PLP 894 Seminar: Santosh Koirala
December 1, 2025 1:30PM - 2:30PM
PSSB A 271 Conference Room
Factors Affecting Bacterial Survival and Field Management of Diverse Pantoea Species in the Allium-Poaceae Pathosystem
Georgia is the top producer of spring-grown onions in the US. Vidalia onion is the state vegetable of GA produced in only 20 legally specified counties. They are yellow Granex-type onions preferred for their low-pungency and sweet flavor. Diverse plant-pathogenic Pantoea species can cause center rot of onion that leads to substantial losses in the field and during storage. Pantoea stewartii subspecies indologenes (Psi), known to cause disease in millets, was recently identified to cause center rot. Psi has not been well-characterized in this novel pathosystem and its transmission risk to onions in cropping systems where millets precede onion-planting is less understood. My Ph.D. research focused on characterizing Psi strains and assessing its transmission risk from crop residue to onions. Additionally, we explored strategies to incorporate biocontrol agents (BCAs) into spray programs for center rot management. We proposed two distinct pathovars within Psi based on their pathogenicity profiles. Despite planting onion seedlings in Psi-infested soil, no bacterial colonization was observed in onion rhizosphere and leaves. Findings from our study to integrate BCAs with copper indicated that, under low disease pressure, rotation interval between BCAs and copper could be extended to 10-14 days without compromising disease control. However, tank-mix application of BCAs with copper offered no additional disease suppression. Overall, onion growers could reduce Psi transmission risk by facilitating crop residue breakdown before onion transplanting and under low disease pressure, copper can be rotated with BCAs in a spray program.
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