桑枝枯菌核病病原菌的分离鉴定及生物学特性研究

Isolation and Identification of a Mulberry Branch-Blight Sclerotiniose Pathogen and Its Characterization

桑枝枯菌核病是危害桑树叶片和枝条的严重真菌病害,其病原菌亦可导致桑椹染病,分离获得病原菌,并研究其生物学特性将有助于精准防控该类病害.利用平板分离法对染病桑枝进行桑枝枯菌核病病原菌的分离纯化,并通过回接实验对其致病性进行检测;利用形态学观察和分子生物学手段对菌株进行鉴定;通过检测菌株生长情况,明确其生物学特性及其侵染叶片时的特征.研究结果表明,分离获得的菌株GXS1接种桑叶36 h后,桑叶出现明显病斑;该菌在马铃薯葡萄糖琼脂培养基(PDA)上菌落呈白色,培养后期能产黑色菌核,基于18S rDNA和ITS rDNA序列的系统发育分析,菌株GXS1与核盘菌(Sclerotinia sclerotiorum)亲缘关系最近;该菌最适生长温度为20℃,最适pH值为5.0,最佳碳源为葡萄糖、蔗糖或果糖,最佳氮源为硝酸钠,最适培养基为PDA;该菌接种桑叶12 h后开始形成侵染垫,接种24 h后侵染垫数量明显增多.

Mulberry branch-blight sclerotiniose is a fungal disease that seriously harms the leaves,branches and fruits of mulberry trees.Isolating the pathogenic microorganism and studying its biological characteristics will greatly help the accurate prevention and control of such diseases.In this study,the pathogenic microorganisms of mulberry branch-blight sclerotiniose were isolated and purified by plate separation method,and the pathogenicity was detected by back infection experiment.Strain identification was carried out based on morphological observation and molecular characteristics.The biological characteristics of the strain and the infected leaves were clarified by detecting the growth of the strains.The results showed that obvious disease spots on mulberry leaves were detected after 36-hour inoculation of the isolated strain GXS1.This strain has white colonies on potato glucose medium(PDA)and can produce black sclerotia in the later stage of culture.Based on 18S rDNA and ITS rDNA sequences,the phylogenetic analysis showed that this strain had the closest relationship with Sclerotinia sclerotiorum.The optimal growth temperature of S.sclerotiorum GXS1 is 20℃,the optimal pH is 5.0,the best carbon source is glucose,sucrose or fructose,the best nitrogen source is sodium nitrate,and the most suitable medium is PDA.Infection cushion of S.sclerotiorum GXS1 was formed after 12-hour inoculation in mulberry leaves,and the number of infected cushions increased significantly after 24 hours inoculation.In summary,this study reported a pathogenic fungus,S.sclerotiorum GXS1,which can cause mulberry branch-blight sclerotiniose.Its biological characteristics and infection characteristics were preliminarily clarified.The study could provide an important theoretical basis for the pathogenic biology study of mulberry branch-blight sclerotiniose.