| Rape Sclerotinia stem rot is a worldwide disease of oilseed rape. It exists in rapeseed-producing countries in the world. The disease occurs in China as well, ranking in the first of the rape's three major diseases. Particularly, the Yangtze River and southeastern coastal areas are the most common and serious. And it seriously impacts the yield and quality of rapeseed. In this paper, 24 isolates of Sclerotiinia sclerotiorum from different areas of Anhui Province and 2 rape varieties, Shanyou 8 and Huyou 15, were used to measure the lesions to evaluate the pathogenicity of the isolates by applying toothpick mycelium inoculation. Then the cell-wall degrading enzyme activity of the tested isolates was detected by DNS method. And the relationship between the enzyme activity and pathogenicity was analysed by mathematical statistical method. The main experimental results are as follows.1. Pathogenicity differentiation of Sclerotinia sclerotiorum isolates from different areasThe pathogenicity of 24 isolates of Sclerotiinia sclerotiorum which obtained from Tongcheng, Wuwei, Ningguo, Jingde and Shouxian in Anhui was investigated by applying toothpick mycelium inoculation respectively at the five to six leaves period. The results showed that all of the tested isolates caused stem rot on rape, and there was a significant difference in the average length of the lesions caused by different isolates, suggesting that there was significant differentiation in pathogenicity of S. sclerotiorum strains to rapeseed among isolates. The pathogenicity of the isolates was related to their localities to some degree.2. Relationship between celluase activity and pathogenicity of the Sclerotiinia sclerotiorum isolatesThe celluase activities of the isolates were tested by DNS method. Celluase could decompose the fiber tissues into low molecular deoxidized-sugar which could change into red-brown compound when reagent with DNS in the alkaline condition. In a certain concentration, absorbance and glucose concentration showed a positive correlation. And then, we could test the celluase activities. The results indicated that there was a considerable difference in the celluase activities, and the difference was closely related to their pathogenicity.The experiment carried out a correlation analysis between lesions length(y) and celluase(x), and the result shows that the two factors have a significant correlation, appearing incremental relation. The coefficient reached 0.9.60 after 24h inoculation on Shanyou 8, with the equation of y=13.208x-1.6134; and after 48h inoculation, the coefficient reached 0.9444, and the equation is y=25.944x-3.2497.When inoculate in Huyou 15, the coefficient is 0.5046 with the equation of y=9.106x-0.8319 after 24h's inoculation; the coefficient is 0.5545 with the equation of y=26.887x-2.8857 after 48h's inonculation.3. Relationship between pectinase activity and pathogenicity of Sclerotiinia sclerotiorum isolatesThe method of test pectinase is similar to celluase. The result shows that t there was a considerable difference in the pectinase activities, and the difference and their pathogenicity have a certain relationship with each other.The experiment carried out a two factor correlation analysis between lesions length(y) and celluase(x), and the result shows that shows that the two factors have a certain correlation, appearing incremental relation as well. The coefficient reached 0.5927 after 24h inoculation on Huyou 8, with the equation y=0.0615x-0.2135; and after 48h inoculation, the coefficient reached 0.5496, the equation is y=26.887-2.8857.When inoculate in Huyou 15, the coefficient is 6596 with the equation of y=0.0847x-0.922 after 24h; the coefficient is 0.7130 with the equation of y=0.2266-2.6439 after 48h inonculation.
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