Reactions and field resistance of some potato varieties and hybrids to the leaf-roll virus.

Abstract

The leaf-roll reactions of a number of potato hybrids and varieties have been defined by external symptoms and the extent of phloem necrosis present in stem sections. There is no constant correlation between the leaf-roll reaction and field resistance of varieties and hybrids. The variety Bismark had the highest leaf-roll resistance of any of the types tested so it should prove a useful parent for this character. The resistance of Bismark and some hybrids is apparently dependent upon a virus-inactivating mechanism, which not only reduces field infection but prevents the transmission of leaf roll to a proportion of the tubers of infected plants. The initial selection of resistant hybrids could be made by sprout inoculating them and keeping those in which a proportion of the tuber progeny was free from leaf roll.