The phenotypically quantitative nature of hypersensitivity of European plum (Prunus domestica L.) against the Plum pox virus and its description using the hypersensitivity index

Abstract

More than 1,300 seedlings of European plum originating from crossing combinations with at least one parent showing hypersensitivity resistance against PPV were analyzed for their reaction to artificial inoculation with PPV using the double grafting method with virus infected interstem. It was shown that the hypersensitivity resistance against the virus is a phenotypically quantitative trait. The different kinds of symptoms observed in the test system, which contribute to the hypersensitivity resistance, range from weak necrosis on the leaf blade and on the stem to the death of the whole young shoots. A hypersensitivity index was developed which helps to determine the degree of hypersensitivity resistance of an individual genotype. Its use is strongly recommended as selection tool in breeding for hypersensitivity resistance.