The nutrition of Phytophthora fragariae

Abstract

An investigation was made into the nutritional requirements of three physiologic races of Phytophthora fragariae using homogenized mycelium as inoculum. The optimal calcium concentrations for growth on a complex amino-acid medium were between 20 and 50 p.p.m. No growth occurred in the absence of Ca ions. Strontium could partially replace Ca for two of the isolates but Ba was wholly ineffective. The Ca requirements of the fungi were independent of the nature of the C or N sources used. Glucose, maltose, sucrose and dextrin were good C sources for the fungi. Fructose, mannose and raffinose were utilized to a limited extent. Organic acids and amino acids were not used as C sources by P. fragariae 11. The fungi did not use nitrate or ammonium N, even in the presence of organic acids and over a fairly wide range of initial pH values. Of 18 amino acids tested, singly, for ability to support growth, DL -alanine, L -proline, L -asparagine, DL -serine, DL -valine and DL -aspartic acid proved to be good sources of N. Ammonium ions inhibited the growth of P. fragariae 11 in a medium containing DL -alanine as the N source.