STUDIES ON BIOLOGY, DISTRIBUTION AND MANAGEMENT OF Meloidogyne spp. ON OKRA

Abstract

The survey of 17 districts of the Punjab province of the country revealed that root-knot nematodes prevailed in 85.25% of okra fields with an average incidence of 38.89%. Hundred percent prevalence was recorded in Multan, Okara, Dera Ghazi Khan, Bahawalnagar, Vehari, Rahim Yar Khan and Rawalpindi districts and a minimum prevalence of 22.4% was found in Lodhran district. The incidence was above 60% in Bahawalnagar, Rahim Yar Khan, Dera Ghazi Khan and Vehari and was only 4.44% in Lodhran. The severity of infection of the nematodes was highest in Bahawalnagar and Vehari, while it was lowest in Lodhran. Of the four most common root-knot species, M. incognita contributed 74.74%, M. javanica 24.02%, M. arenaria 2% and M. hapla 0.78%. Of the twelve cultivars of okra screened for resistance against M. incognita, none was found tolerant, highly resistant or moderately resistant. Two cultivars viz. Selection-31 and Okra Sindha were susceptible and the cultivar Punjab Selection was found highly susceptible. The rest of the cultivars showed moderate susceptibility towards the nematode. All the cultivars caused reduction in various growth parameters to varying levels over their respective controls. When the effect of different inoculum levels of M. incognita was investigated on the highly susceptible okra cultivar ‘Punjab Selection’, all the densities of nematode behaved differently. The reduction in growth parameters and increases in number of galls and egg masses were found directly proportional to the inoculum level as against, the nematodes build up which was found to be inversely proportional. All the tested antagonists proved effective in controlling M. incognita and significantly increased the root and shoot lengths and weights and caused reductions in number of galls and egg masses. Pochonia chlamydosporia and Pasteuria penetrans were found equally effective at a concentration of 8 103 chlamydospores / endospores per gram of soil. Incorporation of leaves of Azadirachta indica, Calotropis procera, Tagetes erecta and Datura stramonium in the soil @ 25, 50 and 75 g / kg of soil controlled M. incognita to varying degree. A. indica and C. procera caused maximum reductions in number of galls, egg masses and reproduction factor (Rf) of the nematode resulting into an increases in various growth parameters.