Title: Rootstock Effect on Growth of Apple Scion with Different Growth Habits Authors
Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: November 23, 2005
Publication Date: February 18, 2006
Citation: Tworkoski, T., Miller, S.S. 2006. Rootstock effect on growth of apple scion with different growth habits. Meeting Abstract. 2005 Cumberland-Shenandoah Fruit Workers Conference 81st Annual Meeting. Volume 31:193. Technical Abstract: Rootstocks are used to propagate scion of preferred cultivars, improve fruit tree tolerance to environmental stress, and control tree size. Size-controlling rootstocks may alter tree morphology by modifying dry weight distribution, shoot elongation, and branch angle. Much work has focused on effects of size-controlling rootstocks on growth and yield of commercial apple cultivars but interactive effects of rootstock and scion with different growth habits have not been elucidated. In the current experiment the objectives were to (1) measure branch growth during a growing season to compare growth rates and termination of growth of the different rootstock-scion combinations and (2) determine rootstock effects on components of seasonal growth of scions with different growth habits. The scion used in this experiment came from trees with different growth habits that were from an F2 generation of hybrids produced by sibcross selections from a ‘Goldspur Delicious’ x ‘Redspur Delicious’ progeny. In 1996 buds were budded to rootstock of EMLA 7, EMLA 111, M.9, and Malus antanovka. Tree growth was measured in April 2003 and 2004. The growth variables included tree height, canopy width, trunk diameter 10 cm above the graft union, crotch angle of main architectural branches, and growth of ten previous season’s shoots per tree. Annual shoot growth from 2002 and 2003 was evaluated for amount and position of sylleptic branches. During 2004, 10 branches per tree were labeled and growth was measured each month from April through October. Rootstock effects on whole tree dimensions were in accord with expectations. Generally, the largest-to-smallest trees grew on seedling, MM.111, M.7, and M.9 rootstocks. These rootstocks did not maintain tree size or shoot elongation by the same amount in all growth habits. Although M.9 tended to reduce growth most, the percent growth reduction differed even between scions with similar growth habits. For example, M.9 reduced tree heights of two different scions, both with excurrent growth habits, by 36 and 13%. Growth habits with decurrent growth habits had more upright branches with narrower branch angles than growth habits with excurrent growth habits. Decurrent growth habits displayed less apical control of proleptic branch growth while having greater apical dominance of sylleptic branches than excurrent growth habits. Decurrent growth habits grown on M.9 rootstock had less apical dominance than on seedling rootstock. The prevalence of rootstock-growth habit interactions highlights the complexity of root-shoot communication in grafted fruit trees. Understanding the processes responsible for such scion-rootstock interactions can assist efforts to obtain tree architecture for a desired orchard management system.