Stimulation of lateral branch formation on Ilex paraguariensis (Aquifoliaceae) seedlings
P. Sansberro A C , L. Mroginski A and R. Bottini BA Instituto de Botánica del Nordeste, Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, 3400 Corrientes, Argentina.
B Cátedra de Química Orgánica y Biológica, Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo, 5528 Chacras de Coria, Mendoza, Argentina.
C Corresponding author. Email: sansber@agr.unne.edu.ar
Australian Journal of Experimental Agriculture 46(5) 707-710 https://doi.org/10.1071/EA04178
Submitted: 19 August 2004 Accepted: 13 September 2005 Published: 12 May 2006
Abstract
Intensive yerba mate (Ilex paraguariensis St. Hil.) orchard management is needed to improve productivity. Full size trees with strong apical dominance are being replaced by smaller, more efficient trees, planted at higher densities for mechanical harvest. The production potential of a high-density field is maximised when cultural methods that control tree size and induce a significant number of well-distributed branches are used. The application of chemical pruning agents to shape the architecture of the seedling may be a viable alternative to induce lateral shoot development in replacement of the hand pruning technique. Nursery grown yerba mate seedlings were treated with a single foliar spray of aqueous solutions containing either benzyladenine (BA), 2,3:4,6-di-o-isopropylidene-2-keto-L-gulonic acid sodium salt (dikegulac) or 2,3,5-triiodobenzoic acid (TIBA), at the beginning of the second flash of growth (summer). A hand-pruned treatment was also included. BA-treated plants produced more new shoots than untreated controls or plants that received other treatments. BA treatment at 8.8 mmol/L increased the number of branches to up to 8 branches per single stem. Control plants sprayed with distilled water did not branch, while hand-pruned plants rarely showed more than 1 branch. Dikegulac was less effective than BA at promoting lateral branch development and its phytotoxicity was concentration dependent. TIBA did not stimulate budbreak; in addition, primary shoot development was delayed and leaf indentations were apparent. The results suggest that BA can be used to obtain high quality multiply-branched yerba mate plants.
Additional keywords: apical dominance, branching, chemical growth regulation, dormancy, yerba mate.
Acknowledgments
The authors thank the Universidad Nacional del Nordeste (UNNE) and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) for financial support. We extend our deep appreciation to Establecimiento Las Marías and Establecimiento La Cachuera for their interest in this work. We also thank Alder Vásquez for preparing the illustrations and anonymous reviewers for their critical comments.
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