SUSTAINABLE MANAGEMENT OF MANGO FRUIT ROT: BIOCONTROL OF Diaporthe BY Streptomyces flaveus RT1-1

Mango is one of Vietnam’s most important tropical fruit trees, valued not only for its appealing taste but also for its rich content of vitamins, minerals, and antioxidants that promote good health. Despite being easy to cultivate and adaptable to various soil conditions, mango trees are often susceptible to diseases that significantly impact their growth, development, yield, and fruit quality. Among these, fruit rot is a major concern, particularly stem-end rot, which can severely affect mangoes after harvest. Currently, disease management primarily relies on chemical fungicides, which pose serious risks to human health, contribute to environmental pollution, promote the emergence of drug-resistant fungi, and disrupt microbial ecosystems. In this study, a stem-end rot-causing fungus was isolated from mango fruits collected at Thanh Xuan Market, District 12, Ho Chi Minh City, Vietnam. The isolated fungus exhibited branched, septate hyphae and distinct α- and β-conidia. Pathogenicity was confirmed by re-inoculation onto fresh mango fruits, which developed typical rot symptoms. Molecular identification based on sequencing of an 820 bp rDNA fragment and phylogenetic analysis revealed that the isolate was closely related to Diaporthe strains. Accordingly, the isolate was named Diaporthe TX12 HCMC. The antifungal activity of Streptomyces flaveus RT1-1 against Diaporthe TX12 HCMC was evaluated through a co-culture assay on PDA. The result showed an average inhibition of 71.83 ± 1.82%, suggesting that extracellular metabolites produced by S. flaveus RT1-1 probably diffused into the agar medium and inhibited the fungal growth. These findings highlight the potential of S. flaveus RT1-1 as a biocontrol agent against Diaporthe-induced stem-end rot in mangoes, offering a promising alternative to synthetic fungicides for management of postharvest fruit rot.