桑褐斑病病原菌的分离及以离体叶片接种测定致病性的方法

Separation of Pathogenic Fungus Causing Mulberry Brown Spot Disease and Determ ination Method of Its Pathogenicity by in vitro Leaf Infection

桑褐斑病是桑树的主要真菌病害,病原为桑粘格孢菌（Septogleum mori Bri et Cav）。分别采用4种方法从发病桑树分离桑褐斑病病原真菌,并以离体叶片接种法测定分离菌株的致病性,比较不同浓度菌液和不同接种方式对离体桑树叶片感染率的影响及观察病斑数随接种时间的变化情况,筛选简便、有效的病原菌分离与致病性鉴定方法。除组织块分离法外,采用分生孢子团块分离法、单孢分离法和改良稀释单孢分离法均可分离得到纯的病原菌株。离体桑树叶片以不同浓度菌液和不同接种方式接种病原菌后,其病斑数以及病情指数差异显著,病原菌以菌落悬浮液涂抹法和孢子悬浮液喷雾法接种均可有效感染离体桑树叶片,其中菌落悬浮液涂抹法处理叶片的病斑数和病情指数最高,分别为108.83和60.00;用于接种的病原菌分生孢子浓度为1×105^-5×10^5m L^-1有利于离体桑树叶片感染致病;随着接种病原菌后的时间延长,发病桑树叶片的病斑数逐渐增加。上述对桑褐斑病病原菌的分离及菌株致病性测定方法,可为桑褐斑病病原菌株的致病性分化研究和桑树种质资源的抗病性评价提供参考。

Mulberry brown spot disease is the major fungal disease of mulberry,and its pathogenic fungus is Septogleum mori Bri et Cav. In order to find a simple and effective measure for pathogenic fungus separation and pathogenicity determination,four different methods were used to isolate pathogenic fungus causing mulberry brown spot disease,and the pathogenicity of isolated fungus was determined by in vitro leaf inoculation method. The infection rates of different pathogen concentrations and different inoculation methods on in vitro mulberry leaf were compared,and variation of disease spots with inoculation time was observed. Except for tissue isolating method,conidium mass separation,single spore isolation and improved dilution single spore separation methods all yielded pure pathogenic fungal strains. The disease spots and disease index of in vitro mulberry leaf were significantly different after inoculation with different pathogen concentrations and by different inoculation methods. Mulberry leaves were effectively infected by pathogenic fungi inoculated by means of colony suspension smearing and spore suspension spraying. The disease spots and disease index of mulberry leaf treated by colony suspension smearing was the highest,being 108. 83 and 60. 00 respectively. When the concentration of conidium was 1 ×10^5 to 5×10^5 spores per m L,it would facilitate infection to mulberry leaf. Moreover,the number of disease spots ininfected mulberry leaves was increased with infection time. The above results provide good references for studying pathogen differentiation of mulberry brown spot disease and disease resistance evaluation of mulberry germplasm resources.