Inheritance of bacterial blight resistance in rice

The inheritance of resistance to bacterial leaf blight was studied in 12 rice cultivars: BR51-91-6, KMP 242, KMP240, AD 3488, CNM 31, CR 138–1040, RP 633-76-1, ADT 30, IR 13240-10-1, IR 1545-339, UPRD 79–79 and RTN 68. These test cultivars were crossecl with a highly susceptible parent T(N)1. The F₁, F₂ and F₃ generations were raised and inoculated with the ‘Ranchi Isolate’ at the maximum tillering stage of vegetative phase by the clipping technique. The resistance in BR 51-91-6, KMP 242, KMP 240, AD 3488, CNM 31, CR 138–1040, RP 633-76-1, and ADT 30 was found to be governed by a single dominant gene. The resistance in IR 13240-10-1 and IR 1545-399 was conditioned by a single recessive gene and in UPR 79–79 and RTN 68 by a pair of complementary genes. Six test cultivars were also crossed with IR 22, a cultivar homozygous for Xa 4 gene and found to have resistance genes nonallelic to Xa 4 and segregated independently of it.