Study On The Pathogenic Bacteria Identification And Resistance Identification Method Of Black Rot Of In Chinese Cabbage

Chinese cabbage black rot disease is growing increasingly as one of the main diseases in China, Therefore, an urgent problem is to setup a convenient, rapid and exact method for identify the resistance of germplasm resources Chinese cabbage (Brassica campestris L. ssp penkinsis) to black rot, which will promote the step of germplasm and new varity breeding. In this research, the pathogenic bacteria was isolated from the disease samples of shaanxi Chinese cabbage field and its pathotype differentiation has been done with various resistance Chinese cabbage varities. then the methods of identification of black rot disease resistance were optimized at seedling stage, cytoledon stage,in vitro cytoledon or seedling leaf respectively. Lastly, the resistance of germplasm resources and hybrids of Chinese cabbage were tested in seedling stag. the major results were as follows:1. First, The 35 Chinese cabbage black rot strains were isolated from the disease samples collected from the major Chinese cabbage production area of Shaanxi Province. The 6 black rot strains with different pathogenicity on Chinese cabbage had been distinguished by the resistance or susceptibility in host-pathogen interaction, which is coded as I, II, III, IV, V and VI, thereinto, type III had the strongest infection capacity, type II was the typical pathogenic strain, type I, IV and V had high host specificity, type I and V had the similar infection capacity and type VI was obviously different with others bacteria strains in infection capacity.2. It was obvious differences that the 6 kinds of pathogenicity occur at Chinese cabbage production area of Shaanxi Province, such as type I and V occurred at four Chinese cabbage production areas, and type I was the major pathogenic bacteria in all areas. In addition, it was found that there was a positive correlation between the pathogenicity and ability of hydrolyzing starch and extent of gelatin liquefaction in bacteria.3. The optimal artificial inoculation and identification method for black rot of Chinese cabbage at seedling stage was established. The key procedures is that inoculating by spray method with 1.0×108 cfu/mL bacteria quantity on the seedling of 4~5 true leaves stage, then kept at 26℃for 12 days.4. The inoculation and identification method at cotyledon stage , in vitro cotyledon or seedling leaf also established. Spray method with 1.0×1010cfu/mL bacterium liquor at 22℃was suitable for cotyledon stage identification, dirpping method with 1.0×1010cfu/mL of bacterium liquor at 22℃was suitable for in vitro cotyledon identification, dirpping method with 1.0×108cfu/mL of bacterium liquor at 26℃aslo was suitable for in vitro seedling leaf identification. It was noted that the method of in vitro seedling leaf identification was best to reflect the truth of resistance to black rot.5. The resistance of 344 germplasms of chinses cabbage were identified at seedling stage, its result showed that there was no immune accession, there was 12 accessions with high resistance, 52 with resistance, 156 with tolerance, 121 with susceptivity and 4 with high susceptivity. The high resistance accessions were Qinbai No2♂, Qinbai No3♂, Jinguan No1, 06S317, 06S1692, 07S11, 07S12, 07S140, 07S544, 07S544, 06S40 and 99S26-M. The high susceptivity accession were 07S158, 06S658, 06J30 and 06S49.