Genetic Diversity and Population Structure of Pigeon
Pea
Bal Krishna Joshi1*, Hari Prasad Bimb1, Devendra Gauchan1, Jwala Bajracharya1, Pitamber Shrestha2 and
Madhusudan Prasad Upadhyay1
1
Nepal Agricultural Research Council, PO Box 1135 Kathmandu, Nepal
Local Initiatives for Biodiversity, Research and Development (LI‐BIRD), Mahendrapul, PO Box 324,
Pokhara
2
Corresponding author: Biotechnology Unit, NARC, Khumaltar, PO Box 1135 Kathmandu
Email: joshibalak@rediffmail.com Tel: 5539658 Fax: 5545485
Running Title: Genetic Structure of Pigeon Pea
ABSTRACT
Knowledge on population genetic structure is essential for effective managements of plant genetic
resources on farm. Eight varieties of pigeon pea (Cajanus cajan L.) including landraces, released
varieties and promising lines of Nepal were compared for the amplitude of polymorphism at the loci of
four enzyme systems: alcohol dehydrogenase (ADH), isocitrate dehydrogenase (IDH), malate
dehydrogenase (MDH) and peroxidase (POX). Polymorphism was observed among the populations and
a total of 25 alleles and 9 loci occurring with different frequencies were recorded for 4 enzymes.
Different combination of banding patterns of these enzymes led intra‐ and inter‐variation with an
understanding of genetic structure of populations under study. Cluster analysis of isozyme data with 4
enzymes grouped pigeon pea varieties into two distinct groups. Landraces (Chanki and Pajawa
populations) were genetically different from improved varieties (Bageshwori and Rampur Rahar 1).
ICPL‐84072 and Chanki possessed highest number of alleles per locus (2.6). ADH‐1 was highly diverse
(Ht=91) with highest mean gene diversity within populations (Hs=0.82). IDH‐1 showed high coefficient
of gene differentiation with highest gene diversity among the populations (Gst=0.54; Dst=0.29). On an
average, genetic variation within populations (0.47) was higher than among populations variation
(0.17). Landraces and promising lines were most diverse with high values of diversity parameters and
they clustered together. Chanki, a commonly grown landrace exhibited high gene diversity and they
were genetically identifiable from homogenous improved varieties.
Key words: Cajanus cajan, genetic diversity, gene differentiation, polymorphism, isoenzymes
Genetic Diversity and Population Structure of Pigeon Pea
INTRODUCTION
Leguminous crop is important as a source of protein and it is also cropped to increase soil fertility. Pigeon
pea (Cajanus cajan L.) is a multipurpose legume crop grown as a sole or intercrop in Nepalese farming
systems with diverse use values as dhal (dehusked seeds as soup), feed (leaves for livestock), firewood,
huts and baskets making by dry stem. The crop is well adapted even in marginal lands.
High diversity in morphological traits of pigeon pea grown in Kachorwa has been reported by Bajracharya et
al (1999), Sherchand et al (1999), Rana et al (2000). Diversity in pigeon pea varied with respect to wealth
category and production environments (Joshi et al 2007). Chanki and Pajawa are common landraces and
Chanki is grown widely in large area by many households. Begeshwori and Rampur Rahar‐1, the two
improved varieties were released by Nepal Agricultural Research Council for Central and Western Nepal
(NARC 2000). In addition to many landraces, 5 wild species are found in Nepal (Neupane 1999). Diversity is
being maintained by farmers to meet their diverse needs in diverse environments. Maesen (1990) has
grouped all cultivars under primary gene pool. The tertiary gene pool of pigeon pea consisting of wild
species is not crossable with primary gene pool. Mallikarjuna and Moss (1995) have studied barriers
between wild and cultivated species. Isozyme band was used to confirm the hybrid nature of the plants.
Diversity measures based on farmers' local variety names and morphology is often used in on‐farm
conservation to relate actual genetic diversity available on farmers' fields. However, morphological diversity
measures often underestimate or overestimate the actual amount of genetic diversity, as they are based on
observable morphological and phenological characteristics rather than actual population genetic structure
of the crop varieties. Thus previous studies on farmers' variety choice and decision are poorly linked with
genetic diversity information. An understanding of genetic diversity of landraces and varieties grown by
farmers is essential to link the farmers' needs and improvement works and developing incentives and
strategies for in situ conservation programmes. Information on which populations are genetically diverse or
contains rare alleles and which households or communities are maintaining such genetically diverse crop
populations, could be linked and it will help in identifying the crop populations or landraces with high
diversity and group of households to target for on‐farm conservation.
Population structures along with genetic relationship and diversity are useful for developing strategy of
conservation and utilization of crop genetic resources. Diversity study at biochemical level is one of the
reliable techniques. Isozyme has been used in many crops for study of genetic diversity and population
structure eg barley (Bajracharya et al 2003a), flax (Mansby et al 2000), grass pea (Chowdhury and Slinkand
2000), chickpea (Kazan et al 1993), broad bean (Torres et al 1995). Isozyme was also used to verify farmers’
naming that was used describing landraces (Bajracharya et al 2003b). Isozymes are inherited non‐
dominantly at individual loci therefore it is possible to assign a genotype as an individual from its
electrophoretic profile (Brown 1979, Wendel and Weeden 1989). This approach is relatively simple that
allows data to be collected quickly from large sample sizes, low cost compared to other molecular
techniques and recognized and made available early in the history of genetic marker development.
Pigeon pea is often self‐pollinated and biannual crop. Because of its different breeding system we can
relate population structure and breeding system with maintenance of diversity on‐farm. Farmers grow
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Genetic Diversity and Population Structure of Pigeon Pea
pigeon pea in small area. Population genetic structure in such a small population if there is diversity could
help in policy formulation for on‐farm management of agricultural biodiversity. Pigeon pea is one of the
mandated crops of the project strengthening the scientific basis of in situ conservation of agro biodiversity
on farm‐Nepal. But it was studied least (Joshi et al 2005). Present study has thus used isozymes to assess
genetic diversity, population structure and genetic relationship among eight pigeon pea populations with
specific objectives: to measure the extent and distribution of genetic diversity, to relate genetic diversity
and farmer division making, to measure intra/inter varietal diversity, to study genetic diversity between
landraces and modern varieties and consistency between farmer names and genetic distinction.
MATERIALS AND METHODS
Plant materials
Eight populations of pigeon pea comprising 2 landraces from Bara (Central Tarai), 2 released varieties for
Central and Western Tarai regions of Nepal and 4 promising lines introduced from India were included in
the study. Each variety/line was considered as a population and 10 samples for each population were
collected from 10 farmers for landraces, 10 production fields for improved varieties and 10 different
research trials for promising lines (Table 1). Samples of improved varieties were obtained from Regional
Agriculture Research Station (RARS), Nepalgunj.
Isozyme analysis
Equal proportions of plumules of 3‐5 seedlings of each sample raised over moistened filter paper in
controlled condition of 30oC for 7 days in dark were used for enzyme extraction in L‐Ascorbic acid buffer
(0.1 mol/L Ascorbic acid, glycerol, and pH 7.4) following the methods of GEVES (GEVES, 1993). The
extracted leaf samples were electrophoresed in tris buffer (0.400 mol/L Tris, pH 8.0 with 105 mol/L citric
acid) using 12% starch gel (potato starch S‐4501, Sigma company, USA) for overnight at 4oC and at constant
4 watt power supply. After electrophoresis, the gels were sliced horizontally and stained for enzymes:
alcohol dehydrogenase (ADH, EC 1.1.1.1), isocitrate dehydrogenase (IDH, EC 1.1.1.42), malate
dehydrogenase (MDH, EC 1.1.1.37) and peroxidase (POX, EC 1.11.1.7) dipping the slices in respective
enzyme trays and enzymes for staining were prepared following the manual developed by Biotechnology
Unit, 2000 (BU 2058). Isozyme banding pattern were scored based on zone of activity and number of bands
developed for respective enzyme. Genetic interpretation of banding pattern could not be done but each
enzyme activity presumed as locus and numbers of bands were recorded for each zone of activity/locus
(Plate 1) and individual band seen for the active zone was scored as presence (1) and absence (0) for
further numerical analysis of the genetic similarity and distance (Wendel and Weeden, 1989). Most anodal
active zone for each enzyme system is coded as locus 1 and based on the migration of band in gel, the most
anodal band of each locus is coded alphabetically as “a”, “b” so on. A locus with two or more alleles is
considered as polymorphic (Chang and Kang 1996, Nei 1975).
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Genetic Diversity and Population Structure of Pigeon Pea
Table 1. Pigeon pea populations used in the study
Population
Source
Sample
size
Code
Description
Bageshwori
RARS, Nepalgunj
10
Ba
Improved. Plants with spreading growth habit,
SMD resistance, thin pods with small grains and
scented on cooking
Chanki
Kachorwa, Bara
10
Ch
Landrace. Tall plants with spread branching
habit, yellow flower, thin pods with small and
light brown grains
ICP‐7035
RARS, Nepalganj
10
IC7
Promising variety
ICPL‐84072
RARS, Nepalganj
10
IC8
Promising variety
Pajawa
Kachorwa, Bara
10
Pa
Landrace. Short statured plants with erect
branching habit, Yellow flower, thick and
spotted pods with bold and brown grains
Pusa 14
RARS, Nepalganj
10
P14
Promising variety
Pusa 9
RARS, Nepalganj
10
P9
Promising variety
Rampur
RARS, Nepalganj
10
RR
Improved. Tall plant with high branching, bold
and white grains
Rahar‐1
RARS, Regional agriculture research station. SMD, Sterility mosaic disease.
Plate 1. ADH isozyme pattern in pigeon pea
Data analysis
A total of 16 bands were used as isozyme characters. Based on combination of the bands and their banding
pattern zymogram were developed. Genetic variability in each population was assessed for alleles per
locus/zone (A), alleles per polymorphic locus/zone (Ap), percentage of polymorphic loci/zones (P) and
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Genetic Diversity and Population Structure of Pigeon Pea
mean gene diversity, variation within (Hs) and among (Dst) populations and coefficient of gene
differentiation (Gst) according to the unbiased method of Nei (1973) using Genestat software (Lewis, 1992).
Further, genetic variations among the populations were measured in all possible pair‐wise comparisons
using Nei’s genetic distance (1973) and cluster analysis (UPGMA). The resulting dendrogram depicted
variation and affinities among the populations. The analytical findings were expedited following the
computer program, NTSYS (Rohlf 1998).
RESULTS
A total of 8 populations comprising of 10 samples of each were assayed for 4 enzymes and 9 zones of
activity as loci were resolved with a total of 16 bands (alleles). One to four loci were resolved for enzymes
over the populations with the maximum 4 loci for POX and all loci were polymorphic. However, two
improved varieties, Bageshwori and Rampur Rahar‐1 were found without a zone of activity for ADH and
MDH but all loci were found in two landraces. Two populations, ICP‐7035 and ICPL‐84072 have alleles with
more homogenously distributed than other populations. Frequency of alleles ranged from 0.06 to 1 (Table
2). All loci except Idh‐1 were polymorphic in two landraces, Chanki and Pajawa. Pusa‐9 has least number of
polymorphic loci. Promising lines, ICPL‐84072 and ICP‐7035 have all polymorphic loci. Except Idh‐1 in Chnaki
and Adh‐2 and Mdh‐2 in Pajawa all other loci were polymorphic. Some of samples across the populations
were observed with no activity and this is assumed as null allele effect. Therefore a total of 25 alleles
including the null alleles of respective enzymes were used in analysis for genetic similarity and distances
among populations.
Isozyme variation
One to four zones of enzyme activity were detected. Zymograms based on allelic combination of these
polymorphic loci were sketched and are shown in Figure 1. Minimum 3 (IDH) to 29 zymograms and
maximum 7 different bands (POX) were observed. None of the bands were observed common over the
populations of pigeon pea under study.
In ADH, two zones of enzyme activity were detected and 7 zymograms and 4 different alleles were
observed in 8 populations of pigeon pea (Figure 1). Zymogram A was common in Bageshwori and Pusa 9.
Pajawa was most diverse for this enzyme with maximum of 6 zymograms (Table 3). IDH detected a single
zone of activity with two alleles and 3 zymograms were observed (Figure 1). Zymogram A was again
common in Bageshwori and Pusa 9, whereas B was in Chanki and ICPL‐84072. Others occurred in low
frequencies (Table 3).
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Genetic Diversity and Population Structure of Pigeon Pea
Table 2. Frequency of allele for 4 isozymes in 8 pigeon pea populations
Locus Allele Populations
Bageshwori Chanki ICPL‐84072 ICP‐7035 Pajawa Pusa‐9 Pusa‐14
Adh‐1
Adh‐2
Idh‐1
Mdh‐1
Mdh‐2
Pox‐1
Pox‐2
Pox‐3
Rampur/Rahar‐1
a
0.00
0.23
0.23
0.23
0.29
0.00
0.00
0.00
b
0.00
0.31
0.38
0.23
0.36
0.00
0.00
0.00
n
0.00
0.46
0.38
0.54
0.36
0.00
0.00
0.00
a
0.00
0.64
0.43
0.54
0.60
0.00
0.00
0.00
b
0.90
0.29
0.29
0.23
0.33
1.00
0.90
1.00
n
0.10
0.07
0.29
0.23
0.07
0.00
0.10
0.00
a
0.20
1.00
0.83
0.67
1.00
0.20
0.00
0.10
b
0.70
0.00
0.17
0.33
0.00
0.70
1.00
0.80
n
0.10
0.00
0.00
0.00
0.00
0.10
0.00
0.10
a
0.00
0.00
0.30
0.80
0.50
0.00
0.00
0.00
n
0.00
0.00
0.70
0.20
0.50
0.00
0.00
0.00
a
1.00
0.23
0.47
0.56
0.53
0.63
0.50
1.00
b
0.00
0.23
0.47
0.44
0.41
0.38
0.50
0.00
n
0.00
0.54
0.07
0.00
0.06
0.00
0.00
0.00
a
0.20
0.20
0.10
0.30
0.10
0.00
0.30
0.50
b
0.60
0.40
0.20
0.10
0.40
0.90
0.40
0.00
n
0.20
0.40
0.70
0.60
0.50
0.10
0.30
0.50
a
0.00
0.00
0.10
0.10
0.00
0.00
0.00
0.60
b
0.60
0.70
0.50
0.30
0.50
1.00
1.00
0.20
n
0.40
0.30
0.40
0.60
0.50
0.00
0.00
0.20
a
0.30
0.70
0.40
0.80
0.90
1.00
0.90
0.00
n
0.70
0.30
0.60
0.20
0.10
0.00
0.10
0.00
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Pox‐4
a
0.30
0.00
0.10
0.20
0.00
1.00
0.90
0.60
b
0.30
0.70
0.40
0.60
0.70
0.00
0.00
0.00
n
0.40
0.30
0.50
0.20
0.30
0.00
0.10
0.40
Table 3. Frequency of zymograms in 8 pigeon pea populations
Population
Bageshwori
Isozymes
ADH
IDH
MDH
POX
A (0.8)
A (0.7)
A (1)
A (0.2)
NA (0.2)
B (0.2)
B (0.2)
NA (0.1)
C (0.1)
D (0.1)
E (0.1)
F (0.1)
G (0.2)
Chanki
B (0.5)
B (1)
C (0.1)
B (0.3)
B (0.2)
NA (0.7)
O (0.1)
D (0.3)
P (0.3)
NA (0.1)
Q (0.1
R (0.1)
S (0.1)
T (0.1)
ICPL‐84072
B (0.1)
B (0.8)
A (0.2)
B (0.1)
C (0.1)
C (0.2)
B (0.3)
E (0.1)
D (0.3)
C (0.2)
O (0.1)
G (0.1)
D (0.1)
P (0.1)
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Genetic Diversity and Population Structure of Pigeon Pea
NA (0.4)
E (0.1)
V (0.1)
NA (0.1)
W (0.1)
Y (0.1)
Z (0.1)
NA (0.2)
ICP‐7035
B (0.4)
B (0.5)
A (0.1)
P (0.4)
D (0.3)
C (0.5)
B (0.1)
S (0.1)
C (0.7)
V (0.1)
F (0.1)
AB (0.1)
NA (0.4)
AC (0.1)
AD (0.1)
NA (0.1)
Pajawa
B (0.3)
A (0.2)
B (0.2)
C (0.1)
B (0.2)
O (0.1)
D (0.3)
C (0.5)
R (0.1)
E (0.1)
NA (0.1)
U (0.1)
B (1)
F (0.1)
V (0.3)
NA (0.1)
W (0.1)
X (0.1)
Pusa 14
A (0.9)
A (1)
B (1)
NA (0.1)
K (0.4)
L (0.3)
M (0.1)
N (0.2)
Pusa 9
A (1)
A (0.7)
A (0.4)
K (0.9)
B (0.2)
B (0.6)
L (0.1)
NA (0.1)
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Rampur/Rahar‐1
A (1)
A (0.8)
A (1)
F (0.1)
B (0.1)
G (0.1)
NA (0.1)
H (0.4)
I (0.2)
J (0.2)
NA, Null allele
Figure 1. Zymograms of 4 isozymes in eight pigeon pea populations.
MDH resolved two zones of activity and 6 zymograms with 3 different alleles were resolved (Figure 1). The
most common zymograms were A (100%) in Bageswori and C (70%) in ICP‐7035. ICPL‐84072 was most
diverse for this enzyme with 6 zymograms (Table 3). Zymograms A and B were common in Bageshwori and
Rampur Rahar ‐1 and C in ICP‐7035 with 70% frequency. POX observed 4 zones of activity and was observed
with highest variables of zymograms. Twenty‐nine zymograms and 7 different alleles were detected.
Zymogram K was common in Pusa 9 with 70% frequency. This enzyme exhibited high variation within and
among populations each with 2 to 8 zymograms.
Genetic diversity and structure
The number of alleles per locus ranged from 1.2 (Pusa 9) to 2.7 (ICPL‐84072) with mean 1.9 across the
populations (Table 4). The percentage of polymorphic loci (P) ranged from 33% (Pusa‐9) to 100% (ICPL‐
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Genetic Diversity and Population Structure of Pigeon Pea
84072 and ICP‐7035) and averaged 71%. The average diversity index (H) among populations ranged from
0.345 (Pusa‐9) to 0.542 (Rampur Rahar‐1) with an average 0.473. Four populations with the greatest
diversity were Bageshwori, Chanki, ICPL‐84072, ICP‐7035 and Rampur Rahar‐1. The highest genetic diversity
was observed in ICPL‐84072 as indicated by the higher values for A (2.667), P (100%) and H (0.518).
The gene diversity at the locus level summarized in Table 5 reveals the consequence of diverse genetic
structures within among pigeon pea populations under study. The average total genetic diversity (Ht) over
eight populations was 0.65 and Mdh1 showed the highest (0.93). Adh‐1, Mdh‐1 and Pox‐4 showed marked
total diversity with values higher than the mean value. The mean intra and inter populations diversities
over eight populations were 0.47 (Hs) and 0.17 (Dst) with range of 0.25‐ 0.82 and 0.09 – 0.29 respectively.
Likewise the mean coefficient of gene differentiation (Gst) was 0.27. It is obvious that the diversity in
pigeon pea is resulted due to the within population variation rather than the variation among the
populations. 27% of the total genetic diversity (Ht=0.65) was accounted by the inter‐population variation
and 73% was due to within‐population variation. It indicated that each population of pigeon pea under
study was composed of divergent individuals with different genetic structures.
Table 4. Descriptive statistics of alleles and loci in eight pigeon pea populations based on 9 loci studied in
10 samples per population
Population
Alleles per
locus (A)
Alleles per polymorphic
locus (Ap)
Proportion of
polymorphic loci (P)
Mean gene
diversity (H)
Bageshwari
1.778
2.500
0.667
0.529
Chanki
2.111
2.571
0.778
0.516
ICPL‐84072
2.667
2.667
1.000
0.518
ICP‐7035
2.556
2.556
1.000
0.491
Pajawa
2.333
2.500
0.889
0.435
Pusa‐9
1.222
2.333
0.333
0.345
Pusa‐14
1.444
2.200
0.556
0.411
Rampur Rahar‐1 1.333
2.500
0.444
0.542
Mean
1.931
2.478
0.708
0.473
SE
0.200
0.052
0.089
0.025
Number of alleles unique to these populations was zero.
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Table 5. Gene diversity in 4 isozymes of eight pigeon pea populations
Locus
Total gene Within
Percentage mean
Among
Coefficient of gene
diversity
population gene gene diversity within populations gene differentiation (Gst)
(Ht)
diversity (Hs)
population (Hs/Ht, %) diversity (Dst)
Adh‐1
0.912
0.820
89.85
0.093
0.102
Adh‐2
0.532
0.330
62.06
0.202
0.380
Idh‐1
0.535
0.248
46.40
0.287
0.536
Mdh‐1
0.929
0.78
83.93
0.149
0.161
Mdh‐2
0.524
0.395
75.53
0.128
0.245
Pox‐1
0.644
0.515
79.96
0.129
0.200
Pox‐2
0.540
0.385
71.30
0.155
0.287
Pox‐3
0.547
0.375
68.57
0.172
0.314
Pox‐4
0.660
0.413
62.47
0.248
0.375
Mean
0.647
0.473
71.32
0.174
0.268
SE
0.054
0.066
*
*
*
Clustering and relatedness
Cluster analysis results depicted as dendrogram in Figure 2 illustrates the genetic relationships and
divergence among the pigeon pea populations of different origin. Clustering of eight populations using
UPGMA and Nei’s genetic distance resulted two distinct groups. Two promising lines Pusa 9 and Pusa 14
were identical and clustered together with improved varieties Bageshwori and Rampur Rahar‐1. On the
other hand two landraces (Chanki and Pajawa) and two promising lines (ICPL‐84072 and ICP‐7035) aligned
together into a cluster. The cluster reflected the sharing and frequencies of alleles and magnitude of
genetic relatedness among these diverse populations of pigeon pea. Two landraces were genetically
different from each other, although they were clustered into the same group.
Isozyme profiles
Profiles of isozymes for each variety are useful for varietal identification. Bands along with their mobility for
a loci of eight populations are given in Figure 3. We can clearly distinguish these populations. Bands were
traveled faster in Chanki, and Pajawa and ICPL‐84072 have higher number of bands. Each cultivar has their
own distinct isozyme profile. Many researchers have developed isozyme profiles of crop species (Romero et
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Genetic Diversity and Population Structure of Pigeon Pea
al., 1993; Joshi and Bimb, 2004; GEVES, 1993). Distinct esterase pattern in pigeon pea was reported
(Mallikarjuna and Moss, 1995). This profile can be used to identify variety, however further research on
stability of this profile is necessary.
Bageshwari
RampurRahar-1
Pusa-9
Pusa-14
Chanki
ICPL-84072
ICP-7035
Pajawa
0.02
0.19
0.36
0.52
0.69
Coefficient
Figure 2. Dendrogram of eight pigeon pea populations based on Nei’s genetic distance.
DISCUSSION
Knowledge about genetic structure and relationships among the populations provides information on
population divergence, which is important from conservation and exploitation of genetic resource for crop
improvement. The values measured for diversity parameters based on allelic information exhibited the
differences in pigeon pea populations and helped to quantify the extent of genetic variation in each of the
population for studied enzymes. This preliminary study was successful to establish allozyme variability in
pigeon pea of Nepal for the first time. Genetic diversity in pigeon pea demonstrated to be due to the high
within population variation and therefore each population was composed of different individuals, which is
a desirable variability for selection and improvement in a breeding programme. Relatively null allele was
higher. This may be due to sick samples or there was non‐genetic variation. In some populations a zone of
activity was not resolved which resulted in the zero frequency of allele. These cases are probably why Ht is
so high for Adh‐1 and Mdh‐1. It needs analysis of F2 progeny of crosses to verify locus and banding patterns.
In Nepal farmers have many landraces indicating high diversity. One hundred local germplasms of pigeon
pea have been collected and characterized in Nepal. Begeshwori, a variety developed from the local
selection is highly resistant to sterility mosaic disease (Neupane, 1999). Agromorphological variation within
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Genetic Diversity and Population Structure of Pigeon Pea
Chanki and Pajawa was reported by Bajracharya et al (1999). Sherchand et al (1998) reported 12 different
farmer named landraces in Bara and Rana et al (2000) reported 5 landraces in Kachorwa. Farmers were
consistent in naming pigeon pea in Kachorwa (Bajracharya et al 1999). Two farmers named landraces
Chanki and Pajawa are genetically different. Farmer’s descriptors for pigeon pea are plant type, seed color,
size, raceme type and taste. In Kachorwa 27.2% households grow pigeon pea and Chanki was the dominant.
Pigeon pea growers have one landrace per household (Rana et al 2000). Pigeon pea was one of the crops
grown under least external inputs and its pulses fetches highest price in market among the pulses.
However, only limited households from resource poor grow the crop (Rana et al 2000). In Kachorwa it is
prestigious crop and grown either in Khet land or in marginal bari land as a sole or mix. Because of its
importance at household levels, crop improvement works should be initiated utilizing existence diversity.
Figure 3. Isozyme profiles of eight pigeon pea populations for 4 isozymes
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Genetic Diversity and Population Structure of Pigeon Pea
Two promising lines of pigeon pea introduced from India were the most closely related. The major branch
of the genetic distance dendrogram separated landraces from improved varieties. Similarly Pusa series
were separated from ICP series. These series are promising lines being evaluated in Nepalgunj. Bageshwori
is Nepal origin and Rampur Rahar‐1 is Indian even though these varieties were grouped in the same cluster.
Two landraces were found diverse as much as that of the most diverse population of promising lines of
pigeon pea. Chanki and Pajawa exhibited higher diversity than Bageshwori and Rampur Rahar‐1. It indicates
that landraces are genetically more diverse than improved varieties. No private alleles were detected in any
of the populations. Genetic statistics were computed based on bulked samples, which is not correct to say
individual genotype. Here all farmers’ plots under each variety were considered as a population and each
farmer’s plot were treated as a sample. Therefore bulked samples were used to make more representative
of concerned plot. For in depth isozymes analysis, large sample size with individual sample treating a single
field, as a population should be further studied.
Pigeon pea being a often self‐pollinated and biannual crop, the individual plants from which seeds were
collected may be heterozygous. Details study including progeny analysis is necessary to verify the banding
patterns and to know the nature of enzyme (either monomeric or dimeric) in pigeon pea.
ACKNOWLEDGMENTS
This study was financially supported by DGIS, IDRC. We thank J Shresth, B Dongol, GB Bajracharya for their
lab works and F Chaudhary, DL Karna, SS Biswokarma and BN Chaudhary for their helps in samples
collection from Kachorwa. Farmers of Kachorwa, and VK Datta, RB KC and DN Paudel, RARS Nepalgunj are
highly acknowledged for providing seeds of pigeon pea.
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