NEMATODES FROM WEST BENGAL (INDIA) XXIV. QUALITATIVE AND QUANTITATIVE STUDIES OF PLANT AND SOIL INHABITING NEMATODES ASSOCIATED WITH PADDY CROP IN COOCHBEHAR DISTRICT

Baqri el. al (1983) published the frrst paper on the qualitative and quantitative estimations of nematodes associated with paddy crop from Burdwan district of West Bengal This is the 24th paper of the series on Nematodes from West Bengal and 4th on qualitative and quantitave studies. During November 1984, forty root and soil samples were collected from 13 localities of the following three blocks of district Coochbehar : Toofangaunj, Pundibari and Dinhata. In all, 32 species have been identified It is evident from the quantitative estimation of important nematode genera that Hirschmanniella gracilis (de Man, 1880) Luc & 'Goodey, 1963 ; Meloidogyne graminicola Golden & Birchfield, 1965; Tylenchorhynchus spp.; helicotylenchus spp. are the important and abundant nematodes in the ,area surveyed.


INTRODUCTION
Baqri el.al (1983) published the frrst paper on the qualitative and quantitative estimations of nematodes associated with paddy crop from Burdwan district of West Bengal This is the 24th paper of the series on Nematodes from West Bengal and 4th on qualitative and quantitave studies.During November 1984, forty root and soil samples were collected from 13 localities of the following three blocks of district Coochbehar : Toofangaunj, Pundibari and Dinhata.In all, 32 species have been identified It is evident from the quantitative estimation of important nematode genera that Hirschmanniella gracilis (de Man, 1880) Luc & 'Goodey, 1963 ; Meloidogyne graminicola Golden & Birchfield, 1965; Tylenchorhynchus spp.; helicotylenchus spp.are the important and abundant nematodes in the ,area surveyed.

MATERIAL AND METHODS
The sampling was made at random The processing of samples and the quantitative estimation was made as described by Baqri e t .ale (1983).The nematode population per 200 ml soil was counted from each sample The nematode population of paddy roots /10 gm was also estimated.

A. QUALITATIVE STUDY:
In all, 15 species belonhing to the Orders Tylenchida and Aphelenchida (Stylet bearing n~matodes) have been identified.Apart from this, 17 soil inhabiting or predaceous species of the order Dorylaimida have also been identified.The identified species are listed below: Order TYLENCIDDA THORNE, 1949 The results of the quantitative estimation of important parasitic genem and other nematodes from the surveyed localities ofCoochbehar district have been furnished in Table I & II.Table I ( Pages 66-68 ) provides the infonnations about the surveyed localities , number of samples collected, range with average and percent of frequency of occurrence of important nematode genera separately and other nematodes Table II ( Page 69 ) gives the analysis of range with average, and percent of frequency of occurrence and dominance of potential nematodes in soil and paddy roots at Coochbehar district.
It is evident from table I that the species of the genera Hirschmanniella, Helicotylenchus, Tylenchorhynchus and Meloidogyne are widely distributed in the area surveyed.Amongst these species, Hirschmanniella gracilis appears to be a key pest of paddy in Coochbehar because of its high degree of dominance in 70% soil samples.Table II also concludes that Hirschmanniella gracilis occurs in 95%.and48% in soil and rooty samples, respectively.The second important namatodes are the H eUcotylenc hus spp.and M eloido gyne graminicola because these have been respectively recorded in 75% and 95% soil samples.Though the frequency of occurrence of M eloido gyne is higher but their dominance has been observed only in 5% soil samples.It may further be noted thatH e licotylenc hus spp.dominated in 20% soil samples.The number of Helicotylenchus and Meloidogyne species recovered from roots was also significant and their occurrence was noted in 20% and 12% root samples respectively The other important nematodes are Tylenchorhynchus spp.Their occurrence in soil and roots was noted in 52% and 30% samples respectively, while they were dominant only in 5% soil samples The presence of other parasitic nematodes was not significant.

SUMMARY
The present paper reports 32 species of the orders Tylenchida , Aphelenchida and Dorylaimida from Coochbehar district (W .Bengal).The results of the quantitative estimation of different parasitic genera reveal that Hirschmanniella gracilis (de Man, 1880) Luc & Goodey, 1963, Tylenchorhynchus spp., Meloidogyne graminicolaGolden & Birch field, 1965 and Helicotyle~chus spp., are the important nematode pests associated with paddy crop in the area surveyed.

ACKNOWLEDGEMffiNTS
The authors are thankful to the Director of Zoological Survey of India, Calcutta, for providing research facilities.We also thank to Indian council of Agricultural Research for providing funds under All India Coordinated Research Projects on Nematode Pests and their Control.

TABLE - I
Baqri,Q.H.,Jana,A.,Ahmad,N.& Das,P.K. (1983).Nematodes from West Bengal (India) VIII.Qualitative and q~antitative studies of plant and soil inhabiting nematodes associated with paddy crop in Burdwan Di~trict.Rec.zool.Surv.India., 80 : 331-340.0\ 0\ Results of the survey of Paddy crop in Coochbehar district, West Bengal.Range of nematodes number with its average per 200 ml of soil.Figures in parenthesis indicate percent frequency of occurrence. ~-

TABLE II
Results of the survey of paddy crop inCoochbehar district, West Bengal.Range of nematodes number (potential parasites) with average per 200 ml soil and 10 gm roots.Figures in parenthesis indicate percent frequency of occurrence with dominance in soil/occurrence in roots.