桂牧1号杂交象草叶斑病病原鉴定及其生物学特性分析

Identification and Biological Characteristics Analysis on the Pathogen of Pennisetum purpureumcv Guimu-1 Leaf Spot Disease

从儋州牧草种质中心资源圃的桂牧叶斑病叶片上分离得到一株致病真菌,通过采用形态学观察、致病性测定、分子生物学等鉴定方法对该致病菌进行了研究。结果表明,菌丝体表面光滑,有横隔,分生孢子呈球棒形或长纺锤形,淡褐色至中等褐色,端部钝圆,基部有明显突出的脐点,有3-12个隔膜,大小约（71.22-76.97）μm×（3.54-6.16）μm。其型态特征与蠕孢属（Exserohilum sp.）描述高度相符。对其核糖体DNA内转录间隔区（ITS）序列进行PCR扩增、测序获得长度为602 bp的序列,经BLAST比对,该序列与嘴突凸脐蠕孢（Exserohilum rostratum）ITS序列同源性达99%。结合致病菌的形态特征和ITS序列分析结果,将其鉴定为嘴突凸脐蠕孢。经生物学特性研究发现：适宜该菌菌丝体生长的温度为25-32℃,最适温度为28-32℃;菌丝体生长的最适p H为6-8;菌丝体生长的最佳碳源为葡萄糖、蔗糖和甘露醇;最佳氮源为硝酸钠,尿素不适合菌丝体生长;全黑暗条件有利于菌丝体生长;菌丝体致死温度为55℃,10 min。杀菌剂室内毒力测定结果显示：对嘴突凸脐蠕孢毒力最强的杀菌剂为咪鲜胺和苯醚甲环唑,EC50分别为0.007 1 mg/L和0.007 2 mg/L;嘴突凸脐蠕孢对戊唑醇最敏感。

The pathogenic fungi strain isolated from leaf of Guimu leaf spot in the center of Danzhou forage germplasm resources nursery was studied by identification methods such as morphological observation, determination of pathogenic, and molecular biology. The results showed that mycelium surface was smooth, there were across, conidium form were a bat or long spindle with hazel to medium brown, tip was obtuse and base had obvious prominent umbilical point, and there were 3-12 diaphragm which about（71.22-76.97） μm×（3.54-6.16） μm.Its type characteristics were highly consistent with Exserohilum sp. The length of 602 bp sequence obtained from the ribosomal DNA internal transcribed spacer（ITS） sequences with PCR amplification and sequencing, was 99%homology with Exserohilum rostratum ITS sequence by the BLAST. According to the morphology of the pathogenic bacteria and ITS sequence analysis, we Identified it was Exserohilum rostratum. The biological characteristics research found that： the suitable fungus mycelium growth temperature was 25-32℃; The optimal temper-ature was 28-32℃; The optimum p H of mycelial growth was 6-8; The best carbon source of mycelial growth was glucose, sucrose and mannitol; The best nitrogen source was sodium nitrate, while urea was not suitable for growth of mycelium; All dark condition was advantageous to the growth of mycelium; Mycelium lethal temperature was55℃ of 10 min. Fungicides indoor toxicity measurement results showed that the strongest fungicides virulence to Exserohilum rostratum were prochloraz and prochloraz, which EC50 was 0.007 1 mg/L, 0.007 2 mg/L respectively;Exserohilum rostratum was the most sensitive to tebuconazole.