Abstract: In order to identify the pathogen causing the black rot of Azolla filiculoides,the biological characteristics of the pathogen and the inhibitory effect of common fungicides on its hyphae growth were studied. The results of the morphologies combined with multi-gene development analysis showed that the pathogen causing the black rot of Azolla filiculoides was Alternaria tenuissima. Biological characteristics of A. tenuissima showed that the optimum temperature for mycelial growth and sporulation of A. tenuissima was 25℃,and it was favorable for mycelial growth and sporulation under all dark conditions. The pH value of 6.0~8.0 were more conducive to sporulation. The growth rate of the fungus was the fastest on CMA medium,and the sporulation was the largest on PSA medium. In the selection of carbon source,the strain of that fungus grew fastest in glycerol,while mannitol was the most beneficial to its sporulation. In the selection of nitrogen sources,the strain grew fastest in potassium nitrate,and the yeast extract was the most beneficial to its sporulation. The results of laboratory toxicity test showed that all 5 fungicides tested had certain inhibitory effects on the mycelial growth of A. tenuissima,among which Benzoxystrobin 32.5% SC had the strongest inhibition,and EC₅₀ was 0.001 2 μg·mL^-1. This was the first report that Alternaria tenuissima is able to cause the black rot of Azolla filiculoides in China.

Key words: Azolla filiculoides, Alternaria tenuissima, Biological characteristics, Toxicity test

摘要： 为了明确引起细绿萍黑腐病病原菌种类，研究该病原菌的生物学特性及常用杀菌剂对其菌丝生长的抑制作用。形态学结合多基因联合发育分析结果表明，引起细绿萍黑腐病的致病菌为细极链格孢(Alternaria tenuissima)。生物学特性表明，细极链格孢菌丝生长和产孢的最适温度均为25℃，全黑暗条件下利于菌丝生长和产孢。pH值在6.0~8.0时更利于其产孢，在CMA培养基上生长速度最快，而在PSA培养基上产孢量最大。碳源选择上，在丙三醇上生长速度最快，而甘露醇最有利于其产孢；氮源选择上，在硝酸钾上的生长速度最快，且酵母浸膏最有利于其产孢。室内药剂毒力测定结果表明，供试5种杀菌剂对细极链格孢菌丝生长均有一定的抑制作用，其中32.5%苯甲嘧菌酯SC的抑制活性最强，EC₅₀为0.001 2 μg·mL^-1。

关键词: 细绿萍, 细极链格孢, 生物学特性, 药剂毒力测定