Inheritance of Resistance to Blight in Pigeonpeas. D. Sharma, Senior Pigeonpea Breeder, Pulse Improvement Program, International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh 502 324, India. J. Kannaiyan, Plant Pathologist, and L. J. Reddy, Pigeonpea Breeder, Pulse Improvement Program, International Crops Research Institute for the Semi-Arid Tropics, Patancheru, Andhra Pradesh 502 324, India. Plant Dis. 66:22-25. Accepted for publication 12 February 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-22.

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.

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