Inheritance of Resistance to Blight in Pigeonpeas

Abstract

Sources of resistance to isolate P2 of the fungus Phytophthora drechsleri f. sp. cajani have been identified in pigeonpea (Cajanus cajan). Observations on F1 and F2 progenies and on backcrosses of resistant and susceptible parents studied by use of the pot culture technique indicated that resistance is governed by a single dominant gene, which is designated Pd1. The F1 and F2 progenies of resistant parents were all resistant, showing that the gene for resistance is the same in all the parents. Field screening of F3 progenies of another set of susceptible × resistant crosses showed a good fit for a 1:2 ratio of true breeding to segregating for resistance in five of the nine crosses. In all nine crosses, most of the individual segregating progenies in F3 showed a good fit to a 3:1 ratio of resistant to susceptible, confirming monogenic dominant inheritance of resistance. All seven resistant parents were of diverse origin, and their F1 progeny showed a high degree of specificity of reaction to isolate P2.