First report of Alternaria angustiovoidea mediated leaf anomalies in Abelmoschus esculentus in Greater Kolkata, India

Okra (Abelmoschus esculentus) is a nutritious domesticated “fruit” that belongs to the Malvaceae family. India esteems to be the largest global producer of lady’s finger and its net annual output accounts for 60,00,000 metric tons. In this investigation, a peculiar kind of leaf spot disease was observed on a diseased leaf sample collected from Howrah, Kamalchowk, West Bengal, India (Latitude: N 22° 59.5770′, Longitude: E 88° 26.3641′). Large brownish spots mottled the leaves, with spots also lining the edges of the leaf. With disease progression, these lesions expanded to form patches, leading to necrosis and defoliation. Fungus isolated from infected plants when cultured showed golden to deep brown mycelial growth. Microscopic characterization revealed ovoid, muriform, or club-shaped multiseptated conidia, often existing in chains, with the majority tapering towards a swollen short beak. ITS sequencing rendered the identity of the infectious agent to be Alternaria angustiovoidea. Phylogenetic results indicated that this pathogen was closely related to Alternaria arborescens, A. tenuissima, and Fusarium equiseti. Koch’s postulates were performed and ratified, where distinct symptoms were seen in okra. Alternaria species, including Alternaria solani cause early blight in tomatoes and potatoes, and Alternaria alternata are often associated with citrus fruit rot, induce plant diseases. Their intrusions are not restricted to plants as exposure to A. alternata and A. tenuissima have been associated with allergies, cutaneous alternariosis, and respiratory conditions in humans. Therefore, the significance of tracing such pathogens and thinking of preventive measures can never be undermined. No previous accounts were found, hence one can claim this is the first time such a peculiar host–pathogen combination scenario has been encased and presented in India.