Identification of Pathogenicity Determinants in Colletotrichum falcatum Using Wild and Mutant Cultures

Abstract

Colletotrichum falcatum causing red rot in sugarcane is a dynamic pathogen exhibiting enormous variation. As pathogen variability plays a crucial role in the breakdown of red rot resistance in sugarcane, investigations were made to characterize possible factors responsible for the development of newer pathotypes in the fungal pathogen. We have studied production of metabolites viz., toxin and melanin and hydrolytic enzymes in relation to disease expression with wild and temperature adapted mutants which are deficient in pathogenicity on sugarcane hosts. The nine major pathotypes used for disease screening programme were found to vary significantly in toxin production. It was found that symptom production on leaves by the pathotypes and loss of electrolytes caused by them on the host tissues increased with their virulence. The pathotypes varied in the production of pectinolytic and cellulolytic enzymes particularly exo-PG and its production corresponded with virulence. Production of melanin during host pathogen interaction was found to have a positive relation with virulence when pathogenicity assay was conducted in stalks and leaves.