Bacteriocin Repertoires in Pseudomonas syringae pv. Tomato

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Crop Production: biological inoculants
• Farm Business Management: risk management
• Pest Management: biological control, chemical control, competition, integrated pest management, prevention
• Sustainable Communities: sustainability measures

Pseudomonas syringae pv. tomato (pto), the causal agent of bacterial speck of tomato, is an increasing problem in the Northeast and Mid-Atlantic region that can cause devastating crop losses. With the wide-spread emergence of chemical resistance in bacteria coupled with increasing severe weather events that favor the disease development, there is a need to find reliable long-term management strategies. One potential solution is by using bacteriocins. Bacteriocins are proteinaceous antimicrobial compounds bacteria use to kill closely related bacteria and are considered promising and safe potential agricultural bactericides and biological control agents. They could provide a sustainable alternative or complimentary strategy for managing problematic bacterial diseases in both conventional and organic systems. Current biological control strategies ignore complex community interactions, and therefore fail to produce reliable outcomes. In order to understand the role bacteriocins play in the development of bacterial speck of tomato, the competitive interactions that correlate to increased disease development due to bacteriocins in pto will be assessed. First, the targets of pto’s bacteriocin repertoire will be identified to determine susceptible community members. Then two ecological strategies (invasion & defending) will be evaluated with microbiome transplant experiments to understand when during the disease cycle (e.g. colonization & epiphytic survival) bacteriocins are most beneficial to the pathogen. This data can be applied to determine how and when to manipulate the foliar microbial community to effectively control the pathogen during critical points of the disease cycle for future microbial community-centered management strategies.

The specific objectives of this proposal are:

1. Determine targets of individual bacteriocins in pto’s Expected outcome: This objective will identify the pathogen’s bacteriocin targets in order to understand how to limit these advantages in a community. I hypothesize that by identifying mutants resistant to knockout strains of pto that contain only 1 bacteriocin, I will be able to identify key components of the genome that contribute to mitigating competitive advantages within the context of a community.
2. Assess level of foliar disease symptoms in tomato plants and determine the change in microbial community composition due to individual bacteriocins, after transplant communities are introduced to plants that have first been inoculated with pto. The purpose of this objective is to identify pto bacteriocins that contribute to disease severity of bacterial speck of tomato and identify microbial community changes due to ptobacteriocins after pto has penetrated the surface of the leaf. I hypothesize that individual bacteriocins will significantly contribute to different amounts of disease symptoms and to changes in community composition after pto has penetrated the leaf surface.
3. Assess the level of foliar disease symptoms in tomato plants and determine the change in community composition due to individual bacteriocins after pto is introduced to a plant that has an established microbial transplant community. The purpose of this objective is to identify pto bacteriocins that contribute to disease severity of bacterial speck of tomato and identify microbial community changes due to pto bacteriocins before pto has penetrated the leaf surface. I hypothesize that individual bacteriocins will significantly contribute to different amounts of disease symptoms and to changes in community composition before pto has penetrated the leaf surface.