2025/10/23 by Natalia Piñeros-Guerrero, Daniel W. Heck, Frank S. Hay +1 · 1 voice
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Fungal Plant Pathogen Control #Plant Disease Resistance and Genetics #Plant Pathogens and Fungal Diseases
paper · doi:10.1094/phyto-06-25-0209-r
openalex created_date 2025/10/23 · openalex publication_date 2025/10/23 · openalex updated_date 2026/07/22
Stemphylium leaf blight (SLB), caused by the fungus Stemphylium vesicarium, is a devastating foliar disease affecting onions in New York state. Primary inoculum sources for SLB epidemics potentially include infected transplants used to establish crops and volunteer onions remaining from the previous season, but little is known about their relative contribution to the population biology of S. vesicarium. In this study, 537 S. vesicarium isolates were obtained during 2022 and 2023 from infected transplants and volunteers, as well as symptomatic main crop plants collected during the mid- and late seasons. To evaluate the relative contributions of infected transplants and volunteers to S. vesicarium populations in New York, nine simple sequence repeat markers were used to characterize the genetic diversity and structure of populations by source and year. A total of 399 multilocus genotypes (MLGs) were identified, of which 27 MLGs were shared among two or more source populations and 28 between year populations. Structure analysis showed that populations from transplants were distinct from volunteers and main crop plants collected during the mid- and late seasons with low admixture. Populations had high genotypic diversity and genetic differentiation, also suggesting a minimal contribution of infected transplants to the New York S. vesicarium populations. The dominance of MLGs from volunteers to main crop populations suggests that the elimination of volunteers should be included in integrated disease management strategies. Crop rotation and hygiene practices to remove and destroy volunteer onions after harvest may be key to reducing the primary inoculum for SLB epidemics.