The Application of Precision Breeding for Crop Improvement Is Fully Consistent with the Plant Lifecycle: The Utility of PB for Grapevine

Precision breeding (PB), in which only defined genetic elements from sexually-compatible parents are utilized, is a logical extension of conventional breeding inasmuch as it is fully consistent with the plant lifecycle.  The PB approach has particular promise to develop improved cultivars of grapevine (Vitis spp.), which is unique among all crop plants due to its special sensory attributes.  A relatively small number of well-known elite cultivars and their landraces account for the majority of world wine production. They are subject to significant disease pressures, making substantial chemical control and sanitation necessary in many regions.  Although better genetic resistance is urgently required to ease production, elite grapevine cultivars cannot be improved by conventional breeding because of major obstacles, which include inbreeding depression, self-incompatibility and a long lifecycle. Due to such limitations, it is not possible to add specific and urgently needed genetic traits to elite cultivars.  However, technology to bypass these obstacles is finally available.  Over the years we developed the crucial cell culture and gene insertion systems for a wide range of grapevine varieties. Completion of the genome sequencing of V. vinifera ‘Pinot Noir’, along with in-depth computational analyses, only recently provided the final piece needed to enable PB of grapevine. A concern expressed against PB has centered on the fact that insertion sites for such genetic elements are random and may cause “unintended consequences”; however such concerns overlook the fact that plant sexual reproduction randomly induces far greater variability through the many types of meiotic crossovers and transposition. Such well-known and expected meiotic variability is the reason that plant breeders must make so many controlled pollinations and evaluate often thousands of progeny in order to find one desirable individual. Precision breeding, which instead utilizes the more stable mitotic pathway, is more predictable, less disruptive, and more efficient than that of conventional breeding because only specific traits are transferred and key obstacles are avoided.  However, with new varieties under development, substantial field evaluation, as is the norm for conventionally-bred crops, will be required to determine whether precision-bred versions of elite cultivars will possess desirable attributes and/or otherwise be useful.