PCR identification and pathotypic analysis of Xanthomonas oryzae pv. oryzae strains from North China

To demonstrate the field prevalence and virulence structure of Xanthomonas oryzae pv.oryzae(Xoo)strains in the north rice-growing regions of China,PCR analysis using 3 pairs specific primers of the genomic DNA of 103 bacterial strains isolated from diseased leaves of rice from Liaoning,Jilin,Hebei and Shandong Provinces was conducted in 2008 and 2009,respectively,and the bacterial pathogenicity on 6 near-isogenic lines of rice(IRBB2,IRBB3,IRBB5,IRBB13,IRBB14 and IR24)containing single Xa resistance gene,which as a set of differential varieties was also tested.The results showed that genomic DNA fragment patterns amplified by PCR of all tested strains were the same as those of the representatives of 9 pathotypes/races(R1-R9)of Xoo,but not Xanthomonas oryzae pv.oryzicola(Xoc).The rice differential varieties showed different resistant and susceptible reactions to Xoo strains,and the sequence of resistance was IRBB5IRBB13IRBB3IRBB14IRBB2IR24.Moreover,the diversity in virulence of Xoo strains on 6 rice near-isogenic lines was observed.Ninety-two strains(89.32%)displayed the same pathotypes of R1-R9,among which 36 strains of R5 and R8 were dominant in population and 9 strains of R9 were virulent on all rice varieties used.Remarkably,7 new pathotypes(R10-R16)of 11 strains were identified as well.