山西太谷区谷子纹枯病病原鉴定及其生物学特性

Identification and Biological Characteristics of Foxtail Millet Sheath Blight in Taigu District of Shanxi Province

谷子是我国北方重要的杂粮作物,纹枯病是造成谷子减产的重要限制性因素之一。为探究谷子纹枯病病原种类,明确其生物学特性,本研究采集山西太谷区的谷子病样,采用组织分离法对病原物进行分离,采用牙签接种法通过柯赫氏法则进行致病性验证;结合病原菌的形态特征、菌丝融合群和rDNA-ITS序列对病原菌进行种类鉴定。在不同温度、光照、pH值、碳源、氮源条件下,采用十字交叉方法测量菌落直径,并观察后期菌核产生情况,明确纹枯病菌的生物学特性。形态学鉴定结果表明,该病原菌菌落白色,具有隔膜,呈直角分枝,基部稍缢缩,后期可产生菌核,初步鉴定为立枯丝核菌;分离的4个菌株的菌丝融合群均鉴定为Rhizoctonia solani AG-4 HG-Ⅲ融合群;菌株的ITS序列与已报道的Rhizoctonia solani AG-4 HG-Ⅲ(IBRS02)相似度达到99%。综合上述形态特征、融合群、rDNA-ITS序列和系统进化树分析,该病原菌被鉴定为R.solani AG-4 HG-Ⅲ。致病性测定结果表明,该病原菌对谷子具有较强的致病性,且对水稻、小麦、高粱等均具有致病性。生物学特性研究结果表明,病原菌在马铃薯葡萄糖琼脂培养基上最适培养温度为25℃,最适pH值为6.0;黑暗条件有利于菌丝的生长,光照条件有利于菌核的形成;蔗糖和硝酸钾分别为最适的碳源和氮源;在马铃薯葡萄糖琼脂培养基上菌丝生长最快,马铃薯葡萄糖琼脂培养基和马铃薯蔗糖琼脂培养基最有利于菌核的形成。本研究结果可为谷子纹枯病的研究和防治提供理论依据。

Foxtail millet is an important coarse cereal and sheath blight caused by Rhizoctonia solani Kunh is one of the limiting factors for its sustainable production in northern China.In order to investigate the species and biological characteristics of the blight pathogen,the samples of foxtail millet sheath blight collected from taigu district of Shanxi Province were isolated by tissue separation method,and pathogenicity test was confirmed through Koch’s postulate’s by toothpick inoculation method.Morphological observation,anastomosis groups identification and rDNA-ITS amplification and sequence analysis were performed to identify the pathogen strain.In order to clarify the biological characteristics of Rhizoctonia solani under different temperature,light,pH value,carbon source and nitrogen source conditions,we used the cross method to measure the colony diameter and observed the formation of sclerotia in the later stage.The results showed that the mycelium of colony was white in color,and the hyphae of pathogen have diaphragms,with nearly right-angled side branches constricted at the base,and the sclerotia could be produced in the later stage.Four isolates obtained from diseased plants were identified as Rhizoctonia solani anastomosis group AG-4 HG-Ⅲ.ITS sequence of the isolates has 99%similarity with the reported R.solani AG-4 HG-Ⅲisolate(IBRS02).Combined morphological characteristics,anastomosis groups,rDNA-ITS sequence and phylogenetic tree,the pathogen was identified as R.solani AG-4 HG-Ⅲ.Artificial infection experiment results showed that the pathogen had strong pathogenicity not only to foxtail millet but also to rice,wheat and sorghum.The optimum culture temperature for pathogen was 25℃on potato dextrose agar medium,and the optimal pH value was 6.0.Dark promoted the growth of mycelial,whereas light was beneficial to the formation of sclerotia.Additionally,sucrose and potassium nitrate were the most suitable carbon and nitrogen sources,respectively.The hyphae of R.solani grew fastest on potato dextrose agar medium,potato dextrose agar and potato sucrose agar medium were the best for conducing the formation of sclerotia.This study can provide a theoretical basis for the research and prevention of foxtail millet sheath blight.