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Abstract

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The influence of five rootstocks, B.9, M.9 NAKBT337, O.3, M.26 EMLA, and M.7 EMLA, and five nutrition treatments applied through a microsprinkler system, on growth characteristics of `BC-2 Fuji' apple trees (Malus domestica Borkh.) was evaluated for two years. Nutrition treatments consisted of 22.4 kg nitrogen (N)/ha (low N), 89.7 kg N/ha (medium N), 156.9 kg N/ha (high N), 89.7 kg N/ha in combination with 78.5 kg potassium (K)/ha, and 156.9 kg N/ha in combination with 78.5 kg K[ha. Trees on M.7 EMLA had larger trunk cross-sectional areas (TCA) and longer limbs and terminal shoots than those on other rootstocks. Trees on B.9 had the smallest TCA and the shortest limbs and terminal shoot. The density of non-flowering spurs in the scion trees increased with the vigor of rootstocks. Trees on B.9 had significantly higher density of fruit spur without bourse shoot than those on other rootstocks in 1998. Bud break in the mixed-buds of trees on of M.7 EMLA was slower than those on B.9 and 0.3 in both years. Over all, trees on B.9, M.9 and 0.3 were less vigorous than those on M.7 EMLA and can be used for high-density orchards. Trees receiving high N had significantly longer terminal shoot than those with low N treatment in both years. Nutrition treatments showed little effect on other growth characteristics of scion trees.

Introduction

Growth and development of fruit trees is affected by the genotype of scion and rootstock, environmental factors, and cultural practices. Numerous studies have shown that rootstock affects tree growth (15, 22, 32), spur and flower development (3, 14, 18), mineral uptake (20), fruit productivity (27, 28), and fruit quality (12) in various apple (Malus domestica Borkh.) cultivars.

Many apple cultivars have unique bud and vegetative growth characteristics (11, 13). 'Fuji' trees (`Rails Janet' x `Delicious') are vigorous (13, 23) and have a strong biennial bearing habit (23). They exhibit a new cycle of growth after bud formation in late August (10). 'Fuji' has become one of the most popular apple cultivars in the world (16, 26, 29, 30). However, a comprehensive report on the vegetative growth and spur development of 'Fuji' is absent from the literature.

The objective of this study was to evaluate the vegetative...

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