Abstract: Streptomyces Sm4‐1986，which has broad spectrum bacteriostatic properties，is a rhizosphere bacterium obtained by Plant Pathology Group in South China Botanical Garden，Chinese Academy of Sciences during the preliminary study.To expand the biocontrol resources of rice sheath blight，we measured the effects of Streptomyces Sm4‐1986 on the pathogenic growth of rice sheath blight，and the control effects of Streptomyces Sm4‐1986 on rice sheath blight by in vitro leaf test，sterile seedling test，pot experiment，and field experiment.We analyzed the inhibitory effect of its metabolites on rice sheath blight and its growth‐promoting effect on rice.The results showed that both metabolites and volatiles of Streptomyces Sm4‐1986 could significantly inhibit the mycelial growth of Rhizoctonia solani，and the inhibition rates were 67.31% and 88.46%，respectively.In in vitro experiments，the disease severity of rice leaf sheath blight decreased by 87. 50% after spraying Streptomyces Sm4‐1986 compared with that of spraying sterile water.The control effects of Streptomyces Sm4‐1986 on rice sheath blight were 100%，72.98%，and 60.35% after five days in sterile seedling test，pot experiment，and field experiment，respectively. After inoculation，the content of MDA in rice leaves sprayed with Streptomyces Sm4‐1986 decreased by 48.06% compared with that sprayed with water.Streptomyces Sm4‐1986 could produce 6‐pentyl‐2H‐pyran‐2‐one（6‐PP），which could significantly inhibit the mycelial growth of Rhizoctonia solani.The concentration required for 50% mycelial growth inhibition（IC₅₀），the concentration required for 90% mycelial growth inhibition（IC₉₀） and the minimum bactericidal concentration（MFC） were 0.007 3，0.11，0.6 mg/mL，respectively. Moreover，6‐PP could significantly promote the growth of rice seedlings.Therefore，Streptomyces Sm4‐1986 can be used as a biological control agent or biological
bacterial fertilizer to control rice sheath blight.

Key words: Streptomyces, Rice sheath blight, Rhizoctonia solani, Bioactive compound, Biological control, 6‐pentyl‐2H‐pyran‐2‐one

摘要： 链霉菌Sm4-1986是中国科学院华南植物园植物病理研究组前期研究过程中获得的1株植物根际细菌，具有广谱抑菌特性。为了拓展水稻纹枯病的生防菌资源，测定了链霉菌Sm4-1986对水稻纹枯病菌生长的影响，采用离体叶片试验、无菌苗试验、盆栽试验以及大田试验，研究了链霉菌Sm4-1986对水稻纹枯病的防效，并分析了其代谢物对水稻纹枯病菌的抑制效果及对水稻的促生作用。结果表明，共培养条件下链霉菌Sm4-1986的代谢物与挥发物均能显著抑制立枯丝核菌菌丝生长，抑制率分别为67.31%与88.46%。叶片离体试验中，喷施链霉菌Sm4-1986后，水稻叶片纹枯病病害严重度较喷施无菌水处理下降87.50%；无菌苗试验、盆栽试验、大田试验中，接种病原菌5 d后，链霉菌Sm4-1986对水稻纹枯病的防效分别达100%、72.98%、60.35%。接种立枯丝核菌后，喷施链霉菌Sm4-1986发酵液的水稻叶片MDA含量较喷施清水处理降低48.06%。链霉菌Sm4-1986能够产生6-戊基-2H-吡喃-2-酮（6-PP），6-PP可以显著抑制立枯丝核菌菌丝生长，菌丝生长抑制率为50%、90%所需质量浓度（IC50、IC90）及最低杀菌浓度（MFC）分别是0.007 3、0.11、0.6 mg/mL；且6-PP可以显著促进水稻幼苗生长。可见，链霉菌Sm4-1986可以作为生物防治剂或者生物菌肥应用于水稻纹枯病防治。

关键词: 链霉菌, 水稻纹枯病, 立枯丝核菌, 活性物质, 生物防治, 6-戊基-2H-吡喃-2-酮