| Rice false smut, caused by Ustilaginoidea virens, is one of the important fungal diseases in the panicles of rice. The disease is not only reduce grain quality and yield, but the chlamydospores contain mycotoxins (ustiloxins) that are toxic to human and animals and contaminate rice seeds and grains. The chlamydospore of U. virens is primary infection source and it has a long dormant period. In order to reveal the differences of structure, relative molecular mass and composition of polysaccharide from the cell wall of the dormant (black or green-black)and non-dormant (yellow) chlamydospore, the following research were conducted.Five different methods were adopted to extract polysaccharide of its black chlamydospore cell wall, the results showed that the optimum extracting method was the complex enzyme-hot water extraction-sevag and the most appropriately extracting conditions were that the complex enzyme, pH, extracting temperature, extracting time and the material ratio were4%,4,70℃,120min,1:75V, respectively. It provides the basis of physical and chemical properties of polysaccharide from chlamydospore cell wall.The crude polysaccharide from cell walls of the black and yellow chlamydospores was obtained by complex enzyme-hot water extraction-sevag, it was purified by H2O2, dialysis, column chromatography, et al. The results showed that the polysaccharide from cell walls of the chlamydospores were white, odorless, soluble in water, insoluble in methanol, ethanol, acetone and other non-polar organic solvents. By the phenol-sulfuric acid method, the contents of polysaccharides in the black and yellow chlamydospore cell wall were separately72.3%and66.7%. By the method of Gel column chromatography (Sephadex G-75), the average molecular mass of polysaccharides in the black and yellow chlamydospore cell wall were separately1.62×10and2.19×10. The polysaccharide content and molecular mass in black chlamydospores cell wall was significantly higher than the yellow.The structure and composition of cell wall polysaccharide of different colors chlamydosporeswere analyzed by ultraviolet absorption spectrum (UV spectrum), infrared absorption spectrum (IR spectrum), congo red test, and gas chromatography (GC). The results showed that polysaccharide from two kinds of the above spores cell wall consisted of the three monosaccharides, galactose, glucose and mannose, while yellow chlamydospore contains a small amount of xylose, mannose, with a average relative molar percentage ratio of58.23:25.32:16.46, The yellow chlamydospores wall was composed of glucose, galactose, mannose and xylose, with a average relative molar percentage ratio of35.48:30.58:24.46:9.45. The composition and composition ratios of the three monosaccharides in polysaccharide from the different colour chlamydospores have obviously different, which the variance is maybe cosely related with chlamydospore dormancy. The research provides the basis for explaining the constitutive dormancy of dormant and non-dormant chlamydospore. |
