Research On Bioassav And Culture Conditions Of Pathogenic Fungi Esteya Vermicola Against Bursaphelenchus Xylophilus

Pinewood nematode （PWN）（Bursaphelenchus xylophilus） was most harmful to Chineseforests at present and caused pine forest devastating damage.Since the pine wood nematodedisease was discovered, the large amounts of human, material and financial resources had beeninvested in the disease fighting at home and abroad．But so far the disease has not beeneffectively controlled, and it still has the trend toward spread．To date, chemical control playedan important role in PWN control. It is so hard to control PWN directly that there are fewresearches in domestic and in abroad. Our laboratory introduced anendoparasitic fungusfromSouth Korea, called Esteyavermicola with high infectivity to PWN demonstrated by previousresearches. This paper aims to study this fungus about infection activity to PWN, nutritionalchatacteristics and preservation conditions, then provide theory reference on PWN biocontrolusing this fungi.The tests demonstrated that conidia shed from the conidiogenous cells can infect toPWN.The conidia from the solid medium with rich nutrition had higher infection activity toPWN.There was significant difference in the infectivity to PWN between the strains as well asCBS115803strain occupies first place, CBS100821strain comes second and CNU120806strain was the lowest. The conidia were readily attached to the PWN on the WA plate byadopting dipping method.Theadherenceandmortalityratefellwiththedecreasingoftheinitialconidiaconcentration, and thetreatment with conidia concentrationof1×109spores·ml^-1can acheived the highest infectivityto PWN.The effects of carbon sources, nitrogen sources, carbon concentration and carbon tonitrogen （C/N） ratio on the growth and sporulation of E. vermincolain liquid and solid culturewere examined.Through analysis and comparision, glucose and yeast powder is the best carbonand nitrogen resources respectively for increasing biomass and sporulation by using liquid andsolid culture methods.The C/N ratio of40:1and12g·L^-1carbon gave the maximum yield of conidia and the C/N ratio of5:1and12g·L^-1carbon gave the maximum biomass in liquidmedium. In addition, the C/N ratio of20:1and8g·L^-1carbon is the best combination formycelia growth;the C/N ratio of10:1and8g·L^-1carbon is the best combination for sporulationin solid medium.A growth curve was obtained in the optimized liquid mediumafter13dayscultivation. The curve showed that5days and11days after cultivation the fungi grow atmaximum in mycelia biomass and conidia yields. It was able to apply to mass production inliquid fermentation.Different environment conditions about temperature（high temperature drying and lowtemperature preservation）, additives and storage atomosphere were tested on the effcet ofconidia germination. The results showed that conidia water content is obviously decline afterdrying, conidia germination was affected as well.The germination capacity of the conidiapreserved longer is relatively lower during drying process and the conidia completelyinactivation after48hours drying. But to keep conidiawater content over40%, its germinationrate will remain at around80%. In addition, conidia mixed with40%glycerin were stored30days in vacuum package under4℃and the germination rate is higher than other treatments.