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ISHS Acta Horticulturae 1138: EUFRIN Thinning Working Group Symposia

The use of combined application of prohexadione-Ca and GA4+7 on the yield and growth of 'Braeburn Mariri Red' apple trees

Authors:   I. Szot, A. Basak, T. Lipa, P. Krawiec
Keywords:   tank-mix spraying, fruit quality, terminal shoot, bioregulator
DOI:   10.17660/ActaHortic.2016.1138.5
Prohexadione-Ca (P-Ca) is a plant bioregulator that has an anti-GA action and that is primarily used to control vegetative growth in apple trees. GAs beside stimulating shoot internode length when applied during the early period of fruit development might induce a larger fruit which also indicates that GAs might play a role in cell growth in apple fruit. Until now the combined application of P-Ca and GAs was not recommended because of the possibility of mutual reduction of their actions. Recently preliminary trials carried out on apple indicate the fruit thinning potential of the P-Ca and GA4+7 tank-mix. The tank mix of P-Ca as Regalis (10% W.G. formulation) and GA4+7 as Novagib was applied at different phenological stages on apples 'Braeburn Mariri Red' trees: at full bloom (BBCH 65) and at 6/8 mm diameter of king fruit (BBCH 71), 10/12 mm diameter of king fruit (BBCH 72) and 14/16 mm diameter of king fruit (BBCH 72). The concentration of P-Ca was 100 mg L-1 and GA4+7 10 mL L-1. Data were compared with untreated control trees. In this experiment the P-Ca and GA4+7 tank-mix did not cause any thinning effect at all the tested treatments. Unexpectedly the fruit set was even better in the treated trees than control, and, although the higher number of fruit, the fruit quality was not compromised. The combined use of P-Ca and GA4+7 resulted in a larger size of fruits than control. These results might be related to the vegetative growth control caused by P-Ca and the consequent limited competition vs. the developing fruits and to a direct effect of GA4+7 application that might have increased fruit growth.

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