Impact of antibiosis in the rhizosphere on pathogenicity gene activation and biocontrol of bacterial-mediated solanaceous plant diseases

针对某些疾病的化学控制措施无效以及公众对在环境中使用化学品的关注，促使人们对植物病原体的生物防治日益感兴趣。已经证明，一些根瘤菌，如假单胞菌，可以在体外或受控条件下使用抗生素控制植物病原体种群，这涉及到抗菌代谢物的产生。然而，抗生素在土壤条件下的效率仍然是可变的，这解释了为什么只有少数产生抗菌代谢物的根细菌菌株被商业化。更好地了解植物根际微生物动力学和抗生素的原位作用将有利于大规模使用假单胞菌进行生物防治。茄类植物，主要是马铃薯和番茄，对加拿大经济很重要。这些作物受到许多病原体的侵袭，造成重大的经济损失。在此，我建议研究产生抗菌代谢物的假单胞菌（Pseudomonas sp.）的定制接种对茄科两种重要的植物致病菌——马铃薯常见痂的疥疮链霉菌（Streptomyces scabies）和密歇根键杆菌（Clavibacter michiganensis subsp）的疾病保护作用。引起番茄细菌性枯萎和溃疡病的密歇根菌。本研究的总体目标是在分子水平上了解抗生素如何在根际起作用，它对细菌病原体定植和感染植物的影响，以及它对茄类疾病的保护作用。具体目标是：1)表征马铃薯和番茄根际假单胞菌抗菌代谢物产生的转录活性及其对控制植物细菌性病害的影响。2)研究根瘤菌抗菌代谢物产生对疥疮S.疥疮和密歇根C. m.m akanensis致病性和毒力基因激活的影响。评估抗菌代谢物是否可以在根际持续产生，并确定这是否可以抑制病原体的致病性和毒力基因激活，这是控制茄科植物疾病的一个有趣途径。

An increased interest in biocontrol of plant pathogens has been fuelled by ineffective chemical control measures against certain diseases and public concern over the use of chemicals in the environment. It has been demonstrated that several rhizobacteria, such as Pseudomonas spp., can control plant pathogen populations under in vitro or controlled conditions using antibiosis, which involves the production of antimicrobial metabolites. However, the efficiency of antibiosis under soil conditions is still variable, explaining why only few antimicrobial metabolite-producing rhizobacterial strains have been commercialized. A better understanding of the microbial dynamics in the rhizosphere of plants and in situ action of antibiosis would favour large-scale use of Pseudomonas spp. for biocontrol. Solanaceous plant species, mainly potato and tomato, are important to the Canadian economy. These crops are attacked by numerous pathogens causing important economic losses. Here, I propose to study the impact of tailored antimicrobial metabolite producing Pseudomonas spp. inoculations on disease protection against two important bacterial plant pathogens affecting Solanaceae: Streptomyces scabies causing common scab of potato and Clavibacter michiganensis subsp. michiganensis causing bacterial wilt and canker of tomato. The general goal of this research is to understand, at the molecular level, how antibiosis operates in the rhizosphere, its effect on the colonization and infection of plants by bacterial pathogens, and the protection it offers against Solanaceous diseases. Specific goals are to: 1) Characterize the transcriptional activity associated with Pseudomonas spp. antimicrobial metabolite production in the rhizosphere of potato and tomato and its impact on controlling bacterial plant diseases. 2) Study the impact of rhizobacterial antimicrobial metabolite production on pathogenicity and virulence gene activation in S. scabies and C. m. michiganensis. Assessing if antimicrobial metabolite production can be sustained over time in the rhizosphere and determining if this can repress pathogenicity and virulence gene activation in pathogens represents an interesting avenue to control Solanaceous plant diseases.