Shifting Populations and Increasing Diversity of Colletotrichum Species Causing Pepper Anthracnose Under Rising Temperatures and Fungicide Selection Pressure.

Abstract

Pepper anthracnose, a devastating and economically important disease in Korea, is caused by diverse Colletotrichum species that differ significantly in their pathogenicity and environmental adaptation. In a three-year study from 2022 to 2024, pathogens were isolated and species characteristics were investigated. Using multilocus phylogenetic analysis and species-specific PCR, seven species were identified: C. scovillei, C. nymphaeae, and C. fioriniae in the C. acutatum species complex; C. fructicola, C. aenigma, and C. gloeosporioides in the C. gloeosporioides species complex; and C. truncatum. C. scovillei remained dominant, but species diversity increased in 2024, with non-dominant species such as C. fructicola and C. truncatum increasing in specific regions. Temperature-dependent assays revealed distinct ecological niches, showing that while C. scovillei prefers a moderate 25°C, high temperature-adapted species like C. fructicola and C. truncatum exhibit enhanced growth and pathogenicity at 30°C. Fungicide sensitivity tests showed that tebuconazole and fluazinam remained effective against all species of Colletotrichum, whereas pyraclostrobin (QoI) resistance was widespread. The mycelial growth inhibition of C. scovillei by pyraclostrobin ranged from 29.5% to 43.3% during 2022-2024, indicating reduced sensitivity. All C. truncatum isolates were resistant, consistently associated with the G143A mutation in the cytb gene. These findings indicate that climate warming and fungicide selection pressure are driving shifts toward more resilient populations, highlighting the need for climate-adaptive disease management through monitoring and fungicide rotation.