Studies on Colletotrichum falcatum Went., causal agent of red rot of sugarcane with special reference to variability and host resistance
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Date
2005-05
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Red rot of sugarcane caused by Colletotrichum falcatum Went. is a serious and wide spread disease of sugarcane. Investigations were undertaken to study the variability among the different isolates of fungus causing red-rot of sugarcane.. Observations were recorded in various laboratory and field trials for studying the variability and host resistance against pathogen. The symptoms were observed a withered top, shriveled, wrinkled and reddening of pith with characteristic bands of clean white areas. mid rib of leave is also affected by the fungus, red patches with ash colour develop on the mid rib. Based on the study of the symptoms, the infected plants in the experimental crop area were easily identified and diagnosed having varied degree of infection and severity. Eight different isolates were taken from different sugarcane growing areas to study the growth pattern of the pathogen, Colletotrichum falcatum on different media, different pH, temperature and light conditions. The difference among the eight isolates of C. falcatum was studied in respect of growth and colony characters on oat meal agar. All the isolates showed septate mycelium and conidia were falcate, non-septate and hyaline. Chlamydospores were also formed in most of the isolates. Among the different isolates (K1, K2, K3, K4, 08, 09, B1 and P1) K1 showed fastest growth rate while isolate B1 was slowest. Studying the growth rate in different media Oat meal agar medium was found to be the best for all the isolates. The growth rate of all the isolates was favoured by neutral pH (pH 7) and temperature around 300C in oat meal agar medium. Exposure to different period of light showed no significant difference on the growth rate of the fungus. Of the fifty-six sugarcane genotypes, fifty-one were found to be resistant, four moderately resistant and one showed moderately susceptible reaction in the ratoon crop. in the direct planted sugarcane genotype evaluation trial fifty were found to be resistant, five moderately resistant and one moderately susceptible.
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