Abstract: To clarify the species and biological characteristics of pathogenic bacteria of Medicago sativa L. leaf blight,and screen out the effective fungicides to control this disease. Leaf samples of alfalfa leaf blight were collected in Zhaodong City and Daqing City,Heilongjiang Province in August,2023. Tissue isolation method was used to isolate and purify pathogenic bacteria,according to Koch’s rule to verify pathogenicity,and the mycelium growth in plate was used to investigate fungicides toxicity on the pathogen. Combined analyses of morphology and molecular biology indicated that the pathogen causing alfalfa leaf blight was Epicoccum nigrum. The results of studied biological characteristics showed that the optimum temperature for mycelial growth was 25℃,which was favorable for mycelial growth under all light conditions and pH value was 10. The mycelium growth rate was the fastest on PSA medium,but the growth rate was the slowest on WA medium. In the choice of carbon source,mycelium grew fastest on maltose and slowest on glycerol. In the choice of nitrogen source,the mycelium grew fastest on tryptone and slowest on urea. The indoor toxicity test showed that 30% pyraclostrobin had the strongest inhibitory effect,and the EC₅₀ value was 0.2819 μg·mL^-1.

Key words: Medicago sativa, Epicoccum nigrum, Pathogen identification, Biological characteristics, Toxicity test

摘要： 为明确紫花苜蓿(Medicago sativa L.) 叶枯病病原菌种类及生物学特性，筛选出有效防治药剂，本试验于2023年8月在黑龙江省肇东市和大庆市分别采集紫花苜蓿叶枯病病样，采用组织分离法分离并纯化病原菌，依据柯赫氏法则验证致病性，通过菌丝生长速率法进行室内药剂筛选。形态学结合分子生物学分析结果表明，引起紫花苜蓿叶枯病的病原菌为黑附球菌(Epicoccum nigrum)。生物学特性研究结果表明，菌丝生长最适温度25℃、最适pH值为10，全光照条件有利于菌丝生长，菌丝在马铃薯蔗糖琼脂(Potato saccharose agar，PSA)培养基上生长速度最快，在水琼脂(Water agar，WA)培养基上生长速度最慢。碳源和氮源选择上，菌丝分别在麦芽糖和磷酸二氢铵上生长速度最快，在蔗糖和硝酸钾上生长速度最慢。室内药剂毒力测定表明，30%吡唑醚菌酯抑菌作用最强，半数效应浓度(Median effect concentration，EC₅₀)为0.2819 μg·mL^-1。

关键词: 紫花苜蓿, 黑附球菌, 病原菌鉴定, 生物学特性, 药剂毒力测定