Comparison of different culture media on the mycelial growth, sporangia and oospore production of Phytophthora infestans

The purpose of this study was to evaluate various culture media, with or wi thout beta-sitosterol, on mycelial growth, sporangia and oospore production by isolates of Phytophthora infestans. Nine media were compared to rye aga r (RA) which is frequently used to culture P. infestans. Poor fungal growth across most isolates was observed on soybean agar, carrot agas and carrot agar with sterols relative to RA. Only clarified V8 juice containing beta-s itosterol (CLV8S) resulted in significantly more sporangia production compa red to RA. All other media performed similar to the RA. No significant diff erences were found in the sizes ( length and width) of sporangia produced a mong the isolates tested on various media. Oospore production was greatest when P. infestans was cultured on carrot agar with beta-sitosterol (CAS) or CLV8S when compared to RA. Responses of isolate matings varied somewhat wi th an A2 isolate from Nova Scotia consistently producing fewer oospores in matings with A1 isolates compared to the other A1/A2 mating combinations. R ye agar and oat meal agar with or without beta-sitosterol as well as clarif ied V8 juice agar with beta-sitosterol are useful for in vitro growth of my celium.