Morphological, physiological and pathological variations among isolates of Colletotrichum falcatum that cause red rot of sugarcane

摘要

Twenty-eight isolates were isolated from samples of different sugarcane varieties infected with red rot during this survey; the culture was maintained on slants and Petri plates at 29±2°C. These isolates showed variability in their optimum radial growth pattern. These isolates were morphologically differentiated into two distinct groups: fifteen had light colour and thirteen had dark colour. Cultural characters of the isolates were divided into five groups viz. light sporulating, sparsely light sporulating, light non-sporulating, dark sporulating and dark non-sporulating. The length of the conidia varied from 25.1 to 30.5 μm and the width of the conidia varied from 4.2 to 5.5 μm; however, all the conidia were found to be falcate. The virulence of various isolates on the cane stalk showed a wide range of variation. However, all the light sporulating and dark sporulating isolates showed more or less similar virulence against a set of standard susceptible cane varieties. In this study, 28 isolates were tested based on fourteen pathological standards, in which six (Cf208, Cf608, Cf908, Cf1508, Cf2109 and Cf2609) were found to be most virulent. We have found that Colletotrichum falcatum isolates were culturally, morphologically and pathologically dissimilar and six new races are found reported in India.