Use of different plant growth regulators for control of shoot branching in apple and pear trees

T. Nečas, J. Wolf, T. Kiss, J. Láčík, T. Letocha
In production of high quality certified fruit trees, new tree growing methods utilizing plant growth regulators (PGRs) are increasingly being used. The main benefit of using PGRs lies in stimulating branching of one-year grafted fruit trees. In our experiment we used two apple cultivars: a well-branching ʻGalavalʼ and a very poorly branching cultivar ʻRubinolaʼ. From cultivars of European pear, we used ʻDecoraʼ as the well-branching cultivar and ʻBohemicaʼ as a poorly branching cultivar. We used the Japanese pear cultivar ʻHosuiʼ to verify the basic reaction to application of the commercial products of PGRs. For the purpose of our experiments we used commercially available products Globaryll 100 (6-BAP 10%, from Globachem, Belgium), Progerbalin LG (GA4 + GA7 1.88% and 6-BAP 1.88%, from L. Gobbi, Italy), GIBB plus (GA4 + GA7 1%, Globachem, Belgium). In addition, we also prepared mixed PGR solutions containing substances such as TIBA, 4-CPPU, paclobutrazol, ethephon, 6-BAP, gibberellic acid4+7, naphthylphtalamic acid, putrescine HCL and 24-epibrassinolide (all products from Duchefa, the Netherlands). The number of branches formed on trees of cultivar ʻGalavalʼ after application of the different PGR products and solutions ranged between 7.3 and 17.1 branches tree-1. The best results in stimulation of branching of ʻGalavalʼ trees was achieved by application of Progerbalin LG + 4-CPPU + putrescine HCL mixture. Branching in the range of 1.0-11.7 branches tree-1 was achieved in cultivar ʻRubinolaʼ, where the most effective branching treatment was Globaryll 100 (from the non-commercial mixtures the most efficient was the application of ethephon + 6-BAP + putrescine HCL). With the European pear cultivars, the achieved values were 6.1-39.9 branches tree-1 after application of different PGR products and solutions, where the best results were obtained by the application of ethephon + 6-BAP + putrescine HCL mixture. In trees of ʻBohemicaʼ cultivar the branching achieved 7.7-15.2 branches tree-1, depending on used PGR product or mixture. In trees of ʻHosuiʼ cultivar the results were 0.5-2.6 of short brachyblasts tree-1 when Progerbalin LG was applied. Application of the other products and mixtures was less efficient. We also obtained interesting results concerning features such as length of new branches, the overall tree height and thickness of the trunk at the root crown and under the first ramification. Significant differences were observed in the influence of the tested PGR products and mixtures over the parameters of the nursery plants.
Nečas, T., Wolf, J., Kiss, T., Láčík, J. and Letocha, T. (2018). Use of different plant growth regulators for control of shoot branching in apple and pear trees. Acta Hortic. 1206, 225-232
DOI: 10.17660/ActaHortic.2018.1206.31
auxins, cytokinins, gibberellic acid, ethephon, knip-boom tree

Acta Horticulturae