Hormone Production and Reception Among Isolates of Phytophthora melonis From Taiwan

Abstract

Isolates Pm-1, Pm-2 and Pm-3 of Phytophthora melonis induced Phytophthora parasitica A2, but not A1 mating type to produce oospores, and produced oospores in response to stimulation by P. parasitica A2, but not A1 mating type. The results suggest their ability to produce hormone α¹ and responsiveness to hormone α². These three isolates, therefore, belong to sexuality type 1 of Group I. Isolates Pm-4, Pm-5 and Pm-6 which were capable of producing oospores in single cultures, did not form oospores when paired with themselves or with A2 mating type of P. parasitica. However, pairing with A1 mating type of P. parasitica induced oospore formation in these three isolates. A1 mating type of P. parasitica also produced oospores as a result of the pairing. The results suggest their ability to produce hormone α² and responsiveness to hormone α¹. Because of the involvement of an inhibitory effect in the pairing of these isolates with A2 mating type of P. parasitica, their ability to produce hormone α¹ and responsiveness to hormone α² could not be determined.