Pathogenicity Assessment of Colletotrichum musae by Artificial Inoculation and Verification of Koch's Postulates in Banana Fruits

Abstract

Colletotrichum musae, the causal organism of banana anthracnose, causes one of the most destructive postharvest diseases of banana, resulting in significant losses in fruit quality, shelf life, and market value. The present study was conducted in the Department of Plant Pathology, Bihar Agricultural University (BAU), Sabour, to isolate and identify C. musae and confirm its pathogenicity through Koch's postulates. The pathogen was isolated on potato dextrose agar (PDA) medium from naturally infected banana fruit exhibiting typical anthracnose symptoms. It was identified as C. musae based on morphological and microscopic characteristics: greyish-white cottony colonies; hyaline, septate mycelia; single-celled, aseptate, hyaline conidiophores; and cylindrical, hyaline conidia containing oil globules. Pathogenicity was evaluated by artificially inoculating healthy, mature green banana fruits using the pinprick method. Typical anthracnose symptoms, characterised by dark-brown sunken lesions, developed within 5–7 days after inoculation, whereas the uninoculated control fruits remained symptomless. Disease severity increased from 19.98% at 1 day after inoculation (DAI) to 99.90% at 7 DAI, with an area under the disease progress curve (AUDPC) of 396.27. The pathogen was successfully re-isolated from the artificially infected fruits and exhibited characteristics similar to those of the original culture, confirming the pathogenicity of the morphologically identified isolate through Koch's postulates. These findings confirmed the pathogenicity of the morphologically identified Colletotrichum musae isolate and provide a basis for future postharvest disease-management studies.