摘要：
Pathogenic isolates were collected from different rice-cropping regions in southern China to dissect the pathogenic differentiation and variation of Xanthomonas oryzae pv.oryzae (Xoo).Two sets of rice-Xoo differential hosts,including Chinese system with five cultivars such as IR26,Javal4,Nangeng 15,Tetep and Jingang 30 and intemational system with a series of near-isogenic lines (NILs) such as IRBB5,IRBB13,IRBB3,IRBB14,IRBB2 and IR24 carrying different known resistance genes,were used to detect pathogenic differentiation for the reaction between host and pathogen with leaf-clipping method at the rice booting stage.The results showed the type of the pathogen were divided into six pathotypes including Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ and Ⅸ based on Chinese differential system,and seven pathogenic races including R1,R2,R3,R4,R5,R8 and R10 based on 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 southern China 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 Ⅸ grew up quickly.%为了解华南稻区水稻白叶枯病菌的致病性分化和变异动态,采集华南地区水稻白叶枯病病叶标样分离病原菌,应用中国鉴别寄主IR26、南粳15、爪哇14、特特普、金刚30和国际水稻已知抗病基因的近等基因系IRBB5、IRBB13、IRBB3、IRBB14、IRBB2、IR24两套鉴别寄主,在水稻孕穗期采用剪叶法接种,依据寄主和菌株的互作反应检测病菌的致病性分化.结果显示,参试菌株可划分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅸ六个致病型和R1、R2、R3、R4、R5、R8、R10七个致病小种.Ⅴ、Ⅳ致病型和R8、R5小种出现频率分别为27.40％、19.30％和44.67％、15.34％,为华南稻区优势种群.Ⅸ、Ⅴ、Ⅳ致病型和R8、R5小种对500份华南稻区品种资源的致病率依次为96.40％、95.00％、50.40％、62.00％和42.60％;Ⅸ致病型毒性最强且发展很快;强致病菌系Ⅴ型已替代Ⅳ型发展为华南优势致病菌系.
