江汉平原水稻白叶枯病菌致病型的变异研究

ON VARIABILITY OFR PATHOTYPES OFXANTHOMONAS PV. ORYZAE IN JIANG HAN PLAIN

１９９２－１９９４年采用中国水稻白叶枯病菌致病型研究方法，测定１０８个以江汉稻区为主的湖北水稻白叶枯病分离菌珠，在５个中国鉴别品种（ＩＲ２６、爪哇１４、南粳１５、特特普和金则３０）成株上的抗感反应，将病菌划分为Ｏ、Ⅰ，Ⅱ，Ⅲ，Ⅳ致病型。Ⅳ型菌３１个，占参试菌株的２８．７％，占采样县（市）的６１．１％，出现频率最高，分布最广，是江汉稻区流行的优势致病型，其次是Ⅲ、Ⅱ型菌。此结果与１９８９～１９９１年测定湖北省白叶枯病致病型结果基本一致，流行优势致病型仍是Ⅳ型，但致病力指数由１９８９～１９９１年的７２．３下降至５９．３，菌株毒力有所减弱。白叶枯病是江汉稻区水稻生产的潜在威胁，而目前种植的水稻品种多不抗ＩＶ型菌，所以今后在育种过程中，要多考虑转育含Ｘａ－４基因品种。在白叶枯病疫区建议种植抗性稳定的扬辐籼２号、扬稻４号、秀水６６４、威优６４等品种。

In 1992-1994, 108 isolates collected in Hubei and isolated from different varieties were identi- fied on five basic differentials i. e. IR2 6 , Java 1 4 , Nanggectgl 5 , Tetep and Jianggang30 by clipping method of inoculation. They were identified to be pathotype 0 , Ⅰ, Ⅱ, Ⅲ and Ⅳ according to disease reaction. From these isolates , the frequency of pathotype IV was the highest . 28. 7 % ) and the distri- bution of pathotype Ⅳ was the widest ( 61. 1% ) followed by pathotype Ⅲ and pathotype Ⅱ . The re- suets were coincident with that dlained in 1 98 9 - 1 99 1 . However the pathogenicity index of pathotype Ⅳ (1992-1994) dropped down from 59. 3 to 72. 3 (1989-1991). Result also show that most cur- rent rice varieties are of no resistance to pathotype IV . It is of the opinion that breeding the varieties with Xa-4 gene for resistence to pathotype IV of Xanthomnas cam pestis . Oryzae should be em- phasized and rice varieties with steady resistance to pathotype IV , i. e. Yang Fu xian , Yang Fu4 , Xi- ao shui 664 and Wei you 64. are to be planted in disease regions.