PERFORMANCE OF DISCOVERY APPLE ON M.9, M.26 AND MM.106 ROOTSTOCKS AT 2 DENSITIES

The apple rootstocks M.9, M.26, and MM.106 were evaluated for their efficiency in bringing 'Discovery' apple trees into production. The experiment, carried out over a ten-year period compared two planting densities at 1666 and 3333 trees per ha. Tree vigour differences between rootstocks were measured in term of trunk growth, tree volume, weight of branches pruned off and final weight of the above-ground parts of the trees. Fruit production is presented both as total yield and as the weight of first class fruit. Fruit colour development is also shown. Cropping efficiency is calculated and presented in relation to the different vigour measurements. The results confirm that 'Discovery' is slow to come into production. M.9 was the most productive rootstock, but due to vigour differences MM.106 gave the same yields per tree, although the latter had the lower yield efficiency. M.26 performed poorly; its vigour was similar to M.9 but it produced the lowest yields.