Response of Plum Cultivars Grafted on Hypersensitive Rootstocks under Field Natural Infection with Plum Pox Virus

Five plum cultivars 'Katinka', 'Common prune type Schufer', 'Jojo', 'Cacaks beste', and 'Cacaks fruchtbare' grafted on the four hypersensitive rootstocks, 'Docera 5', 'Docera 6', 'Docera 9', and 'Dospina 22' were evaluated for the susceptibility to PPV infection during four years (2009-2012). PPV sources were plum trees, infected with PPV strain-D, grown at the vicinity of the tested plum cultivars. Plants were evaluated every year by visual inspection, and the presence of PPV was detected by ELISA and RT-PCR. The number of PPV infected plants was rising gradually every year. 41% of plum trees died or was systemically PPV infected in the fourth year of evaluation. Results proved very high susceptibility of plum cultivars grafted on rootstocks hypersensitive to PPV.