Mechanisms of Resistance to the Dark-Headed Stem Borer. Chilo polychrysus (Meyrick) in Rice Varieties

Abstract

Nine reported resistant varieties, W1263, MTU15, Jayanti, IR36, IR44, IR50, Ir9828-23-1, IR13429-57-1 and IR19362-183, and one susceptible variety, RD7, were studied under greenhouse conditions at the Rice Research Institute, Bangkhen, and under field conditions at the Pathumthani Rice Research Center. Larveae of Chilo polychrysus (Meyrick) showed a distinct preference for feeding on the susceptible varigety and egg-masses were also more concentrated on this variety. In general there was a close correlation between the number of egg-masses the resittant varieties. Resistant varieties, in addition to having a higher number of healthy tillers, also had a greater ability to replace damaged tillers, relative to the susceptible variety. The study indicated that the mechanisms of resistance of rice varieties to the dark-headed stem borer were, non-preference for feeding and oviposition, antibiosis and, tolerance to heavy infestation.