Key factors influencing fate and activity of bacterial inoculants and their effect on the indigenous microbial community in the rhizosphere

如果拮抗细菌的根际竞争力和生防效率更可预测，则拮抗细菌的使用可能是保护植物免受土传病原菌侵害的环境友好的替代方案。本项目旨在验证土壤类型和植物种类影响接种菌株根际竞争力和生防效率的假设。反之，根际微生物群落的结构多样性可能直接或间接地受到接种物的影响，这可能会导致根系形态和分泌模式的变化，从而影响接种物的根际竞争力。在一系列针对立枯丝核菌（Rhizoctonia solani）的体外拮抗剂中，两个菌株（假单胞菌（Pseudomonasjessenii）RU 47和萨氏沙雷氏菌（Serratia alummuthica）3Re 4 -18）反复显示出显著的减轻由立枯丝核菌（Rhizoctonia solani）引起的莴苣底腐病症状和严重程度的能力。solani AG 1-IB.这两种模式菌株产生几个因素可能有助于其生物控制活性，这至少在后者菌株的群体感应调节。尽管菌株RU 47仅定殖于莴苣的根表面，但菌株3Re 4 -18也在根组织内部检测到。在Großbeeren的蔬菜和观赏作物研究所（IGZ）现场的独特实验装置将使我们能够在田间条件下测试土壤类型对同一地点两种拮抗剂根际竞争力（莴苣）的影响。在第三年，将测试两个菌株在莴苣和马铃薯上的定殖能力和拮抗性能。将使用DsRed标记的菌株进行生长室实验，以评估土壤类型和植物物种如何影响定殖模式、根形态和渗出模式。一个多相的方法，包括先进的方法将被用来解开接种菌株，病原体，土著微生物群落和植物之间的复杂的相互作用。

The use of antagonistic bacteria could be an environmentally friendly altemative to protect plants from soil-borne pathogens if the rhizosphere competence and biocontrol efficiency of the antagonists would be more predictable. In this project, we aim to test the hypothesis that the soil type and plant species influence the rhizosphere competence and biocontrol efficiency of inoculant strains. Vice versa the structural diversity of the indigenous microbial community in the rhizosphere might be affected by the inoculation either directly or indirectly due to the interaction of the inoculant with the plant, which might result in changes of the root morphology and exudation patterns, with potential impact on the rhizosphere competence of the inoculants. Amongst a collection of in vitro antagonists towards Rhizoctonia solani previously tested under growth chamber and field conditions, two strains (Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18) repeatedly showed a remarkable ability to reduce disease symptoms and severity of bottom rot disease on lettuce caused by R. solani AG 1-IB. Both model strains produce several factors potentially contributing to their bio-control activity, which at least in the latter strain are quorum sensing regulated. Whereas strain RU47 colonized only the root surface of lettuce, strain 3Re4-18 was also detected inside of the root tissue. The unique experimental setup at the field site of the Institute of Vegetable and Ornamental Crops (IGZ) in Großbeeren will enable us to test the influence of soil types on the rhizosphere competence (lettuce) of both antagonists at the same site under field conditions. In the third year the colonizing ability and the antagonistic performance of both strains will be tested on lettuce and potato. Growth chamber experiments with DsRed-tagged strains will be performed to assess how the colonization patterns, the root morphology and the exudation patterns are influenced by the soil type and the plant species. A polyphasic approach comprising advanced methods will be used to unravel the complex Interactions between inoculant strains, the pathogen, the indigenous microbial community and the plant.