EARLY PERFORMANCE OF 'DISCOVERY' APPLES ON 8 ROOTSTOCKS GROWING IN A NORTHERN CLIMATE

Abstract

Trees of 'Discovery' apples growing on dwarf and semi-dwarf rootstocks were assessed in field trials at two sites (western and eastern Norway) at 60o North. The rootstocks included two selections of M.9 (EMLA, RN.29), two from the Polish (P) series (P.59, P.60), three from the Geneva (G) series (G.30, G.78730-026, G.202) and M.26. Trees were planted in the spring of 1997 as two-year-old feathered trees, spaced 1.5 x 4 m, trained as slender spindles and evaluated for five subsequent years. Soil management involved grass in the alleyways and herbicide strips 1-m wide along the tree rows. Tree size was significantly affected by the rootstocks after five years growth. P.59, G.78730-026 and M.9 RN.29 produced the smallest and G.30 and G.202 the largest trees as measured by trunk cross-sectional area. P.59 and G.30 had the greatest yields per tree, followed by G.202, P.60 and M.9 EMLA. Trees on P.59 were the most yield-efficient followed by the two M.9 clones. The fruit yield efficiency, measured as number of fruits per trunk-cross-sectional area showed similar results. The different rootstocks hardly affected the individual fruit weights. Fruit quality, characterized by the content of soluble solids, was in general high and did not differ between trees on the various rootstocks.