Isolation and identification of Colletotrichum species causing anthracnose on pepper in Sichuan and the antibacterial activity of capsaicinoids

ZHU Li; LIU Yushan; SHANG Di; ZHANG Jun; ZHANG Weishan; SUN Ting; CAI Chen; ZHONG Minhan; REN Yali

doi:10.16861/j.cnki.zggc.2025.0696

Abstract：To clarify the species composition and dominant pathogens of pepper anthracnose in Sichuan province,and to investigate the inhibitory effects of capsaicinoids(capsaicin and dihydrocapsaicin)on the growth of the pathogens,provid-ing a basis for the development of green control strategies,this study collected 16 diseased pepper fruit samples from 11 counties/districts in Sichuan,including Chengdu and Luzhou.The pathogens were isolated via tissue separation,purified through single-spore isolation,and species identification based on pathogenicity tests,morphological characteristics,and polygenic phylogenetic analysis.In vitro toxicity of capsaicinoids was assessed using mycelial growth inhibition assays.The results showed the pathogens causing pepper anthracnose belonged to three species:Colletotrichum scovillei,Colleto-trichum truncatum,and Colletotrichum fructicola.Among them,C.scovillei was the dominant species,with an isolation frequency of 50.00%,and exhibited the strongest pathogenicity across five major cultivated pepper varieties.Certain con-centrations of capsaicin and dihydrocapsaicin significantly inhibited the mycelial growth across all three pathogens..The inhibitory effects of the two compounds were similar against the same pathogen but varied among different pathogens.Specifically,the strongest inhibition was observed against C.truncatum,with EC50 values of 43.48 and 46.89 mg·L-1 for capsaicin and dihydrocapsain,respectively,while the weakest inhibition was against C.fructicola.In summary,C.scovil-lei,C.truncatum,and C.fructicola were identified as the main pathogens causing pepper anthracnose in Sichuan in 2024,with C.scovillei being dominant species in the sampled areas and demonstrating strong pathogenicity.Capsaicin and dihy-drocapsaicin exhibited significant inhibitory activity against these major pathogens,particularly C.truncatum.Given their natural origin and environmental compatibility,capsaicinoids hold potential as natural additives for developing green pes-ticides or synergists for chemical pesticides in the control of pepper anthracnose.