Sustainable sugarcane cultivation in India through threats of red rot by varietal management

Abstract

Sugarcane is traditionally cultivated in India since time immemorial to extract gur and Khandsari sugar. In the country, white sugar manufacturing started ~300 years ago the with imported Saccharum officinarum genotypes. After 1850s, sugar industry expanded rapidly and such expansion also led to emergence of new threats in the form of red rot caused by the dreaded fungal pathogen Colletotrichum falcatum. The new threat caused production losses in the then Presidencies of Madras, Bombay and Bengal. Sugarcane Breeding Institute (SBI) was established in 1912 to breed sugarcane varieties for red rot resistance with other desirable agronomical traits. The Institute achieved commercial success by releasing the first interspecific hybrid variety Co 205 during 1918 and release of many such varieties to the subtropical region revolutionized sugarcane cultivation by improved cane yield leading to attaining self-sufficiency in sugar requirement. Although the new varieties sustained the boom, red rot started attacking the elite varieties in different decades through a series of epidemics. These epidemics hindered sugarcane cultivation for a while in different states; however after each epidemic, new varieties were deployed to counter the disease onslaught and saved sugar industry from the brink. Many superior varieties with red rot resistance have benefitted the industry, but evolution of new C. falcatum pathotypes caused breakdown of resistance and made the life of many elite varieties short-lived. In the recent decades, variation in C. falcatum was characterized, designated into new pathotypes and new pathotypes were used for red rot screening. The historical red rot epidemics in the country over the decades resembled to ‘boom and bust cycle’ reported in cereal rust diseases. Domination of single variety combined with flood during monsoon seasons/ waterlogging favoured red rot epidemics. Lessons from the past red rot epidemics suggest complete removal of all the susceptible varieties from cultivation, adoption of a mosaic pattern of varieties in command areas combined with disease management practices like practicing crop hygiene, utilization of biocontrol agents and mechanized delivery of fungicides through setts to manage the disease and to sustain sugarcane cultivation