Newly planted apple orchards in the USA comprising the highly biennial cultivar, “Honeycrisp”, are prone to flower within the first two years from planting and set fruit. These processes limit canopy development and subsequent yield potential. GA4+7 can inhibit floral formation processes of apples. The timing and dose for eliminating return bloom of young “Honeycrisp” trees, however, is unclear. A factorial experimental design to test GA4+7 application timing and rate produced significant reductions in return bloom for both factors and their interaction. Treatment responses demonstrated that florigenic processes in “Honeycrisp” occurred early. The most pronounced reduction in return bloom followed the 2-week after full bloom (WAFB) application timing, increasing with increasing rate. The effect on return bloom was progressively diminished over the next two weeks of applications but remained significantly lower than the control. Three successive applications timed one week apart eliminated return bloom of spurs at the highest rate. Both factors and their interaction also significantly reduced return bloom of terminal buds of leaders; in contrast to floral buds on spurs, the response of terminal buds on leaders improved with delayed application timings. Timing exerted a stronger effect than rate on return flowering of the terminal buds of leaders. Leader growth was positively affected by GA4+7, the year of application, when three successive applications were made. Tree height, overall growth, expressed as the increase in trunk cross-sectional area, and limb number were also significantly improved by GA4+7 but varied in their responses to application timing and rate, and were inconsistent. Overall, successive applications of GA4+7 had good efficacy for inhibiting floral initiation of meristems on spurs and terminals while improving the vegetative growth of young “Honeycrisp” trees.
References
[1]
Marino, F. and Greene, D.W. (1981) Involvement of Gibberellins in the Biennial Bearing of “Early Mcintosh” Apples1. JournaloftheAmericanSocietyforHorticulturalScience, 106, 593-596. https://doi.org/10.21273/jashs.106.5.593
[2]
Schmidt, T., Elfving, D.C., McFerson, J.R. and Whiting, M.D. (2009) Crop Load Overwhelms Effects of Gibberellic Acid and Ethephon on Floral Initiation in Apple. HortScience, 44, 1900-1906. https://doi.org/10.21273/hortsci.44.7.1900
[3]
Lakso, A.N. (2004) Handbook of Environmental Physiology of Fruit Crops. CRC Press, 7-14.
[4]
Hirst, P.M. and Ferree, D.C. (1995) Rootstock Effects on the Flowering of “Delicious” Apple. I. Bud Development. JournaloftheAmericanSocietyforHorticulturalScience, 120, 1010-1017. https://doi.org/10.21273/jashs.120.6.1010
[5]
Hoover, E., Silva, N.D., Mcartney, S. and Hirst, P. (2004) Bud Development and Floral Morphogenesis in Four Apple Cultivars. TheJournalofHorticulturalScienceandBiotechnology, 79, 981-984. https://doi.org/10.1080/14620316.2004.11511877
[6]
McArtney, S., Hoover, M., Hirst, P. and Brooking, I. (2001) Seasonal Variation in the Onset and Duration of Flower Development in “Royal Gala” Apple Buds. The Journal of Horticultural Science and Biotechnology, 76, 536-540.
[7]
Foster, T., Johnston, R. and Seleznyova, A. (2003) A Morphological and Quantitative Characterization of Early Floral Development in Apple (Malus x domestica Borkh.). AnnalsofBotany, 92, 199-206. https://doi.org/10.1093/aob/mcg120
[8]
Li, Y.J. (2022) Crop Load and Thinning Timing Effects on Flower Bud Initiation in “Gala” and “Honeycrisp” Apples and Observations of Flower Bud Initiation in “Gala”, “Empire”, “Fuji” and “Honeycrisp” Apple Trees. MS Diss, The University of Guelph, 76, 536-540.
[9]
Mimida, N., Komori, S., Suzuki, A. and Wada, M. (2013) Functions of the Apple TFL1/FT Orthologs in Phase Transition. ScientiaHorticulturae, 156, 106-112. https://doi.org/10.1016/j.scienta.2013.04.001
[10]
Greene, D.W. (2000) Reducing Floral Initiation and Return Bloom in Pome Fruit Trees—Applications and Implications. HortTechnology, 10, 740-743. https://doi.org/10.21273/horttech.10.4.740
[11]
Greene, D. (2019) Optimizing Plant Growth, Yield and Fruit Quality with Plant Bioregulators. In: Achieving Sustainable Cultivation of Temperate Zone Tree Fruits and Berries, Burleigh Dodds Science Publishing, 299-346. https://doi.org/10.19103/as.2018.0040.09
[12]
Guitton, B., Kelner, J.J., Celton, J.M., Sabau, X., Renou, J.P., Chagné, D., et al. (2016) Analysis of Transcripts Differentially Expressed between Fruited and Deflowered “Gala” Adult Trees: A Contribution to Biennial Bearing Understanding in Apple. BMCPlantBiology, 16, Article No. 55. https://doi.org/10.1186/s12870-016-0739-y
[13]
Xing, L., Zhang, D., Li, Y., Shen, Y., Zhao, C., Ma, J., et al. (2015) Transcription Profiles Reveal Sugar and Hormone Signaling Pathways Mediating Flower Induction in Apple (Malusdomestica Borkh.). PlantandCellPhysiology, 56, 2052-2068. https://doi.org/10.1093/pcp/pcv124
[14]
Luckwill, L.C. (1974) A New Look at the Process of Fruit Bud Formation in Apple. Proceedings of the XIX International Horticultural Congress, Vol. 3, 237-245.
[15]
Hoad, G.V. (1978) The Role of Seed Derived Hormones in the Control of Flowering in Apple. ActaHorticulturae, 80, 93-104. https://doi.org/10.17660/actahortic.1978.80.14
[16]
Greene, D.W. (1993) Effects of GA4 and GA7 on Flower Bud Formation and Russet Development on Apple. JournalofHorticulturalScience, 68, 171-176. https://doi.org/10.1080/00221589.1993.11516340
[17]
McArtney, S.J. and Li, S. (1998) Selective Inhibition of Flowering on “Braeburn” Apple Trees with Gibberellins. HortScience, 33, 699-700. https://doi.org/10.21273/hortsci.33.4.699
[18]
Tromp, J. (1982) Flower-Bud Formation in Apple as Affected by Various Gibberellins. JournalofHorticulturalScience, 57, 277-282. https://doi.org/10.1080/00221589.1982.11515053
[19]
Looney, N.E., Pharis, R.P. and Noma, M. (1985) Promotion of Flowering in Apple Trees with Gibberellin A4 and C-3 Epi-Gibberellin A4. Planta, 165, 292-294. https://doi.org/10.1007/bf00395054
[20]
Haberman, A., Ackerman, M., Crane, O., Kelner, J., Costes, E. and Samach, A. (2016) Different Flowering Response to Various Fruit Loads in Apple Cultivars Correlates with Degree of Transcript Reaccumulation of a tfl1‐Encoding Gene. ThePlantJournal, 87, 161-173. https://doi.org/10.1111/tpj.13190
[21]
Flachowsky, H., Szankowski, I., Waidmann, S., Peil, A., Trankner, C. and Hanke, M. (2012) The MdTFL1 Gene of Apple (Malus x domestica Borkh.) Reduces Vegetative Growth and Generation Time. TreePhysiology, 32, 1288-1301. https://doi.org/10.1093/treephys/tps080
[22]
Kotoda, N., Iwanami, H., Takahashi, S. and Abe, K. (2006) Antisense Expression of MdTFL1, a TFL1-Like Gene, Reduces the Juvenile Phase in Apple. JournaloftheAmericanSocietyforHorticulturalScience, 131, 74-81. https://doi.org/10.21273/jashs.131.1.74
[23]
Elsysy, M.A. and Hirst, P.M. (2019) Molecular Basis of Flower Formation in Apple Caused by Defoliation and Gibberellins. JournaloftheAmericanSocietyforHorticulturalScience, 144, 414-419. https://doi.org/10.21273/jashs04760-19
[24]
Unrath, C.R. and Whitworth, J. (1991) Suppression of Apple Bloom with Gibberellin Sprays. JournalofHorticulturalScience, 66, 155-157. https://doi.org/10.1080/00221589.1991.11516138
[25]
Greene, D.W. (1989) Gibberellins A4+7 Influence Fruit Set, Fruit Quality, and Return Bloom of Apples. JournaloftheAmericanSocietyforHorticulturalScience, 114, 619-625. https://doi.org/10.21273/jashs.114.4.619
[26]
Marini, R.P. (2003) Approaches to Analyzing Experiments with Factorial Arrangements of Treatments plus Other Treatments. HortScience, 38, 117-120. https://doi.org/10.21273/hortsci.38.1.117
[27]
Reynolds, L.P., Jacobs, G. and Theron, K.I. (2005) Reproductive Bud Development in Pears (Pyruscommunis L.) with the Emphasis on Bourse Shoot. Acta Horticulturae, 671, 451-454.
[28]
Kon, T. and Schupp, J. (2018) Apple Crop Load Management with Special Focus on Early Thinning Strategies: A US Perspective. Horticultural Reviews, 46, 255-298.
[29]
Robinson, T.L., Gonzalez, L., Cheng, L., Ziang, Y., Peck, G., Arnoldussen, B., et al. (2023) Studies in Precision Crop Load Management of Apple. ActaHorticulturae, 1366, 219-226. https://doi.org/10.17660/actahortic.2023.1366.25
[30]
Buban, T. and Faust, M. (1982) Flower Bud Induction in Apple Trees: Internal Control and Differentiation. Horticultural Reviews, 4, 174-203.
[31]
Elsysy, M.A. and Hirst, P.M. (2017) The Role of Spur Leaves, Bourse Leaves, and Fruit on Local Flower Formation in Apple: An Approach to Understanding Biennial Bearing. HortScience, 52, 1229-1232. https://doi.org/10.21273/hortsci12136-17
[32]
Elsysy, M.A. and Hirst, P.M. (2023) Flowering in “Honeycrisp” Apple Shows That Spurs Are Semiautonomous Organs. JournaloftheAmericanSocietyforHorticulturalScience, 148, 108-116. https://doi.org/10.21273/jashs05281-22
[33]
Elfving, D.C., Visser, D.B. and Henry, J.L. (2011) Gibberellins Stimulate Lateral Branch Development in Young Sweet Cherry Trees in the Orchard. InternationalJournalofFruitScience, 11, 41-54. https://doi.org/10.1080/15538362.2011.554066
[34]
McArtney, S. and Obermiller, J.D. (2015) Effect of Notching, 6-Benzyladenine, and 6-Benzyladenine plus Gibberellin A4 + A7 on Budbreak and Shoot Development from Paradormant Buds on the Leader of Young Apple Trees. HortTechnology, 25, 233-237. https://doi.org/10.21273/horttech.25.2.233
