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Effect of paclobutrazol and pinching on growth and fruiting of apple trees. II. Effect on Jonagold grown on two rootstocks

Władysław Poniedziałek, Kazimierz Nosal, Stanisław Porębski

Department of Pomology
Faculty of Horticulture, Agricultural University
29 Listopada 54, 31-425 Kraków, Poland

Jonagold apple trees planted in autumn 1986 were sprayed in the period 1989-1991 with paclobutrazol (PBZ) at different concentration or frequency. Another treatment consisted in the pinching of sprouts inside the tree canopy. Paclobutrazol significantly reduced shoot growth in the season 1989-1990 and increased the number of inflorescences but had no effect on the trunk cross-section area. As the result of paclobutrazol application the yield was significantly higher, by up to 36% on M 26, and tended to be higher on MM 106, by up to 28%. A similar increase in the crop efficiency index was noted. Paclobutrazol did not change the mean fruit weight. Pinching reduced the number of inflorescences, total yield, and crop efficiency index. Thus the effect of this factor was opposite to that of paclobutrazol. In general, the results presented here are in accordance with the previous studies on the cultivar Gloster (Poniedziałek et al., 1992), except for a stronger effect of paclobutrazol on the yield of Jonagold than on Gloster and the nil effect of pinching on mean fruit weight.

Poniedziałek W., Nosal K., Porębski S., 1992. Effect of paclobutrazol and pinching on growth and fruiting of apple trees. II. Effect on Jonagold grown on two rootstocks. Folia Horticulturae IV/2: 79-86.