INHIBITION OF GROWTH OF PHYTOPHTHORA-INFESTANS BY PHOSPHATE AND PHOSPHONATE IN DEFINED MEDIA

Growth of three isolates ofPhytophthora infestans was inhibited in a glucose-mineral salts media when phosphate concentrations were in excess of 1 mM. Phosphate inhibition was also observed inP. mirabilis, although not to the same extent. No inhibition of growth was observed inP. erythroseptica in the presence of phosphate concentrations up to 10 mM. The presence of subinhibitory concentrations of phosphonate resulted in a slight stimulus in the growth ofP. infestans at some phosphate concentrations. It is suggested that this is the result of competition between phosphate and phosphonate for a common transporter, resulting in reduced uptake of phosphate and slightly reduced phosphate toxicity. © 1992 Academic Press, Inc.