Morpho-molecular characterization of Choanephora cucurbitarum, causing twig blight of chilli in Karnataka

Abstract

Twig blight of chilli is a complex disease associated with multiple pathogens and has emerged as a major constraint to chilli cultivation, causing recurrent outbreaks, substantial yield losses and posing a serious threat to crop productivity. In the present investigation, a random roving survey was undertaken in major chilli-growing regions of Karnataka to assess the incidence and severity of the twig blight disease. Symptomatic plant samples were collected and subjected to isolation on potato dextrose agar. The obtained cultures were characterized based on their cultural and morphological traits. Colonies were white, submerged and exhibited rapid growth, with secondary mycelium developing within two days and the reverse side of the plate showing a pale-yellow pigmentation. Sporangiospores were brown, ellipsoidal and devoid of striations or papillae. For molecular confirmation, genomic DNA was amplified using universal primers (ITS-1 and ITS-4), yielding a ~600 bp fragment of the Internal Transcribed Spacer (ITS) region of rDNA. Sequencing and BLAST analysis against the NCBI database sequences confirmed the identity of the pathogen as Choanephora cucurbitarum.