Performance of 'Fuji' and 'McIntosh' Apple Trees After 5 Years as Affected by Several Dwarf Rootstocks in the 1999 NC-140 Apple Rootstock Trial

Abstract

'Fuji' and 'Mclntosh' apple trees ( Malus × domesticaBorkh.) on CG.4013, CG.5179, CG.5202, G.16N (liners from stool beds), G.16T (liners from tissue cultured plants), M.9 NAKBT337, M.26 EMLA, Supporter 1, Supporter 2, and Supporter 3 rootstocks were planted at seven sites per cultivar throughout North America as a uniform trial coordinated by the NC-140 Technical Committee. Partial plantings were established at three sites per cultivar.CG.3041 and CG.5935 were included in eight and four sites per cultivar, respectively. After five growing seasons, trees on M.9 NAKBT337 showed the greatest loss, with 33% mortality. Tree size measurements of trunk cross-sectional area, tree height, and canopy spread were all affected by rootstock and were used to allocate each rootstock into four preliminary size categories. Trees on CG.4013 were semidwarfs, larger than those on M.26 EMLA. Trees on CG.5202 and CG.5935 were large dwarfs, similar in size to M.26 EMLA. Trees on CG.5179, CG.3041, G.16N, and G.16T were moderate dwarfs, between trees on M.26 EMLA and M.9 NAKBT337 and likely similar to the larger M.9 clones. Trees on Supporter 1, Supporter 2, and Supporter 3 were small dwarfs, similar in size to trees on M.9 NAKBT337. 'Fuji' trees on CG.4013 were similarly yield efficient to trees on M.26 EMLA; however, comparable 'Mclntosh' trees were significantly more efficient than those on M.26 EMLA. Trees on CG.5202 and CG.5935 were similarly yield efficient to those on M.26 EMLA, and trees on G.16N, G.16T, CG.3041, and CG.5179 were similarly yield efficient to those on M.9 NAKBT337. In the small dwarf category, trees on Supporter 1, Supporter 2, and Supporter 3 were similarly yield efficient to those on M.9 NAKBT337. Average fruit weight was only modestly affected by rootstock, and the rootstock influence was not consistent between the two cultivars.