The effect of elicitors isolated from the mycelial walls of Colletotrichum falcatum (the red rot pathogen of sugarcane) and from C. lindemuthianum (a non-pathogen) in suspension-cultured cells of sugarcane was studied. Both the elicitors induced the synthesis of enzymes of the phenylpropanoid pathway such as PAL, TAL and 4CL and also resulted in the enhanced accumulation of phenolics. However, a specific induction of the defense parameters at higher levels was recorded in suspension cells treated with the pathogen elicitor and no such differential response was observed in the case of the non-pathogen elicitor. Elicitor induced necrosis and browning of cells were observed which suggests an additional evidence that elicitors simulate pathogen infection and thus provide a valuable reason that study on elicitor induced responses may be useful in understanding the host defense mechanisms against the red rot pathogen at molecular level.
Authors:P. Malathi, P. Padmanaban, R. Viswanathan, D. Mohanraj and A. Ramesh Sundar
The control of sugarcane red rot was studied in model experiments with carbendazim and thiophanate methyl. In axenic cultures carbendazim inhibited the pathogen more efficiently than thiophanate methyl (MIC 1 and 100 mgL-1, respectively). However, under greenhouse conditions, the reverse picture was revealed. Carbendazim, the metabolite of thiophanate methyl, exhibited lower efficacy against red rot disease than its precursor. Fungicides applied before infection reduced the disease incidence and improved both germination of setts and plant survival. Soaking of sugarcane setts in a 0.25% suspension of fungicides for 24 h before planting was found to be more effective in controlling debris-borne infection than soaking for 1 h period at elevated doses. The persistence of effects both on disease incidence and on promoting plant growth can be observed up to 60 days after planting (DAP).