Malus ×domestica Borkh. cv. Honeycrisp has been widely planted in North America during the past two decades. However, it is susceptible to many disorders that result in high postharvest losses. Excessive vegetative vigor in apple trees can reduce fruit calcium (Ca) concentrations and increase bitter pit incidence in apple fruit. Plant growth regulators are used routinely in tree fruit orchards to control vegetative growth to increase light penetration into the canopy. The objective of this study was to determine whether shoot growth inhibition using the application of prohexadione-calcium (P-Ca; Apogee®) or stimulation via application of gibberellic acid (GA3; ProGibb®) affected bitter pit incidence in ‘Honeycrisp’ apple. In 2016 and 2017, the experiment was conducted in a commercial ‘Honeycrisp’ orchard with five treatments [untreated control, 62.5 mg·L–1 P-Ca (low P-Ca); 125 mg·L–1 P-Ca (high P-Ca); 16 mg·L–1 GA3 (low GA3); and 32 mg·L–1 GA3 (high GA3)]. Treatments were applied twice during the growing season. Shoot length and the number of internodes for new growth were measured 4 weeks apart after treatment. Overall yield and fruit quality were assessed at harvest, and bitter pit incidence was assessed after 4 months of storage. Low and high P-Ca rates limited shoot growth extension; high GA3 increased shoot extension compared with the untreated control. However, the number of internodes did not change substantially for each shoot. The number of internodes is one of the primary factors affecting leaf area and, consequently, the transpiration balance between fruit and leaves. In both years, treatments with either GA3 or P-Ca did not affect fruit elemental concentration or bitter pit incidence. These results indicate that growth-inhibiting plant growth regulators that reduce shoot extension may not be useful for managing bitter pit incidence in ‘Honeycrisp’ apple.
Funding for the project was provided by the Washington Tree Fruit Research Commission AP-15-101. This work was also supported by the U.S. Department of Agriculture National Institute of Food and Agriculture, Hatch/Multi-State Project 227451.
We thank Katie Mullin and Michelle Reid for technical support for the project, and Chris Sater for editing assistance in writing.
BiancoR.L.PolicarpoM.ScarianoL.2015Effects of rootstock vigour and in-row spacing on stem and root growth, conformation and dry-matter distribution of young apple treesJ. Hort. Sci. Biotechnol.786828836
Bianco,R.L.Policarpo,M.Scariano,L.2015Effects of rootstock vigour and in-row spacing on stem and root growth, conformation and dry-matter distribution of young apple trees786828836)| false
GreeneD.W.LordW.J.1983Effects of dormant pruning, summer pruning, scoring, and growth regulators on growth, yield, and fruit quality of ‘Delicious’ and ‘Cortland’ apple treesJ. Amer. Soc. Hort. Sci.108590595
Greene,D.W.Lord,W.J.1983Effects of dormant pruning, summer pruning, scoring, and growth regulators on growth, yield, and fruit quality of ‘Delicious’ and ‘Cortland’ apple trees108590595)| false
RademacherW.van SaarloosK.Garuz PorteJ.A.Riera ForcadesF.SenechalY.AndreottiC.SpinelliF.SabatiniE.CostaG.2004Impact of prohexadione-Ca on the vegetative and reproductive performance of apple and pear treesEur. J. Hort. Sci.696221228
Rademacher,W.van Saarloos,K.Garuz Porte,J.A.Riera Forcades,F.Senechal,Y.Andreotti,C.Spinelli,F.Sabatini,E.Costa,G.2004Impact of prohexadione-Ca on the vegetative and reproductive performance of apple and pear trees696221228)| false
RaeseJ.T.1995 Effect of low soil pH from different fertilizers on performance of apple and pear trees p. 803–807. In: R.A. Date N.J. Grundon G.E. Rayment and M.E. Probert. (eds.). Plant–soil interactions at low pH. Kluwer Academic Publishers Springer Dordrecht
RobinsonT.LopezS.IungermanK.ReginatoG.2009Crop load management for consistent production of Honeycrisp applesNew York Fruit Qrtly.172428
Robinson,T.Lopez,S.Iungerman,K.Reginato,G.2009Crop load management for consistent production of Honeycrisp apples172428)| false
ShearC.B.1980 Interaction of nutrition and environment on mineral composition of fruits p. 41–50. In: D. Atkinson J.E. Jackson R.O. Sharples and W.M. Waller (eds.). Mineral nutrition of fruit trees. Butterworths London UK
SongJ.DengW.BeaudryR.M.ArmstrongP.R.1997Changes in chlorophyll fluorescence of apple fruit during maturation, ripening, and senescenceHortScience32891896
Song,J.Deng,W.Beaudry,R.M.Armstrong,P.R.1997Changes in chlorophyll fluorescence of apple fruit during maturation, ripening, and senescence32891896)| false