Optimizing production of quality nursery plants for fruit tree cultivation

Orchards that are fully mechanized from planting to harvest is a logical next fruit production goal. To achieve this, simplified training systems must be developed, starting with economic, efficient and easy to manage nursery tree scions. Well-feathered single- or bi-axis scions, bare root planted and trained as a continuous hedgerow, could be a suitable solution for pome and stone fruit. In mild climates with long growing seasons, potted trees of small dimensions could be used to rapidly obtain medium-high density ‘fruiting walls’ where no regular axis distribution is required as long as canopy continuity is satisfied.Both of these approaches need specific research in the nursery and orchard to regulate the physiological status for efficiently achieving both early bearing and rapid lateral growth. Research should start with breeding to select new varieties suitable for the optimized approach. For stone fruits, the challenge is to promote natural lateral (sylleptic) branching and a high growth rate during nursery scion formation, then shift to predominately proleptic shoot growth and a reduced growth rate after the second year. The target would be to obtain all the laterals well-distributed along the trunk and with wide crotch angles during the first growing season. Each lateral would then become a short branch with high flower differentiation, resulting in a uniform fruiting wall with a high potential for efficient mechanical fruit thinning, harvest and pruning (possibly in the summer). For pome fruits, the challenge is to produce suitable trees on more vigorous rootstocks to overcome some replant problems. The use of wellfeathered, pre-formed scions with one or two axes, with training as a hedgerow system, remains the most convenient solution to reduce tree vigour and induce early bearing.