Isolation of pathogenic Streptomyces spp. and determination of variability among the strains collected from potato

A study was undertaken during 2008-2009, 2009-2010 and 2010-11 cropping seasons to isolate the variability(s) of Streptomyces spp. from lesion of common scab affected potato tubers in the Northern parts of Bangladesh (Rangpur division). There were twelve different pathogenic species isolated, which were different for colony colour, spore colour, spore ornamentation, spore chain morphology, other physiological characteristics (temperature, pH, melanin production, colour secret in oatmeal broth medium, carbon utilization and growth response in NaCl solution) and pathogenic reaction. Overall all collected isolates grow well within temperature range of 25°C to 30°C. In the present investigation, it was observed that isolates S2 and S11 could grow at pH 4.50. It was found that the growth of isolates increased as the pH value of medium increased. Considering all the characteristics of different isolates, isolate S5 agreed with the description of S. scabies having smooth, grey spores borne in spiral chains, producing melanin and utilizing eight recommended ISP diagnostic sugars with raffinose as a sole source of carbon. Rest eleven isolates could not identify.