Differential accumulation of 3-deoxy anthocyanidin phytoalexins in sugarcane varieties varying in red rot resistance in response to Colletotrichum falcatum infection

Sugarcane synthesizes a complex mixture of phytoalexins in response to inoculation with Colletotrichum falcatum Went, causative agent of red rot. To determine induction and accumulation of these compounds, field grown sugarcane plants of two varieties viz., Co 93009 and CoC 671 which are resistant and susceptible to red rot respectively, were inoculated with C. falcatum and tissue extracts were analyzed by HPLC at different intervals after inoculation for the presence of phytoalexins. Analyses of HPLC profiles revealed the induction of five major compounds in response to pathogen inoculation/injury. Among the five detected compounds only two were found to be induced specifically due to pathogen inoculation. One of the two pathogen induced compounds was found to be accumulated only in the resistant variety but completely absent in the susceptible variety. Using standards, the two pathogen induced compounds were identified as luteolinidin and apigeninidin and the results revealed that these phytoalexins induced specifically in red rot resistant variety in response to attempted pathogen infection and susceptible variety failed to synthesize these compounds. The results suggest the possible role of these compounds in red rot resistance.