Performance of ‘Starkspur Supreme Delicious’ Apple on 9 Rootstocks Over 10 Years in the NC-140 Cooperative Planting

Abstract

In 1980-81, trees of ‘Starkspur Supreme Delicious’ on 9 rootstocks were planted at 27 sites in the United States and Canada according to guidelines established for cooperative testing by NC-140. The greatest tree losses occurred with the rootstocks O.3 (38.9%) followed M.27 EMLA (27.7%), MAC.24 (26.1%), M.9 EMLA (24.4%) and M.9 (20.0%), with M.7 EMLA (3.3%) and OAR.1 (6.1%) having minimal losses. MAC.24 produced the largest trees, followed by OAR.1 and M.7 EMLA, with M.27 EMLA producing the smallest trees. Trees on M.9 EMLA, M.9 and MAC.9 did not differ in tree size. Trees on MAC.24 produced excessive suckers and those on MAC.9 produced an adventitious swelling at and below the soil line. Trees on MAC.24, OAR.1 and M.7 EMLA produced much less fruit/unit trunk cross-sectional area than the smaller trees. Calculating production potential per hectare using actual 10-year-old size, trees on MAC.9 had the greatest potential, followed by M.26 EMLA, O.3, M.7 EMLA, and M.9 EMLA, while trees on OAR.1 had the lowest potential. Comparison over 5 years showed a tendency for fruit on trees of M.27 EMLA and OAR.1 to have smaller average fruit size.