A Preliminary Analysis of Pathotypes of Xanthomonas oryzae pv. oryzae and the Resistant Reactions of Main Japonica Rices in the Yunnan Plateau

The pathogenicity of 36 isolates of Xanthomonas oryzae pv. oryzae (Xoo), which were collected from japonica rices in the Yunnan Plateau, was evaluated on 29 rice varieties including a set of 7 varieties to identify pathogenicity, ie. Haonuoyang, TN1, Kogyoku , Zhengzhuai, IR26, Nanjing 33 and Kinmaze, which may be considered as a set of differential varieties for Xoo races from Yunnan japonica rice. The efficiency of the 7 varieties was further confirmed. The results showed reversible and specific reactions between isolates and varieties. The isolates were classified into 9 pathotypes from pathotype I to Ⅸ according to their pathogenic reactions on the 7 rice varieties. The pathotype Ⅴ was the epidemic while pathogen Ⅶ was the most pathogenic. Most japonica varieties being grown in the Yunnan plateau were susceptible to Xoo. The rice lines IRBB21 (Xa-21), Zhachanglong (Xa-22t,Xa-24t)and IR1545-339 (xa-5), which were resistant to all the isolates tested, can be used as donors of resistant genes for bacterial blight in japonica rice breeding in the Yunnan Plateau.