The bottlenecks in obtaining an efficient transformation protocol for RNAi-based sharka resistant peach

Stone fruits, especially peach (Prunus persica), are among the most important tree species grown in the Mediterranean basin subjected to viral infections, in particular caused by Plum Pox Virus (PPV), the etiologic agent of Sharka disease, which leads to significant agronomic and economic losses. At the moment, there are no means of direct struggle against such infection but only means of prevention, which are often not effective and associated to environmental sustainability issues and costs for farmers. For these reasons, many programs of genomic studies and traditional breeding are aimed at understanding the mechanisms of resistance. A possible integrative strategy to classical breeding techniques is represented by the use of genetic engineering technology to obtain transgenic plants of cultivars and rootstocks bearing resistance genes. Prunus, in particular peach, is considered one of the most recalcitrant species for what concern in vitro regeneration and transformation, especially when the starting plant material originates from mature tissues. The study here described has the main objective of transferring and adapt the protocol previously developed in grape (Mezzetti et al., 2002) to the in vitro regeneration, via organogenesis, and Agrobacterium-mediated transformation of the peach rootstock GF677 (Prunus persica x Prunus amygdalus). The ultimate purpose is the introduction of an anti PPV RNAi construct, named ihp35S-PPV194.