生防菌剂对西瓜根际土壤微生物群落和尖孢镰刀菌属的影响

Effects of biocontrol agents on watermelon rhizosphere soil microbial community and Fusarium oxysporum f.sp.

【目的】了解不同生防菌剂对西瓜根际微生物群落结构和尖孢镰刀菌(Fusarium oxysporum f.sp.)的影响,为生防菌剂抑制西瓜枯萎病的机理研究提供依据。【方法】将西瓜苗移栽到连作20年西瓜的土壤中,设置B6、WF19、BW和对照4个处理,分别根部注施生防菌剂解淀粉芽孢杆菌B6、油菜假单胞菌WF19、B6和WF19复合菌液(各菌液细菌含量均为1×108 CFU/mL)及无菌水1 mL/株,在西瓜采摘后采集根际土壤,测定土壤pH、有机质(OM)、全氮(TN)、硝态氮(NO^(-)_(3)-N)、铵态氮(NH^(+)_(4)-N)、全磷(TP)、有效磷(AP)、全钾(TK)、速效钾(AK)含量及过氧化氢酶(CAT)、碱性磷酸酶(ALP)、脲酶(URE)、蔗糖酶(SUC)活性,并利用高通量测序(Illumina Hiseq)技术分析西瓜根际土壤的微生物群落变化。采用路径分析和SEM结构方程评估土壤环境因子、生物酶活性和微生物功能对尖孢镰刀菌的影响。【结果】生防菌剂B6提高了土壤4种生物酶活性和TN、TP、AP、NO^(-)_(3)-N、NH^(+)_(4)-N、OM含量,降低了AK和TK含量;WF19提高了土壤CAT、ALP和SUC活性,降低了URE活性和TN含量,增加了土壤TP、AP、TK、AK、NO^(-)_(3)-N、NH^(+)_(4)-N和OM含量;BW提升了土壤NO^(-)_(3)-N含量、CAT和SUC活性,降低了URE和ALP活性,减少了土壤中TN、TP、TK、AP、AK、NO^(-)_(3)-N和OM含量。根部注施生防菌剂后,WF19和BW处理土壤中尖孢镰刀菌的相对丰度降低,B6处理土壤中赤霉菌属的相对丰度降低。AP、TP含量和URE活性与细菌群落结构的关联性最大,AP、TK含量和URE活性与真菌群落结构的关联性最大;硝酸盐呼吸、固氮和亚硝酸盐氨化对尖孢镰刀菌具有负效应,效应系数分别为-2.27,-1.55和-0.57。【结论】生防菌剂通过调节土壤养分含量和生物酶活性影响生态系统的养分循环,进而影响土壤微生物群落结构和功能多样性,降低病原菌的相对丰度,从而发挥防治枯萎病害的作用。

【Objective】This study investigated the effects of different biocontrol agents on microbial community structure and Fusarium oxysporum f.sp.to provide basis for understanding the inhibition of watermelon Fusarium wilt by biocontrol agents.【Method】Watermelon seedlings were transplanted into the watermelon soil with continuous cropping for 20 years,and they were divided into four treatments of roots injection with 1 mL biocontrol agents of Bacillus amyloliquefaciens B6(B6),Pseudomonas brassicacearum WF19(WF19),B6 and WF19 compound bacterial solutions(bacterial content of each bacterial solution was 1×108 CFU/mL,BW)and sterile water(control).After watermelon harvest,rhizosphere soil was collected,and soil pH,contents of organic matter(OM),total nitrogen(TN),nitrate nitrogen(NO^(-)_(3)-N),ammonium nitrogen(NH^(+)_(4)-N),total phosphorus(TP),available phosphorus(AP),total potassium(TK)and available potassium(AK)and activities of catalase(CAT),alkaline phosphatase(ALP),urease(URE)and sucrase(SUC)were measured.The changes of microbial communities in the rhizosphere soil of watermelon were analyzed by high-throughput sequencing(Illumina Hiseq)technology.The effects of soil physical and chemical factors,enzyme activities and microbial functions on Fusarium were evaluated based on path analysis and SEM structural equation.【Result】Biocontrol agent B6 increased the activities of four soil enzymes and the contents of TN,TP,AP,NO^(-)_(3)-N,NH^(+)_(4)-N and OM,but decreased the contents of AK and TK.WF19 increased CAT,ALP and SUC activities,decreased URE activity and TN content,and increased TP,AP,TK,AK,NO^(-)_(3)-N,NH^(+)_(4)-N and OM contents in soil.BW increased soil NO^(-)_(3)-N content and CAT and SUC activities,while decreased URE and ALP activities and soil TN,TP,TK,AP,AK,NO 3--N and OM contents.After biocontrol agents application,the relative abundance of Fusarium oxysporum f.sp.decreased in WF19 and BW treatments,and that of Gibberella decreased in B6 treatments.AP and TP contents and URE activity had the greatest correlation with bacterial community structure,while AP and TK contents and URE activity had the greatest correlation with fungal community structure.Nitrate respiration(-2.27),nitrogen fixation(-1.55)and nitrite ammonization(-0.57)had negative effects on Fusarium oxysporum f.sp.【Conclusion】Biocontrol agents affected the nutrient cycle of the ecosystem by regulating soil nutrient content and soil enzyme activity,impacted soil microbial community structure and functional diversity,and reduced relative abundance of phypathogen,so as to inhibit fusarium wilt.