Distribution and abundance of Rotylenchulus reniformis in cotton growing areas in north India.

A random survey was undertaken to determine the distribution and abundance of Rotylenchulus reniformis and concomitant nematodes in cotton (Gossypium spp.) growing area of north India. 184 soil samples were collected from cotton field of different location of Punjab, Haryana and Uttar Pradesh. It was found that reniform nematodes are wide spread occurrence in all three states. Absolute frequency of R. reniformis was 56.5 in Punjab, 30.0 in Haryana and 42.3% in Uttar Pradesh. The relative frequency of R. reniformis in the total nematode community in Punjab, Haryana and Utttar Pradesh was 10.2, 21.8 and 16.8%, respectively. In Punjab the mean population densities indicated heavier infestation (178/200cm3) in farmer's field compared to less infestation (48/200cm3) in the research farm. Application of negative binomial distribution indicated that distribution of R. reniformis was highly aggregated (k=0.07) but was relatively less aggregated in research farm (k=0.55). This indicates that there were pocket of high infestation in farmer's field in the rural area indicating monoculture or poorly planned cropping systems with predominance of host crops. The predominant plant parasitic nematodes associated with cotton in this region were Meloidogyne incognita, M. javanica, Pratylenchus zeae, P. thornei, Hoplolaimus indicus, Tylenchorhynchus spp. and Helicotylenchus spp.