STUDIES ON THE NUTRITION OF PHYTOPHTHORA CRYPTOGEA

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Abstract
Phytophthora cryptogea, cause of a root disease of alfalfa, grew well over a wide range of pH values (5.6–7.2) on a synthetic medium containing sucrose as the carbon source. The fungus also grew well on glucose and soluble starch. L-Asparagine was the most favorable source of nitrogen, but failed to support growth of a variant obtained from a single germinated oospore. Low concentrations of CaCl2∙2H2O stimulated growth of P. cryptogea, P. drcehsleri, P. parasitica, and P. boehmeriae. The minimal concentration of thiamine for growth was between 12 and 25 μg/liter. Soil extract, representing 50% or 90% of the volume of the synthetic medium, did not supply the thiamine requirement or stimulate growth of the fungus. Alfalfa root extract, alone or added to the synthetic medium, not only satisfied the thiamine requirement of the fungus but produced about 30% more mycelial growth than the complete synthetic medium.