Veg. Sci. 36(2) : 100-102 (2009)
Short communication
COMMUNITY ANALYSIS OF PLANT PARASITIC NEMATODES ASSOCIATED WITH VEGETABLE CROPS IN VARANASI SATYANDRA SINGH, AB RAI AND MATHURA RAI Indian Institute of Vegetable Research, P.B. # 5002, P.O. BHU, Varanasi-221005, U.P. Plant parasitic nematodes are hidden enemies of agricultural crops and infect almost all the crop plants. They can directly cause plant diseases or may act as predisposing agent to several other micro-organisms. Nematodes successfully colonize a vast variety of habitats than any other group of multicellular animals. So they are an extremely important limiting factor in vegetable production. In India, their damage potential is very high and the national loss due to plant parasitic nematodes in 24 different crops in monetary terms has been worked out to the tune of 21068.73 million rupees which needs due attention (Jain et al., 2007). According to Dasgupta (1998) many factors such as soil type, soil moisture, temperature, host crop, nematode species, farming practices etc., influence distribution, dynamics and shift of population densities of nematodes. First time a survey was conducted with the objective to assess the nematode community structure associated with tropical vegetable crops grown at Indian Institute of Vegetable Research (IIVR) experimental research farm. The present investigation was carried out at IIVR research farm area during Jan.-Feb., 2009. Random soil samples were drawn from root zone with the help of a shovel at the depth range of 10-15 cm. Each sample was mixed thoroughly to make soil uniform in all aspects and was placed in an individual plastic bag. A sub sample of 250 ml soil was processed using Cobb’s (1918) sieving and decanting method followed by Baerman’s funnel technique (Southy, 1986) for the extraction of soil nematodes. Aliquot of each processed sample was collected after 48 hours and nematodes were counted by taking 1 ml of this nematode suspension with the help of counting dish under microscope. An average of three counting was considered and multiplied with total volume of the nematode suspension. A total of 22 samples were collected and processed for extraction of plant parasitic nematodes and were expressed as the number of
individuals per 250 ml of soil. Mean abundance, population range, population percentage, absolute frequency, relative frequency, absolute density, relative density and prominence value of each nematode species were calculated by applying the method adopted by Norton (1978). It is clear from the data (Table 1) that different nematode species were associated with different crops and showed polyphagous nature. Six plant parasitic nematodes were isolated and identified from the rhizosphere soil and root samples taken from IIVR research farm. The isolated and identified nematode species were Meloidogyne incognita, Rotylenchulus reniformis, Dorylaimus sp., Tylenchorynchus vulgaris, Hoplolaimus indicus and Helicotylenchus sp. Among the above listed nematodes, the endoparasitic rootknot nematode, M. incognita and semi-endoparasitic reniform nematode, R. reniformis both were most abundant and frequently encountered nematode species and isolated and identified in 20 samples out of 22 samples. Root-knot nematode, M. incognita was found to be infested almost all crops (polyphagous in nature) listed in Table-1 and the highest numbers of juveniles (1080) were isolated from the rhizosphere of brinjal crop. The least numbers of M. incognita was recorded from bean even below economic injury level. Like wise reniform nematode, R. reniformis also impacted polyphagous nature and contrary to M. incognita its presence in the rhizosphere of bean plants was noteworthy in one sample whereas it did not appear in another sample of same crop. Ectoparasitic stunt nematode, T. vulgaris prefer tomato as suitable host having highest number of nematodes but did not prefer chilly, cauliflower and broccoli as host. Ectoparasitic lance nematode H. indicus also not found infesting chilly and recorded highest in pea, only behind the root-knot nematode. The sheath nematode, Helicotylenchus sp. was found to be comparatively low density and even not detected from the rhizosphere of chilly and broccoli.
COMMUNITY ANALYSIS OF PLANT PARASITIC NEMATODES ASSOCIATED WITH VEGETABLE CROPS
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Table 1. Occurrence of plant parasitic nematodes at IIVR research farm Crop Tomato Tomato Pea Brinjal Chilly Pea Pea Pea Brinjal Tomato Tomato Brinjal Cauliflower Bean Cauliflower Broccoli Brinjal Pea Pea Pea Broccoli Bean
M. incognita 616 576 528 840 294 684 480 884 1080 378 544 504 200 76 528 108 640 828 288 300 -
R. reniformis. 168 96 280 504 380 120 260 280 126 224 210 520 608 792 504 160 276 432 60 80 -
Nematodes population per 250 ml soil Dorylaimus sp. T. vulgaris H. indicus Helicotylenchus sp. 308 196 336 416 532 160 64 748 968 360 120 288 294 114 190 76 76 360 140 200 160 104 312 160 440 360 168 504 462 126 504 128 462 294 84 280 80 200 168 190 76 308 108 432 280 320 400 200 322 216 108 216 60 150 210 90 160 360 524 126 168 -
Saprophytes 1848 2304 2552 1880 1554 1976 2720 2184 3200 1848 1856 1680 2480 2508 3080 2880 8320 8320 3240 2100 2480 3276
Table 2. Plant parasitic nematode community analysis at IIVR research farm Population percentage 10.73
Absolute frequency 90.91
Relative frequency 19.42
Absolute density 188.65
Relative density 16.14
Prominence value 1798.75
276
60-792
6.29
90.91
19.42
110.55
9.46
1054.01
212 177
60-524 108-504
4.83 4.03
77.27 72.73
16.50 15.53
84.87 70.80
7.26 6.06
746.01 603.78
248
76-462
5.65
81.82
17.48
99.35
8.50
898.61
88
76-360
11.65
35.27
3.02
260.51
Sharma et al. (2002) also reported that M. incognita is the most studied nematode species in India and they ranked it first among plant parasitic nematodes recorded from India in terms of damaging agricultural
2000
1200 1000 800 600 400 200 0 1
2
3 4 Nematode species
5
Helicotylenchus sp
1400
T.vulgaris
1600
H.indicus
1800 Dorylaimus sp
On the basis of mean abundance, frequency percentage, population percentage and density percentage the important nematode species was M. incognita which is most harmful nematode pest of vegetables contained a high mean population (472), population percentage (10.73%), absolute (90.91) and relative (19.42) frequency, absolute (188.65) and relative (16.14) density (Table-2) and also on the basis of highest prominence value (1798.75), it ranked first followed by R. reniformis, H. indicus, Dorylaimus sp., T. vulgaris and Helicotylenchus sp. (Fig.1.).
54.55
R.reniformis
2.01
M.incognita
Meloidogyne incognita Rotylenchulus reniformis Dorylaimus sp. Tylenchorynchus vulgaris Hoplolaimus indicus Helicotylenchus sp.
Mean Population abundance range 472 76-1080
Prominence value
Nematode sp.
6
Fig.1. Prominence value of plant parasitic nematodes associated with vegetable crops
crops. Maximum relative density (5.66%) was also recorded for Meloidogyne spp. (Rathore et al., 2005)
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SINGH ET AL.
followed by Tylenchorhynchus sp. (5.0%), Pratylenchus sp. (4.22%), Helicotylenchus sp. (4.01%) and R. reniformis (3.9%). Contrary to present findings maximum prominence value (65.2) was recorded in case of Helicotylenchus sp. followed by R. reniformis sp. (32.1), Tylenchorhynchus sp. (12.0), Pratylenchus (2.9) and least prominence value (1.3) was recorded in case of Meloidogyne spp. (Patel et al., 2008) and also on the basis of prominence value, Prasad Rao et al., (2007) reported that R. reniformis, H. dihystera and M. incognita were the prominent ones in descending order. It is concluded from the study that M. incognita is predominant species of nematode, infesting all the vegetable crops grown at IIVR research farm. This might be due to fact that M. incognita is polyphagous in nature and availability of susceptible suitable host through out the year. Future studies may be able to elucidate the reasons for the nematode species specific effects among host crops and find the explanations for the high species richness of nematodes in vegetable crops.
Reference Cobb NA (1918). Estimating the nema population of the soil. Agricultural Technology Circular-1. Bureau of plant Industry, U.S., Department of Agriculture, pp. 48.
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