Optimization of media composition for in vitro shoot proliferation and root induction of three new cold-hardy and dwarfing or semidwarfing clonal apple rootstocks

Authors: SUN, QINGRONG - Shandong Institute; SUN, HONGYAN - Shandong Institute; LI, LINGUANG - Shandong Institute; Bell, Richard; LI, XIN - Shandong Institute; LI, QIN - Shandong Institute; TAO, JIHAN - Shandong Institute

Submitted to: Journal of Horticultural Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2014
Publication Date: 7/1/2014
Citation: Sun, Q., Sun, H., Li, L., Bell, R.L., Li, X., Li, Q., Tao, J. 2014. Optimization of media composition for in vitro shoot proliferation and root induction of three new cold-hardy and dwarfing or semidwarfing clonal apple rootstocks. Journal of Horticultural Science and Biotechnology. 89(4):381-388.

Interpretive Summary: Tree fruit rootstocks had been used to influence precocity, tree size, fruit quality, yield efficiency, mineral uptake, and to withstand adverse environmental conditions. But some apple rootstocks with excellent horticultural characteristics are difficult to propagate with conventional methods such as layerage or cuttings. The laboratory technique known as micropropagation can be used to rapidly propagate new rootstocks developed from breeding programs for use in experimental trials and for large-scale production of rootstocks for commercial production. Major factors that influence shoot proliferation and rooting were examined and optimal media were developed for efficient micropropagation and rooting of the apple rootstocks ‘GM256’, ‘71-3-150’, and ‘60-160’. The optimal proliferation medium for new shoot production and shoot quality for each of the three apple rootstocks was determined. Dark incubation during rooting for at least five days resulted in the highest rooting percentages and root numbers for all rootstocks. The optimum media and cultural conditions for shoot proliferation and rooting identified in this study can be used to maximize the production of these new promising apple rootstocks for further study and commercial production.

Technical Abstract: Tree fruit rootstocks had been used to influence precocity, tree size, fruit quality, yield efficiency, mineral uptake, and to withstand adverse environmental conditions. But some apple rootstocks with excellent horticultural characteristics are difficult to propagate with conventional methods. Tissue culture can be used to rapidly propagate new rootstocks developed from breeding programs for use in experimental trials and for large-scale production of rootstocks for commercial production. The aim of this study is to rapidly propagate several newly introduced apple rootstocks which are cold-hardy and dwarfing or semi-dwarfing and to improve their rooting ability by tissue culture. Major factors that influence proliferation and rooting were examined and optimal media were developed for efficient micropropagation and rooting of in vitro shoots of rootstocks ‘GM256’, ‘71-3-150’, and ‘60-160’. The optimal proliferation medium for all three apple rootstocks was Quoirin and Lepoivre with 0.5 mg/1 6-Benzylaminopurine and 0.05 mg/l indole-3-butyric acid. Shoot explants of ‘60-160’ on MS proliferation medium, three-quarter-strength MS, or one-half-strength MS showed shoot tip necrosis and hyperhydricity. The percentage of rooting and root number was superior under dark culture in all three rootstocks. The highest rooting for all three rootstocks was obtained on one-half-strength QL containing 0.5 mg/l indole-3-butyric acid (IBA) and two percent sucrose, but rooting of ‘60-160’ was not significantly different between two rooting media under the same cultural conditions.