Genetic analysis of Myanmer rice cultivars for resistance to bacterial blight

Rice cultivars from Myanmer were classified into five groups based on their reaction pattern to bacterial blight (BB) races by EDO et al. (1991). A random sample of cultivars from each group was genetically analyzed to verify their grouping. The selected cultivars were crossed with IR 24 which is susceptible to all Philippine races of BB. The F1 and F2 populations were inoculated by clipping method(KAUFFMAN et al. 1973). The segregation data revealed that single dominant genes conferred resistance in cultivars belonging to CAS 209, TKM 6 and Java 14 groups and single recessive gene conveyed resistance in cultivars belonging to DZ 192 group. The cultivars belonging to Mond Ba group were found to have two dominant genes for resistance. Allelic relationships of genes of cultivars belonging to different groups were tested by inoculating F1 and F2 population from crosses of these cultivars with respective tester of each group. The results revealed that all the cultivars belonging to Java 14, TKM 6, DZ 192 and CAS 209 groups had Xa-3, Xa-4, xa-5 and Xa-10 genes for resistance. The results confirmed that cultivars with Xa-10 and Xa-4 predominated amongst BB resistant cultivars from Myanmar and the frequency of cultivars with Xa-3 and xa-5 was very low