Botrytis cinerea, the culprit behind botrytis blight, also known as gray mold, has long plagued greenhouse crops as the most prevalent and economically destructive disease. Although fungicides have traditionally been the go-to method for control, there’s growing concern over certain Botrytis strains developing resistance to these chemical treatments. However, a ray of hope emerges from the deployment of beneficial bacteria, which are proving to be effective biological control agents for disease management.
A research team led by the Jones Laboratory at Ohio State University has undertaken an exhaustive examination of beneficial bacteria to identify strains capable of mitigating Botrytis blight in petunia. These groundbreaking experiments have spotlighted specific strains of Pseudomonas bacteria as highly effective microbial biocontrol agents (MBCAs). In addition, these bacteria have been meticulously characterized to unveil their potential modes of action in reducing the severity of Botrytis blight.
Crucially, the American Floral Endowment (AFE) has played a pivotal role in facilitating this research through a generous research grant. For those keen to delve deeper into the comprehensive findings, the complete reports can be found in part 1 and part 2 of the research. Interested readers can also find additional information in the research paper authored by South et al. in 2020.
Furthermore, the AFE’s Thrips and Botrytis Research Library, which has recently been released, offers valuable resources for managing Botrytis blight. The library, generously provided free of charge by the industry’s sponsors, serves as a one-stop repository. It is packed with informative webinars, insightful fact sheets, and engaging articles that delve into the latest research and implementation strategies. What’s more, it offers resources in both English and Spanish, including research reports that growers can promptly integrate into their business practices.
Methods and Results:
The research team explored the notion that a consortium or community of bacteria might be more effective in controlling diseases like Botrytis blight compared to a single bacterial strain. To put this theory to the test, they evaluated individual strains and combinations of strains on detached flowers of Petunia × hybrida ‘Carpet Red.’ The selected flowers were four days post-opening, as older flowers tend to be more susceptible to Botrytis infection.
Each flower was treated by spraying it with a specific bacterial solution. After allowing the bacteria solution to dry on the flowers for two hours, the flowers were exposed to a Botrytis spore solution. These infected flowers were then enclosed within Plexi-glass chambers, hermetically sealed with weather stripping to create a high-humidity environment, and covered with cloth to reduce light exposure. These conditions were maintained at room temperature to optimize disease development. After 48 hours, each flower was meticulously assessed for disease severity using a rating scale ranging from 0 to 4.
The results were highly promising. The research demonstrated that combinations of bacterial strains, including 14B11, 15H3, AP54, 14B11+AP54, and 15H3+AP54, significantly reduced the severity of Botrytis disease on petunia flowers. However, combinations such as 14B11+15H3 and 14B11+15H3+AP54 did not yield the same positive results, indicating that certain strains have adverse interactions and should not be used jointly in treatment.
This breakthrough underscores the potential of combining multiple bacterial strains as a powerful tool in creating effective MBCAs that can combat a diverse range of floriculture crops. The researchers have also pinpointed key laboratory assays that should be conducted to assess bacteria for their suitability in consortium formulations. Through both laboratory tests and plant trials, the team has identified bacteria consortia that act as potent MBCAs against Botrytis in petunia, as well as individual strains that stand as highly efficient standalone solutions in reducing the severity of the disease.