THE OCCURRENCE OF THE A2 MATING-TYPE OF PHYTOPHTHORA-INFESTANS IN THENETHERLANDS - SIGNIFICANCE AND CONSEQUENCES

Phytophthora infestans (Mont.) de Bary, the causal agent of potato lat e blight, was first discovered in Europe in 1845. Until 1980, only Al mating type isolates were known to occur in Europe. The absence of A2 mating type isolates restrained the fungus from sexual reproduction. I n the early 1980s, A2 mating type isolates were discovered in Europe. Presumably, a new introduction of P.infestans isolates originating fro m Mexico had taken place. In this paper, the significance of the prese nce of A1 and A2 mating type isolates in the Netherlands is reviewed. Now that both mating types are present, sexual reproduction can occur and its consequences for the control of potato late blight are discuss ed.