EUROPEAN RACES OF PHYTOPHTHORA FRAGARIAE AND RESISTANCE TO THEM
Nine races were found in a survey of isolates of P. fragariae var. fragariae from red stele outbreaks throughout Europe. Using a combined British/American series of differentials only three corresponded to races reported from N. America. Cultivars which are susceptible to all races yielded simple races with a restricted host range, whereas isolates from cultivars with some race resistance, or from baited soil samples, have generally yielded more complex races. Race lability in culture is not uncommon especially among the more complex races, which tend to lose virulence, and complete loss of pathogenicity has also been found.
Kennedy, D.M. and Duncan, J.M. (1993). EUROPEAN RACES OF PHYTOPHTHORA FRAGARIAE AND RESISTANCE TO THEM. Acta Hortic. 348, 469-476