FIRST REPORT OF COCHLIOBOLUS SPICIFER CAUSING LEAF SPOT DISEASE OF TRIANTHEMA PORTULACASTRUM

Abstract

Trianthema portulacastrum Simmons (Horse purslane) weeds showing symptoms of light brown to blackish leaf spot were observed during survey conducted in between 2011-13 in Haryana, India. A fungus was consistently isolated from leaf lesions on potato dextrose agar (PDA) upon incubation 25°C for 7 days. The pathogen identity was verified by the International Mycological Institute (IMI), CABI Bioscience UK (IMI Number 503552) based on its morphological and by ITS rDNA sequence analysis. The sequence obtained from this sample showed 100% identity to sequences of Cochliobolus spicifer Nelson and its anamorphic state Bipolaris spicifer Bainier (Cunha et al., 2012). The best matches included strains from reference culture collections e.g. JN192387 (CBS 274.52). Reproduction of symptoms in inoculated healthy leaves fulfilled Koch’s postulates and confirmed pathogenicity. C. spicifer has been isolated from a wide variety of plants e.g. Arachis, Capsicum, Gossypium, Musa, Piper, Solanum, Triticum, Vicia and Vigna and reported from Europe, Africa, the Middle East, Asia, Australasia and South America. A total of nine fungal pathogens have been reported on T. portulacastrum weed from various parts of the globe (Aneja et al., 2014). Literature search reveals that the leaf spot disease caused by C. spicifer on T. portulacastrum has not yet been reported worldwide.