【摘要】 为研究造成黑龙江省尚志市地区龙牙楤木叶斑病的主要病原菌和病原菌生物特性，筛选出对该病原菌具有较强抑制作用的生物杀菌剂，为防控该病害提供依据。以采集的龙牙楤木病叶样本作为研究对象，取病健交界处的组织，采用组织分离法获得病原菌，通过形态学观察及分子系统发育学方法对菌株进行鉴定，结合科赫氏法则验证致病性以确定病原菌种类。同时测定不同培养基、pH、光照、碳氮源对病原菌菌丝生长的影响。此外，利用菌丝生长速率法探究8种药剂对病原菌的抑制能力，并借助毒力方程计算出半数效应浓度(50%effective concentration,EC₅₀)。结果表明：从龙牙楤木病叶共分离25株病原真菌，将菌株LY10回接至水培25 d的健康龙牙楤木叶片，产生了与林间相同的症状。该菌株在PDA上的生长状态最好；pH值为4～10的范围内均能生长，最适pH为7;12 h光暗交替的光照条件对菌株生长最有利；对多种碳、氮源适应能力较强，以甘露醇、酵母膏作碳、氮源时菌丝生长最快。8种室内药剂筛选结果表明，30%吡唑醚菌酯·苯醚甲环唑、30%四氟醚唑、15%戊唑醇的EC₅₀值分别为2.569 8×10^-6、0.001 7和0.019 2 mg/L，对LY10的抑制作用较好，10%丙硫菌唑的EC₅₀值为11.344 9 mg/L，抑菌效果最差。通过形态学观察及ITS序列的分子生物学鉴定分析，表明引起黑龙江省尚志市地区龙牙楤木叶斑病的病原菌为亚隔孢壳属的Didymella segeticola，这为后续制定龙牙楤木叶斑病的防控策略以及研究其病原菌的致病机制提供了病原依据。更多还原

【Abstract】 This study aimed to identify the main pathogen causing leaf spot disease on Aralia elata in Shangzhi City,Heilongjiang Province,characterize its biological properties,and screen biocides with strong inhibitory effects against this pathogen thereby providing a basis for disease prevention and control.Using collected diseased A.elata leaf samples as research materials,tissues at the junction of diseased and healthy areas were sampled.Pathogens were isolated via the tissue isolation method,and strains were identified through morphological observation and molecular phylogenetics analysis.Pathogenicity was verified following Koch’ s postulates to confirm the pathogen species.Meanwhile,the effects of different media,pH values,light conditions,and carbon/nitrogen sources on the mycelial growth of the pathogen were determined.Additionally,the mycelial growth rate method was used to evaluate the inhibitory ability of 8 agents against the pathogen,and the 50% effective concentration(EC₅₀) was calculated using virulence equations.The results showed that a total of 25pathogenic fungal strains were isolated from the diseased A.elata leaves.When strain LY10 was inoculated back onto healthy A.elata leaves hydroponically cultured for 25 days,the same symptoms as those observed in the field were induced.Strain LY10 exhibited the best growth on PDA medium.It could grow within a pH range of 4-10,with an optimal pH of 7.Alternating light-dark conditions（12 h each） were most favorable for its growth.It showed strong adaptability to various carbon and nitrogen sources,and mycelial growth was fastest when mannitol and yeast extract were used as the carbon and nitrogen sources,respectively.The results of in vitro agent screening indicated that 30% pyraclostrobin·difenoconazole,30% tetraconazole,and 15% tebuconazole had favorable inhibitory effects on LY10,with EC₅₀ values of 2.569 8×10^-6mg/L,0.001 7 mg/L,and 0.019 2 mg/L,respectively.In contrast,10% prothioconazole had the weakest inhibitory effect,with an EC₅₀ value of 11.344 9 mg/L.Combined morphological observation and molecular identification based on ITS sequences confirmed that the pathogen causing A.elata leaf spot disease in Shangzhi City,Heilongjiang Province was Didymella segeticola.This study provides a pathogenic basis for formulating subsequent prevention and control strategies for A.elata leaf spot disease and researching the pathogenic mechanism of the pathogen.更多还原