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Historical Aspects
The knowledge of nematodes
can be traced to pre-Christ era. Mention of certain epithets in Indian
scriptures (4000-6000 B.C) and Egyptian records (1553 B.C) indicate a
possible awareness of at least animal nematodes. Lacking the Microscopes
in the early periods, larger animals, visible to naked eye, were
naturally first recorded and investigated. These large forms were
parasites of animals and human beings. The Guinea worm, Dracumculus
medinemsis, causing serve pain and swelling in arms and legs of humans,
and the round worm, Asaris lumbricoides, appear in the early Egyptian
writings. Aristotle (384-322 B.C) in his articles has also made frequent
references to animal parasitic nematodes. Comparatively, information on
plant parasitic nematodes are of recent origin.
mention a few.
long considered due to soil disorders or deficiency and now established
as nematode problems, lend support to the suggestion that nematodes may
have been one of the important contributors to the 'soil exhaustion'
during the Roman period.
Shakespeare's mention of 'sowed cockle reap'd no corn' in his drama
Love's Labour's Lost in 1594 could be the first mention of a plant
parasitic nematode. However, during the post-Christ era, the first
published record is that of a free living nematode, Turbatrix aceti
in 1656. Almost 94 years later, Needham, a clergyman
discovered the first plant parasitic nematode when in 1/432,
he recorded the worms present inside galls or 'cockles' of wheat. He
described these worms in the following words: 'Upon opening the small
black grains of smutty wheat, which they here distinguish from the
blighted corn, the latter affording nothing but black dust, into which
the whole substance of ear is converted, I perceived a soft fibrous
substance, a small portion of which 1 placed on my object plate. It
seemed to consist wholly of longitudinal fibres bundled together; and
you will be surprised, perhaps that I should say, without any least sign
of life or motion. 1 dropped a globule of water on it in order to try,
if the parts when separated might be viewed more conveniently when to my
great surprise these imaginary fibres as it were, separated from each
other, took life, moved regularly not with a progressive but twisted
motion and continued to do so for a space of 9 to 10 hours, when I threw
them away. I am satisfied that they are the species of aquatic animals
and may be denominated worms, eels, or serpents, which they very much
resemble.
Vibrio
tritici was the name given for the
ear-cockle nematode in 1799. Later, it was reported from some
grasses under the name of V. agrostis. Another species, V.
graminis, was added to the literature when it was found to be
present on Fescue grass. Davaine in 1S57 gave a detailed
description of its life cycle. The root-knot nematodes were the next
plant parasitic nematodes discovered in 1855 on greenhouse cucumbers.
The disease was described as producing galls on roots and containing
eggs and 'vibrios'. This was closely followed by the record of
Anguilluia
dipsaci (Ditylenchus
dipsaci) infesting teasel,
Dipsacus fullonum, in 1857. Not long after these reports, the
sugarbeet cyst nematode was discovered in 1S59. More than ten
years elapsed before the nematode was studied and named as Heterodera
schachtii. The sugarbee industry was very important, at this time,
and for this reason, the discovery of this nematode problem attracted
lot of attention. It was found that this nematode was responsible for
the prevailing 'beet sickness' problem. A number of scientists got
interested in the problem and put forth a number of publications amongst
which there was a classic contribution on the life cycle of the nematode10.
The other important plant parasitic nematodes discovered during the 19th
century were: Heterodera goettingiana on pea roots;
Ditylenchus radicicola on Poa annua and other grasses; and the
foliar nematode, Aphelenchoides fragariae, on strawberry plants.
The 19th
century was marked also with the first attempt at controlling the
nematodes with the use of chemicals and one of the first was the use of
carbon disulfide against sugarbeet cyst nematode.
Besides the
discovery of important plant parasitic nematodes in this century, the
period was marked also with important taxonomies! contributions,
notably by Dujardin in 1845 on Dorylaimus and Rhabditis;
monographs by Bastian in 1865 and Butschli in 1873; the classical
monograph by deMan17 in 1884 entitled "Die emheimschen, frei
in der rainen Erde und im sussen-Wasser lebenden Nematoden der
Niederlandischen Fauna' which, to this day, has stood the test of
changing concepts and still ranks as one of the finest contributions to
the science of nematology. Another important name needing mention is
that of Oerley who in 1880 contributed a monograph on Anguillulidae,
with illustrations and information on 202 species belonging to 27 genera
of free living and plant parasitic nematodes.
Besides
Heterodera, Ditylenchus and Aphelenchoides, the other plant
parasitic nematodes described during the 19fh century were; Kalenchus,
Longidorus, Paratylenchus, Radophoius. Roiylenckw, Trichodorus and
Xiphinema,
in this period
can be best described in two phases: (1) the pre-World War II period ;
and (2) the post-World War II period. The first period is dominated by
the personality of Nathan Augustus Cobb, who after a chequered career
joined the United States Department of Agriculture in Washington and
from the year 1915 till his death in 1932 devoted his full energies to
the study of the science of nematology. The coining of the word 'nematology'
is credited to him and his compilation 'Contributions to a Science of
Nematology is a tribute to his knowledge and mastery of the subject. He
was instrumental in evolving many of the techniques like wet scree-ing
to separate nematodes from soil, methods of preserving and mounting
nematodes, section cutting, etc., which are still in vogue today. He is
considered as the Father of modern nematology and was the man behind the
establishment of the Division of Nematology at the United States
Department of Agriculture.
Almost
simultaneously with the contributions of Cobb in the U.S.A., Micoletzky
in Austria started compiling and bringing together published works on
soil and fresh water nematodes which he published as 'Die freilebenden
Erd-Nematoden in 1922. In this compilation, he presented keys for
identification of the species. At the same time, Tom Goodey in England
and I.N. Filipjev in Russia made tremendous impacts on the development
of nematology in their respective countries. Tom Goodey, besides being
the Head of the Department of Nematology at the Rothamsted Experiment
Station, U.K., published two books: (1) Plant parasitic nematodes and
the diseases they cause, 1933 ; and (2) Soil and fresh water nematodes,
1951, which proved invaluable aids in the study of the subject. The
former book dealt with the disease aspect while the latter contribution
was mainly of taxonomic nature. He published also a number of scientific
papers based ort his research work.
Filipjev
was equally active in his country and besides contributing to the
taxonomic concepts, wrote a book in Russian which was later translated
into English by his colleague J.H. Schuurmans-Stekhoven under the title
of 'A manual of Agricultural Helminthology with the publication date as
1941.
Several new
plant parasitic nematodes were discovered and added to the growing list
of nematode species. Thorne, as Head of the Division of Nematology at
the United States Department of Agriculture in U.S.A., initiated the
concept of maintaining catalogued collections and specimens for ready
use of all those interested in the science. By the time he retired in
1956, he had built up a valuable collection of more than 36,000
specimens.
Post-World War II Period: The
period up to pre-World War U was marked with descriptions of new;
species, identification of new nematode problems and the nematode
species associated with them, development of new techniques and
taxonomic concepts and writing of books and monographs. No attempt could
be made to achieve field control of nematode problems since there was no
inexpensive chemical that could be used profitably in any control
programmed. In this respect, the post-World War U period is outstanding
for the almost simultaneous discovery of dichloropropene +
dichloropropane (D-D) mixture by Carter in 1943 and ethylene dibromide (EDB)
by Christile in 1945. These two soil fumigants were not only very
effective against the nematodes but also were comparatively inexpensive
to apply. These nematicides replaced all the earlier chemicals like
chloropicrin and carbon disulfide which were expensive as well as highly
toxic and could be used profitably under greenhouse conditions only.
Besides nematicidal in value, DD and EDB had low toxicity to fungi and
bacteria and therefore, these proved to be highly useful in
demonstrating the effects of nematodes on plants.
Despite the
revolutionary era started by the discovery of these chemicals, proof of
nematode pathogenicity and fulfilling all the Koch's postulates was not
achieved so far. Even as early as 1914, Byars had developed techniques
to study life cycle of nematode (root-knot) under sterile tomato
culture. However, this aspect was
not studied
seriously till 1955 when Mountain used tissue culture technique to
obtain sterile cultures of nematodes. He succeeded in culturing
Pratylenchus minyus on excised maize roots, growing in sterile
nutrient agar. The technique was useful in demonstrating development and
production of root damage by P. minyus on seedlings growing
under sterile conditions. At a later date (1959), Mountain and Patrick26
were able to obtain sterile P. penetrans population by treating
the nematodes with bactericide and fungicide solutions. These nematodes
were then inoculated to sterile peach seedlings, growing in tubes, under
sterile conditions. Production of lesions on the roots was recorded
within 90 minutes of inoculations and isolations from these lesioned
areas failed to show any bacterial or fungal infections and yielded only
nematode populations. It was, therefore, demonstrated that P.
penetrans could invade and kill peach root tissues in the absence of
bacteria or fungi.
About this time, another landmark was set
up by Christie and Perry when in 1951, they demonstrated conclusively
that Trichodorus, an ectoparasite, was a serious problem of crops
in Florida, U.S.A. This opened up the path for detailed studies on other
ectoparasitic nematodes which had been neglected hitherto for want of
informations and techniques to study them.
These
researches opened up great possibilities and avenues in the study of
nematodes and a number of new findings and discoveries helped in the
rapid strides in advancing our knowledge of the subject as well as in
initiating worldwide interest and activities. The discovery of golden
nematode infestation in potato in Nassau County, Long Islands, U.S.A.
and the destruction of 20 million pepper trees in Indonesia, primarily
by Radopholus similis, activated various agencies of the state
and federal governments. The need for trained personnel stimulated
organization of workshops and training programmers resulting into much
publicity about plant parasitic nematodes as important factors in
limiting agricultural production. Thus, new job opportunities were
provided to the agricultural scientists.
sIn
the late fifties, an outstanding discovery was made about
the role of
nematodes in transmitting virus diseases. It was demonstrated that the
fanleaf virus of grapevine is transmitted by the nematode, Xiphinema
index. This added new dimensions to the investigations on the
nematode-micro-organism complexes. Several virologists, battling with
the soil borne viruses, found the breakthrough in the problem with more
and more evidences of nematodes acting as vectors for such viruses.
The history
of scientific advancement in nematology would be incomplete without the
mention of the name of Myuge who in I956 demonstrated that
there are more proteolyctic substances in the galled root-knot tissues
than in the healthy tissues. He demonstrated also that alcohol extracts
of the galled tissues can induce galling in healthy tissues. Earlier,
Linford3" in 1937 had shown that the root-knot larvae
inject salivary juices in the host tissues while feeding but this was
not seriously taken up till Miyuge's work provided the required
stimulation to the nematologists.
Historically, starting of formal lectures and practical classes at the
University of California, U.S.A. in 1948 assured the future of
nematology in relation to other Rallied disciplines. Subsequently,
several other universities in the U.S.A. included study of nematology in
their curriculum.
By 1955,
nematologists or workers interested in the subject had grown in numbers,
large enough for an organization of a scientific society in Europe. It
was first named as the Society of European Nematologists but with more
and more people, from other parts of the world exhibiting an interest in
joining the Society, the name was changed to European Society of
Nematologists. The activities of the Society started with the issue of
newsletters and subsequently a full fledged scientific journal under the
name of Nematologica was started in 1956- It is published quarterly from
Leiden, The Netherlands. The Society of Nematologists (SON) in the
U.S.A. was the next one to be organized in 1961. It also started with a
newsletter and later a journal under the name of Journal of Nematology
was put forward by the Society in 1969. The Nematological Society of
India was founded in 1969 followed by publication of its journal from
1971 under the name of Indian Journal of Nematology. The
organization of
Tropical American Nematologists (OTAN) came into being in 1971 and a
society was also formed in Japan in 1972. The latest in (he series is
the formation of Afro-Asian Society of Nematologists (AASN) in 1984.
These developments indicate the rapid strides the science has made
within the last 25 years or so.
Amongst the
Middle East, African and Asian countries, India has emerged as one of
the most important research centre for the nematological investigations.
Therefore, a brief mention is being made here about the developments of
nematological research in the country.
More
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Historical Aspects
● Nematology in India
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