First report of twig blight of Ban Tulsi (Croton bonplandianus Bail.) caused by Choanephora cucurbitarum (Berk. & Ravenel) Thaxt. in India

Abstract

In August 2015, twig blight disease of ban tulsi (Croton bonplandianus Bail.) caused by Choanephora cucurbitarum (Berk. & Ravenel) Thaxt. was observed for the first time, in the Gangetic alluvial region of West Bengal, India. A severe disease incidence (40-50%) showed twig blight symptoms starting with shoot apical meristem (SAM), leaf, and blossom blight symptoms. Typical symptoms were characterized by over-projecting black pin head like emerging sporangiola which formed mycelial cushion on the infected surface. The present report describes the identification of the causal pathogen as C. cucurbitarum based on its morphology and the internal transcribed spacer of its ribosomal DNA (rDNA - ITS) sequences with 100% identity of NCBI-GenBank published Choanephora database. Optimum temperatures, 28-30°C, coupled with high relative humidity (80-90%) during the monsoon season enhances the disease's progress. To the best of our knowledge this is the first report of twig blight of C. bonplandianus, caused by C. cucurbitarum, in India as well as globally.