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ARS Home » Northeast Area » Geneva, New York » Plant Genetic Resources Unit (PGRU) » Research » Publications at this Location » Publication #425534
Research Project: Development of Improved Apple Rootstocks with Tolerance to Biotic and Abiotic Stresses

Location: Plant Genetic Resources Unit (PGRU)

Title: Plant Growth Regulators Increase the Rooting of Apple Rootstocks Grown in Stoolbeds

Author
item ADAMS, RICHARD - Cornell University
item Fazio, Gennaro
item ALDWINCKLE, HERBERT - Cornell University
item ROBINSON, TERENCE - Cornell University

Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2025
Publication Date: 7/1/2025
Citation: Adams, R.R., Fazio, G., Aldwinckle, H.S., Robinson, T.L. 2025. Plant Growth Regulators Increase the Rooting of Apple Rootstocks Grown in Stoolbeds. Journal of the American Pomological Society. https://doi.org/10.71318/46p8ah59.
DOI: https://doi.org/10.71318/46p8ah59

Interpretive Summary: Clonal apple rootstocks are mostly propagated by layering, a system that produces rooted cuttings from suckers that are produced yearly by mother shrubs. The rate of rooting in the cuttings is related to the genetic propensity of the rootstocks, with some producing few roots per cutting, an undesirable trait. This research aimed to increase rooting by spraying certain plant growth regulators. The best treatment which improved rooting in apple rootstock layering beds was prohexadione calcium. Apple rootstock nurseries will benefit from adapting this knowledge in their propagation protocols.

Technical Abstract: Poor rooting is a common problem of many dwarfing apple rootstock genotypes when propagated by layering. Four field experiments were performed in 2008 and 2009 to improve rooting of dwarfing rootstocks. Locations included Ephrata, Washington; Angers, France; and Canby, Oregon. The experiments compared the application of various plant growth regulators at various times of the year on B.9, M.9T337, M.9EMLA and G.41 rootstock stool beds. The chemicals used were prohexadione Ca (250 ppm or 1,000 ppm), indole-butyric acid (IBA) (1,000 ppm or 10,000 ppm) and naphthaleneacetic acid (NAA) (50 ppm or 200 ppm). IBA sprayed early in the season before mounding with sawdust consistently increased the rooting percentage; however, the treatment was expensive. Foliar applications of prohexadione Ca in the summer also increased the rooting percentage and reduced the number of spines with variations in response due to dose, location and timing. NAA applied foliarly in the summer did not increase rooting percentage.