Effect of Various Carbon Sources on Growth and Sexual Reproduction of Aphanomyces euteiches

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Abstract
Growth and sexual reproduction of 6 isolates of A. euteiches were studied in synthetic media containing glutamic acid, mineral salts, phosphate buffer, methionine or sodium thiosulfate, and various C sources at 5 g C/liter. Forty-three C sources representing monosaccharides, oligosaccharides, polysaccharides, pectic substances and derivatives, carbohydrate derivatives, and Krebs-cycle intermediates were tested. Glucose and maltose were the best C sources, whereas galactose, fructose, ribose, cellobiose, glycerol, and sodium pyruvate supported considerable but less growth than glucose and maltose. Pectic substances were slightly utilized for growth. Mannose was utilized adaptively only after 25 days of incubation or when it was supplied with glucose or galactose. Glucose autoclaved in the medium supported higher growth than when it was sterilized by Millipore or Seitz filtration. Tests with washings from Seitz filter pads indicated that these contained a toxic or inhibitory principle. Glucose and fructose were the best C sources for sexual reproduction. Oospore production depended more on the inherent ability of the isolates than on the availability of C sources for growth.