| Summary: | <i>Cajanus</i><i> </i><i>scarabaeoides</i> (L.) Thouars is the closest wild relative of cultivated pigeonpea, <i>Cajanus</i><i> </i><i>cajan</i><i> </i>(L.)<i> </i>Millspaugh<i>. </i>However, unlike cultivated pigeonpea which is very susceptible to insects, especially <i>Helicoverpa</i><i> </i><i>armigera</i><i> </i>(Hubner), this wild pigeonpea is strongly insect resistant. Since <i>H. </i><i>armigera</i> causes damage to many important crops resulting in economic losses up to 2 billion USD/year, improvement in resistance to this insect in crops is highly desirable. Here we investigate insect resistance components in <i>C. </i><i>scarabaeoides</i><i> </i>and explore the possibility of transferring one or more of those factors to cultivated pigeonpea. A detached leaf assay was used to assess antibiosis and antixenosis resistance mechanisms in <i>C. </i><i>scarabaeoides</i>. Artificial diet supplemented with lyophilised leaf powder was employed to investigate the antibiosis resistance mechanism. Data on larval mortality and larval and pupal weights were collected. Time taken for neonate larvae to pupate and for pupae to develop to the moth stage were determined through daily observations. Preliminary results showed that <i>H. </i><i>armigera</i> larval weight was significantly reduced and larval development stages were prolonged when reared on different accessions of <i>C. </i><i>scarabaeoides</i> as compared to the susceptible check, <i>C. </i><i>cajan</i> (ICPL 87). Interspecific hybridization was carried out between <i>C. </i><i>scarabaeoides</i> and a commercial pigeonpea variety<i>. </i>Results from insect challenge assays and trichome identification indicate that the hybrids have similar levels of insect resistance to their wild parent. Proteomic analysis is being used to identify possible antibiosis factors.
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