Yield and fruit quality of 'Regina' sweet cherry (Prunus avium L.) comparing five semi-dwarfing rootstocks in combination with Kym Green Bush or Vogel central leader training systems

Since the mid-2000s, ‘Regina’ grafted to ‘Gisela 6’, ‘Gisela 12’, ‘Krymsk 5’ and ‘Krymsk 6’ rootstocks have been a common scion/rootstock combination for Oregon sweet cherry (Prunus avium L.) growers. The most common training system for ‘Regina’ has been the Vogel central leader. However, labor scarcity and increased labor costs cause growers to seek alternative training systems that will produce high yields of good quality fruit with improved labor efficiency. A seven-year study of ‘Regina’ on five different rootstocks: ‘Mazzard’, ‘Gisela 6’, ‘Gisela 12’, ‘Krymsk 5’ and ‘Krymsk 6’ on two different training systems: Kym Green Bush (KGB) and the Vogel central leader (VCL) found that there were significant differences in yield, fruit quality and fruit size when comparing different training systems. Rootstock had little effect on fruit firmness but all fruit were significantly firmer (ranging from 330.0374.2 g mm^-1) than the minimum industry standard (275 g mm^-1). Total soluble solids TSS was highest from fruit grown on ‘Krymsk 6’ rootstocks (22.08-21.62%) and lowest on fruit grown on ‘Mazzard’ rootstocks (20.07-20.90%). Pedicel fruit retention force had significantly firmer attachments from trees grafted to ‘Krymsk 6’ (1580.4-1413.3 g), and the weakest attachments from trees grafted to ‘Mazzard’ (1341.5-1390.5 g). VCL training of ‘Regina’/‘Gisela 12’ resulted in the highest average yield tree^-1 (19.06 kg tree^-1) followed by VCL training of ‘Regina’/‘Gisela 6’ (14.48 kg tree^-1). Lowest average yield tree^-1 was obtained for the KGB training of ‘Regina’/‘Mazzard’ (3.93 kg tree^-1). For all rootstock by training system combinations, VCL markedly out yielded KGB where ‘Regina’ is concerned.