Host Range Test, Variety Resistantce And Fungicides Screening Of Auricularia Polytricha Slippery Scar Infected By Schtalidium Lignicola

Auricularia polytricha having important edible and medical value is wildly cultivated in Fujian, Sichuan and Henan province of China, which is rich in polysaccharides and edible fibers. Slippery scar disease caused by Scytalidium lignicola, is infectious and frequently leads to a substantial reduction in the yields of A. polytricha. The pathogen only infected the vegetative mycelia of A. polytricha, not the fruit bodies.Three pathogens of slippery scar disease were isolated from samples of diseased cultivated bags collected from Shifang of Sichuan province, Zhangzhou of Fujian province and Zhumadian of Henan province by conventional tissue isolation. Morphological observation, analysis of ITS sequence and pathogenic verification of the three pathogens were investigated. Furthermore, we compared the culture characteristics of A. polytricha strains with which of S. lignicola, determined the host range of S. lignicola, screened the resistance of A. polytricha strains and examined the selective fungitoxicity of selected fungicides in the article. The results were showed as the following.1. The result of morphological characteristics and ITS analysis showed that the three pathogens were S. lignicola which were coincident in the morphological characteristics of mycelia, chlamydospore and colony, homology of ITS sequence and pathogenicity.2. The results indicated that S. lignicola could only infect A. polytricha strain and displayed the symptom of slippery scar among the11kinds of wood-rotting fungus were tested in host range trials. While it did not show pathogenic to Auricularia auricular, Lentinula edodes, Pleurotus ostreatus, Agrocybe chaxinggu, Ganoderma lucidum, Pleurotus geesteranus, Pleurotus eryngii, Hypsizigus marmoreus, Flammulina velutiper and Hericium erinaceus, making it clear that S. lignicola have host-specificity to A. polytricha.3. There existed certain difference between S. lignicola and the host in culture characteristics, comparing from the aspects of temperature, pH, light, carbon concentration and carbon to nitrogen (C:N) ratio. The mycelium of S. lignicola and A. polytricha could grow under temperature condition range from25℃to33℃, while the optimum temperature is31℃. Appropriate growth pH of the pathogen range from5to7, among of which the optimum pH is6; while the appropriate growth pH of the host range from6to8, among of which the optimum pH is7. Light could inhabit the growth of both significantly in culture. The optimum growth carbon concentration of both is6g/L under certain conditions of carbon to nitrogen ratio. The optimum carbon to nitrogen ratio of S. lignicola is40:1under certain conditions of carbon concentration, but the optimum carbon to nitrogen ratio of the host had no obvious regularity.4. Analysis of resistance for16A. polytricha strains to S. lignicola. The results showed that16A. polytricha strains did not showed defense responses upon infection by5. lignicola significantly. The mycelium of S. lignicola directly covered and invaded into the hyphae of host strains and there did not exist antagonistic lines obviously between them in vitro confrontation trials. To test resistance for A. polytricha strains in vivo test, the mycelia of pathogen was inoculated in the center of hyphal surface when the mycelia of host had grown over all the cultivated bags. Compared with the disease index, there existed significant difference among the tested strains, only Shang hai1and APP61showed strongly resistant. While Shang hai land APP61showed weakly resistant in field trials of screening for resistant varieties and did not exist significant difference comparing with other’s strains in resistant ability, which showed that the performance of resistance was not outstanding in the appropriate environment of field (high humidity, much pathogens)5. The most effective fungicide in inhibiting in vitro growth of S. lignicola was chlorothalonil75%WP (mean ED50=0.306μg ml-1), followed prochloraz-Mn50%WP (mean ED5o=0.332μg ml-1) and thiophanate-methyl70%WP (mean ED50=0.601μg ml-1). Based on the selectivity index, prochloraz-Mn50%WP and chlorothalonil75%WP were selected to be tested in field trials. The selective fungitoxicity of chlorothalonil75%WP inhabited by high temperature and high pressure showed that thermostability of which was poor.6. The results of screening for efficient chemicals in fields showed that it can be inhabited and control the slippery scar disease at the rate of78.855%and87.5-93.75%by the means of mixing the selected fungicides with cultivation materials at the active ingredient rates range from1:800to1:1000g·kg-1and daubing with medium of fine earth on the diseased area at the active ingredient rates range from1:250to1:500g·kg-1respectively.