Abstract

Stem borers, Busseola fusca (Fuller) Noctuidae, Lepidoptera and Chilo partellus (Swinhoe) Pyralidae, Lepidoptera, are serious insect pests of maize. However, genotypes showing exclusive resistance to each of these borers and with resistance to both species have not been identified in Kenya. The objective of this study was to evaluate tropical maize inbred lines for resistance to the two species. 112 maize inbred lines were artificially infested with the stem borers at three sites in Kenya. Each row of each line received three different treatments in different parts, namely infestation with B. fusca larvae, infestation with C. partellus larvae, and protection with beta 25 g/L cyfluthrin pesticide. Data was collected on leaf feeding damage rating, cumulative stem tunnel length, number of exit holes, number of dead-hearts, stalk strength and selected agronomic traits. There were significant differences among the test genotypes, (p<0.01) for resistance to B. fusca and C. partellus, for all the traits measured. The results also showed that most of the test genotypes were susceptible to B. fusca and less so to C. partellus. Twenty one (21) lines showed resistance to both B. fusca and C. partellus in at least two sites, and only four lines showed resistance to both species across the locations. Among all the test genotypes, 26 lines showed resistance to C. partellus only, while five entries had resistance to B. fusca only. Furthermore, 84 and 28 entries showed susceptibility to B. fusca and C. partellus, respectively. The others were categorized as either moderately resistant or moderately susceptible to either species. The identified inbred lines variously resistant to B. fusca and C. partellus may be used as parents in hybrid breeding programmes that emphasize stem borer resistance or as sources of resistance in breeding programs.

Key words: Busseola fusca, Chilo partellus, combined resistance, tropical maize inbred lines.