First Report of Colletotrichum siamense (Ascomycota, Glomerellaceae) Causing Severe Leaf Spots and Blights Disease on Annona reticulata in Kerala, India, Investigated Through Phenetic and Molecular Phylogenetic Analysis

Custard apple (Annona reticulata) is a fast-growing semi-evergreen tree well known for its nutritional and medicinal properties to treat against various kinds of diseases. During investigation, the leaf spots and blight disease was observed on A. reticulata in Kerala, India. The causative agent was isolated and identified as Colletotrichum siamense, based on symptomatic inspection, cultural morphology, microscopic characteristics, and concatenate multigene molecular phylogenetic analysis using internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and β-tubulin (TUB2) genes. Koch’s postulates were fulfilled through in vitro pathogenicity and confirmed the pathogenic nature of C. siamense. To the best on our knowledge, and consulting with upto-date literature, this is the first report of C. siamense causing leaf spots and blights disease on A. reticulata from India. The study highlights the need for surveillance and effective management of this foliar disease in A. reticulata within tropical ecosystems to protect its cultivation and commercial value.