Introgression of phytophthora blight disease resistance from Cajanus platycarpus into short duration pigeonpea [Cajanus cajan (L.) Millsp.]

Phytophthora blight is an important disease of pigeonpea. Resistance to this disease is not present in the germplasm collection. Cajanus platycarpus (accession ICPW 61), a wild species of pigeonpea, has many desirable characters including resistance to P₃ (highly virulent) isolate of Phytophthora blight. Unfortunately C. platycarpus cannot be crossed with cultivated pigeonpea by conventional techniques. Hybrids were obtained by the use of embryo rescue techniques. F₁ hybrids were 100% pollen sterile, hence were treated with colchicine to double their chromosome number. The resultant plants had double the chromosome number and were tetraploids. F₁ plants were subjected to the pathogen. The results of this screening experiment showed that it was possible to transfer resistance to Phytophthora blight from the wild species C. platycarpus to cultivated pigeonpea. The results of F₂ data indicated that the nature of resistance to be monogenic and recessive.