THE INFLUENCE OF NITROGENOUS COMPOUNDS ON GROWTH OF PYTHIUM SPECIES

Abstract

The utilization of N compounds by P. ultimum Trow (strain I and II), P. rostratum Butler, and P. irregulare Buisman was examined in a chemically denned medium under controlled conditions in surface culture. All species were able to metabolize nitrate, ammonium, and organic nitrogen, and the amount of growth varied with the nitrogen source. In general, yeast extract, peptone, glycine, serine, histidine, cysteine, asparagine, aspartic acid, and glutamic acid supported favorable growth, whereas γ-aminobutyric acid, threonine, and alanine supported poor growth of these fungi. The addition of succinic acid at 0.02 M concentration to ammonium compounds further increased growth of four isolates.Preferential utilization of amino acids from a given mixture was recorded using paper chromatographic techniques. All four isolates gave more vegetative growth on mixtures of amino acids than when they were supplied singly.