Potato Blight and Leaf-Roll Virus

Abstract

OBSERVATIONS on the potato variety Ulster Supreme made at Cambridge in 1956 indicated that blight (Phytophthora infestans) was present on approximately twice as many tubers derived from plants infected with leaf-roll virus as on those from neighbouring virus-free plants (virus-free being used in this communication to mean free from visible symptoms of virus disease). The appearance of potato blight in August 1957 made possible an examination and comparison of the foliage of virus-free and leaf-roll infected plants. At an early stage in its development it was apparent that the primary foci of infection were often associated with patches of plants infected with leaf-roll virus and that some plants within these patches were completely destroyed at a time when surrounding virus-free plants were only slightly or moderately blighted. Leaves picked on three occasions from an area showing 50 per cent leaf-roll infection, from the same level of the crop and showing no visible blight lesions, were incubated. On each occasion blight lesions developed on about half the rolled virus-infected leaves whereas none developed on those which were virus free.