Intensive orchard management systems utilizing dwarfing rootstocks has now become common place as a standard practice in North America for apple production.
Growers in North America are increasingly becoming aware of the correlative relationship between plant density and production.
Growing trees in a V shape can achieve the goal of increased plant density with minimal inhibition to light penetration into the canopy.
A trial was established in 1993 at the Clarksville Horticultural Experiment Station, Clarksville, Michigan, USA with 'Imperial Gala' planted on 19 rootstocks in a split plot design with main plots established and grown in the GŁttingen V and V trellis wire system.
All trees were planted at a spacing of 0.75 x 4.0 m, representing a density of 3320 trees per ha.
Trees were trained as slender spindle and leaned to 20 degrees from the vertical, alternating direction along the row.
The sub plots within system tested and compared the performance of 19 rootstocks, including Mark, Bud.9, M.9, M.9 EMLA, Vineland 605-1, Vineland 605-3, P.2, P.22, M.9 NAKTUINBOUW 337, M.9 NAKTUINBOUW 338, M.9 NAKTUINBOUW 339*, M.9 NAKTUINBOUW 340, M.9 Janssen NAKTUINBOUW 337, RN 29, MAC 39, CG 10, Burgmer 751, Burgmer 756, and Burgmer 984. There were no significant differences in most performance characteristics between the two orchard systems.
Cropping over the trial period was not significantly different among the top 14 rootstocks.
The rootstocks that ranked among the top 5 in production include M.9 NAKTUINBOUW 340 (sister clone of NAKTUINBOUW 337), Burgmer 984 (M.9 clone from Germany), Mark, Bud.9 and Burgmer 751. The bottom 4 rootstocks in cumulative yield since 1993 include V.1, P.22, CG.10 and Mac 39