Taxonomic and phylogenetic assessment of selected fungal pathogens associated with banana fruits in the local markets of northern Thailand

Abstract

Bananas are susceptible to various postharvest diseases caused by a diverse range of pathogens. The present study focused on the identification and characterization of two prevalent banana fruit diseases, anthracnose and speckle, in three provinces of northern Thailand. Symptomatic banana fruits were collected from local markets. Surface-sterilized, infected banana skin segments were used to isolate the associated fungi on potato dextrose agar. Morphologically distinct isolates of Colletotrichum spp. and Corynespora sp. were obtained from the anthracnose lesions and speckles, respectively. Fungal identification was based on morphology and phylogenetic analyses of the ITS, LSU, act, cmdA, tub2, chs-1, and gapdh sequences. Colletotrichum musae and C. siamense were identified as the causal agents of post-harvest anthracnose in the bananas Kluai Namwa (Musa acuminata × M. balbisiana; ABB genomic group; Pisang Awak) and Kluai Khai (M. acuminata; AA genomic group; Sucrier), respectively. Corynespora torulosa was found to cause speckles in Kluai Namwa fruits. Koch’s postulates were successfully established by inoculating fresh and unripe banana fruits with the identified strains, and confirmed the pathogenicity. Colletotrichum musae, C. siamense, and C. torulosa were re-isolated from the inoculated fruits and justified with morpho-molecular data. To our knowledge, this is the first confirmed occurrence of C. torulosa causing banana fruit speckles in Kluai Namwa in Thailand. In addition, we document the presence of C. siamense, causing post-harvest anthracnose in Kluai Khai. This study contributes to a better understanding of post-harvest banana diseases and addresses the current challenges in the commercial banana industry in northern Thailand.