bins, surge bin, under shade, etc);
 packaged seed (seed in bags or cans and placed in warehouses);
 distribution (seed in transit or retailers storehouse); and
 on-farm segments (period from purchase to planting).
Each segment of seed storage has its own contribution for seed deterioration
if seed handling is improper.
Seed longevity in storage depends on
 variety (starchy or proteinaceous);

 initial seed quality (germination and vigor);
 initial moisture content;
[64]
 relative humidity and temperature;
 seed maternal environment; and
 storage pests (insects and fungi).
As a general rule seeds with more starch content, have better longevity than
those with higher protein content. Seed lots having good germination and
vigor at the beginning store longer than those with lower quality. Initial
moisture content should be as low as possible (<13%) before wheat seeds are
taken to warehouses. For maintenance of germination and vigor wheat, seed
moisture content should not exceed 12% and relative humidity and
temperature should be maintained at 60% and 18oC. Temperature higher than
21oC in combination with higher relative humidity triggers insect and fungal
growth in the seed lot. Store sanitation is an important step and seeds should
be stored separately from fertilizers, chemicals and other inputs.
Seed packaging is an important step in proper seed storage though package

selection depends on quantity of seed desired in each package, level of
protection desired, cost of package, value of the seed, storage condition and
facilities for seed drying. In Ethiopia, wheat seed is n packed in jute or woven
polyethylene bags that allow moisture penetration from high relative humidity
in the warehouse. Seed packaging materials can be classified into three
categories in relation to moisture and vapor:
 Moisture and vapor pervious containers: These containers allow entry of water in
the form of vapor and liquid and suited only for short-term storage. The seeds in
these containers absorb moisture from the warehouse environment and achieve
moisture equilibrium. Eg. Jute bags;
 Moisture impervious but vapor pervious containers: Such containers prevent entry
of water in form of liquid but allow entry in the form of vapor. Seeds cannot be
stored for longer period in hot humid environments. Eg. Polyethylene bags of
<300 gauge thickness and fertilizer bags; and
 Moisture and vapor proof containers: Containers that do not allow entry of water
in both liquid and vapor forms are suitable for long-term storage even under hot
humid conditions. Such bags can be used to store nucleus or breeders’ stock seed
for more than one year. For example, Polyethylene bags of >700 gauge
thickness, and aluminum foil.
[65]
Seed Marketing
Marketing efficiency and problems
The concept of marketing efficiency and the problems associated with it are
quite broad. However, the concept could be defined as the process of ensuring
that the product, effectively promoted, will have the power to produce the
intended result. For example, an efficient internal information system that
allows consumer orders to be anticipated and filled promptly can help lower
the logistical costs. Marketing efficiency can be realized through two main
avenues, namely market communication and distribution.
Market communications
Market communications include the following aspects
 developing promotional materials;

 using public relations to create a favorable image of the seed supplying
organization;
 using effective techniques to sell seed to buyers; and
 properly selecting and using dealers.
There is need for the seed marketer to be in touch with the seed consumer.
High quality seed of a superior variety may be priced correctly and distributed
properly but may fail to sell well because communication with potential
buyers was ineffective. To be efficient, seed enterprises and seed marketing
groups must establish their credentials with buyers. Thereafter,
communication is essential to stimulate sales. The promotional and public
relations aspects of market communications allow for complete marketing
efficiency.
[66]
Distribution
The second major consideration in assessing seed marketing efficiency is the
distribution network. Distribution completes the process that converts the
physical and biological properties of seed produced to economic value for the
seller. Distribution needs to be considered in terms of marketing channels and
logistic functions. Seed passes from the producer to the user through a
marketing channel. Since producers can sell directly to final customers, they
must feel that they gain certain advantages by following the marketing
channels. When many outlets are necessary, producers often find it
advantageous to market seed through a chain of intermediaries rather than
directly. This is because intermediaries carry some of the financial load of
distribution and they expand the skills, experience, efficiency and consumer
contacts that are needed in marketing.
[67]
Product Option, Targeting Species and
Quantities
Farmers’ decision to choose certified or uncertified seed, especially, where
seeds are produced under either enforced (legal) or voluntary rules and
regulations for quality assurance, forms the basis of a product option. Such
opportunities must be studied in terms of the relevant industries’ market size
and market structure so that choices can be narrowed down. When targeting
species and quantities, we have to determine which segment of the total seed
market we are interested in and the quantity required. Marketing research,
demand measurement and forecasting must be done. Seed marketing research
at national and private enterprise levels is necessary for determining actual
demand for seed at a given time.
Economics of seed production

In Ethiopia, the majority of seed producers are using favorable seasons to
produce seed. Seed production by such methods provides good yields in good
years but often results in shortages in bad years. This is probably the main
reason for the extreme price variation that farmers face in different years.
Commodity prices are naturally affected by supply and demand. They may
also be government controlled, in which case such market forces have no
influence. Supply naturally depends on the area available for harvest, the
range of species, yield and storage times. As an opportunist crop, these aspects
may be compounded by less than ideal resources in terms of choice of fields
and expertise, especially when considering yields of 1.8-2 t/ha and not the 3 to
8 t/ha obtained from wheat crops. Demand is even more variable and depends
on farmers’ income, the price of the seed and that of other seeds, the price of
the final goods such as meat and milk and farmers’ household and
demographic characteristics. Domestic markets depend on dairy and beef
industry incentives, farmers’ adoption and seed replacement rates, extension,
promotion and availability in terms of quantity, location and price. All such
aspects are dependent on the national economic status. Export possibilities
depend on the availability of funding, exchange rates and the economic status
of client countries. Seed prices are usually based on the cost of production,
[68]
conditioning, marketing ;including distribution and profit. Ex-farm prices are
usually based on variable and not fixed costs that include depreciation on
machinery and buildings, repair and maintenance, salaries, loan, interests, and
taxes and development costs which would be incurred whether a seed crop
was grown or not. Variable costs cover the materials, labour and/or user cost
of any equipment needed: land preparation, fertilizer
[69]
Inputs for Seed Production
Land
It is a major input for seed production. The main considerations with respect
to this variable are availability (owned/rented), quality, and size.
Small-scale seed producers who own land obviously have more flexibility in
its use. Those who rent it may face an additional constraint of having to
produce seed while incurring costs through rent payment.
The quality of land available for seed production determines the scale of
inputs especially as good, viable seeds are produced on land that is more
productive. Farm size determines how much of the farmers’ crop will be
produced primarily for seed production. Since farmers’ emphasis is usually on
profit maximization, the opportunity cost of using land for forage seed
production as against an alternative usage is of critical importance.
Labor
Many small-scale seed producers enter into the production system with
very little capital. The commonest source of capital amongst these farmers is
usually another farmer The scale of production is usually small with a low
level of intensification. Smallholders find it difficult to sustain large-scale seed
production as they often lack the resources and other work force related to
larger-scale production of seed. The management potential of seed production
requires experience to allow a high level of success. However, success is
partly dependent on how seed producers go about trying to solve or tackle
problems or issues related to seed production.
[70]
Risks and Uncertainties in Defining
Seed Demand
Farmers entering the seed enterprise do it for economic reasons and therefore
expect economic returns. If the crop fails, a farmer may be less inclined to
start again in the next season. There is therefore an element of risk and
uncertainty in forage seed production. The risks begin right from the planning
stage where funds are needed for capital inputs such as building, machinery,
transport and equipment, working capital for running expenses and for the
purchase of seed and other raw materials. Several factors are known to
influence the overall demand for seed in a given year as well as over the long
term. Over-production occurs when actual demand is found to be lower than
estimated. This can result from several problems such as seed distribution,
movement of farmers to other crops that are known to be more profitable,
marketing problems and unrealistic estimates. Over-production may lead to
price collapse thus bringing about a lower farm income.
A seed organization management must be alert to changes in the trend of

demand. Attempting to define future demand is a problematic issue in any
seed enterprise. Demand can be estimated as minimum, medium or maximum.
Defining demand is more difficult for a new seed enterprise than one that has
been in operation for many years. Demand forecasting can be based on buyer
and seller comments or on surveys conducted in a well-organized system.
Demand has to be met by adequate seed production and it is essential that
advance pre-planting season notice of demand be given. Estimates of future
demand should be able to take into account factors such as basic seed reserves,
unreliable rainfall, storage, and seed characteristics.
[71]
Costs in Seed Production
Field costs include costs due to land preparation, ridging, greater crop care,
input costs, mechanization costs etc. The field cost structure in specialist seed
production is high and often needs extra funds. This is mainly due to the
increased work force needed to achieve higher standards of land preparation.
The overall cost structure depends on the level of mechanization. Normally, it

does not pay to use a machine on a very small area. The more work the
machine is given the lower the cost per hectare, because of the spreading of
the fixed costs. At some point, the cost must become less than using hand
labour. The area at which the costs are equal is the "break-even" point. If land
development is needed for the establishment of seed farms, this will also be a
field cost. For production on existing farms converted to seed production, the
opportunity cost of land should be included in the annual cost of production.
Activities that take place in the warehouse include drying, processing and
storage. These three processes are usually mechanized and costly; drying and
processing are capital intensive. Investment costs for buildings, equipment and
seed stores are high while the cost of labor is relatively minor. It may be
economically better for smallholder farmers to sell seeds direct from the field
or produce them under contract rather than to invest in this costly equipment.
Seed-price relationships
Several factors need consideration when setting the price for seed. These
factors include
 Marketing objectives;
o Survival,
o current profit maximization,
o market share leadership,
o product quality leadership
 Price sensitivity of product; and
 How costs vary at different output levels.
[72]
[73]
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Manual for Quality Seed Production in Wheat.

Book · January 2014

East African Agricultural Productivity Project View project

Mycotoxin prevalence and mitigation in farm-stored grains View project

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Genetically pure seed of a wheat variety possesses unique economic and

Table 1. The difference between seed and grain

Table 2. Factors responsible for deterioration of wheat varieties

Factors Phenomena Corrective actions

Climate and location

Extremely high temperature during anthesis causes desiccation of pollen

Land clearing and preparation

Planting the crop

Using herbicides requires some knowledge of the right product for a

Rouging and Field Inspection

Rouging follows a systematic procedure and should be carried out at the

In wheat, all off-types, including those that appear due to residual

The procedures in field inspections include

The procedures for counting include the following

Diseases and insect pest management

Scab or fusarium head blight

Fusarium head blight

Sooty head molds

The management of the disease includes using genetic resistance, foliar

Fusarium root, crown, and foot rots

Russian Aphids (Diuraphis noxia)

Aphids exist in different stages like winged (alates), and wingless

Aphids feeding on wheat Symptoms of BYDV on flag leaves in wheat

Adult Hessian Fly

Termites (Odontotermis obesus, Microtermis obesi)

Armyworm (Mythimna separate)

. Armyworm on wheat leaf

The important requirements for seed drying are:

Common drying methods used by informal growers include:

Drying in bags on a rack: Small amounts of seed in loose-weave jute

Conditions that cause the loss of seed viability in storage include:

For wheat, high seed moisture, i.e., above 11 to 12 % is the most

Evaluating seed quality

Most are adequate for national seed testing requirements, although

In most seed-testing laboratories, only three of them, namely analytical

Components of seed quality

 Genetic: Genetic purity (trueness to type) of a variety can be deteriorating due

 ability and resources available;

Seed purity standards for certified seeds

Objectionable weed species are harmful in one or more of the following

Objectives of maintenance breeding

Sources of seed contamination

 Genetic Contamination:-this is the residual segregation, spontaneous mutations or

Methods of seed maintenance

o Purification. It is used in situations where there is no organized procedure

Maintaining Nucleus Seed of Varieties

The following steps are critical in maintaining breeder’s seed

 The breeder’s seed of local varieties could be maintained by growing them in

Characters be used during inspection and their acceptance range of variation

Character Stages Varieties

Based on the above factors, different seed multiplication models may be