Effect of Fatty Acid Natural Product 2E,4E-Decadienoic Acid on Tobacco Rhizosphere Microbial Communities
[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.
Trichoderma asperellumBacillus subtilistobacco black shankcoculture2E,4E-decadienoic acid(DDA)rhizosphere microbial community
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