BACTERIAL SPECK OF TOMATO: EVALUATING SUPPRESSIVE MICROBIAL COMMUNITIES FOR SUSTAINABLE DISEASE MANAGEMENT.

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Commodities

• Vegetables: tomatoes

Practices

• Pest Management: biological control

Pennsylvania cultivates about 4,000 acres of fresh market tomatoes each year, worth $15-20 million. Bacterial speck (Pseudomonas syringae pv. tomato) causes large economic losses to the tomato industry, particularly in seedling production greenhouses, due to planting dense populations and overhead watering. Current management relies on using treated disease-free seeds and disease-free transplants. However, limited effective pesticides and host resistance options necessitates exploring alternative disease management strategies such as biocontrol. Previous research focuses on individual strains of biocontrol agents, which leads to limited efficacy. To address this problem, our lab has explored the natural foliar microbiome as the biocontrol of foliar diseases in tomato. Disease suppression developed following the serial transfer of foliar communities between sensitive host plants. Building upon this work, my project aims to evaluate the efficacy of whole microbial communities in reducing disease incidence in tomato transplants and across diverse strains of the pathogen. Microbial communities will be applied to tomato seedlings, followed by pathogen inoculation at various timepoints or with different strains in a controlled growth chamber setting. Results will reveal the potential of microbial communities in mitigating disease incidence in transplants and their broad-spectrum effectiveness. These findings will help develop sustainable disease management strategies. Results will be disseminated at the Mid-Atlantic Fruit and Vegetable Convention and the National and Northeastern Divisional American Phytopathological Society meetings. Additionally, I will publish the findings as a Penn State Extension Report and in a peer-reviewed journal for widespread accessibility.

I aim to reduce incidence of bacterial speck in tomato transplants in a controlled environment setting. My hypothesis is that inoculating tomato seedlings with suppressive microbial communities will help to mitigate bacterial speck incidence, and the disease suppression will persist over time and across the diverse strains of pathogen.

The specific objectives of this proposal are:

1. Objective 1: to assess the efficacy of suppressive microbial communities to mitigate bacterial speck in ‘Mountain Fresh Plus’ tomato transplants. The suppressive microbial communities, developed by Ehau-Taumaunu and Hockett (2023) will be evaluated for disease suppression on tomato transplants within a growth chamber environment. The bacterial pathogen will be introduced at 2, 7, and 14 days after microbial community inoculations. The primary focus of the initial phase is to quantify and analyze the effectiveness of suppressive communities in reducing bacterial speck incidence in transplant tomato seedlings. Furthermore, this study elucidates whether the disease suppression persists over an extended period, our ultimate goal. Similar study previously done by Koninkx (2023) reported reduced incidence of bacterial spot of tomato in transplant production setting.

Expected outcome: It is expected that application of suppressive microbial communities will reduce bacterial speck incidence in the tomato transplants.

2. Objective 2: to evaluate the efficacy of suppressive microbial communities on multiple strains of Pseudomonas syringae pv. tomato. The aim is to investigate whether the suppressive microbial communities developed in the presence of one specific strain (DC3000) by Ehau-Tamaunu and Hockett (2023) exhibit consistent effectiveness against diverse strains of the pathogen prevalent in Northeastern United States. By introducing different strains subsequent to community inoculations, we will understand the adaptability and broad-spectrum efficacy of these suppressive communities. The strains against which communities will be assessed include Pto T1, and a New York isolate (Kraus et al. 2017; Orfei et al. 2023)

Expected outcome: This objective will identify the efficacy of microbial communities against diverse strains of Pseudomonas syringae pv. tomato.