Searching for and analysis of bacterial blight resistance genes from Thailand rice germplasm

In Thailand, rice (Oryza sativa L.) is the main food and agricultural product for export. However, the production of rice has faced many problems and bacterial blight disease is one of the problems in rice growing. Bacterial blight resistance Xa4, Xa7, xa5 and xa13 genes were discovered in 155 Thai rice cultivars using polymerase chain reaction-based gene-linked and gene-specific markers and the specific allele was compared with susceptible rice cultivars and with rice carrying each resistance gene. The results showed the same alleles as in the Xa4 resistance gene (89.68%), followed by the Xa7 resistance gene (11.61%), while the same alleles as xa5 and xa13 resistance genes were not found in the Thai rice germplasm studied. A new allele of Xa7 was found and part of the DNA sequence was analyzed and compared to alleles obtained from resistant and susceptible rice lines. Sixteen cultivars carried the same alleles as the Xa4 and Xa7 resistant alleles. Phenotyping of 12 rice cultivars was performed using the leaf-clipping method and inoculation with three isolates of Xoo (TB0002, Xoo5 and Xoo6). Three rice cultivars (Kan Phu Daeng, Phuyai Li and RD23) had resistance to all three Xoo isolates. These cultivars will be useful as genetic sources in rice breeding programs in the future.