Reaping the Potential of Wild Cajanus Species through Pre-Breeding for Improving Resistance to Pod Borer, Helicoverpa armigera, in Cultivated Pigeonpea (Cajanus cajan (L.) Millsp.)

Abstract

Pod borer (Helicoverpa armigera) causes the highest yield losses in pigeonpea, followed by pod fly (Melanagromyza obtusa). High levels of resistance to pod borer are not available in the cultivated genepool. Several accessions of wild Cajanus species with strong resistance, and different resistance mechanisms (antixenosis and antibiosis) to pod borer have been identified. These accessions can be utilized to improve the pod borer resistance of cultivated pigeonpea. Using pod borer resistant Cajanus scarabaeoides and Cajanus acutifolius as pollen donors and popular pigeonpea varieties as recipients, pre-breeding populations were developed following simple- and complex-cross approaches. Preliminary evaluation of four backcross populations consisting of >2300 introgression lines (ILs) under un-sprayed field conditions resulted in identifying 156 ILs with low visual damage rating scores (5.0–6.0) and low pod borer damage (<50%). Precise re-screening of these ILs over different locations and years resulted in the identification of 21 ILs having improved resistance to pod borer. Because these ILs were derived from wild Cajanus species, they may contain different alleles for different resistance components to pod borer. Hence, these ILs are ready-to-use novel and diverse sources of pod borer resistance that can be utilized for improving the pod borer resistance of cultivated pigeonpea.