In vitro grafting : a new tool to transmit pome fruit phytoplasmas to non-natural fruit tree hosts.

Abstract

Long-term maintained, homogeneous in vitro shoot cultures of Pyrus communis infected with pear decline (PD) phytoplasmas and Malus pumila infected with apple proliferation (AP) phytoplasmas were used to inoculate by in vitro grafting the non-natural plant hosts Pyronia veitchii and Prunus marianna. Healthy intergeneric heterografts and autografts with phytoplasma-infected graft tips were performed as controls. The transmission rate, as revealed by PCR detection of the respective phytoplasma, was 35% for the transmission of PD phytoplasmas from Pyrus to Pyronia compared to 75% for the Pyrus/Pyrus-smtograft control, and 52% for the transmission of AP phytoplasmas from Malus to Pyronia compared to 90% for the Malus/Malus-autogratt control. Only one AP-inoculated Pyronia plantlet exhibited AP-typical symptoms. No transmission of PD or AP phytoplasmas to Prunus could be achieved.