Population Structure and Mating Type Distribution of Sclerotinia sclerotiorum in Sunflower-Growing Regions

Abstract

Sclerotinia sclerotiorum is a cosmopolitan necrotrophic fungal pathogen responsible for white mold disease, causing significant yield losses in sunflower production systems worldwide. Understanding the population structure and mating type distribution of the pathogen is essential for elucidating its reproductive biology, genetic variability, and epidemiological potential. The present study investigated the population structure and mating type distribution of S. sclerotiorum isolates collected from major sunflower-growing regions. Diseased sunflower plants exhibiting characteristic stem rot, head rot, and white mycelial growth were sampled, and fungal isolates were obtained using standard isolation procedures. Molecular characterization was performed using polymerase chain reaction (PCR)-based assays targeting mating type idiomorphs to determine the distribution of MAT1-1 and MAT1-2 types within populations. Genetic diversity and population structure were further analyzed using molecular markers to assess variation among isolates across different geographical locations. The results revealed the presence of both mating types in most sampled regions, indicating the potential for sexual recombination and increased genetic variability within pathogen populations. Variation in mating type ratios was observed among locations, suggesting regional differences in population dynamics and reproductive strategies. High levels of genetic diversity were detected, reflecting the adaptive potential of the pathogen under diverse environmental and agronomic conditions. The coexistence of both mating types supports the possibility of ascospore production, contributing to long-distance dispersal and disease spread in sunflower fields. The findings provide valuable insights into the epidemiology and evolutionary biology of S. sclerotiorum and highlight the importance of population monitoring for disease forecasting. This study supports the development of effective disease management strategies aimed at reducing white mold incidence and improving sunflower productivity.