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Abstract Pathogenic isolates were collected from different rice-cropping regions in southern China to dissect the pathogenic disintegration and variation of Xanthomonas oryzae pv. oryzae (Xoo). Two sets of tice-Xoo differential hosts, including Chinese system with such five cultivam as Ш26, Javal4, Nangengl5, Tetep and Jingang 30 and international system with a series of near-isogenic lines ( NHs) including ШВВ5, [RBB13, IRBB3, IRBB14, ШВВ2 and IR24 carrying different known resistance genes,were used to detect pathogenic disintegration for the reaction between host and pathogen with leaf-dippdngmethod at the rice booting stage. The results showed the type of the pathogen were divided intosix pathotypes, i. e. , I, II, III, IV, V and IX based on the Chinese differential system, and seven patliogenicraces including R1, R2, R3, R4, R5, R8 and RIO based an the international differential system. The pathogenicity frequency of Xoo pathotypes V and IV and pathogenic races R8 and R5 were 27.40% , 19.30% and 44.67% , 15.34% , which were considered to be the prevailing races in southern China. Pathogenic rates of pathotypes IV, V, IX and races R8, R5 against 500 varieties derived from souihemChina were 96.40% , 95.00% , 50.40% , 62.00% , and 42.60% , respectively. Among which pathotype IX was the most virulent pathotype. The pathotype V became preponderant pathotype and the new pathotype [X grew up quickly.
Key words Xanthomonas oryzae pv. oryzae; Differential variety; Pathotype; Race
Bacterial blight is an important disease in the southern part of China, which seriously threatens the safe production of rice. Because the pathogen of this disease harms rice plants within vascular bundles, there is still no safe efficient systemic bactericide, and chemical prevention is ineffective. Furthermore, the Xwvtkomonas oryzae pv. oryzae (Xoo) infects injured parts mainly through miming water, and mechanical injury caused by typhoon rainstorm and flood create favorable conditions for its epidemic outbreak with the characteristics of acute occurrence, fast propagation and difficult control111. The control of this disease with resistant varieties is the most effective and harmless choice, while the selection of corresponding resistant gene directing at the pathogenicity of Xoo and its variability is a basis for the breeding for disease resistance, as well as a key link for the application of resistant varieties. Therefore, the accurate...