Study On Physiological Differentiation Of Xanthomonas Oryzae Pv. Oryzae In Northeast China And Resistance Of Rice Varieties To Race 9

Screening and planting resistant varieties is the most cost-effective way to control bacterial blight of rice. Adaptation and selection between Xanthomonas oryzae pv. oryzae and resistant varieties, and even coevolution under the condition of natural ecosystems, resulting to dynamic balance between pathogenicity of the pathoen and resistance of varieties. Single planting resistant varieties of rice reduces genetic diversity and accelerates the resistant loss of varieties, and further accelerate virulent differentiation and pathogenic variation of Xanthomonas oryzae pv. oryzae, thus bringing breeding for disease resistance a lot of trouble. Therefore, it has great significance understanding physiological differentiation, dynamic monitoring, virulent differentiation and population structure of the pathogen, and rational distribution of resistant varieties in the various regions of Northeast China.After investigating bacterial blight incidence, we found that the disease had a severe incidence in relatively farther southern and high temperature region, and it has being extending. By pathogenic and PCR test, 171 strains has been obtained. Among the strains, there were 44 strains from Heilongjiang province; 60 from Jilin Province; 77 from Liaoning Province. This job laid the foundation for further identification of physiological race and surveillance of genetic evolution for Xanthomonas oryzae pv. oryzae.The 171 strains were identified as physiological races with differential variety IRBB2(Xa2), IRBB3(Xa3), IRBB5(Xa5), IRBB13(Xa13), IRBB14(Xa14) and IR24(Recurrent parent), and it was found that the frequency of various physiological races appeared significantly different. Dominant race was R1 in three provinces in the Northeast China, and its frequency was 71.72%, which was significantly higher than all other races; followed by for the race R9 its frequency 12.41%; race R5 and race R7 was not found.Race R9 is the most toxic race among the identified six races. With representative strain JYJ152 for race R9, resistance of 30 rice varieties was tested from Jilin Province. The results showed that high resistance(HR) and high susceptible(HS) varieties of rice were not found, and there were 13 resistant varieties, 7 susceptible varieties, as well as 6 medium resistant varieties and 4 medium susceptible varieties. the highest frequency of variety reaction is resistant type, and its frequency is 43.30%. This result suggests that there are rich resistant resources for bacterial blight in Jilin Province. These resources could be using for controlling the disease in rice production in Northeast China.