Molecular identification and characterization of pathogenicity of fungal pathogens associated with crown rot disease in banana from Odisha, India

Crown rot disease on banana varieties (Champa, Patakpura and G9) was identified in Odisha's 10 coastal districts during the post-harvest storage stage in 2022-23. Five crown fragments were taken for isolation from each variety of bananas based on symptom developments. Agar plate and standard blotter technique isolation procedures have been used to isolate 1210 fungal colonies, of which 584 representative colonies were purified from banana crown fragments. Different fungal colonies were purified, characterized and identified using morphological and molecular methods from G9 (244), Patakpura (205) and Champa (135) fungal colonies. Morphological identification of Fusarium and Colletotrichum isolates was madeusing colony morphology, pigmentation, the growth rate on the PDA plate and microscopic observation. Molecular identification of Fusarium and Colletotrichum isolates was done by amplifying the internal transcribed spacer (ITS) region of the conserved ribosomal DNA, which includes 5.8S rDNA. Fusarium verticillioides, Fusarium equiseti, Fusarium oxysporum and Colletotrichum gloeosporioides were the 4 fungal isolates identified. The sequences of these fungi were deposited in the GenBank database (NCBI) under the accession numbers OQ363325 (Fusarium verticillioides), OP735534 (Fusarium equiseti), OQ438654 (Fusarium oxysporum) and PP448030 (Colletotrichum gloeosporioides). The neighbor-joining method was used to conduct phylogenetic analysis on the gene sequences. Pathogenicity test results revealed that all 4 isolated fungal strains produced similar crown rot symptoms on 3 varieties of banana fruits. Disease severity index and AUDPC indicated that the Fusarium strain is the most aggressive crown rot pathogen and the G9 is the more susceptible banana variety to crown rot pathogens in Odisha.