白术枯斑病原鉴定、生物学特性及其对不同药剂的敏感性研究

 白术(Atractylodes macrocephala Koidz.)是浙江省传统中药材“浙八味”之一。近年来在磐安县白术主产区发生一种新的枯斑病。为明确致病菌及其生物学特性和对杀菌剂的敏感性,本研究通过病原菌分离培养、柯赫氏法则验证、形态学特征观察,及ITS、LSU、rpb2和tub2多基因序列分析,发现引起该枯斑病的病原菌为Phoma exigua。生物学特性测定表明:该菌菌丝生长的最适温度为28℃,最适pH为8,最适碳源与氮源分别为可溶性淀粉和蛋白胨;分生孢子萌发最适温度24℃、相对湿度100%;菌丝和分生孢子的致死温度分别为47℃和54℃。不同药剂敏感性测定结果表明:咯菌腈对该菌菌丝生长的抑制作用最强,EC₅₀为0.24 μg·mL^-1;吡唑醚菌酯和嘧菌酯对其分生孢子萌发具有较强的抑制作用,EC₅₀分别为0.10和0.16 μg·mL^-1。由P. exigua 引起的白术枯斑病为国内外首次报道。

Biological characteristics and fungicide sensitivity of firstly reported Phoma exigua causing spot blight on Atractylodes macrocephala

The aim of present studies was to identify, isolate and purify the causal agent of Atractylode macrocephala spot blight from diseased leaves using conventional method in addition to their biological characteristics and response to different fungicides. The morphological characteristics, and pathogenicity test along with multi-locus phylogenetic analyses based on ITS, LSU, rpb2 and tub2 of the pathogen were carried out. The result demonstrated that the pathogen was Phoma exigua. The optimum conditions for mycelial growth of the pathogen were temperature 25℃, pH value 8, carbon sources starch and nitrogen sources, peptone. The optimum conditions for the conidium germination were temperature 24℃ and RH 100%. The lethal temperatures of mycelia and conidia were 47℃ and 54℃,respectively. The sensitivity to different fungicides of the pathogen was determined. The results indicated that the EC₅₀ values of fludioxonil was 0.24 μg·mL^-1, with the highest activity inhibiting mycelial growth among the 10 tested fungicides. The pyraclostrobin and azoxystrobin were efficient inhibitors of conidial germination, with respective EC₅₀ values of 0.10 and 0.16 μg·mL^-1.