Prune cv. Jojo resistance to different strains of Plum pox virus

Trees of prune (Prunus domestica L.), cv. Jojo, were inoculated by chip budding with three different strains of PPV isolated from European plum in the Czech Republic. These isolates included Plum pox virus M strain (PPV-M), Plum pox virus D strain (PPV-D) and a PPV-recombinant both strains (PPV-Rec). The results of the evaluation of the inoculated trees over 2 years are presented. Trees of plum cv. Jojo behaven differently to infection with the three PPV strains. A strong hypersensitive reaction appeared a year after inoculation with PPV-M and PPV-Rec strains, although not all inoculated tree died. PPV must have been present in the tissue of cv. Jojo because the virus was transferred to the rootstock St. Julien. Plants of the rootstock became systemically infected with the PPV-M and PPV-Rec strains, showing severe PPV symptoms. The presence of PPV was proved by ELISA in leaves of rootstock St. Julien, but not in leaves of cv. Jojo. Inoculation with strain PPV-D resulted in partial hypersensitive reaction of plants of cv. Jojo, but after initial stunting and partial death of shoots recovering of plants was observed.