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

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.