Abstract
Phytophthora sp. was isolated from an alfalfa-field soil in Shintoku, Hokkaido in 1978. The fungus exhibited a petaloid pattern with an abundant aerial mycelium on potato-dextrose agar. Young hyphae had no septa, but became septate with age. Hyphae on malt-extract agar tended to be gnarled and tuberculate (coralloid). Clusters of hyphal swellings of 7-10μm diam. were abundant on alfalfa seedlings. Sporangia (mean 53.7×32.4μm) were nonpapillate or inconspicuously papillate and noncaducous, and proliferation and sympodial elongation occurred. The majority of sporangia were ovoid or ellipsoidal, but some were elongated, flattened on one side, constricted, or kidney-shaped. The fungus grew on corn-meal agar from 5 to 36C with an optimum growth temperature of 28C. All of the isolates were of the A2 mating type. The fungus was pathogenic to alfalfa and other plants. These characters suggested that the fungus was P. cryptogea Pethyb. & Laff. or P. drechsleri Tucker. Since many reports suggested that these two species were conspecific, comparisons were made by means of disc electrophoresis to obtain protein patterns of both identified species and the present isolates. Electrophoretic results confirmed the conspecificity of both species, and the isolates were identified as P. cryptogea due to priority.
