Genetic analysis of resistance to bacterial blight, Xanthomonas oryzae pv. oryzae, in rice, Oryza sativa L.

Abstract

Forty resistant rice cultivars were studied for the inheritance of resistance to bacterial blight using Philippine races of Xanthomonas oryzae pv. oryzae (Xoo). Results showed that all the varieties have at least two recessive genes for resistance. One of these genes governs resistance to race 1 (PXO61) while the other gene confers resistance to race 6 (PXO99). In addition to the recessive genes, nine of the varieties possess another dominant gene which also confers resistance to race 1. Allelism tests revealed that the recessive genes governing resistance to race 1 in 39 varieties are allelic to xa5 while the dominant genes in the nine varieties are allelic to Xa4. The recessive gene conferring resistance to race 1 in cultivar Sada Diga is inherited independently of xa5. Similarly, the recessive genes governing resistance to race 6 in all the varieties are non-allelic to xa13. The allelic relationships of these genes with xa-24(t), a new recessive gene identified in cultivar DV86 which conveys resistance to race 6 are now being investigated.