INCIDENCE OF THE A2 MATING-TYPE OF PHYTOPHTHORA-INFESTANS ON POTATO CROPS IN NORTHERN-IRELAND

Of 250 isolates of Phytophthora infestans obtained from Northern Irela nd potato crops between 1981 and 1993, only six proved to be of the A2 mating type, the remainder being A1. The first A2 isolate was obtaine d from a tuber in 1987. The frequency of A2 isolates from 1987 onwards was 3%, a lower incidence than has been reported for England and Wale s and the Republic of Ireland. There was no association between phenyl amide resistance and mating type.