Studies On The Biochemical Mechanism Of Pathogenic Differentiation Of Scleratinia Sclerotiorum

Sclerotinia stem rot, distributing worldwide in all the rapeseed production countries and districts, has been one of the most devastating disease on rapeseed production, impacting the yield and quality of the rapeseed seriously. In this paper,30strains were obtained from different areas in Anhui Province, among which, two resistant varieties and two infectious varieties were selected as test materials, such as Zhongyou821, Deyou5and Wanyoul4, Zayoul, respectively. The pathogenicity of the strains above was investigated by applying isolated leaves inoculation. For better understanding the pathogenic mechanism of Sclerotinia sclerotiorum, mechanical analysis on the difference of metabolizing oxalic acid and other enzymes was performed on those varieties with significant difference in pathogenicity. The main results are as follows:1Research on pathogenicity differentiation of sclerotinia sclerotiorum’m Anhui ProvinceThe pathogenicity of30isolates of Sclerotinia sclerotiorum which obtained from different districts in Anhui Province was investigated by applying insolation and identification. Four varieties with different resistance to sclerotium blight were selected as test materials, and the pathogenicity of the strains above was investigated by applying isolated leaves inoculation. The results show that, the test materials can cause pathogenesis after inoculation, and significant differentiation exists among different pathogenesis. The pathogenesis of different rapeseed varies with the same strain. The pathogenesis of different strains varies significantly, and the4test materials varies greatly.2Relationship analysis of producing oxalic acid and average pathogenicity of Sclerotinia sclerotirum to rape seedlingsThe oxalic acid content of rapeseed leaves after being infected with sclerotinia sclerotiorum was measured by titration of potassium permanganate, and the theory is that oxidation reaction can react between the oxalic acid and the potassium permanganate. Use the potassium permanganate titrate oxalic acid, and on the basis of the color of product to determine the end of the reaction. According to the reaction of chemical formular and the usage amount of potassium permanganate to calculate the content of oxalic acid. The results show that, the variation of oxalic acid of rapeseed leaves after being infected by different strains is significant, and the secretion of oxalic acid increases with an higher pathogenesis of the strains. The pathogenesis of the strains shows highly correlation with the ability to produce oxalic acid (R2=0.8126), but no direct correlation with the orientation of the strains.3Dynamics of different enzymes in rapeseed leaves after being inoculated with oxalic acid and sclerotinia sclertiorumThe optimal concentration of oxalic acid was determined as6mmol/L with two different methods was applied on the rapeseed leaves, such as soaking the leaves in oxalic acid and inoculating sclerotinia scleriorum. The variation of the activity of PPO, POD and cellulase in leaves was analyzed. The results show that, both sclerotinia scleriorum and oxalic acid can improve the activity of PPO and POD in rapeseed leaves, thus improving the pathogenesis.96hours after the sclerotinia sclertirum being inoculated, the activity of the cellulase reached the maximum, indicating that plenty of cellulase can be secreted with the inoculating of sclerotinia scleriorum. Therefore, the destruction of sclerotinia scleriorum to the cell walls is fastened, and inducing the decay of the leaves quickly. Meanwhile, the oxalic acid secreted by sclerotinia scleriorum reduced the pH value and made the activity of the enzyme reaches its summit, showing that oxalic acid and sclerotinia scleriorum are the main factors of pathogenesis.4Dynamics of different component content of pectase in rapeseed leaves after being inoculated with sclerotinia sclertiorumThe glycosidic bond of polygalacturonic acid can be hydrolyzed by polygalacturonase(PG), and galacturonic acid is produced. Spectrophotometer method can be used to measure the reducing aldehyde of the product, the PG activity can be characterized by the amount of galacturonic acid. The results show that, strains cultured in vitro conditions, reached a peak of enzymatic activity in the first5d and after3d since the rapeseed leaves being inoculated with strains, the activity of PG enzyme reached the maximum, and the secretion of PG varies with different pathogenesis of the strains significantly, and the pathogenesis of the strains was related with the enzyme activity to some extent.The activity of pectin methyl esterase(PE) can be measured with its hydro lysates, since pectic acid and methanol as the products can be acquired with the removal of pectin methyl group from pectin. The results show that, strains cultured in vitro conditions, reached a peak of enzymatic activity in the first3d and after24hours since the rapeseed leaves being inoculated with strains, the activity of PE enzyme reached the maximum, and the secretion of PE varies with different pathogenesis of the strains significantly, and the pathogenesis of the strains was related with the enzyme activity to some extent.