Interspecific transfer of resistance to Plum pox virus from almond to peach by grafting

Grafting almond variety Garrigues' onto GF305' peach seedlings heavily infected by Plum pox virus (PPV) progressively produces the disappearance of viral symptoms and drastically reduces virus accumulation in GF305' rootstock, in most cases to undetectable levels. This response appears to be specific between almond and peach, as it was not consistently observed by grafting Garrigues' onto other Prunus species such as plum (Adesoto') or apricot (Real Fino'). The ability to induce resistance to PPV in GF305' was transmitted to the sexual descendants of Garrigues. Furthermore, grafting Garrigues' onto GF305' before PPV inoculation completely prevented virus infection, showing that the resistance is constitutive and not induced by the virus. This fact suggests that resistance may be due to the transfer of a defence factor from Garrigues' almond through the graft union and its interaction with specific factors of GF305' peach to produce the antiviral response. These results open new avenues to potential protection against PPV in peach, the most economically important species among stone fruits.