Studies On The Pathogenic Substances Produced By Valsa Mali

Apple valsa canker is one of the major diseases of apple tree, which is caused by ValsaMali Mayabe et Yamada and leads to decay of apple tree stem cortex. The pathogen can infectthe apple tree branches, trunks, fruits and other multiple parts. It makes the apple trees weakand branches dead. In recent years, the disease occurs widespreadly in the main appleproducing areas of our country, severely reducing the apple output and quality, leading seriouseconomic loss to apple industry. The reason has greatly related to the unclear pathogenicvirulence factors and its pathogenic mechanism.Therefore, the project started from the pathotoxins secreted from pathogen duringinfecting. Inhibition of lettuce seed bud growth and tobacco leaf inoculation method was usedfor the detection of biological activity. GC-MS was used for the analysis of organic acidscomposition in fermentation broth. Using HPLC assay for the detection of phlorizindegradation by various components in fermented liquid and finding out which is the maincomposition leading the degradation of phlorizin. Using macroporous adsorption resin, ethylacetate extraction, silica gel column chromatography, thin layer chromatography and othermeans for further extraction and separation of fermentation liquid. Spectroscopic method wasused for chemical structure identification of the toxin component. It has great significance tomake clear the pathogenic mechanism and guide field disease control.The bioassay results indicated that: the inhibition rate on lettuce seed bud growth by20d’fermentation liquid reached57.91%and fermentation liquid, proteins, residul fermentationliquid all have pathogenic role on tobacco leaves. GC-MS results showed that the filtratecontained7kinds of organic acids and respectively was2-hydroxy propionic acid, glycolicacid, malonic acid, succinic acid, malic acid, palmitic acid, octadecanoic acid. Their relativecontents were4.42%,0.56%,0.56%,59.10%,5.87%,3.66%,0.65%. The mycelium dryweight was48mg per100mL in10day’s fermentation liquid using phlorizin as carbonsource. The degradation rate of phlorizin by the pathogen was92.46%after10days’ reaction,while the rate reached99.88%by starch fermentation filtrate. Proteins of1mg/mL candegrade90.4%of phlorizin after5days’ treatment. Organic acids and residual liquid, on theother hand, could merely degrade1.6%and5.9%of phlorizin, respectively. The phlorizindegradation rate is98.7%by organic acids and proteins. And the phlorizin degradation rate increased as the proteins concentration and reaction time increased. Proteins, which possiblywere cell wall degradation enzymes, produced by pathogen play an important role in phlorizindegradation. The organic acids can strengthen enzymes’ activity. The activity tracking methodwas used for further extraction and separation of the proteins free residual fermentation liquidand a small molecular toxin component was got. Its spectral character indicated that thecompound’s chemical structure may be:2-ethyl-3-methyl-4-isopropyl-benzoic acid.