Culturable Molds and Their Mold-causing Potential on Hunan Tobacco Leaves at Different Processing Stages

To investigate the diversity of mold species cultured on tobacco leaves during processing stage, samples were collected from Hunan production areas at three distinct stages: post-flue-curing before redrying, post-redrying before aging, and during aging. The isolated molds were cultured, classified, and subjected to species identification. Mold-causing potential tests were conducted on strains isolated from the surfaces of tobacco leaves. Analysis revealed the isolation and purification of 10 culturable mold isoltes across different stages. Upon BLAST comparison, these isolates were categorized into 2 phyla and 8 genera. Following the flue-curing before redrying stage of tobacco leaves in Hunan's counties and cities, Aspergillus flavus was predominant, whereas after redrying stage and during aging stage, A. fumigatus and Penicillium citrinum dominated, respectively. Additionally, among the four isolates from moldy tobacco leaves during aging stage, Periconia epilithographicola and Botryotrichum murorum were discovered for the first time, P. citrin and Cladosporium asperulatum were the primary mold-causing fungi on the tobacco leaves from Hunan production areas during aging stage. Except for Lichtheimia sp. and A. fumigatus, the other 8 out of the 10 isolated mold strains were observed with mycelial growth on tobacco leaves at 90% relative humidity, which confirmed their mold-causing potential. The study identified the dominant microbial communities and the spoilage potential of major mold-causing fungi on tobacco leaves across various processing stages, offering a practical reference for mold prevention and control in Hunan's tobacco-producing regions.