Revealing Pathogens and Disease‐Associated Ascomycetes in Post‐Harvest <i>Citrus</i> and <i>Psidium</i> Fruits in Markets in Northern Thailand

ABSTRACT Diseases caused by fungal pathogens are a major cause of losses in fruit crops in Thailand, degrading fruit quality during both pre‐ and post‐harvest stages, reducing the marketable yield and in some cases producing mycotoxins that pose serious health risks to humans. This study focuses on identifying Ascomycota associated with post‐harvest fruit diseases and understanding their pathogenicity in northern Thailand. Symptomatic fruits of Citrus and Psidium were randomly collected from various local markets. The study investigated the presence of six ascomycetes: Lasiodiplodia pseudotheobromae , Colletotrichum gloeosporioides and Fusarium sulawesiense from Citrus species, as well as Phyllosticta capitalensis , Colletotrichum endophyticum and Neopestalotiopsis formicarum from Psidium species. Species boundaries were confirmed using morphology and DNA‐based multigene phylogenetic analyses. Pathogenicity assays confirmed that L. pseudotheobromae and C. gloeosporioides caused symptoms on young and healthy citrus fruits, whereas symptoms did not develop with C. endophyticum , N. formicarum and F. sulawesiense .