Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: November 23, 2005
Publication Date: July 17, 2006
Citation: Tworkoski, T., Miller, S.S. 2006. Rootstock effect on growth of apple scions with excurrent and decurrent growth habits. Meeting Abstract. Proceedings of the 32nd Annual Meeting of the Plant Growth Regulation Society of Amerida 32:142. July 24-27, 2005, Newport Beach, California. Technical Abstract: Rootstocks are used to propagate scions of preferred cultivars, improve fruit tree tolerance to environmental stress, and to control tree size. Improved fruiting from size-controlling rootstocks has been accompanied by altered tree morphology. In the current experiment the goal was to improve understanding of rootstock effects on growth and development of apple scions with different growth habits. Apple scions with excurrent and decurrent 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 excurrent growth habits grew rapidly in April and May and achieved most seasonal growth earlier than scions with decurrent 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 significantly affect orchard management systems.