Ch-1 Nematology Introduction
Ch-1 Nematology Introduction
Ch-1 Nematology Introduction
For ease of study and host specify the nematodes may be studied under the heading of:
1. Free living nematodes
This is a group of nematodes focused less, as not considered economically important.
They may be marine (Chaetostoma, Chromadora, Deontostoma. etc.) or fresh water
nematodes (Plectus, Dorylaimus, Mononchus, Rhabditis etc.). There are some free living
soil inhibiting nematode genera.
Some important genera of free living nematodes:
Caenorhabditis elegans and C. briggsae: free living, soil inhibiting, bacterial feeding.
Caenorhabditis elegans: used as model organism (proposed by Sydney Brenner in 1965)
to study development, neurobiology, and aging, due to its small life cycle (3 days), small
size (1.5 mm adult), small genome (97 million base pairs spread among six
chromosomes), and anatomical simplicity (>1000 cells), including the 302-cell
hermaphrodite nervous system. In addition it is the only organism to have
its connectome (neuronal "wiring diagram") completed.
Brenner, Sulstin and Horvitz received Nobel prize in Physiology or Medicine in 2002, for
their work on cell linage pattern and role of genes in regulating and apoptosis in
Caenorhabditis elegans.
Caenorhabditis Genetic Center: at National Institute of Aging, University of Missouri,
USA. This institute is responsible for maintenance, genetic map, genetic nomenclature,
storage, and distribution of mutants.
Panagrellus redivivus: biological indicator of pollution in both terrestrial and aquatic
ecosystems.
2. Parasites of vertebrates
a) Parasites of humans
i) Ascaris lumbricoides: intestinal roundworm, infecting approx. 25% of world
population. It causes anemia, and heavy infection may lead to intestinal
blockage.
ii) Enterobius vermicularis: parasite of caecum (1cm long). Cause severe itching
in anal area, due to egg lying by the female in perianal area.
iii) Wucheraria bancrofti: filarial worm, parasite of lymphatic system, causing
inflammation of limbs and genital organs the disease is known as elephantiasis.
In India more prevalent in coastal areas of South India, West Bengal, Bihar,
and Odisha. The nematode is transmitted by mosquitoes.
b) Parasites of vertebrates other than human
i) Trichuris spp.: Whipworm (30-50 cm long). Parasite in colon, rectum, and
appendix of dogs and pigs, etc.
ii) Dioctophyma renale: Giant kidney worm (up to 90 cm long), parasite of dog.
iii) Haemonchus contortus: blood sucking nematode of sheep, goat, and cattle
stomach, may cause anaemia.
iv) Ascaridia galli: most common ascarid worm parasite in small intestine of
chicken.
3. Parasites of invertebrates
i) Mermis nigrescens: parasites of grasshopper
ii) Romanomermis culicivorax: parasites of mosquitoes (Aedes, Anopheles,
Culex, etc.). Used as biological control of mosquitoes.
iii) Steinernema and Heterorhabditis: used as biological control of a large incest
group. These nematodes carry and release bacteria (Xenorhabdus and
Photorhabdus spp.) inside insect haemocoel which leads to septicemia and
kills the insect host, in return it provide nutrition to insect cadaver.
4. Parasites of plants
The phyto-parasite nematodes are mainly root parasites while few are parasite to
aerial plant parts. The most common genera of plant parasitic nematodes
are Aphelenchoides (foliar nematodes), Ditylenchus, Globodera (potato cyst
nematodes), Heterodera (cyst nematodes), Meloidogyne (root-knot nematodes),
Pratylenchus (lesion nematodes), and Xiphinema (dagger nematodes).
Several phytoparasitic nematode species also act as a vector of viruses. Few
examples are: Xiphinema index, vector of grapevine fan leaf virus, Xiphinema
diversicaudatum, vector of arabis mosaic virus.
The soils in a hectare of all agro ecosystems typically contain billions of plant parasitic as
well as beneficial nematodes. The damage to plants caused by nematodes is often overlooked
because the associated symptoms, including slow growth, stunting and yellowing, can also be
attributed to nutritional and water related disorders.
1743 – Needham – Discovery of wheat seed gall nematode Anguina tritici, the first plant
parasitic nematode to come to the attention of the early investigators.
1855 - Berkeley – observed root-knot nematode (Meloidogyne spp.) from root galls of cucumber
plants in greenhouse in England.
1857 - Kuhn – Reported the stem and bulb nematode, Ditylenchus dipsaci infesting the heads of
teasel.
1859 - Schacht – described the reason behind sugarbeet decline in Europe as cyst nematode.
1871 – Schmidt – named Sugarbeet cyst nematode was as Heterodera schachtii.
1873 - Butschli – Descriptions of the morphology of free –living nematodes.
1879 – Cornu – first specific mention of root knot nematode as a causal agent of root knot of
Onobrychis sativa, caused by Anguillula marioni (Meloidogyne sp.).
1884 - deMan – Taxonomic monograph of soil and fresh water nematodes of the Netherlands.
1889 – Atkinson and Neal – Publication about the root-knot nematodes in the United States.
1891 – Ritzema-bos – discovered the foliar nematode Aphelenchoides fragariae on strawberry.
1892 – Liebscher – reported pea cyst nematode Heterodera goettingiana on pea.
1892- Atkinson-Report of root-knot nematode and Fusarium complex in vascular wilt of cotton.
1907- N.A.Cobb – joined the USDA and considered to be the Father of American
Nematology
1913 – N.A.Cobb – published a book ’Contributions to the Science of Nematology”.
1914 – N.A.Cobb – coined the term “nematology”. Contributions to the Science of Nematology.
1918 – N.A. Cobb – Development of methods and apparatus used in Nematology.
1933 – T. Goodey – Book on “Plant parasitic nematodes and the diseases they cause”
1934 – Filipjev – Book on “Nematodes that are importance for Agriculture” translated from
Russian to English in 1941 by S.Stekhovan uner the title “A Manual of Agricultural
Helminthology”.
1943 – Carter-Description of nematicidal value of D-D which is used in the era of soil
fumigation.
1945 – Christie – Description of the nematicidal value of EDB.
1948 – Allen – Taught the World’s first formal university course in Nematology at the
University of California, Berkeley.
1950 – Oostenbrink – Wrote a Book of on “The Potato Nematode, A dangerous parasite to
Potato Monoculture”.
1951 – Christie and Perry – Role of ectoparasites nematodes as plant pathogens. T.Goodey –
Wrote a book on “Soil and fresh water nematodes”. Food and Agriculture Organisation of
the United Nations organized the first International Nematology course and
Symposiumheld at Rothamstead Experiment Station, England.
1953 – discovery of Borrowing nematode (Radopholus similis) causal organism behind
spreading decline of citrus in Florida (USA).
1955 – discovery of root lesion nematode “Pratylenchus penetrans” causing peach replant
problem in Canada. Frist ever attempt to study etiology of a nematode alone was made by
Mountain and Patrick on the same nematode, they also proved ‘Koch’s postulate’ in order to
prove pathogenicity of this nematode for the first time. In the same year, European Society of
Nematologists founded.
1956 – Nematologica – The first journal published entirely for Nematology papers from The
Netherlands.
1958 – Hewitt, Raski and goheen – first report of virus transmission by nematodes (Xiphinema
index transmitting fan leaf grapevine virus, in grapevine), in USA.
1961 – Society of Nematologists founded in the United States.
1967 – Organization of Tropical American Nematologists founded.
1969 – Journal of Nematology was first published by the Society of Nematologists, USA.
1973 – Nematologa Mediterranea – published from Italy.
1978 – Revue de Nematologie published from France
1930s – 1990s – Barron, Duddington, Mankau, Linford, Sayre and Zuckerman – they provided
an insite on the Biological control of plant – parasitic nematodes. Enhanced
understanding of antagonists and related biology enhancing the potential for practical
biocontrol.
1940-s – 1990s – Triantaphyllou – Provided advancement in Cytogenetics, modes of
reproduction/sexually – and information data base for genetics/molecular research.
Enhanced understanding of evolution and taxa interrelationships.
1950s – 1990s – Caveness, Jones, Oostenbrink, Sasser and Seinhorst – International programme
such as International Meloidogyne project – They expanded educational base of
nematologists world wide and provided ecological – taxonomic data base.
1960s- 1990s – Nickle, Poinar and Steiner – Biological control of insects with nematodes.
1960s- 1990s – Brenner, Dougherty and Nicholas – Caenorhabditis elegans developmental
biology and genetics – model system – provided fundamental information on cell lineage,
behavior, gene function ageing and overall genome for this model biological system.
In addition to the above, now the research advancement are in progress in the following areas in
USA from the year 1990. Molecular markers for resistance gene provide efficiency of breeding
for resistance. Cloning of resistance genes - Elucidation of the molecular fundamental
knowledge based on mechanisms of pathogenesis. Cloning of resistance genes- Elucidation of
the molecular. mechanism of resistance. Transgenic host resistance to plant parasitic nematodes
– Great potential, but limitied model system to date.