Occurrence of the rare A2 mating type of Phytophthora infestans on imported Egyptian potatoes and the production of sexual progeny with A1 mating types from the UK



Phytophthora infestans from blighted potato tubers imported from Egypt and on sale to the public in North Wales were all of the A2 mating type which was thought, until recently, to be confined to Mexico, Zygotes from Welsh and Egyptian matings germinated readily; progeny were variable. The threat posed by a general spread of the A2 mating type is discussed.