2018 ASHS Annual Conference

Jessica M. Guseman, Kevin Webb, Courtney A Hollender, Doug Raines, Kenong Xu, Amy Tabb and Chris Dardick, Appalachian Fruit Research Station, USDA ARS, Kearneysville, WV

Tree management is the single most important factor that influences orchard productivity, starting with time of tree establishment and rootstock grafting followed by the continual pruning and training of the tree throughout its life. A broad range of management systems and strategies have been designed to maximize time to harvest, yield, and fruit quality while minimizing labor costs and chemical inputs. Currently, there is a sizeable knowledge gap in our understanding of the underlying growth and development mechanisms of trees which limits our ability to devise new solutions and/or genetically improve tree architectures. In particular, the growth patterns of branches including their growth dynamics and orientations as well as their interactions through apical dominance and apical control are poorly understood. Here we used gene expression profiling to compare shoot tips of apical and subtending 1^st order lateral branches of young peach trees having different growth habits (standard, pillar, or weeping). Apical shoots in trees having a standard or pillar architecture displayed a cellular program that was clearly distinct from laterals, marked predominantly by down-regulation of a large set of genes. In contrast, very few significant differences were found when comparing lateral branches at different positions in the canopy or among shoot tips of weeping trees. Collectively, the data has important implications for understanding branch growth behavior and establishes a novel genetic program that is uniquely associated with apical shoots. Practical aspects of the work potentially related to management practices and/or breeding will be discussed.