Varietal Break Down to Red Rot in the Sugarcane Variety Co 0238 Mimics Vertifolia Effect: Characterizing New Colletotrichum falcatum Pathotype CF13

• Published in: Sugar tech : an international journal of sugar crops & related industries 2022-10, Vol.24 (5), p.1479-1496
• Main Authors: Viswanathan, R., Singh, Sujeet Pratap, Selvakumar, R., Singh, Dinesh, Bharti, Y. P., Chhabra, M. L., Parameswari, B., Sharma, Anuradha, Minnatullah, Md
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Breakdown; Colletotrichum falcatum; Crop losses; Cultivation; Drug resistance in microorganisms; Economic impact; Epidemics; Flooding; Food processing industry; Fungal diseases; Life Sciences; Monoculture; Mycoses; Pathogenicity; Pathogens; Red rot; Research Article; Sugarcane; Virulence; Waterlogging
• ISSN: 0972-1525; 0974-0740; 0972-1525
• DOI: 10.1007/s12355-021-01070-7

Red rot, a fungal disease caused by Colletotrichum falcatum Went is the major constraint for sugarcane production in India and many other Asian countries. Recurrent epidemics of the disease cause varietal breakdown in popular varieties, thereby elite varieties with red rot resistance succumb to new variants of the pathogen and cause huge economic losses. We investigated on the recent devastating red rot epidemic that struck the popular cv Co 0238, cultivated in ~ 2.2 M ha in Uttar Pradesh (UP) (82.21% cane area) and 0.16 M ha in Bihar (64.12% cane area) states by pathotyping of 67 C. falcatum isolates including 45 from the cv Co 0238 and 22 from other varieties along with seven designated pathotypes on a set of 20 host differentials. The differential interaction studies conducted at five locations in the states of UP, Haryana and Punjab revealed that all the Cf0238 isolates maintained a discrete pathogenicity pattern of infecting the host cv Co 0238. Further, all the designated pathotypes and other host isolates did not show their virulence on the cv Co 0238. Similarly, all the Cf0238 isolates (45) maintained an avirulence behaviour on CoJ 64, the susceptible differential at all the locations. These pathogenicity data of new C. falcatum isolates from Co 0238 and other varieties on the host differentials clearly showed emergence of a specific pathotype capable of infecting the predominant variety under cultivation Co 0238 in the subtropical region. Reason for the sudden outbreak and extensive crop losses in thousands of hectares is attributed to monoculture of the variety in more than 80% area in the region due to ‘Vertifolia effect’. The monoculture also created a selection pressure from the pathogen to adapt to the host and caused breakdown of resistance favoured by waterlogging and flooding in the region. We have designated the new virulent isolate from Co 0238 as a new C. falcatum pathotype CF13 based on detailed characterization for pathogenicity and is recommended for screening sugarcane varieties for red rot resistance. This study also indicated repeat of boom and bust cycle in sugarcane–red rot interaction due to monoculture, leading to emergence of a virulent pathotype and large-scale destruction of the crop under cultivation.