Physical and chemical factors affecting growth of three isolates of Koleroga noxia on coffee

Physical and chemical factors affecting the growth of K. noxia isolates were studied. On PDA-thiamine colony growth rate of isolates I and II was three and a half times faster than that of isolate III. Isolates I and II had maximum growth in the temperature range of 25 and 30ðC, while the isolates III manifested good growth between 15 and 20ðC. K. noxia isolates I and II recorded maximum dry weight after 20 days of incubation, whereas isolate III gave maximum dry weight only after 35 days of incubation. All the three isolates of K. noxia registered maximum dry mycelial weight on the medium with pH 7, followed by pH 6, 5 and 4. But the dry weight recorded by the isolates I and II was almost double the weight by isolate III in the respective pH. Ability to assimilate the different nitrogen sources by the three isolates were similar with maximum growth on L-asparagine, followed by potassium nitrate and urea. The K. noxia isolates I and II differed from each other on assimilation of different vitamins. Isolate I grew best on biotin as vitamin source, whereas the isolate II and III showed similar behaviour on thiamine. The physical and chemical factors on the growth of K. noxia isolates showed the possibilities of existence of different strains of the pathogen.