Published online by Cambridge University Press: 11 June 2012
Previous reports (Black, 1943, 1945) on the resistance of potatoes to the blight fungus (Phytophthora infestans) have shown the existence of at least two major genetic factors (Ra and Rb) in the host, and the occurrence of not less than two strains (A and B) of the pathogen.
From the studies then reported, it was concluded that the two genes had been brought into the potato from different phyletic sources and that one, Ra, when in the dominant state, conferred resistance to strain A, while similarly Rb conferred resistance to strain B.
This paper was assisted in publication by a grant from the Carnegie Trust for the Universities of Scotland.