38. Inheritance of resistance to bacterial blight of four Yunnan rice varieties

He-Ping Gao, Xing-Hua Lin, Gong-Xing Yu, Duan-Pin Zhang and Yue-Feng Xie
Department of Agronomy, Huazhong Agric. University, Wuhan, 430070 China

     Bacterial blight caused by Xanthomonss oryzae is a serious disease of rice in China. After testing 6184 Yunnan local varieties with 10 bacterial strains from China, Philippines and Japan, some resistant varieties were identified. The inheritance of resistance was studied in 4 Yunnan varieties: Dui-jin-zi (DJZ), Zha-chang-long (ZCL), Hao-nuo-yang (HNY) and Gan-zha-gu (GZG). Zhen-zhu-ai (ZZA) was used as a susceptible parent.

    The F1 plants of crosses between 4 varieties and ZZA were resistant. The F2 population segregated into 3R:1S ratio. The B1F1 progenies with ZZA segregated into IR:1S ratio. In these studies, bacterial strain Pxo61 was used for evaluating resistance.
Table 1. F2 and B1F1 data for segregation of resistant (R) and susceptible (S) plants. Four Yunnan resistant varieties were
crossed to a susceptible variety (ZZA) and inoculated with "Pxo61"
 

Cross 
combination 		 Number of plants
 		 Total Expected
ratio		 Chi square
R S
F2
DJZXZZA 286 94 300 3:1 0.004
ZCLXZZA 305 101 406 3:1 0.003
HNYXZZA 254 81 335 3:1 0.08
GZGXZZA 292 82 374 3:1 1.43
B1F1
(DJZX ZZA) X ZZA 38 28 66 1:1 0.23
(ZCLX ZZA) X ZZA 18 19 37 1:1 0.03
(HNYX ZZA) X ZZA 36 35 71 1:1 0.01
(GZGX ZZA) X ZZA 33 32 65 1:1 0.02
F2
DJZXZCL 333 24 357 15:1 0.07
HNYXGZG 272 16 288 15:1 0.13
HNYXDYZ 276 27 303 15:1 3.22
HNYXZCL 274 18 292 15:1 0.004
GZGXDJZ 156 15 171 15:1 1.45
GZGXZCL 421 19 440 15:1 2:48

These results suggested that the resistance of the four Yunnan varieties was controlled by a dominant gene (Table 1).
    The F2 populations of crosses between some of varieties: DJZ X ZCL, HNY X GZG, HNY X DYZ, HNY X ZCL, GZG X DJZ and GZG X ZCL segregated into a 15R: 1S ratio. It therefore appears that the resistance genes of DJZ, ZCL, HNY and GZG are not allelic to each other. These varieties seem to have at least two independent genes for bacterial blight resistance (Table 1).
    Furthermore, the Yunnan varieties were crossed with Kyogoku, Tetep and other varieties having known resistance genes. From the F2 R:S ratios observed, it appeared that GZG has a resistance gene allelic to Xa-3; DJZ as well as HNY have resistance genes independent of Xa-I, Xa-2, Xa-3, Xa-4, xa-5 and Xa-14. The resistance gene of ZCL is not allelic to Xa-I and Xa-14, but it is linked with Xa-4, with recombination value of 13 ± 4.5%. Varieties DJZ, ZCL and HNY may possibly have a new resistance gene to bacterial blight.