Analysis of the Impact of Treatments Stimulating Branching on the Quality of Maiden Apple Trees
1
Institute of Horticulture Production, University of Life Science, 28 Głęboka Street, 20-612 Lublin, Poland
2
Department of Applied Mathematics and Computer Sciences, University of Life Science, 28 Głęboka Street, 20-612 Lublin, Poland
*
Author to whom correspondence should be addressed.
Agriculture 2024, 14(10), 1757; https://doi.org/10.3390/agriculture14101757
Submission received: 31 July 2024
/
Revised: 24 September 2024
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Accepted: 2 October 2024
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Published: 5 October 2024
(This article belongs to the Special Issue The Impact of Environmental Factors on the Quality of Horticultural Commodities)
Abstract
:Nursery material intended for establishing intensive apple orchards should be characterised by a dominant and straight leader with an appropriate number of shoots that develop at the right height and are regularly spaced along the leader. The use of well-branched trees can lead to fruiting in the first year after planting. However, many apple varieties have difficulty forming lateral shoots due to strong apical dominance. The aim of the study was to assess the effectiveness of treatments stimulating the branching of maiden apple trees of the ‘Gloster’ variety. The research was carried out in 2017–2019 at a private nursery farm located in eastern Poland. The studied trees were subjected to a mechanical branching stimulation treatment, which consisted of pinching off 4–5 of the youngest leaves located below the growth cone, and chemical branching stimulation treatments, which consisted of applying growth regulator mixtures in the form of an aqueous solution, i.e., BA+GA3 and BA+GA4+7. The conducted studies showed that the type of branching-stimulating treatment had a significant effect on the height and trunk diameter of the maiden trees, the number of lateral shoots, the average length of one shoot and the sum of the lengths of all sylleptic shoots. The maiden trees treated with BA+GA3 were characterised by the best quality among the analysed combinations. Maiden apple trees treated with BA+GA3 were the tallest (2017—167.7 cm; 2018—175.3 cm; 2019—164.4 cm), produced the largest number of shoots (2017—6.5 pcs; 2018—6.8 pcs; 2019—6.3 pcs) and had the largest sum of lateral shoot lengths (2017—148.0 cm; 2018—155.4 cm; 2019—140.6 cm) among the evaluated combinations. The number of treatments and the concentration of applied growth regulators had a significant effect on the structure of the crown of the maiden apple trees of the ‘Gloster’ cultivar.
1. Introduction
Apple trees are one of the main horticultural crops in the world [1]. It is estimated that the global planted area of this crop in 2021 was 4,825,629.0 ha, and the yield reached approximately 93.1 million tonnes [2]. At the same time, intensive orchard production characterised by high yields due to high tree planting densities requires high-quality planting material with well-developed crowns [3]. The presence of apple tree shoots is crucial for their fruiting [4,5,6,7]. High-quality apple tree planting material should be characterised by a dominant, straight central canopy with an adequate number of shoots that develop to the right height and are regularly spaced along the canopy. These shoots should reach the right length and bifurcation angle. Trees with these characteristics root quickly after planting, effectively fill the space in the rows and efficiently capture light in the early stages of growth [8]. Growers typically choose dwarf and semi-dwarf trees for their quick production of apple fruit and quick return on investment, making these plants more desirable. The use of well-branched trees can lead to fruiting as early as the first year after planting. Branching treatments, including mechanical as well as chemical methods, are used to produce well-branched trees [9,10].
Strongly branched apple trees promote faster crown formation, which facilitates pruning and reduces maintenance costs [11]. Furthermore, well-branched apple trees are crucial for commercial orchards to achieve maximum yields. However, many varieties find it difficult to form these lateral branches under commercial nursery conditions due to strong apical dominance. There are several methods to aid the formation of these branches in nurseries [12]. Shoot branching, which is formed by the growth of axillary buds, is a key element of the aboveground architecture of plants. An important quality parameter in apple seedling production is the number of shoots formed. Unfortunately, at present, the molecular mechanism regulating bud activation and cell cycle processes in apple trees is still poorly understood [13]. The axillary buds of apple trees, located in the leaf angles, usually remain dormant due to the correlative inhibition exerted by the apical buds [14]. The number of branches is largely determined by the formation, release and growth of axillary buds. Humans have attempted to regulate shoot branching according to their needs to improve agricultural production [15,16].
Diversity in plant structure, the result of evolution and artificial selection, is controlled by complex, integrated networks of genetic and environmental signals [17]. Various plant hormones that interact with environmental signals play a major role in regulating branching [18]. These factors can act alone or together to influence the formation of plant architecture. However, a full understanding of the mechanisms controlling or regulating lateral branch development is still a long way off. Although many genes involved in the regulation of these branches have recently been identified, their overarching regulators and target effects are largely unknown. The consideration of factors influencing lateral branch formation is the foundation of rational plant breeding and the cultivation of optimal plant types [16].
Currently, the most common methods used to branch apple trees in nurseries are chemical methods based primarily on growth regulators as well as mechanical methods, such as apical leaf pinching, which is aimed at breaking apical dominance and stimulating lateral shoot development.
Plant growth regulators are naturally biosynthesised chemical compounds that interact with plant physiological processes. Their synthetic counterparts initiate a variety of biochemical and physiological processes related to plant growth and development [19]. Exogenous growth regulators based on benzyladenine and gibberellins show strong potential for use in apple branching [20]. Both benzyladenine and BA+GA4+7 and BA+GA3 are effective in temporarily interrupting apical dominance [21]. Growth regulators based on 6-benzyladenine (6-BA), used alone or in combination with gibberellin GA4+7 (6-BA+GA4+7) or GA3 (6-BA+GA3), are commonly used to increase the intensity of lateral shoot development in juvenile trees [22].
The aim of this study was to evaluate the effectiveness of treatments to stimulate the branching of ‘Gloster’ apple trees. The effects of different modes, the number of branching treatments and the concentrations of applied growth regulators on the growth and quality of nursery stock were evaluated.
2. Materials and Methods
The study was carried out in 2017–2019 at a private nursery farm located in the village of Karczmiska in the municipality of Karczmiska, Opolski County, Lubelskie Province (GPS: 51.247144, 22.033154). The experiment evaluated the growth and quality of maiden apple trees of the ‘Gloster’ cv. grafted on M.9 RN29 rootstock after the application of branching stimulation treatments. The experiment was set up in a randomised block design and included 11 combinations with 5 replications (one replication was a plot with 15 plants).
2.1. Treatments
The following combinations were used in the experiment:
- 1.
- Control—trees not subjected to branching stimulation treatments;
- 2.
- Pinching out of 4–5 youngest leaves—1 x season;
- 3.
- Pinching out of 4–5 youngest leaves—2 x season;
- 4.
- 4.5 mL of Globaryll 100 SL + 0.45 g of Florgib/1 L of water—1 x season;
- 5.
- 4.5 mL of Globaryll 100 SL + 0.45 g of Florgib/1 L of water—2 x season;
- 6.
- 6.8 mL of Globaryll 100 SL + 0.63 g of Florgib/1 L of water—1 x season;
- 7.
- 6.8 mL of Globaryll 100 SL + 0.63 g of Florgib/1 L of water—2 x season;
- 8.
- 4.5 mL of Globaryll 100 SL + 45 mL of Gibb Plus 11 SL/1 L of water—1 x season;
- 9.
- 4.5 mL of Globaryll 100 SL + 45 mL of Gibb Plus 11 SL/1 L of water—2 x season;
- 10.
- 6.8 mL of Globaryll 100 SL + 67.5 mL of Gibb Plus 11 SL/1 L of water—1 x season;
- 11.
- 6.8 mL of Globaryll 100 SL + 67.5 mL of Gibb Plus 11 SL/1 L of water—2 x season.
The experiment was carried out every summer when the apple trees were in their second year and last year in the nursery and had reached a height of about 75 cm. Depending on the combination, treatments were carried out once or twice per season; the first treatment occurred when the trees reached a height of about 75 cm and the second was 7 days later.
The chemical branching stimulation treatments consisted of an aqueous solution application of Globaryll 100 SL (BA—6-benzyladenine—100 g/L (9.50%), Florgib (GA3—gibberellic acid—204 g/kg (20.4%)) and Gibb Plus 11 SL (GA4+7—gibberellin GA4+7—10 g/L (0.97%)). BA—6-benzyladenine—is a substance belonging to the cytokinin group, which stimulates the growth and metabolism of plants. This hormone regulates many biochemical processes at the cellular level of plants, but it has a particularly strong influence on cell division. Florgib is a growth regulator based on gibberellic acid (GA3; stimulates elongation of cells and shoot elongation), which has a unique formula of rapidly dissolving tablets. The gibberellin GA4+7 causes excessive cell elongation. The aqueous solution was sprayed on the six youngest well-developed lateral buds together with the leaves just below the growth cone. The adjuvant Superam 10 AL was added to the preparation of the solution at a dose of 0.5 mL per 1 L of water each time in order to prolong the durability of the effect of the mixtures. This formulation was only used in combinations where growth regulators were applied. During the experiment, regular protection of the nursery against diseases, pests and weeds was carried out according to the recommendations of the orchard protection programme.
2.2. Measurements
In autumn, after the end of growth, the following measurements and observations were made: diameter of the rootstock stems at 10 cm above the soil surface, diameter of the whorl stems at 30 cm from the ground, height of the trees, number of lateral shoots, length of sylleptic shoots and the sum of the lengths of the sylleptic shoots. The diameters of rootstocks and whorls were measured using callipers with an accuracy of 0.1 mm. The height of the trees from the point of budding to the apical bud of the main shoot was measured using a scaler to the nearest 1 cm. On each oculant, lateral shoots were counted and their length measured.
The results obtained in the experiment were statistically analysed using the one-factor analysis of variance method. Inference was based on significance p < 0.05. All statistical analyses were performed using Statistica 13.
The average air temperature in the months from April to October in the consecutive years of the study was higher than the multi-year average (Table 1). Analysis of the above weather parameter showed that the temperature in all months in 2017–2019 was higher than for the multi-year average. It was shown that, in the summers of 2018 and 2019, the average air temperature reached the same level, i.e., 15.7 °C, and was higher than the multi-year average by 2.5 °C. Optimal environmental conditions, such as light, temperature and precipitation, are the most important factors influencing plant growth [22]. Excessive deviations in at least one of the above-mentioned environmental parameters may have a negative effect on plant growth and development and may disturb aromatic vegetative development. Koyuncu and Ersoy [23], studying different apple varieties in nurseries grown under controlled greenhouse and field conditions, observed that trees grown under protected conditions had higher vegetative growth and smaller trunk cross-sectional areas than trees grown under orchard conditions.
Total rainfall in the months of April to October differed significantly between study years. It was found that the driest year was 2019, with a total rainfall of 400 mm. In 2018, rainfall reached 461 mm. In 2017, the rainfall level was the highest and differed significantly from the multi-year average, reaching 692 mm.
Analysis of weather conditions would indicate that the effectiveness of the treatments used in 2019, when the total rainfall was lower than the multi-year average, could have been lower than in other years of the study. Water deficit during the period of intensive tree growth may have a negative impact on growth and quality parameters.
3. Results and Discussion
Tables of Total Rainfall
The height of ‘Gloster’ apple trees in autumn after growth was significantly affected by the type of branching stimulation treatment and the year of the study (Table 2). It was found that the trees treated with BA+GA3 each year were significantly taller than the others. A significant effect of the type of branching treatment on the height of apple trees of the ‘Rubinola’ and ‘Topaz’ cultivars was shown by Laňar et al. in their study [24]. Different results were obtained by Gąstoł et al. [20] when evaluating apple trees of the ‘Boskoop’ cultivar, where preparations based on growth regulators did not affect tree growth. In the present study, it was shown that in 2018, the perianths of the studied apple cultivar were significantly higher than in the other years of the study; this relationship was not shown in the case of trees treated with BA+GA4+7. Similar relationships were shown in the work by Gąstoł et al. [20] and Kaplan et al. [25].
It was shown that the applied branching stimulation treatments and the year of the study had no significant effect on the diameter of the rootstock stems. The above study confirmed the previous results of Kaplan et al. [26], whose aim was to evaluate the effect of the branching treatment on the growth and quality of ‘Gloster’ and ‘Jonagold’ apple trees’ perianths. Research conducted in 2017–2019 by Kaplan et al. [25] on the apple cultivars ‘Alwa’ and ‘Najdared’ showed that the diameter of rootstock trunks was significantly affected by branching treatments.
The diameter of the trunks of the whorled trees depended significantly on the type of treatment given. Control trees and trees pinched annually were significantly thicker than those treated with BA+GA4+7. There was no significant effect of test year on the trait studied. Carra et al. [22], evaluating the effect of 6-benzyladenine (6-BA) and 6-benzyladenine + gibberellin 4 and 7 (6-BA+GA4+7) on the growth and quality of apple trees of the cultivars ‘Early Red One’ and ‘Fuji’, showed no significant effect of branching treatments on the stem diameter of trees. Doric et al. [27] observed differences in the trunk diameter of grafted young apple trees of the ‘Gala’ cultivar after three sprayed applications of 6-BA at concentrations of 250 and 350 mg L−1. The application of this treatment resulted in a decrease in the trunk diameter compared to untreated trees, while, in the case of the ‘Jonagold’ cultivar, the trend was the opposite. Steiner et al. [28] showed a reduction in stem diameter in ‘Golden Delicious’ apple trees treated with branching treatments. Rossi et al. [29] showed that a single spray of 6-BA+GA4+7 at different concentrations (0, 500, 1000 and 1500 mg L−1) reduced the trunk diameter of young grafted ‘Catarina’ apple plants, but the difference was not statistically significant. Literature data indicate an ambiguous effect of growth regulators on the stem thickness of trees subjected to branching treatments, so the mechanism of the effect of this type of preparation on tree diameter has not been precisely determined.
The number of lateral shoots ranged from 1.3 to 6.8 and was significantly dependent on the branching treatment and the type of growth regulators used. In the first two years of the study, it was shown that control and pinch-treated trees produced significantly fewer lateral shoots than chemically treated branching trees. In 2019, this relationship was shown in the combination of leaf pinching and a chemical treatment. It was shown, not depending on the year of the study, that the whorls treated with BA+GA3 produced significantly more shoots than those treated with BA+GA4+7. Laňar et al. [24] also found that the number of lateral shoots was significantly influenced by the method of branching treatment and the type of growth regulators used. No significant effect of the year of study on the trait studied was shown in the present study. A similar trend was shown by Gąstoł et al. [20]. The sum of lateral shoot lengths ranged from 3.1 to 155.4 cm and varied significantly. Significant differences were found between all the combinations used. Significantly, the smallest sum of lateral shoot lengths was obtained in control trees and the largest in BA+GA3 treated trees. Trees subjected to mechanical branching treatments formed a significantly lower sum of lateral shoot lengths than those treated with chemical treatments. It was shown that the type of mixture used, in the case of chemical branching, had a significant effect on the trait under study. Trees treated with the BA+GA3 solution produced a significantly higher sum of lateral shoot lengths than those treated with BA+GA4+7. There was no significant effect of the year of testing on the trait studied. Kumawat et al. [8], evaluating the effect of branching stimulation treatments on the quality of ‘Oregon Spur’ apple trees, showed that trees with a higher number of lateral shoots produced a higher total sum of lateral shoot lengths, a relationship that was confirmed in the present study.
The length of lateral shoots is directly related to the productivity of trees in the orchard and is crucial in determining the quality of nursery stock [8]. Statistical analysis for the parameter determining the length of one shoot showed identical relationships to those for the sum of lateral shoot lengths. Although the control trees formed significantly fewer lateral shoots than those treated with growth regulators, their length was also, significantly, the smallest among the evaluated trees. This does not confirm the observations of other authors [8,27,30,31].
On trees treated with BA+GA3, the mean shoot length was significantly lower than after the application of BA+GA4+7. As confirmed in other studies [8,27,31], the production of a greater number of lateral shoots by a tree can have an effect on reducing the length of these shoots; this was fully confirmed in the present study.
The height of the whorls was significantly modified by the type of branching-stimulating treatment (Table 3). It was shown that trees treated with BA+GA3 were significantly taller than the others. A significant effect of the number of applications on the studied trait was shown only for trees treated with pinching. Laňar et al. [24], evaluating apple trees of the ‘Rubinola’ and ‘Topaz’ cultivars, showed a significant effect of the number of benzyladein (BA) treatments on tree height.
The diameter of rootstock trunks significantly depended on the type of branching treatment and the number of applications. The highest values of this parameter were obtained in maiden trees treated once and twice with BA+GA3 and in those treated twice with BA+GA4+7. The rootstock trunks of maiden trees treated once were significantly thicker than those treated twice. This trend was not confirmed in trees treated with BA+GA4+7.
The trunk diameter of perianths treated once with branching treatments were significantly larger in the pinching combination than in those treated with BA+GA4+7. With two treatments, it was shown that the trunks of perianths sprayed with BA+GA3 were significantly thicker than the others. There was no clear effect of the number of treatments on the traits under study.
The number of lateral shoots and the sum of lateral shoot lengths in the BA+GA3-treated trees were significantly higher than in the other combinations, regardless of the number of treatments. The number of treatments did not show any significant effect on the number of lateral shoots in maiden trees treated with BA+GA3. In the case of trees treated with BA+GA3 and BA+GA4+7, it was found that trees sprayed twice formed a significantly higher number of lateral shoots and total lateral shoot lengths than trees treated once. This trend was confirmed in trees treated with pinching by analysing the sum of lateral shoot lengths. The effect of the number of treatments on the number of lateral shoots was confirmed by Laňar et al. in their study [24].
The average shoot length in trees treated with pinching was significantly lower than in the other combinations, regardless of the number of applications. Trees treated twice with branching-stimulating treatments formed significantly longer shoots than those treated once.
The size of the dose had no significant effect on the height of apple trees (Table 4). Trees treated with BA+GA3 were significantly taller than those treated with BA+GA4+7. Laňar et al. [24] showed that doubling the dose of Progerbalin ®LG had a significantly negative effect on the height of apple trees.
The stem diameter of rootstocks of trees treated with the lower dose of BA+GA3 was significantly smaller than those treated with the higher dose. At the higher concentration, trees treated with BA+GA3 had significantly thicker trunks than those that received applications of BA+GA4+7.
The diameter of the trunks of trees treated with the lower dose of BA+GA3 was significantly smaller than those treated with the higher dose, while the opposite trend was shown for the application of BA+GA4+7. Trees treated with BA+GA3 were significantly thicker than those that received applications of BA+GA4+7, and this was independent of the application rate.
The number of lateral shoots on trees treated with a higher dose of the BA+GA3 mixture was significantly higher than those that received applications of the higher dose of BA+GA4+7. The effect of the concentration of growth regulators applied on the number of lateral shoots was confirmed in numerous studies [8,20,22,24].
The sum of lateral shoot lengths in trees treated with the BA+GA3 solution at a higher concentration was significantly higher than those that received applications of the lower dose. The sum of lateral shoot lengths on maiden trees treated with BA+GA3 was significantly greater than those that received applications of the lower dose. Trees treated with the BA+GA3 solution produced a significantly higher sum of lateral shoot lengths than those treated with BA+GA4+7.
Mean shoot length was significantly dependent on the type of solution applied. The whorls treated with BA+GA4+7 formed significantly longer shoots than those that received applications of BA+GA3.
The PCA showed the influence of the concentration of the applied preparations on the number, the average length and the sum of the lengths of the lateral shoots. The above-mentioned parameters defining the quality of the crown structure were analysed jointly for the types of growth regulators used and their concentrations. The sum of the total variable PCs for the analysed parameters defining the structure of the crown in maiden apple trees of the ‘Gloster’ cultivar was 100% (for PC1 98.14% and for PC2 2.86%, respectively) (Figure 1). Analysing the quality of the trees expressed by the number, average length and the sum of the lengths of lateral shoots, a very high similarity and dependence was observed between BA+GA3 and BA+GA4+7 in low and high doses, regardless of the number of applications. The presented analysis clearly indicates that the factor that most strongly determines the effectiveness of using growth regulators is the number of applications, not the type of preparation used.
Figure 2 shows a comprehensive analysis of the growth and quality of the maiden ‘Gloster’ trees. The above analysis was developed based on the following parameters: growth of the maiden trees; diameter of the rootstock and maiden trunks; and number, average length and sum of the lengths of side shoots. As can be seen from the presented dendrogram (Figure 2a), for the parameters determining the growth and quality of maiden apple trees of the ‘Gloster’ variety after a single application of treatments to stimulate branching, there is one cluster focusing on the pinching procedure and another focusing on the mixture of growth regulators: BA+GA4+7 and an outlier in the form of the mixture BA+GA3. In the case of the dendrogram (Figure 2b), determining the growth and quality of maiden apple trees of the ‘Gloster’ variety after two applications of branching-stimulating treatments, slightly different relationships were observed, maiden trees of the ‘Gloster’ variety after two applications of branching-stimulating treatments created one cluster consisting of the mixture of the growth regulators BA+GA4+7 and BA+GA3 and an outlier in the form of the pinching procedure.
4. Conclusions
1. The type of branching-stimulating treatment of the apple cv. ‘Gloster’ had a significant effect on the height, stem diameter, number of lateral shoots, average length of one shoot and the sum of the lengths of all sylleptic shoots.
2. The year of the study had a significant effect on the height and number of lateral shoots of the studied apple cultivar.
3. Maiden apple trees treated with BA+ GA3 were, significantly, the tallest (2017—167.7 cm; 2018—175.3 cm; 2019—164.4 cm), produced the largest number of shoots (2017—6.5 pcs; 2018—6.8 pcs; 2019—6.3 pcs) and had the largest sum of lateral shoot lengths (2017—148.0 cm; 2018—155.4 cm; 2019—140.6 cm) among the evaluated combinations.
4. The number of treatments and the concentration of applied growth regulators had a significant effect on the crown structure of ‘Gloster’ apple trees. Trees chemically treated for branching formed a significantly higher number and total length of lateral shoots after two applications and a higher concentration of a growth regulator than after a single application and a lower dose.
Author Contributions
Conceptualization, M.K. and K.E.K.; methodology, M.K.; software, K.E.K.; validation, M.K., K.E.K. and K.B.; formal analysis, K.B.; investigation, M.K.; resources, K.E.K.; data curation, K.B.; writing—original draft preparation, M.K., K.E.K. and K.B.; writing—review and editing, M.K. and K.E.K.; visualization, K.E.K.; supervision, M.K. and K.E.K.; project administration, K.E.K.; funding acquisition, M.K. All authors have read and agreed to the published version of the manuscript.
Funding
The cost was incurred from financial resources from the IDUB University Development Strategy for 2024–2026 in the discipline of Agriculture and Horticulture as part of the task “Stage: 1, payment from funds: SUBB.RNN.24.019”.
Data Availability Statement
The data presented in this study are available on request from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
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Figure 1.
PCA analysis for the effect of the applied concentrations of growth regulators, regardless of their type, on the quality of the crown structure of maiden apple trees of the ‘Gloster’ variety.
Figure 1.
PCA analysis for the effect of the applied concentrations of growth regulators, regardless of their type, on the quality of the crown structure of maiden apple trees of the ‘Gloster’ variety.
Figure 2.
Branching tree diagram for the growth and quality of maiden apple trees of the ‘Gloster’ variety (a) for a single number of treatments, regardless of the concentration of applied growth regulator and the year of research; (b) for twice the number of treatments, regardless of the concentration of applied growth regulator and the year of research.
Figure 2.
Branching tree diagram for the growth and quality of maiden apple trees of the ‘Gloster’ variety (a) for a single number of treatments, regardless of the concentration of applied growth regulator and the year of research; (b) for twice the number of treatments, regardless of the concentration of applied growth regulator and the year of research.
Table 1.
Average monthly air temperatures and total precipitation according to the agrometeorological station in Lublin during the months of April to October in 2017–2019.
Table 1.
Average monthly air temperatures and total precipitation according to the agrometeorological station in Lublin during the months of April to October in 2017–2019.
| Air Temperature, °C | ||||||||
|---|---|---|---|---|---|---|---|---|
| IV | V | VI | VII | VIII | IX | X | Mean from IV to X °C | |
| 2017 | 8.0 | 14.1 | 19.6 | 18.9 | 20.2 | 13.5 | 8.5 | 14.7 |
| 2018 | 7.5 | 16.7 | 18.8 | 20.6 | 20.8 | 15.5 | 10.0 | 15.7 |
| 2019 | 9.5 | 13.4 | 21.5 | 19.4 | 20.3 | 14.5 | 11.0 | 15.7 |
| Multi-year Average | 7.4 | 13.0 | 16.3 | 18.0 | 17.2 | 12.6 | 7.6 | 13.2 |
| Total Precipitation, mm | ||||||||
| IV | V | VI | VII | VIII | IX | X | ∑ Precipitation | |
| 2017 | 55.0 | 29.1 | 282.0 | 107.9 | 48.0 | 80.0 | 90.0 | 692.0 |
| 2018 | 40.0 | 56.0 | 65.0 | 124.0 | 72.0 | 68.0 | 36.0 | 461.0 |
| 2019 | 49.0 | 93.0 | 37.0 | 38.0 | 102.0 | 52.0 | 29.0 | 400.0 |
| Multi-year Average | 39.0 | 60.7 | 65.9 | 82.0 | 70.7 | 53.7 | 40.1 | 400.0 |
* IV—April; V—May; VI—June; VII—July; VIII—August; IX—September; X—October.
Table 2.
Effect of branching stimulation treatments on growth and quality of ‘Gloster’ cv. apple trees in 2017–2019.
Table 2.
Effect of branching stimulation treatments on growth and quality of ‘Gloster’ cv. apple trees in 2017–2019.
| 2017 | 2018 | 2019 | p-value | |
| Height of maiden apple trees in autumn, cm | ||||
| Control | 153.8 ± 9.7 Bb * | 163.4 ± 10.1 Ba | 153.2 ± 9.5 Bb | 0.1064 |
| Pinching leaves | 154.3 ± 8.6 Bb | 161.2 ± 9.0 Ba | 151.2 ± 8.4 Bb | 0.0001 |
| BA+GA3 ** | 167.7 ± 5.2 Ab | 175.3 ± 5.4 Aa | 164.4 ± 5.1 Ac | 0.0001 |
| BA+GA4+7 *** | 155.4 ± 24.0 Ba | 162.4 ± 25.1 Ba | 152.3 ± 23.6 Ba | 0.1064 |
| p-value | 0.0001 | 0.0001 | 0.0001 | |
| Diameter of rootstocks, mm | ||||
| Control | 24.0 ± 2.9 Aa | 25.1 ± 3.0 Aa | 24.3 ± 3.0 Aa | 0.0711 |
| Pinching leaves | 22.6 ± 2.2 Aa | 23.7 ± 2.3 Aa | 23.0 ± 2.2 Aa | 0.1841 |
| BA+GA3 | 23.8 ± 3.0 Aa | 24.9 ± 3.2 Aa | 24.2 ± 3.1 Aa | 0.2166 |
| BA+GA4+7 | 22.9 ± 2.2 Aa | 23.9 ± 2.3 Aa | 23.2 ± 2.2 Aa | 0.0641 |
| p-value | 0.0810 | 0.0810 | 0.0810 | |
| Diameter of maiden trees, mm | ||||
| Control | 17.2 ± 2.2 Aa | 17.8 ± 2.3 Aa | 17.6 ± 2.3 Aa | 0.9377 |
| Pinching leaves | 16.7 ± 7.7 Aa | 17.2 ± 7.9 Aa | 17.1 ± 7.8 Aa | 0.4447 |
| BA+GA3 | 15.8 ± 1.4 ABa | 16.4 ± 1.5 ABa | 16.2 ± 1.4 ABa | 0.1852 |
| BA+GA4+7 | 14.5 ± 1.4 Ba | 15.0 ± 1.5 Ba | 14.8 ± 1.5 Ba | 0.2494 |
| p-value | 0.0078 | 0.0078 | 0.0078 | |
| Number of lateral shoots, pcs | ||||
| Control | 1.4 ± 1.1 Cb | 1.3 ± 1.1 Cab | 2.7 ± 4.8 BCa | 0.8974 |
| Pinching leaves | 1.8 ± 1.4 Ca | 1.9 ± 1.5 Ca | 1.7 ± 1.4 Ca | 0.0228 |
| BA+GA3 | 6.5 ± 1.4 Aa | 6.8 ± 1.5 Aa | 6.3 ± 1.4 Aa | 0.2439 |
| BA+GA4+7 | 3.9 ± 1.5 Ba | 4.0 ± 1.5 Ba | 3.7 ± 1.4 Ba | 0.6263 |
| p-value | 0.0001 | 0.0001 | 0.0001 | |
| Total length of lateral shoots, cm | ||||
| Control | 3.3 ± 2.9 Da | 3.4 ± 3.1 Da | 3.1 ± 2.8 Da | 0.8738 |
| Pinching leaves | 24.9 ± 23.9 Ca | 26.1 ± 25.1 Ca | 23.6 ± 22.7 Ca | 0.8549 |
| BA+GA3 | 148.0 ± 50.3 Aa | 155.4 ± 52.9 Aa | 140.6 ± 47.8 Aa | 0.3428 |
| BA+GA4+7 | 106.7 ± 54.0 Ba | 112.1 ± 56.7 Ba | 101.4 ± 51.3 Ba | 0.6151 |
| p-value | 0.0001 | 0.0001 | 0.0001 | |
| Average length of one shoot, cm | ||||
| Control | 1.7 ± 1.3 Da | 1.8 ± 1.3 Da | 1.7 ± 1.3 Da | 0.9898 |
| Pinching leaves | 10.3 ± 9.5 Ca | 10.4 ± 9.6 Ca | 10.1 ± 9.3 Ca | 0.9851 |
| BA+GA3 | 22.4 ± 4.8 Ba | 22.7 ± 4.8 Ba | 22.1 ± 4.7 Ba | 0.8242 |
| BA+GA4+7 | 26.6 ± 8.8 Aa | 26.9 ± 8.9 Aa | 26.2 ± 8.7 Aa | 0.9236 |
| p-value | 0.0001 | 0.0001 | 0.0001 | |
* Significant difference: A, B, C and D indicate significant differences in the column using capital letters, while a, b and c indicate significant differences in the row using small letters, for significant differences at α = 0.05. ** BA+GA3—regardless of the dose of applied growth regulators and the number of treatments. *** BA+GA4+7—regardless of the dose of applied growth regulators and the number of treatments
Table 3.
Influence of the number of branching stimulation treatments on the growth and quality of ‘Gloster’ apple trees, irrespective of the year of the study.
Table 3.
Influence of the number of branching stimulation treatments on the growth and quality of ‘Gloster’ apple trees, irrespective of the year of the study.
| Number of Treatments | Pinching Leaves | BA+GA3 | BA+GA4+7 | p-Value | |
|---|---|---|---|---|---|
| Height of maiden apple trees in autumn, cm | 1 ** | 161.9 ± 9.3 Ab * | 168.3 ± 6.3 Aa | 154.5 ± 7.4 Ac | 0.0001 |
| 2 *** | 149.2 ± 4.1 Bc | 169.9 ± 7.5 Aa | 158.9 ± 33.8 Ab | 0.0001 | |
| p-value | 0.0001 | 0.1549 | 0.2799 | ||
| Diameter of rootstocks, mm | 1 | 23.7 ± 2.6 Ab | 25.1 ± 3.2 Aa | 23.3 ± 2.6 Ab | 0.0002 |
| 2 | 22.5 ± 1.7 Bb | 23.5 ± 2.9 Ba | 23.4 ± 1.8 Aa | 0.0112 | |
| p-value | 0.0018 | 0.0021 | 0.7077 | ||
| Diameter of maiden trees, mm | 1 | 18.5 ± 10.7 Aa | 16.2 ± 1.4 Aab | 14.5 ± 1.7 Bb | 0.0001 |
| 2 | 15.5 ± 1.3 Bb | 16.0 ± 1.5 Aa | 15.0 ± 1.1 Ab | 0.0001 | |
| p-value | 0.0148 | 0.4698 | 0.0302 | ||
| Number of lateral shoots, pcs | 1 | 2.0 ± 1.4 Ac | 6.0 ± 1.2 Ba | 2.8 ± 1.0 Bb | 0.0001 |
| 2 | 1.6 ± 1.4 Ac | 7.1 ± 1.4 Aa | 5.0 ± 1.0 Ab | 0.0001 | |
| p-value | 0.1668 | 0.0001 | 0.0001 | ||
| Total length of lateral shoots, cm | 1 | 21.0 ± 20.7 Bc | 122.5 ± 34.8 BAb | 63.8 ± 35.4 Bb | 0.0001 |
| 2 | 28.8 ± 26.1 Ac | 173.5 ± 50.8 Aa | 149.7 ± 29.1 Ab | 0.0001 | |
| p-value | 0.0432 | 0.0001 | 0.0001 | ||
| Average length of one shoot, cm | 1 | 7.2 ± 6.2 Bb | 20.5 ± 4.0 Ba | 22.5 ± 9.8 Ba | 0.0001 |
| 2 | 13.3 ± 11.0 Ac | 24.3 ± 4.6 Ab | 30.6 ± 5.1 Aa | 0.0001 | |
| p-value | 0.0001 | 0.0001 | 0.0001 |
* Significant difference: A, B and C indicate significant differences in the column using capital letters, while a, b and c indicate significant differences in the row using small letters for significant differences at α = 0.05. ** Single number of branching procedures, regardless of dose and year of study. *** Double number of branching procedures, regardless of dose and year of study.
Table 4.
Effect of the branching stimulation solution dose on the growth and quality of ‘Gloster’ apple trees, irrespective of study year.
Table 4.
Effect of the branching stimulation solution dose on the growth and quality of ‘Gloster’ apple trees, irrespective of study year.
| Concentration Value | BA+GA3 | BA+GA4+7 | p-Value | |
|---|---|---|---|---|
| Height of maiden apple trees in autumn, cm | small ** | 168.9 ± 9.2 Aa * | 154.6 ± 8.3 Ab | 0.0001 |
| large *** | 169.3 ± 7.0 Aa | 156.7 ± 24.5 Ab | 0.0001 | |
| p-value | 0.6368 | 0.3252 | ||
| Diameter of rootstocks, mm | small | 23.4 ± 2.2 Ba | 23.8 ± 2.0 Aa | 0.1244 |
| large | 24.3 ± 3.1 Aa | 23.3 ± 2.2 Ab | 0.0017 | |
| p-value | 0.0033 | 0.0725 | ||
| Diameter of maiden trees, mm | small | 15.6 ± 1.5 Ba | 15.2 ± 1.4 Ab | 0.0172 |
| large | 16.1 ± 1.4 Aa | 14.8 ± 1.5 Bb | 0.0001 | |
| p-value | 0.0025 | 0.0104 | ||
| Number of lateral shoots, pcs | small | 5.0 ± 1.8 Ba | 3.5 ± 1.4 Bb | 0.0001 |
| large | 6.6 ± 1.4 Aa | 3.9 ± 1.5 Ab | 0.0001 | |
| p-value | 0.0001 | 0.0127 | ||
| Total length of lateral shoots, cm | small | 115.6 ± 48.4 Ba | 97.9 ± 42.1 Ab | 0.0001 |
| large | 148.6 ± 50.2 Aa | 106.7 ± 53.8 Ab | 0.0001 | |
| p-value | 0.0001 | 0.1128 | ||
| Average length of one shoot, cm | small | 22.5 ± 6.5 Ab | 27.3 ± 8.8 Aa | 0.0001 |
| large | 22.2 ± 4.6 Ab | 26.5 ± 8.8 Aa | 0.0001 | |
| p-value | 0.7094 | 0.4569 |
* Significant difference: A and B indicate significant differences in the column using capital letters, while a and b indicate significant differences in the row using small letters for significant differences at α = 0.05. ** small: lower dose of applied growth regulators, i.e., BA (Globaryll 100 SL 4.5 mL) + GA3 (0.45 g Florgib) and BA (Globaryll 100 SL 4.5 mL) + GA4+7 (Gibb Plus 11 SL 45 mL/1 L of water), regardless of the number of applications and the year of testing. *** large: higher dose of applied growth regulators, i.e., BA (Globaryll 100 SL 6.8 mL) + GA3 (0.63 g Florgib) and BA (Globaryll 100 SL 6.8 mL) + GA4+7 (Gibb Plus 11 SL 67.5 mL/1 L of water), regardless of the number of applications and the year of testing.
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MDPI and ACS Style
Kapłan, M.; Klimek, K.E.; Buczyński, K. Analysis of the Impact of Treatments Stimulating Branching on the Quality of Maiden Apple Trees. Agriculture 2024, 14, 1757. https://doi.org/10.3390/agriculture14101757
AMA Style
Kapłan M, Klimek KE, Buczyński K. Analysis of the Impact of Treatments Stimulating Branching on the Quality of Maiden Apple Trees. Agriculture. 2024; 14(10):1757. https://doi.org/10.3390/agriculture14101757
Chicago/Turabian StyleKapłan, Magdalena, Kamila E. Klimek, and Kamil Buczyński. 2024. "Analysis of the Impact of Treatments Stimulating Branching on the Quality of Maiden Apple Trees" Agriculture 14, no. 10: 1757. https://doi.org/10.3390/agriculture14101757
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