Sustainable sugarcane production in India vis a vis impact of sugarcane diseases

Abstract

Sugarcane is a major commercial crop grown in tropical and subtropical regions of the country. During the last 100 years, the country has witnessed epidemics of various diseases like red rot, smut, wilt, rust, leaf scald and yellow leaf (YLD). The loss caused by red rot is phenomenal, in which many elite varieties like Co 312, Co 419, Co 997, Co 1148, CoC 671 and CoJ 64 were removed from cultivation. During each epidemic, new virulent pathotypes of red rot emerged and posed challenge to sugarcane cultivation. Still, red rot remains to be major disease of sugarcane in the country and wilt and smut are the other two major diseases seriously affecting cane production. In addition the new disease YLD causes serious damage to cane productivity in many states. Severity of pokkah boeng and rust is also growing in many parts of the country. Sugarcane viruses causing mosaic and YL and ratoon stunting bacterium systemically infect sugarcane, over the years they reduce cane and sugar yield. The reduced performance of sugarcane varieties due to these non-fungal diseases is referred as ‘varietal degeneration’ and this phenomenon has been recorded in both tropical and subtropical regions in the country. Here combined infection of two or more viral/bacterial pathogens accelerates the damage to the crop and this is due to infection of one pathogen making the plant more susceptible to another. In this way, a variety degenerates faster and its potential comes down over the years and under Indian situation this phenomenon has been ignored. The propagation material in sugarcane ‘setts’ plays vital role in the primary spread of diseases hence selection of healthy planting material plays a vital role in raising a healthy crop. Disease resistant varieties play a crucial role in managing many of the diseases in sugarcane and several varieties have been developed to manage the diseases in the past. In addition, different agronomical approaches and physical method like heat therapy are being effectively used to manage the diseases in sugarcane. Recently, multiplication of sugarcane through tissue culture is being advocated to produce disease-free planting materials. However there is a need to diagnose of pathogens in sugarcane setts or tissue culture seedlings for effective disease management practice. Meristem culture combined with molecular diagnosis has become a proven technology to eliminate Sugarcane yellow leaf virus causing YLD in sugarcane and to manage the disease. Development of molecular diagnostics techniques has also facilitated precise identification and characterization of sugarcane viruses. Also this technique has the potential to detect more than one pathogen in one reaction and diagnosis is also amenable to automation. The review focuses on the prevailing disease situation, emerging new diseases, varietal degeneration in sugarcane, disease management using disease resistant varieties along with healthy seed nursery programme