Characterization of sooty blotch and flyspeck fungi on mango (Mangifera indica L.) in Peninsular Malaysia

Sooty blotch and flyspeck (SBFS) disease complex, characterized by black smudges and clusters of spots on fruit surfaces, is commonly observed on mango. This study aimed to characterize the SBFS fungi associated with mango in selected orchards in Peninsular Malaysia using morphological, molecular, and pathogenicity approaches. A total of 87 symptomatic fruits were collected from eight orchards in Perak, Pahang, and Perlis during sampling conducted between October and November 2019. The number of colonies per fruit (CPM) and the percentage of fruit surface covered by SBFS were recorded. Thirty-one purified fungal cultures representing four genera (Zasmidium, Peltaster, Exophiala, and Scolecobasidium) were identified using morphological characters. Phylogenetic analysis of the ribosomal DNA sequences of the internal transcribed spacer (ITS) and large subunit (LSU) regions delineated three genera (Zasmidium, Exophiala, and Scolecobasidium) and a previously unknown Peltaster-like species. Twelve isolates were confirmed as SBFS pathogens using a modified version of Koch's postulates on asymptomatic fruit with two inoculation methods (1) in situ in an orchard and (2) on excised fruit. Significant interactions were observed between states and infection levels (CPM and surface coverage) (P = 0.0001), as well as between states and fungal genera (P = 0.004). This study provides the first comprehensive characterization of the taxonomic diversity and pathogenicity of SBFS fungi on mango in selected regions of Malaysia, providing a foundation for future nationwide studies.