Host plant resistance to insect pests in pigeonpea Potential and limitations

Host plant resistance to insects is one of the components of pest management in pigeonpea. Considerable progress has been made in developing techniques to screen for resistance to Helicoverpa armigera. However, some of these techniques cannot be used to evaluate material for resistance to spotted pod borer, Maruca virtrata, pod fly, Melanagromyza obtusa, pod wasp, Tanaostigmodes cajaninae and the pod bugs, Clavigralla spp. Genotypes with resistance to H. armigera, M. vitrata, M. obtusa, and C. chinensis have been identified, but the levels of resistance are low to moderate in the cultivated germplasm. However, high levels of resistance have been identified against H. amigera in wild relatives of pigeonpea. Considerable information has been generated on mechanisms of resistance to H. armigera and M. vitrata, but there is limited information on inheritance of resistance, and the molecular markers associated with resistance to insects. The progress in transferring insect resistance into the improved varieties has been limited, and there is a need to introgress resistance genes fromthe wild relatives intothe culigenand/or develop pigeonpea cultivars expressing Bt genes to confer resistance to pod borers. Cultivars with moderate levels of resistance in combination with other components of pest management will play a major role in increasingthe productivityof pigeonpea.