Identification, Characterization, Pathogenicity, and Fungicide Sensitivity of Postharvest Fungal Diseases in Culinary Melon from Northern Thailand

Culinary melon (<i>Cucumis melo</i> subsp. <i>agrestis</i> var. <i>conomon</i>) is widely cultivated throughout Thailand and represents an important agricultural crop. During 2023-2024, anthracnose, charcoal rot, and fruit rot caused by fungi were observed on postharvest culinary melon fruits in northern Thailand. This study aimed to isolate and identify fungal pathogens associated with these postharvest diseases in culinary melons, as well as to assess their pathogenicity. Eight fungal strains were isolated and identified through morphological characterization and multi-gene phylogenetic analysis. <i>Colletotrichum chlorophyti</i> and <i>C. siamense</i> were identified as the causal agents of anthracnose, <i>Fusarium sulawesiense</i> caused fruit rot, and <i>Macrophomina phaseolina</i> was responsible for charcoal rot. Pathogenicity tests were conducted, and the fungi were successfully re-isolated from the symptomatic lesions. Moreover, sensitivity tests for fungicides revealed that <i>C. siamense</i> was completely inhibited by copper oxychloride and copper hydroxide. <i>Colletotrichum chlorophyti</i> was inhibited by benalaxyl-M + mancozeb, copper hydroxide, and mancozeb. In the case of <i>M. phaseolina</i>, complete inhibition was observed with the use of benalaxyl-M + mancozeb, mancozeb, and propineb. Copper hydroxide successfully inhibited <i>F. sulawesiense</i> completely. To our knowledge, this study is the first to report <i>C. siamense</i> and <i>C. chlorophyti</i> as causes of anthracnose, <i>F. sulawesiense</i> as a cause of fruit rot, and <i>M. phaseolina</i> as a cause of charcoal rot in postharvest culinary melon fruits in Thailand. It also marks the first global report of <i>C. siamense</i>, <i>M. phaseolina</i>, and <i>F. sulawesiense</i> as causal agents of these respective diseases in culinary melon. Furthermore, the results of the fungicide sensitivity tests provide valuable information for developing effective management strategies to control these postharvest diseases in the future.