Susceptibility of Prunus rootstocks against Marcus and Dideron isolates of Plum pox virus by graft-inoculation

Sharka (Plum pox virus, PPV) is one of the most important diseases affecting stone fruits. While there is much information on the reaction of cultivars to PPV infection, details about rootstocks are scarce. In this study, we evaluated 28 stone fruit rootstocks belonging to different Prunus species against the Marcus and Dideron strains of PPV. Rootstocks were evaluated under controlled conditions during two growing seasons using two inoculation methods: direct inoculation of own-rooted rootstocks and grafting onto PPV-infected GF305 peach seedlings. Our results showed a generalised susceptibility of the rootstocks evaluated. Evaluating own-rooted rootstocks was more efficient than the traditional method of grafting onto infected GF305 seedlings. As expected, PPV-M was found to be more aggressive than PPV-D, producing symptoms and occurring in a higher number of plants, as shown by ELISA. The most susceptible rootstocks were Myran, Viking, Myro pg Pecher, Julior, Myrobolan 29C, Rubira, Myrobolan B, MrS 2/5, Jaspi and MP8. The least susceptible were GF677, Myrotop, Citation and ZH6. These results highlight the necessity to breed PPV-resistant rootstocks for the different stone fruit species.