Characterization of Rice Bacterial Leaf Blight pathogen (Xanthomonas oryzae pv. oryzae) in Cambodia and identification of effective rice R-genes.

Bacterial leaf blight is a serious disease of the rice crop in Cambodia, affecting rice yield across the country every year. In 2016, rice production losses accounted for 9.22 million tones in both wet and dry seasons. This study aimed to identify the single resistance gene effective against Xoo and finger printing of the isolated Xoo from Cambodia provinces. A total of 145 samples from five provinces in Cambodia were subjected to genotyping and pathotyping that each isolate was extracted using the Easy-DNA kit (Invitrogen, USA) following the manufacturer's protocol and was PCR-amplified with a set of multiplex primers as method. Based on the results was showed the significant effect of each isolate to all rice near-isogenic line and non-significant of each rice differential varieties. Among of One hundred and forty-five isolates were selected 16 isolates as candidate to subjected the virulence evaluation on 24 near-isogenic lines (NILs) and a local variety (Sen Pidor) as shown in among the 16 isolates of BLB were classified into 7 pathotypes (A to G). We classified these races into 4 large groups based on the pathogenicity test with analysis of Least Significant Difference (LSD). Group 1 contains pathotypes A, G, group 2 contains pathotypes B, F, group 3 contains pathotypes C, E and group 4 contains pathotypes D which pathotypes in three group accounted for 12.5%, 18.75%, 18.75% and 50% of the total strains, respectively. All race was virulent on the rice lines possessing single resistant genes Xa4, xa5, Xa7, Xa11, xa13, Xa14, Xa21, with most races producing the lesion lengths the sane as on the susceptible check variety IR24. These resistance genes could ne used for a breeding program for resistance to BLB in Cambodia.