Morphological, pathogenic and physiological variability among Pythium isolates causing soft rot of ginger

Soft rot caused by Pythium ultimum is a highly destructive disease in ginger growing areas of Sirmour district of Himachal Pradesh. All the isolates of Pythium were found to vary in the colony characters. The isolates also differed in respect of septa, mycelia, sporangia and oospores. All the isolates were found to be pathogenic though they differed in the level of per cent rotting. Isolate 5 was most virulent and caused 30 per cent rotting after seven days of incubation as compared to other isolates. Physiological variability was also recorded for all Pythium isolates on eight different solid and liquid media. Maximum mycelial growth was obtained in isolate 6 in solid media and for isolate 2 in liquid media, respectively. All Pythium isolates were able to grow at temperatures ranging from 5 -30°C and pH 3.0–8.0 levels with the maximum mycelial weight at 25°C by isolate 4 and pH 6.5 by isolate 5.