Mechanisms of stem borer resistance in sorghum.

A number of sorghum genotypes resistant to the spotted stem borer (Chilo partellus Swinhoe) have been identified using natural and artificial infestations at ICRISAT. Resistance is attributed to ovipositional nonpreference and antibiosis mechanisms. The major plant characters identified include early panicle initiation and rapid internode elongation. In resistant genotypes, these factors were reflected in the success of first instar larval establishment in the leaf whorl, interval between hatching and larvae boring in the stem, larval mass, and survival rate. Success of the first instar larvae to establish in the whorl is also influenced by physical and chemical plant characteristics. A chemical factor in the surface wax of some sorghum genotypes is associated with larval disorientation.