脂肪酸类天然产物2E,4E-癸二烯酸对烟草根际微生物群落的影响

Effect of Fatty Acid Natural Product 2E,4E-Decadienoic Acid on Tobacco Rhizosphere Microbial Communities

【目的】脂肪酸类化合物2E,4E-癸二烯酸(2E,4E-decadienoic acid,DDA)为枯草芽孢杆菌(Bacillussubtilis)Tpb55与棘孢木霉(Trichodermaasperellum)HG1共培养发酵产物,对疫霉具有特异性抑制作用。论文旨在评价DDA防治烟草疫霉(Phytophthoranicotianae)引起的烟草黑胫病的效果及其对根际土壤微生物群落的影响,为该类天然产物在植物疫霉病害防治上的应用提供依据。【方法】通过温室盆栽试验测定DDA对烟草黑胫病的防治效果,采用实时荧光定量PCR技术检测处理后根际土壤中烟草疫霉DNA拷贝数,利用Illumina Hiseq高通量测序分析烟草根际土壤细菌、真菌和卵菌群落结构,基于冗余分析和Mantel检验研究土壤养分因子与微生物群落结构的相关性。【结果】与对照(0.5%DMSO)处理相比,1.25 g·L-1的DDA溶液灌根处理组烟草黑胫病病情指数和烟草根际烟草疫霉DNA拷贝数分别降低77.06%和84.35%,土壤pH由6.72增至6.82,电导率增加102.11%,有机质含量则降低13.05%。DDA灌根处理对烟草根际土壤真菌和细菌多样性和丰富度无显著影响,但卵菌的OTU水平、香农指数、Chao1指数和ACE指数显著增加,辛普森指数显著降低。主坐标分析结果显示,DDA处理显著影响烟草根际卵菌群落结构(r=0.667,P=0.028),对真菌(r=0.259,P=0.305)和细菌(r=0.593,P=0.098)则无显著影响。DDA处理组烟草根际土壤Phycicoccus、地杆菌属等革兰氏阳性细菌菌属的相对丰度显著增加,德沃斯氏菌属、鲍特氏菌属、假黄单胞菌属等革兰氏阴性细菌菌属丰度显著降低,曲霉属、Albifimbria、Arcopilus、树粉孢属等植物有益真菌菌属得到显著富集,疫霉属相对丰度显著下降、腐霉属丰度显著上升。Mantel检验结果表明,施用DDA引起的土壤理化性质变化对根际微生物群落无显著影响。【结论】2E,4E-癸二烯酸(DDA)作为一种新型天然脂肪酸化合物,能够有效防治烟草黑胫病、降低烟草根际黑胫病菌数量,并特异性调控烟草根际卵菌群落结构,具有防治作物卵菌病害的应用潜力。

【Objective】The fatty acid compound 2E,4E-decadienoic acid(DDA)was obtained from coculture of Bacillus subtilis Tpb55 and Trichoderma asperellum HG1,which has a specific inhibitory effect on Phytophthora.The objective of this study is to evaluate the effects of DDA on tobacco black shank(caused by P.nicotianae)and on the microbial community of tobacco rhizosphere soil,and to provide a basis for the application of such natural products in the prevention and control of plant Phytophthora disease.【Method】To evaluate the control efficacy of DDA against tobacco black shank,a pot experiment was performed,and the DNA copies of P.nicotianae in tobacco rhizosphere soil were detected by real-time fluorescence quantitative PCR technique.The bacterial,fungal and oomycetal communities in tobacco rhizosphere soil were analyzed through Illumina Hiseq high-throughput sequencing,and the correlation between soil nutrient factors and microbial community structure was assayed based on redundancy analysis and Mantel test.【Result】Compared with the control treatment with 0.5%DMSO,the treatment with 1.25 g·L-1 DDA for root irrigation showed 77.06%and 84.35%decrease for black shank disease index and P.nicotianae DNA copy number,respectively.DDA treatment also significantly increased the soil pH from 6.72 to 6.82,improved the soil conductivity by 102.11%,and decreased the soil organic matter by 13.05%.DDA treatment had no significant effect on the diversity and richness of fungi and bacteria in tobacco rhizosphere soil.However,the OTU level,Shannon index,Chao1 index,and ACE index of oomycetes significantly increased,while the Simpson index significantly decreased.The PCoA results showed that DDA treatment significantly affected the structure of tobacco rhizosphere oomycete community(r=0.667,P=0.028),but had no significant effect on fungi(r=0.259,P=0.305)and bacteria(r=0.593,P=0.098).The relative abundance of gram-positive bacterial genera such as Phycicoccus and Terrabacter significantly increased in DDA treatment,while the abundance of gram-negative bacterial genera including Devosia,Bordetella and Pseudoxanthomonas significantly decreased.Some beneficial fungi such as Aspergillus,Albifimbria,Arcopilus were enriched by DDA.For oomycetes,the relative abundance of Phytophthora was significantly decreased,but that of Globisporangium increased.The Mantel test results indicated that the changes in soil physicochemical properties caused by the application of DDA had no significant impact on the rhizosphere microbial community.【Conclusion】2E,4E-decadienoic acid(DDA),as a novel natural fatty acid compound,can effectively prevent and control tobacco black shank,reduce the pathogen DNA copy number in tobacco rhizosphere soil,and specifically regulate the structure of oomycete community.It has the application potential in the prevention and control of crop oomycete diseases.