Nature of resistance in selected rice varieties and population fluctuation of green leafhoppers,Nephotettix virescens (Distant) andNephotettix nigropictus (Stål)

Abstract

In multiple 'Choice tests with 30-day-old plants of resistant and, susceptible varieties. both the species of green leafhoppers, N ephotettix »irescens (Distant) and N ephotettlx niqropictus (Stal) exhibited relative non-preference to highly resistant varieties (Ptb 2, Ptb 7 and Ptb 18) both for settling and oviposition. Even when 100 first instar nymphs were caged on individual 25-day-old plants of highly resistant varieties, the plants suffered very low damage and also induced high mortality of nymphs. Different ages of the plants had no influence on the antibiosis mechanism of resistant varieties. Feeding behaviour studies revealed that both the species made more punctures and excreted less honeydew while feeding on resistant varieties than on susceptible ones. Histological studies indicated no mechanical barrier for feeding in resistant varieties.. Field investigations indicated that resistant varieties viz Ptb 18, Ptb 2 and Ptb 7 harboured less population of green leafhoppers and had relatively nil or very low incidence of tungro virus disease. An year round survey in the rice ecosystem and marshy habitat where Leersia hexandra grows in abundance revealed that although both the species coexisted in rice fields, Nephotettix niqropictus alone was present in the marshy habitat.