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United States Department of Agriculture

Agricultural Research Service

Title: Rootstock Effect on Growth of Apple Scions with Different Growth Habits

Authors
item Tworkoski, Thomas
item Miller, Stephen

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 2006
Publication Date: February 1, 2007
Citation: Tworkoski, T., Miller, S.S. 2007. Rootstock effect on growth of apple scions with different growth habits. Scientia Horticulturae 111 p. 335-343.

Interpretive Summary: Apple tree cultivars often are propagated as scions by grafting shoot buds on to rootstock that can improve survival and control tree size. Size-controlling rootstocks can improve yield but they also can modify shoot elongation, dry weight distribution, and branch angle. Apple cultivars have a variety of canopy dimensions and shapes (i.e. growth habits) that strongly affect orchard training and management systems. The goal of the current experiment was to determine the effects of different size-controlling rootstocks on growth, branching, flowering and yield of apple scions with different growth habits. Apple scions with diverse growth habits were grafted on various size controlling rootstocks and evaluated after six years of growth in the field. Overall tree size, internode length, shoot elongation rate, time to budbreak, and branch angle, were most influenced by scion. Across all rootstocks, scions with spreading (wide branch angle) growth habits grew rapidly in April and May and achieved most seasonal growth earlier than scions with upright (narrow branch angle) growth habits that grew slowly early in the season. In all growth habits and rootstocks, growth rate slowed appreciably but did not cease by August and growth did not terminate earlier for any one scion-rootstock combination. Across all scions, the dwarfing rootstock, M.9, consistently had the lowest and seedling rootstock had the greatest tree height and diameter. However, no one size controlling rootstock consistently influenced dates of bud break and full bloom, shoot elongation rate, or duration of growth. Significant interactions indicated that effects of size-controlling rootstock on components of shoot growth will vary with apple tree growth habit. Understanding and modifying the processes responsible for such scion-rootstock interactions can assist efforts to obtain tree architecture for a desired orchard management system.

Technical Abstract: Apple scions with diverse growth habits were grafted on various size controlling rootstocks and morphological characteristics were measured after six years of growth in the field. Scion had more influence than rootstock on monthly growth rate. Across all rootstocks, scions with spreading growth habits grew rapidly in April and May and achieved most seasonal growth earlier than scions with upright growth habits that grew slowly early in the season. In all growth habits and rootstocks, growth rate slowed appreciably but did not cease by August and growth did not terminate earlier for any one scion-rootstock combination. Across all scions, the dwarfing rootstock, M.9, consistently had the lowest and seedling rootstock had the greatest tree height and diameter. However, no one size controlling rootstock consistently influenced dates of bud break and full bloom, shoot elongation rate, or duration of growth. Significant interactions indicated that effects of size-controlling rootstock on components of shoot growth will vary with apple tree growth habit. These effects on phenology and development can be significant to growers.

Last Modified: 10/1/2014
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