Glucose Inhibition and Inheritance of Pigment-Producing Ability In Phytophthora

SUMMARY

Pigment production by Phytophthora drechsleri was greatest in a synthetic, glucose-free medium to which casein hydrolysate and tyrosine had been added. Glucose strongly inhibited the production of pigment. Pigment production by single-oospore cultures from A¹ × A² crosses of either P. drechsleri or P. capsici varied from none to abundant regardless of the pigment-producing ability of the parents. Pigment-producing ability appeared to be under polygenic control. When pigment-producing ability and mating type were used as genetic markers, the phenotypic response of single-oospore isolates from the A¹/Br⁺ side, the A²/Br⁺⁺ side, and those from the zone of fusion was similar. This evidence indicated that the oospores were the result of crossing of A¹ and A² parents and not of selfing.