Screening for red rot resistance in sugarcane

Abstract

Red rot of sugarcane caused by Colletotrichum falcatum Went is a serious fungal disease affecting sugarcane stalks, the economical part of sugarcane in different countries. In India, the disease has been a menace for sugarcane cultivation and many elite varieties were removed from cultivation due to their susceptibility to the disease. The commercial varieties are recommended for cultivation in India if they possess red rot resistance. Hence screening for red rot resistance became an integral part of varietal development in the country. Plug method of pathogen inoculation is the most common method used for red rot screening in sugarcane and here, severity score is being assigned based on the red rot symptoms inside the canes. The key parameters of the lesion such as lesion width, nodal transgression and nature and severity of white spots determine the disease severity. Since a bore-hole injury is caused on the stalk to inoculate the pathogen, there is an apprehension that natural barrier is breached to introduce the pathogen in this method. So many other methods were developed to facilitate the pathogen to enter the cane tissues in a natural way. However the disease reaction in these methods is influenced by environmental factors which lead to disease escapes under field conditions. Recently a controlled condition testing was developed to screen large number of progenies using cane tops in a short time. Overall, the plug method is used to assess resistance potential of a genotype in a fool proof way in sugarcane varieties proposed for commercial cultivation and the controlled condition testing is followed initially to screen large population