Initial Population Density and its Effect on the Pathogenic Potential and Population Growth of the Root Knot Nematode Meloidogyne incognita in Four Species of Cucurbits

摘要

Root knot nematodes are responsible for tremendous amount of crop loss in Cucurbits. Hence, pot culture experiments were conducted under greenhouse conditions to study the effect of population density on the pathogenic potential of M. incognita in Lageneria ciceraria, Cucumis sativa, Momordica charantia and Cucurbita pepo. The 10,100 and 1000 second stage juveniles (L2) were inoculated into the rhizosphere of 15 day old seedlings and percent changes in the growth parameters of infected plants vis-avis control recorded manually, after 30 and 60 days along with the number of root galls and final nematode population extracted from roots and soil. Estimation of RGS and rate of reproduction was calculated by standard methods from the data obtained. Statistical significance of the means was analyzed by ANOVA using Ms Office Excel. All the four cucurbits were found to be highly or moderately susceptible to infection with M. incognita and population growth of the nematode was found to be a determining factor in the pathogenesis of the infection. A general response was a disturbance in the plant growth pattern due to limitation in water and nutrient translocation from infected roots to above-ground plant tissues. An inverse relationship was found to existbetween population density, population growth and severity of root galls. The on set of galls has been considered to be a protective measure of the plant for restriction of parasitic movement and maintenance of stable parasite population. The root knot nematodes have been considered to use both r and k strategies for their efficient survival and perpetuation of species depending on inter and intra-specific competition prevailing.