Natural Infection of European Stone Fruit Yellows Phytoplasma and of Its Experimental Transmission in Different Plum Varieties

摘要

In a plum varietal collection in Rome, some of plants showed premature sprouting and blossoming in winter, or gum production and phloem necrosis in spring; molecular tests to verify phytoplasma presence were carried out from 1995 through 1998. Twelve Japanese plum (Primus salicina L.) varieties were tested with the number of analysed trees varied from one to three per variety. Nucleic acids were extracted from leaf midribs and used in direct and nested PCR with phytoplasma general and specific primers. RFLP analyses with Sspl and Rsat on PCR products identified the involved phytoplasma as belonging to the European stone fruit yellows group(16SrX - B) . At least one plant of Simka, Black Diamond, Black Star, Casselman, Cali-ta, Black Gold,. Pobieda and Ozark Premier varieties were positive to phytoplasma, showing a spreading of the infection over the time. In several cases, no correlation was found between symptoms and phytoplasma presence. Patches of apricot tissue infected by phytoplasmas of the same group mentioned above were grafted on three healthy plants from each of the following plum varieties: Black Amber, Ozark Premier and Sorriso di Primavera for their susceptibility test to infection. One plant of Sorriso di Primavera, two of Black Amber and all the three tested plants of Ozark Premier were infected at a different degree of susceptibility to European stone fruit yellows disease (ESFY) among Japanese plum varieties.