Early Performance of ‘Starkspur Supreme Delicious’ on 16 Rootstocks in the NC-140 Cooperative Planting

Abstract

In 1984 trees of ‘Starkspur Supreme Delicious’ apple (Malus domesticaBorkh) on 16 rootstocks were planted at 30 sites in North America according to guidelines established for cooperative testing by the North Central Regional Cooperative Project (NC-140). After 5 years, 17% of the trees on P.22 had died, but tree loss on all other rootstocks except, MAC.39 and P2, was below 10%. Seedling rootstocks produced the greatest number of root suckers with minimal suckering on other rootstocks. Based on trunk cross-sectional area, trees on the following rootstocks were similar to trees on seedling in size: P.18, A.313, B.490, M.4 and MAC.1. Trees on CG.24 and P.1 were between M.7 EMLA and seedling in size. The following rootstocks produced smaller trees than M.26: B.9, MAC.39, P.22, P.2, P.16 and C6. B.9, C6, P.16, P.22, P.2 and M.26 EMLA induced fruiting, while trees on seedling, MAC.1, A.313, and CG.24 lacked precocity. Variation in performance of these rootstocks across the 30 sites was considerable and demonstrates the importance of cooperative testing.