First report of Colletotrichum truncatum associated with anthracnose disease on tuberose (Polianthes tuberosa) in India

Abstract

Tuberose (Polianthes tuberosa) is an important commercial flower crop grown in Karnataka for its beautiful and fragrant cut flowers. Recently, an association of anthracnose disease (incidence ranged from 18 to 27%) characterized by the dark concentric sunken necrotic lesions with spore mass in the acervuli on leaves and peduncles of Tuberose was observed in a field survey conducted during October 2015 to March 2016. The pathogen was isolated on PDA medium. The fungal colony on PDA was grayish to dark gray. Conidia were falcate, one-celled, hyaline. Based on the micro-morphological, and cultural characteristics the pathogen was identified as Colletotrichum truncatum. The ITS-rDNA, GAPDH and ß-tubulin sequences of the pathogen were sequenced using ITS1/ITS4, GDF1/GDR1, T1/Bt2b primer pairs. nBLAST search and phylogenetic analysis confirmed that the pathogen was C. truncatum. Koch's postulates were conducted on 45-day-old tuberose plants by foliar application of conidial suspension of C. truncatum. Development of typical anthracnose disease was recorded after 18 days of post-inoculation and the pathogen's identity was confirmed by re-isolation and identification. The anthracnose disease associated with Tuberose is a major constraint for the production of quality cut flowers. This is the first report of C. truncatum causing anthracnose on Tuberose in India.