Pathogenicity Differentiation And Molecular Detection Of Verticillium Dahliae In Jiangsu Province

Verticillium wilt, one of the serious diseases of cotton, is a worldwide soil-borne disease. In the different area, even in the same cotton field the symptom types, the disease incidence and the disease index of cotton Verticillium wilt are all different Whether the disease resistance difference of plant individuals or the pathogenicity differentiation of the pathogen in the soil made the difference? It is a good theoretical question and an important reality practical problem. Therefore,we carried out the reseach on the pathogenicity differentiation of verticillium dahliae and got the results as followes.1. The culture characteristics of the strains in jiangsu province showed that the most of them were sclerotium type, then filament type, and the middle type were fewest. The results also showed that the culture characteristics of the strains isolated in the same cotton field even in the same plant were different.2. In order to get the best medium for iosolated verticillium dahliae from soil, Mian Xuan 1 medium, Lv-jindian medium and cotton leaves mediun were selected. The result indicated Mian Xuan 1 was best. It was the simplest and less contamination.3. The microsclerotia of Verticillium dahliae were isolated from the soil sample collected in August 2008 in Dafeng county, jiangsu province.The results showed that the amount of the microsclerotia, were significantly correlative with soil layers. In heavy disease area there was about 70% microsclerotia in 0 to 20 cm deep earth, 20% microsclerotina from 20.1 cm to 30cm deep earth and about 10% microsclerotia in 30 cm to 40 cm deep earth.. There was only few that under 40 cm soil layers. In light disease area there was about 71.2% microsclerotia in 0 to 20cm deep earth, 18% microsclerotina from 20.1 cm to 30cm deep earth and about 10.8% microsclerotia in 30.1cm to 40cm deep earth. There was only few that under 40.1cm soil layers. Thus, deep plowing, or the upper surface of the soil treatment, which is one effective methods.to prevention and treatment Verticillium dahliae .4. 64 strains of verticillium dahliae from jiangsu province were detected by using PCR technology to monitor their pathotypes. The fragment (500bp) was amplified from 54 strains by using the specific primers D1, D2 of defoliation pathotype of verticillium dahliae and the size was accordant with other defoliation pathotype of verticillium dahliae reported in the literature, which indicated that these strains were defoliation pathotype of verticillium dahliae. The fragment (1500bp) was amplified from 10 strains by using the specific primers ND1 and ND2 of non-defoliating pathotype of verticillium dahliae. The defoliation pathotype of verticillium dahliae pathogen occupied 84.38% of the tested strains, these results indicated that the verticillium dahliae in jiangsu province was still mainly belong to defoliation pathotype at present.5. The pathogenicity tests of 52 strains of Verticillium dahliae isolated from jiangsu province and 4 control strains were carried out in greenhouse. According to their reaction in hosts,56 strains were classified into 3 types of pathogenicity:type I (severe pathogenic type), type II (intermediate pathogenic type), and type III(weak pathogenic type). Type I was 17.86%, Type II was 71.43%, and type III was 10.71%, respectively. The defoliation strains were found in these strains. These results also explained that both non-defoliating and defoliating symptoms appeared in the same cotton field and indicated that Verticillium dahliae was a mix of easy to variant genotype groups, which composed of different sub-groups of individuals with different pathogenicity.