Abstract: To clarify the pathogenic characteristics and potential for chemical control of soybean Phomopsis seed decay in Zhoukou City，Henan Province，typical diseased soybean stems were collected for pathogen isolation and identification.The effects of temperature and humidity on mycelial growth and spore germination were determined，and the in vitro fungicidal activity of ten fungicides against the isolate was assessed using the mycelial growth inhibition method，and seed⁃coating trials were conducted to evaluate the protective efficacy of each treatment in terms of seed germination and suppression of pathogen infection.The results showed that one fungal strain，designated ZK⁃2024，was obtained. Based on morphological characteristics and phylogenetic analysis of multi⁃locus DNA sequences（rDNA ITS and TEF1‑α），the isolate was conclusively identified as Diaporthe longicolla，the causal agent of soybean Phomopsis seed decay. The optimal temperature for mycelial growth was 30 ℃，while the optimum for conidial germination was 25 ℃. High humidity significantly promoted both mycelial growth and conidial germination，with a statistically significant interaction between temperature and humidity.Fungicide screening revealed that 90% carbendazim water⁃dispersible granules and 430 g/L tebuconazole suspension concentrate exhibited the strongest inhibitory activity against the isolate ZK⁃2024，with median effective concentrations（EC₅₀）of 0.366 0 mg/L and 0.444 4 mg/L，respectively.In seed⁃coating trials，seeds treated with pyraclostrobin plus infested soil achieved a germination rate of 93.33% and showed no mycelial coverage，significantly outperforming all other fungicide treatments.This performance was statistically comparable to the untreated control（non⁃coated seeds+sterile soil）.In summary，this study reported the first successful field isolation and molecular identification of Diaporthe longicolla in Zhoukou.It elucidated key biological traits of the pathogen and identifies carbendazim and tebuconazole as highly effective fungicides for in vitro suppression.Moreover，pyraclostrobin demonstrated excellent protective efficacy in seed⁃coating assays under controlled conditions，highlighting its potential as a candidate seed treatment agent for managing Phomopsis seed decay in soybean.

Key words: Diaporthe longicolla, Biological characteristics, Toxicity test, Screening of antifungal drugs, Carbendazim, Pyraclostrobin

摘要： 为明确河南省周口市大豆拟茎点种腐病的病原特性及化学防治潜力，在周口市采集大豆拟茎点种腐病典型症状大豆茎秆样品进行病原菌分离鉴定，测定温湿度对菌株生长及孢子萌发的影响，采用菌丝生长速率法测定10种杀菌剂对其的室内毒力，并通过拌种试验评估各药剂对种子发芽及病原菌侵染的保护效果。结果表明，分离得到1株真菌，命名为ZK-2024，结合形态学特征及基于rDNA ITS 和TEF1-α 的多基因序列系统发育分析结果，最终确定获得的菌株为大豆拟茎点种腐病菌Diaporthe longicolla。该菌株菌丝生长最适温度为30 ℃，分生孢子萌发最适温度为25 ℃，湿度对其生长与萌发均有显著促进作用，且温湿度存在显著交互作用。抑菌药物筛选结果表明，90%多菌灵水分散粒剂和430 g/L戊唑醇悬浮剂对大豆拟茎点种腐病菌ZK-2024的抑菌效果最明显，半数效应浓度（EC₅₀）分别为0.366 0 mg/L和0.444 4 mg/L。在拌种药剂筛选中，吡唑醚菌酯+菌土处理的大豆种子发芽率为93.33%，菌丝包裹率0，显著优于其他药物处理，与未拌种+无菌土处理（对照）无显著差异。综上，首次在周口市田间分离并鉴定了大豆拟茎点种腐病菌，明确了其关键生物学特性，并筛选出多菌灵与戊唑醇为其高效抑菌药剂，吡唑醚菌酯在室内拌种试验中表现出优异的种子保护效果，具备作为候选拌种药剂的潜力。

关键词: 大豆拟茎点种腐病菌, 生物学特性, 毒力测定, 抑菌药物筛选, 多菌灵, 吡唑醚菌酯