Morphological and molecular characterization of Lasiodiplodia theobromae associated with leaf spot and blight disease of Coscinium fenestratum (Gaertn.) Colebr.-a new host record from India.

Abstract

Coscinium fenestratum is a medicinally significant critically endangered plant found in Western Ghats of India. The leaf spot and blight was observed in Kerala during 2021 with disease incidence of 40% in 20 assessed plants in 0.6hectare. The associated fungus was isolated on potato dextrose agar medium. A total of six morpho-culturally identical isolates were isolated and morphologically identified. Based on morpho-cultural features, the fungus was identified at genus level as Lasiodiplodia sp., which was further authentically confirmed as Lasiodiplodia theobromae by molecular identification with a representative isolate (KFRIMCC 089) using multigene (ITS, LSU, SSU, TEF1-α, and TUB2) sequence analysis and concatenated phylogenetic analysis (ITS-TEF1-α-TUB2). Pathogenicity tests were also assessed in vitro and in vivo using mycelial disc and spore suspension of L. theobromae, and the isolated fungus's pathogenic behaviour was confirmed after re-isolation and morpho-cultural features. Literature survey reveals that there are no reports of L. theobromae on C. fenestratum from all over the world. Hence, C. fenestratum is being firstly reported as a new host record for L. theobromae from India.