Physiological and pathological aspects of some new isolates of <i>Colletotrichum falcatum</i> causing red rot disease in <i>Saccharum</i> spp. complex

The paper deals with morphological and physiological variability of <i>Colletotrichum falcatum</i> Went on different temperature, pH, medium, nitrogen sources, carbon sources and also first time reporting of the two National Pathotypes from North East Zone of Uttar Pradesh, India. Thirty-four isolates were isolated from infected samples of different sugarcane varieties during survey and maintained on Oat Meal Agar (OMA) slants as well as on the Petri dishes at 30±1 °C. These isolates showed the variability in their optimum radial growth pattern. The optimum radial growth of all isolates was recorded at 8, 10 and 12 days. Six isolates exhibited maximum radial growth (90 mm diam) in 8 days, while the other 10 isolates attained same growth in 10 days. Remaining 14 isolates took 12 days to attain same growth. Pathogenecity of 34, isolates has been tested on 12 host differentials of sugarcane genotypes only SES594 was found resistant and others showed the variable response, while highly susceptible reaction to be found in three isolates (R0704, R0720 and R0728). These three isolates gave maximum spores on OMA followed by PDA medium and higher dry mycelium weight was observed in Richard’s liquid medium as compared to others. The maximum growth was recorded for these three isolates on potassium nitrate and sodium nitrate as nitrogen sources. Growth regulators like IAA and IBA at lower concentration enhances the growth while higher concentration showed adverse affect. When these three isolates were compared with the national level pathotypes, viz. Cf01 (Co1148), Cf08 (CoJ64) and Cf09 (CoS767) reaction in differential and spores inoculation technique it was found that isolates showed similar reaction like National Level pathotypes. Hence, it was concluded that these three isolates are belonging to new pathotypes.