Inheritance of Resistance to Bacterial Blight in Seven Cultivars of Rice. R. K. Sahu, Graduate Student, The International Rice Research Institute, P.O. Box 933, Manila, Philippines. G. S. Khush, Principal Plant Breeder, The International Rice Research Institute, P.O. Box 933, Manila, Philippines. Plant Dis. 73:688-691. Accepted for publication 27 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0688.

The mode of inheritance and allelic relationships of resistance genes for bacterial blight (caused by Xanthomonas campestris pv. oryzae) were investigated in seven rice cultivars. Four races of the bacterial blight pathogen from the Philippines were used for studying the disease reactions of parental, F₁ and F₂ populations. The reactions of F₁ and F₂ populations from the crosses of seven cultivars with three testers (TN1, IR22, and CAS209) revealed that ADT22, Mondba, Hegarmanah-2, and BR116-3B-53 each have Xa-4 and Xa-10 genes for resistance. The cultivars Arairaj, BR11, and Chhatari have only the Xa-10 gene. These seven cultivars and CAS209 constitute a new group, distinct from the three known groups of cultivars resistant to bacterial blight. This new group is here designated group IV, or the CAS209 group.

Keyword(s): dominant, nonallelic, Oryza sativa, recessive.