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

The purpose of this study was to evaluate various culture media, with or without β-sitosterol, on mycelial growth, sporangia and oospore production by isolates ofPhytophthora infestans. Nine media were compared to rye agar (RA) which is frequently used to cultureP. infestans. Poor fungal growth across most isolates was observed on soybean agar, carrot agar and carrot agar with sterols relative to RA. Only clarified V8 juice containing β-sitosterol (CLV8S) resulted in significantly more sporangia production compared to RA. All other media performed similar to the RA. No significant differences were found in the sizes (length and width) of sporangia produced among the isolates tested on various media. Oospore production was greatest whenP. infestans was cultured on carrot agar with β-sitosterol (CAS) or CLV8S when compared to RA. Responses of isolate matings varied somewhat with an A2 isolate from Nova Scotia consistently producing fewer oospores in matings with A1 isolates compared to the other A1/A2 mating combinations. Rye agar and oat meal agar with or without β-sitosterol as well as clarified V8 juice agar with β-sitosterol are useful forin vitro growth of mycelium.