Effect of rootstock vigor and in-row spacing on stem and root growth, conformation, and dry-matter distribution of young apple trees

The effects of M.9 and MM.106 rootstocks and in-row spacing (0.4, 0.7, and 1 m) on the vegetative behavior of three-year-old apple (Malus domestica Borkh) trees were studied. Analysis of digital images was used to estimate canopy and root growth and conformation (shape and size), whereas dry matter distribution was used to determine partitioning to various plant parts. Trees on less vigorous M.9 rootstocks showed reduced stem and root growth as they produced less and/or shorter shoots and less and/or shorter and thinner roots. Canopy spread area (CSA) and volume were similar for trees on both rootstocks and differences in stem length density (stem length per unit canopy volume; SLD) compens…