First Report of Colletotrichum siamense Causing Anthracnose on Mango Fruit in Tropical Production Systems

Abstract

Anthracnose, caused by species within the Colletotrichum gloeosporioides complex, represents the most destructive postharvest disease of mango (Mangifera indica L.) in tropical and subtropical production systems, resulting in extensive fruit rot, unmarketable yield fractions, and significant economic losses across the supply chain from orchard to consumer markets. While Colletotrichum gloeosporioides sensu lato has historically been regarded as the predominant causal agent of mango anthracnose, the application of contemporary molecular phylogenetic approaches has progressively revealed that multiple cryptic Colletotrichum species contribute to disease etiology, necessitating rigorous species-level identification to underpin accurate disease surveillance and targeted management interventions. This study reports the first confirmed occurrence of Colletotrichum siamense Prihastuti, L. Cai & K.D. Hyde as a causal agent of anthracnose on mango fruit in tropical production systems. Symptomatic mango fruits displaying characteristic sunken, darkened lesions with salmon-colored acervuli under humid conditions were systematically collected from commercial orchards. Fungal isolates were obtained through standard single-spore isolation protocols and subjected to comprehensive morphological characterization encompassing colony morphology, conidial dimensions, appressorium shape, and growth rate on potato dextrose agar. Pathogenicity was confirmed through wound and unwound inoculation assays on mature mango fruits in accordance with Koch's postulates. Molecular identification was accomplished through multi-locus phylogenetic analyses utilizing the internal transcribed spacer region, ACT, TUB2, CHS-1, GAPDH, and CAL gene sequences, unambiguously resolving isolates within C. siamense. This first report substantially expands the known host range and geographic distribution of C. siamense and highlights the necessity of species-specific diagnostic protocols for effective anthracnose management in tropical mango production.