土传植物病原青枯菌 Ralstonia solanacearum （RS）的环境胁迫进化适应能力强，其对生防菌产生适应性进化可能是生防产品难以稳定控病的重要原因之一。前期研究发现相对于单一措施，寄生侵染型噬菌体和竞争型生防细菌配合能有效提高土传青枯病防控效率。本研究拟从噬菌体协同生防细菌阻控RS进化适应性的角度，运用Trade-off理论，阐明两者协同高效抑病的作用机制。我们推测当RS面对双重生物胁迫时，可能1）通过减少 对致病力的投入，来维持其生存；2）对一种生物胁迫产生进化抵抗时，会降低其对另一种生物胁迫的抵抗能力；导致其整体生存或致病能力下降。拟以拮抗竞争型生防细菌、营养竞争型生防细菌和寄生侵染型噬菌体为材料，应用微生物生态学、实验进化学和转录组学等研究方法，从生理和基因水平上揭示不同生物胁迫下RS进化适应的Trade-off机制，为开发高效稳定的生防产品提供理论和技术支撑。

The increasing demand for food supply requires more efficient control of plant diseases. Biocontrol, the use of natural antagonists or competitors, has recently re-emerged as a promising alternative to chemical pesticides. However, it is well know that pathogen quickly evolves to adapt the changing surrounding environment, especially the abiotic (e. g., chemical pesticides) and biotic (e. g., interference competition and parasitism) pressures, making it difficult to consistently reproduce the beneficial effects of biocontrol. Previous study shows that the incidence of bacterial wilt disease of tomato caused by the pathogen Ralstonia solanacearum (a soilborne bacterial pathogen) is significantly reduced by combination of R. solanacearum-antagonistic bacterium (interference competition) and R. solanacearum-specific phages (parasitism), compared with interference competition or parasitism treatment alone or the control treatment. Here we will use real-time experimental evolution to study these complex dynamics in laboratory and tomato plant rhizosphere. We will concentrate on devastating plant pathogen, R. solanacearum bacterium and three different biocontrol agents: pathogen-specific viruses (phages) and bacterial competitors, Bacillus amyloliquefaciens T-5 that show direct antagonism towards the pathogen, Ralstonia pickettii QL-A6 that could not produce antibacterial substrates and only compete fiercely from plant-derived nutrients in the rhizosphere. We will first study the effect of application of bacterial competitors alone or combining with phage on pathogen invasion both in the lab and greenhouse conditions. On the basis of the trade-offs theory, we expect the pathogen resistance evolution will be constrained by applying different biocontrol agents in combination. The evolved pathogen colonies will be isolated from different biocontrol agents’ combination treatment, and their phenotypic, physiological and genetic changes will be evaluated and compared with those of the ancestral pathogen. We expect that when facing the pressures from competitive biocontrol bacteria and parasitic phage, the pathogen R. solanacearum 1) will loss the virulence to maintain its survival in certain environment; 2) will loss the ability to be resistant to one pressure if it evolves to be resistant to this other pressure; and finally loss its ability to survive and infect host plant. We will also compare which biotic pressures (interference competition, nutrition competition and parasitism) drive pathogen evolution process more and which direction to evolve by using the transcriptome study. Finally lab, greenhouse and field experiments will be carried out to test how abiotic environment (resource level and temperature) affect the success of biocontrol outcomes. Proposed research will help to understand eco-evolutionary dynamics in complex microbial communities and offers a novel and predictive framework for applied agriculture to manipulate plant root communities in evolutionary stable manner.