Identification Of The Pathogenic Fungus Of Chestnut Rot Disease And Indoor Screening Of Fungicides

In recent years,the chestnut rot has become more and more serious in the eastern Hebei province,which not only makes the quality of chestnuts decline,but also causing serious economic losses to chestnut farmers.In order to identify the pathogen species of chestnut rot disease,this article used tissue separation method to separat and purify the pathogen of disease fruits,identified the pathogenicity by Koch’s rule,and determined the pathogen species by morph ological observation and molecular biology.The results showed that:the main pathogens causing chestnut rot were Colletotrichum gloeosporioides,Alternaria alternata,Trichothecium roseum,Fusarium Oxysporum and Penicillium commune.The culture conditions of two pathogens（Colletotrichum gloeosporioides,Alternaria alternata）of chestnut rot were studied.The results showed that:the optimum temperature for mycelium growth of Colletotrichum gloeosporioides was 25℃;the optimum carbon source was sucrose;beef extract and yeast extract（as nitrogen source）were most beneficial to the growth of mycelia;the suitable medium was sandcastle weak,tomato+oatmeal,chestnut residue,chestnut and mung bean medium;the optimum pH value was 9;a full light condition was conducive for the mycelium growth;the lethal temperature was 55℃ for 10minutes;it was not beneficial to the growth of mycelia in a completely static environment.In terms of sporulation,the maximum sporulation was 7.2×10⁵ cell/ml at 25℃;the most carbon source was lactose for sporulation;the yeast extract as nitrogen source was suitable for spore formation;the suitable medium for spore formation was oat+potato medium;a full dark condition was conducive to sporulation.pH 7 and 8 were good for sporulation.The optimum temperature for mycelium growth of Alternaria alternata was 25℃;suitable carbon source was sucrose;the peptone was beneficial to the growth of mycelia;a full light condition was most conducive for the mycelium growth;the pathogen had a strong adaptability to pH,it could grow well between 4¹1,and the optimal pH was 6;the lethal temperature was 55℃for10 minutes;It was not beneficial to the growth of mycelia under completely static ventilation.In lab,the results showed that:difenoconazole,carbendazim and tebuconaz ole had the best inhibitory effect on Colletotrichum gloeosporioides in the preliminary screening test,with an inhibition rate of more than 90%.And the optimal concentration of the three agents was determined by setting a gradient for bacteriostasis test,the results showed that:the EC₅₀0 of tebuconazole,carbendazim and difenoconazole were 4.6745mg/L,9.0026mg/L and 9.0186mg/L,respect ively.Propiconazole,prochloraz and difenoconazole had the best control effect on Alternaria alternata in the preliminary screening test,and the inhibition rates were 100.00%,89.71%and 89.46%respectively.And the optimal concentration of the three agents was determined by setting a gradient for bacteriostasis test,the results showed that:the EC₅₀0 of difenoconazole prochloraz,and propi conazole were 1.9158mg/L,2.7789mg/L,5.0890mg/L,respectively.