Genetic Transformation of Peach Rootstock and Cultivar to Induce Resistance Against PPV Virus Through Post-Transcriptional Gene Silencing

Prunus, in particular peach, is considered one of the most recalcitrant species for what concerns in vitro regeneration, especially when the starting plant material originates from mature tissues. Furthermore, in terms of peach genetic transformation, few examples exist in literature and most of them demonstrate the difficulty in obtaining stable transformants. The present study describes an efficient method of in vitro regeneration, via organogenesis, starting from meristematic bulk tissues, characterized by a high competence to produce adventitious shoots and useful for genetic transformation of Prunus persica cultivar Big Top (R) Zaitabo*' and rootstock GF677. This protocol constitutes one of the few examples of peach in vitro regeneration starting from adult tissue present in the literature. It has been used to genetically transform the rootstock GF677 and the cultivar ` Big Top (R) Zaitabo*', through the development of two different methods of transformation, one mediated by Agrobacterium tumefaciens, applied on slices from meristematic bulk, and the other by the biolistic technique applied on slices from meristematic bulks and on vegetative apex. The transformation experiments were conducted using hairpin genetic constructs for the induction of Plum pox virus (PPV) resistance through the mechanism of post-transcriptional gene silencing (PTGS). To our knowledge, this is the first example of a successful attempt of a peach rootstock and cultivar stable genetic transformation and it represents a good promise for the future production of silenced GF677 plants to be tested for the capacity to induce PPV resistance also in the grafted scion.