ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbe and Virus Interactions with Plants
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1666712
Spatiotemporal analysis of the structure and genetic diversity of Stemphylium vesicarium populations in New York onion fields
Provisionally accepted
- Cornell University Plant Pathology and Plant-Microbe Biology Section, Ithaca, United States
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Stemphylium leaf blight (SLB), caused by the hemibiotrophic fungus, Stemphylium vesicarium, is the dominant foliar disease affecting onions in New York (NY), U.S.A. The development of integrated disease management strategies for SLB is challenged from the lack of information surrounding phylodynamics and evolutionary patterns of the causal organism. This study evaluated the spatiotemporal patterns of genetic diversity, differentiation and population structure of 210 S. vesicarium isolates from populations collected over six years (2016 to 2022) across five onion production regions in NY using nine microsatellite loci. A total of 158 multilocus genotypes (MLGs) were identified among the 210 isolates, indicating high genetic diversity and genotypic variation. Low genetic differentiation was observed across spatial and temporal populations, with greater genetic variation within populations than between them. Population structure analyses using multiple approaches revealed no clear temporal or spatial genetic patterns, although isolates from 2016 and the Orange County region showed some genetic divergence. Additionally, significant linkage disequilibrium among loci suggested a predominantly clonal population structure in all regions, except the Finger Lakes, which displayed nonsignificant linkage disequilibrium. These findings highlight the complex population biology and dynamics of S. vesicarium, characterized by high genetic diversity, admixture, and mixed reproduction modes and emphasize the challenges in managing SLB, as these characteristics can enable rapid population adaptation to diverse environmental conditions and management practices.
Keywords: Allium, genetic diversity, microsatellites, onion, Population Biology, population structure, Stemphylium vesicarium
Received: 17 Jul 2025; Accepted: 26 Aug 2025.
Copyright: © 2025 Subedi, W. Heck, Hay, Guerrero and Pethybridge. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Sarah Pethybridge, Cornell University Plant Pathology and Plant-Microbe Biology Section, Ithaca, United States
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