Molecular basis of red rot resistance in sugarcane

Abstract

Red rot of sugarcane caused by Colletotrichum falcatum Went is one of the devastating diseases of sugarcane causing significant loss to sugarcane production in India and other Asian countries. Complex polyploidy and lack of information on inheritance to red rot in sugarcane make breeding for red rot resistance more difficult. Hence researchers have studied the mechanism of red rot resistance in sugarcane in detail. Initial studies based on biochemical tools identified oxidative enzymes and red rot pigments in disease resistance. Further studies revealed the role of pathogenesis-related (PR) proteins and 3-deoxyanthocyanidin phytoalexins especially luteolinidin and apigeninidin in red rot resistance. Recent studies using semiquantitative RT-PCR after pathogen inoculation from sugarcane cultivars varying in red rot resistance, revealed differential accumulation of transcripts of the flavanoid biosynthetic pathway like coumarate-4- hydroxylase, chalcone synthase, chalcone reductase, flavanoid 3′-5′ hydroxylase and flavanoid glycosyl transferase and this transcript analysis, further confirmed the role of sugarcane phytoalexins in red rot resistance. Similarly the role of PR- proteins like chitinase and β- 1,3-glucanase was established at the transcript level. Detailed molecular studies using differential display (DD)-RT-PCR identified expression of more number of differentially expressed transcripts during the host-pathogen interaction. Full length sequences of many potential transcripts were identified and are being characterized. Also to identify specific proteins involved in host resistance, proteomic approach has been attempted by optimizing sample preparation from stalk tissues, 2-D electrophoresis (2-DE), down-stream processing of identified spots and bioinformatics. Several resistance associated proteins spots were identified and they are being analyzed critically. Overall, application of molecular techniques was found to be useful in identifying transcripts/proteins involved in host defence. Further studies are in progress to validate their specific involvement in red rot resistance.