Volatile organic compounds from Streptomyces rochei TRM68247: fumigant biocontrol against postharvest diseases of Korla fragrant pear and identification of active antifungal components

Abstract

Long-term application of synthetic fungicides leads to severe residue risks and pathogen drug resistance during postharvest storage of Korla fragrant pear ( Pyrus sinkiangensis ), making it urgent to develop low-residue gaseous biopreservation agents. This study investigated the fumigant biocontrol capacity of volatile organic compounds (VOCs) produced by desert-derived Streptomyces rochei TRM68247 against two dominant postharvest pathogens, Valsa pyri and Alternaria gaisen . Whole-genome sequencing was performed to identify biosynthetic gene clusters (BGCs) associated with volatile secondary metabolism. Volatile compounds were profiled by GC-MS, and core bioactive substances were screened and validated by in vitro dual-plate assays. Fumigation efficacy was further evaluated on pear twigs and on wounded, inoculated fruits under simulated storage conditions, with commercial eugenol included as a positive control. Strain TRM68247 harboured abundant BGCs supporting stable production of antifungal volatiles under storage conditions. GC-MS identified 44 volatile components, among which 2-ethyl-1-hexanol and 3,5-di-tert-butylphenol were screened as core bioactive substances. In vitro dual-plate tests showed that 2-ethyl-1-hexanol exerted broad and strong inhibitory activity against both fungi. Fumigation with VOCs from TRM68247 significantly retarded lesion expansion and blocked deep pulp infection, and the control efficacy against fruit black spot was comparable to that of commercial eugenol. VOCs from S. rochei TRM68247 are promising candidate fumigants for reducing postharvest rot loss of Korla fragrant pear, and the present work supplies two natural volatile antifungal compounds for the development of green fruit-preservation technology.