Red rot of sugarcane (Colletotrichum falcatum Went)

Abstract

Red rot of sugarcane was recorded more than 100 years before in Java, India, Argentina, USA and other countries and it is one of the most devastating diseases of sugarcane. Its epiphytotic occurrences caused severe crop losses in different countries. Since the cultivated sugarcane Saccharum officinarum has failed across the countries, systematic inter-specific hybridization between S. officinarum and the wild species S. spontaneum referred as ‘nobilization’ was done to develop resistant varieties and the disease was managed in most of the countries. However, in the countries especially in Asia, varietal breakdown to red rot caused severe epiphytotics, by which the resistant varieties failed in the field at regular intervals. New pathogenic strains of Colletotrichum falcatum with higher virulence were found responsible for varietal breakdown in sugarcane. Extensive cultivation of a single variety over large areas led to extensive crop damages due to ‘vertifolia’ effect as witnessed after the famous epiphytotics of Co 213, CoC 671 and Co 0238 in different decades in India. The current epiphytotic on the ruling variety Co 0238 has caused loss of more than one billion US dollars in the current season in the country. The recent studies have explained a clear varietal adaptation by C. falcatum and it gradually acquires virulence to overcome the host resistance. Detailed studies were done on pathogenic variation, epidemiology, screening methods, disease resistance mechanism, identifying effectors, pathogenicity determinants, antifungal genes and transgenics. Recently complete genome and transcriptomes of C. falcatum were sequenced and pathogenicity hot spots and candidate secreted effector proteins were identified and this will further help to identify the candidate genes for further genetic manipulation. Inspite of poor understanding on inheritance of resistance to C. falcatum in sugarcane, new varieties with red rot resistance were developed and deployed after each of the epiphytotic to save the crop. Further, other management practices including bioagents, chemicals and inducers were attempted and improved efficacy by mechanized sett treatment showed promising results to manage the disease under field conditions. To complement resistant varieties, other agronomic practices like clean seed, crop hygiene, maintaining varietal purity, removal of the susceptible varieties from cultivation and quarantine measures are suggested to reduce the disease severity in the field.