The Diversity Of Sclerotinia Sclerotiorum From Different Areas In Hubei Province

Sclerotinia stem rot (SSR) of oilseed rape caused by Sclerotinia sclerotiorum is a worldwide and stubborn disease.It causes serious damage to oilseed rape production, both on yield and quality. In this paper, the diversity of some important biological characteristics of S. sclerotiorum isolated from Hubei province were studied, such as cultural characteristics, sclerotia yield and pathogenicity. We selected some strains to analyze the difference of mycelium compatibility and pathogenicity. And the difference of pathogenic factors between weak infectious strains and strong infectious strains were compared. Results were listed as follows:One thousand sclerotiorum strains were isolated from diseased plants of ten rapeseed production districts in Hubei province, which includes Wuxue, Jingzhou, Dangyang, Huangzhou, Huanggang, Xiantao, Xiaogan, Tiammen, Jingmen and Qianjiang city. The cultural characteristics of 1000 sclerotiorum strains have been observed on PDA medium, and the results showed that there were abundant diversities between them, they were divided into eight types based on colony color and mycelium abundance.Otherwise, the characteristics of sclerotia, the distribution of sclerotia has three types.The results of mycelium growth rate, pathogenicity and sclerotia yield of 1000 S. sclerotiorum strains showed that there were abundant diversities.The regression analysis between three factors revealed that there were obvious regression relations between mycelium growth rate and pathogenicity of S. sclerotiorum (P<0.05), and remarkable regression relations between mycelium growth rate and sclerotia yield (P <0.01),however, pathogenicity had no significant correlation with sclerotia yield of S. sclerotiorum (P>0.05).Sixty S.sclerotiorum strains from above ten districts were randomly selected to conduct mycelium compatibility test on MP medium, and the results showed that 60 strains were divided into 27 mycelium compatibility groups (MCGs). Twelve MCG were made up only one strain compatible with itself, and other groups were consist of 2-9 strains.Mycelium compatibility groups are not significantly related to geographical location, mycelium growth rate and pathogenicity of S. sclerotiorum strains (P>0.05).In order to understand the mechanism of weak pathogenicity of S.sclerotiorum, production of oxalic acid, pectinase, laccase, protease and amylase between weak pathogenic strains JZJL-46, TMHS-27 and strong pathogenic strain JZJL-13 were compared. The results showed that three strains could normally produce OA and pectinase, and the level of OA and pectinase produced by strain JZJL-13 with strong pathogenicity was significant higher than that of strains JZJL-46 and TMHS-27 with weak pathogenicity. Strains JZJL-13 and TMHS-27 could normally produce laccase, and the level of laccase produced by strain JZJL-13 was higher than that of strain TMHS-27, strain JZJL-46, which could not produce laccase.Strain JZJL-13 also could normally produce protease and amylase, however, strains TMHS-27and JZJL-46 could not produce protease and amylase. These results suggest that production of oxalic acid, pectinase, laccase, protease and amylase may be very important for pathogenicity of S.sclerotiorum.The above result showed that there were abundant diversities in biological characteristics of S. sclerotiorum isolated from Hubei province, such as cultrural characteristics, sclerotia yield, pathogenicity and mycelium compatibility, and pathogenicity of S. sclerotiorum were related to oxalic acid, pectinase, laccase, protease and amylase.