Canopy Architectural Characteristics of Ten New Olive (Olea europaea L.) Genotypes and Their Potential for Cultivation in Super-High-Density Orchards

In recent years, there has been growing interest in olive genotypes (Olea europaea L.) suitable for super-high-density (SHD > 1200 trees/hectare) orchards. To date, only a few cultivars are considered fitting for such cultivation system. In this study, the first results on the architectural characteristics of the canopy of ten new olive genotypes are presented. Their suitability for SHD orchards was evaluated and compared with the cultivar ‘Arbequina’, which is considered suitable for SHD olive orchards and, for this reason, was used as the control. Several canopy measurements were taken, and some architectural parameters, such as branching frequency, branching density, and branch diameter/stem diameter ratio were calculated. The branching frequency value was greater than 0.20 in ‘Arbequina’ and in only four of the genotypes. The branching density in five genotypes was similar to ‘Arbequina’. ‘Arbequina’ had the lowest value for the branch diameter/stem diameter ratio, and only three genotypes had similar values. These initial results showed that only one genotype has all canopy architectural characteristics comparable to those of the cv. ‘Arbequina’. Further studies are needed to evaluate the production traits of these new genotypes and complete their characterization.


Introduction
The cultivated olive (Olea europaea subsp.europaea, var.europaea) is the second most worldwide oil fruit tree crop species.Extra virgin olive oil, EVOO, is one of the most valuable foods due to its high content of healthy fatty acids and minor constituents [1][2][3].The genotype plays an important role in influencing the bioactive compound profile of olive fruits [4,5], and breeding programs can provide beneficial variability for EVOO quality, but also for agronomical characters useful for olive cultivation [6][7][8][9].Therefore, it would be very useful to use breeding programs to find genotypes that combine high oil quality with agronomic characteristics that make them suitable for the new planting models that are being increasingly applied in olive growing.
In the last years, there has been increased interest in super-high-density (SHD) cultivation systems that have some important advantages, such as rapid achievement of full production, efficient mechanization of olive harvesting, and partial/full mechanization of pruning [9][10][11][12].SHD orchards are characterized by close planting distances (the most used is 4 m × 1.5 m), thus requiring the use of low vigor and compact varieties [11][12][13][14].
Plants 2024, 13, 1399 2 of 11 In this regard, the study of tree architecture, which describes the habit of growth of trees, is crucial to understand the suitability of a genotype for the cultivation in high-density systems [15].Indeed, the few studies carried out on the architectural features of the olive tree highlight that there is a great variability among genotypes [16].Rosati et al. [13] provided a detailed description of the structural/architectural characteristics of trees which make them suitable for cultivation in SHD orchards and indicated the parameters that should be considered when evaluating the tree architecture.In particular, the proposed parameters include diameter and node number of the main stem (central leader) and number, as well as diameter and angle of insertion, of the main branches inserted in the central leader.These parameters allow us to characterize the growth habit of the genotype.In particular, the branching density (i.e., the number of lateral ramifications per unit length of the central axis) is especially important because it strongly affects the compactness of the canopy [17]: a high branching density, coupled with small shoot diameter, gives a higher compactness than low branching with thicker shoots.In this regard, it is also important to consider that branching seems also to be influenced by the propagation method utilized: micro-propagated olive trees showed a higher number of primary branches on the central axis than trees obtained by cutting [18].Therefore, high branching and small diameters of the vegetation seem like important architectural characteristics that make cultivars suitable for SHD orchards.
At the time, there are very few cultivars that meet the requirements of the SHD system [12].Therefore, it would be very useful to have more genotypes suitable for this kind of orchard.They could be identified and selected by investigating/evaluating the architectural characteristics of the available olive germplasm, also including minor varieties, and/or new genotypes produced by breeding.
The aim of the present work was to evaluate the architectural characteristics of some new genotypes obtained from a breeding program in order to assess their potential for cultivation in SHD orchards.

Results
The average length of the main branches was the shortest (around 36 cm) in 'I-79 free pollinated' (G) (identification letters of the different genotypes are reported in Table 1), which was similar to 'Arbequina', while it was the longest (about 64 cm) in 'Fs-17 × Bouteillan' (A) (Figure 1).All other genotypes had values ranging from 40 to 50 cm in length.The length of the internode evaluated on the same main branch varied from about 1.4 cm in 'Bouteillan × Nostrale di Rigali' (D) to just over 2 cm in the genotypes 'Nociara free pollinated 1' (H) and 'Nucalia 1 × Don Carlo' (L) (Figure 2).The length of the internode evaluated on the same main branch varied from about 1.4 cm in 'Bouteillan × Nostrale di Rigali' (D) to just over 2 cm in the genotypes 'Nociara free pollinated 1' (H) and 'Nucalia 1 × Don Carlo' (L) (Figure 2).Internode length in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The angle of insertion of the main branches on the central leader was low (i.e., more vertical) for the genotypes 'I-79 free pollinated' (G), 'Nociara free pollinated 1' (H), and 'Nociara free pollinated 2' (I), with average values just under 50 degrees.This was lower than that of the cultivar 'Arbequina', while it was highest (i.e., more horizontal) for the genotype 'I-77 × Kalamata' (F), which showed values around 70 degrees (Figure 3).Length of the main branches in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 1.
Length of the main branches in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The length of the internode evaluated on the same main branch varied from about 1.4 cm in 'Bouteillan × Nostrale di Rigali' (D) to just over 2 cm in the genotypes 'Nociara free pollinated 1' (H) and 'Nucalia 1 × Don Carlo' (L) (Figure 2).Internode length in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The angle of insertion of the main branches on the central leader was low (i.e., more vertical) for the genotypes 'I-79 free pollinated' (G), 'Nociara free pollinated 1' (H), and 'Nociara free pollinated 2' (I), with average values just under 50 degrees.This was lower than that of the cultivar 'Arbequina', while it was highest (i.e., more horizontal) for the genotype 'I-77 × Kalamata' (F), which showed values around 70 degrees (Figure 3).  1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The angle of insertion of the main branches on the central leader was low (i.e., more vertical) for the genotypes 'I-79 free pollinated' (G), 'Nociara free pollinated 1' (H), and 'Nociara free pollinated 2' (I), with average values just under 50 degrees.This was lower than that of the cultivar 'Arbequina', while it was highest (i.e., more horizontal) for the genotype 'I-77 × Kalamata' (F), which showed values around 70 degrees (Figure 3).
The order of genotypes for branching density was slightly different.In fact, 'Nociara free pollinated 2' (I) dropped compared to the others, while 'Fs-17 × Cipro' (E) gained (Figure 5).The genotypes 'I-77 self-pollinated' (B), 'Fs-17 × Cipro' (E), 'Nucalia 1 × Don Carlo' (L), 'I-77 × Kalamata' (F), and 'I-79 free pollinated' (G) had values statistically similar to that of 'Arbequina'.The total branching density (obtained by summing the branching density as in Figure 5 and the branching density of second-order, expressed as the number of lateral shoots more than 5 cm long inserted along the main branches, per The order of genotypes for branching density was slightly different.In fact, 'Nociara free pollinated 2' (I) dropped compared to the others, while 'Fs-17 × Cipro' (E) gained (Figure 5).The genotypes 'I-77 self-pollinated' (B), 'Fs-17 × Cipro' (E), 'Nucalia 1 × Don Carlo' (L), 'I-77 × Kalamata' (F), and 'I-79 free pollinated' (G) had values statistically similar to that of 'Arbequina'.The total branching density (obtained by summing the branching density as in Figure 5 and the branching density of second-order, expressed as the number of lateral shoots more than 5 cm long inserted along the main branches, per cm of the central leader), was high in 'I-77 self-pollinated' (B), and 'Fs-17 × Cipro' (E) and with values statistically similar to that of 'Arbequina' (Figure 6).cm of the central leader), was high in 'I-77 self-pollinated' (B), and 'Fs-17 × Cipro' (E) and with values statistically similar to that of 'Arbequina' (Figure 6).Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 6.
Total branching density in ten new olive genotypes and the 'Arbequina' cultivar.In the Y axis, we considered the main branches and the shoots inserted on the main branches.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The ratio between the diameter of the main branch and the diameter of the central leader (diameter ratio) was equal to 0.48 in 'Arbequina' (the lowest of all), while the highest value (0.64) was found in 'Bouteillan × Nostrale di Rigali' (D) (Figure 7).'Nucalia 1 × Don Carlo' (L), 'Nociara free pollinated 2' (I), and 'Fs 17 × Bouteillan' (A) had values similar to that of 'Arbequina'.Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
cm of the central leader), was high in 'I-77 self-pollinated' (B), and 'Fs-17 × Cipro' (E) and with values statistically similar to that of 'Arbequina' (Figure 6).Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 6.
Total branching density in ten new olive genotypes and the 'Arbequina' cultivar.In the Y axis, we considered the main branches and the shoots inserted on the main branches.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The ratio between the diameter of the main branch and the diameter of the central leader (diameter ratio) was equal to 0.48 in 'Arbequina' (the lowest of all), while the highest value (0.64) was found in 'Bouteillan × Nostrale di Rigali' (D) (Figure 7).'Nucalia 1 × Don Carlo' (L), 'Nociara free pollinated 2' (I), and 'Fs 17 × Bouteillan' (A) had values similar to that of 'Arbequina'.In the y axis, we considered the main branches and the shoots inserted on the main branches.The letters on the x axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The ratio between the diameter of the main branch and the diameter of the central leader (diameter ratio) was equal to 0.48 in 'Arbequina' (the lowest of all), while the highest value (0.64) was found in 'Bouteillan × Nostrale di Rigali' (D) (Figure 7).'Nucalia 1 × Don Carlo' (L), 'Nociara free pollinated 2' (I), and 'Fs 17 × Bouteillan' (A) had values similar to that of 'Arbequina'.The ratio between the length of the main branch and its basal diameter ranged from 92 for 'Arbequina', to 66 for 'Nociara free pollinated 2' (I), about 29% less than the Spanish cultivar (Figure 8).Five genotypes (A, B, C, E, and L) had values similar to 'Arbequina'.Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between were compared using Fisher's LSD test (p < 0.05).
The diameter ratio was negatively correlated with branching frequency (Figure 9).Diameter ratio (i.e., average ratio between main branch diameter and central leader diameter under the branch insertion) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The ratio between the length of the main branch and its basal diameter ranged from 92 for 'Arbequina', to 66 for 'Nociara free pollinated 2' (I), about 29% less than the Spanish cultivar (Figure 8).Five genotypes (A, B, C, E, and L) had values similar to 'Arbequina'.

Figure 7.
Diameter ratio (i.e., average ratio between main branch diameter and central leader diameter under the branch insertion) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The ratio between the length of the main branch and its basal diameter ranged from 92 for 'Arbequina', to 66 for 'Nociara free pollinated 2' (I), about 29% less than the Spanish cultivar (Figure 8).Five genotypes (A, B, C, E, and L) had values similar to 'Arbequina'.Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The diameter ratio was negatively correlated with branching frequency (Figure 9). .Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table 1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
The diameter ratio was negatively correlated with branching frequency (Figure 9).Correlation between the diameter ratio and the branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.Each point is one of the genotypes listed in Table 1.

Discussion
The aim of the present study was to evaluate the architectural characteristics of the canopy of the new olive genotypes, previously selected for high oil quality, in order to determine their suitability for use in new SHD plantations.The cultivar 'Arbequina' was used as control, as previous studies showed that it has tree architectural characteristics very suitable for SHD orchards [13,14,[19][20][21].Indeed, 'Arbequina' has a high branching frequency.This character is negatively correlated to the diameter of lateral branches as well as to the diameter of one-year-old shoots, enabling the branch/shoot biomass to be concentrated in a small volume (compact canopy).These are desirable characters for trees to be used in SHD olive orchards [13].
The average branch length along the central leader is an important parameter when planting olive trees at very high densities [22].In fact, long branches create problems in olive orchard systems with short distances between rows because the branches occupy too much inter-row space.Furthermore, they can interfere with straddle machine harvesting, as the long lateral branches, which exceed the limit compatible with the harvest tunnel width, can be broken or damage the machine [21][22][23].Therefore, for SHD olive orchards, it is preferable to have genotypes that develop lateral branches that are not excessively long.The average length of branches of the Arbequina cultivar was close to the average value across all genotypes.The genotype 'Fs-17 × Bouteillan' (A) had an average branch length much longer than all the other genotypes, on average 20 cm longer than those of 'Arbequina', while the genotype 'I-79 free pollinated' (G) had the shortest value, on average 9 cm less than Arbequina (Figure 1).
Rosati et al. [14] found that the branch insertion angle on the stem is not a relevant parameter in the characterization of 21 cultivars grown in a SHD olive orchard, but it gives an idea of the plant canopy habit.In the present study, 'I-79 free pollinated' (G), 'Nociara free pollinated 1' (H), and 'Nociara free pollinated 2' (I) had branch insertion angles around 50 degrees, which indicate an upright canopy habit, while all the other genotypes had higher angles, indicating an expanded canopy habit (Figure 3).In SHD olive orchards, narrow branch insertion angles could reduce light penetration into the internal parts of the canopy, with consequent reduction of the production efficiency and air circulation [23].The branch insertion angle, in addition to being genotype dependent, is also affected by the space between the trees, in turn affected by the plantation distances, with wider angles found in wider distance plantations [24].
The branching frequency and the branching density are the most relevant parameters to assess whether a genotype is suitable for planting density intensification [13].High values for these parameters imply a high ability to fill the available canopy volume with Correlation between the diameter ratio and the branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.Each point is one of the genotypes listed in Table 1.

Discussion
The aim of the present study was to evaluate the architectural characteristics of the canopy of the new olive genotypes, previously selected for high oil quality, in order to determine their suitability for use in new SHD plantations.The cultivar 'Arbequina' was used as control, as previous studies showed that it has tree architectural characteristics very suitable for SHD orchards [13,14,[19][20][21].Indeed, 'Arbequina' has a high branching frequency.This character is negatively correlated to the diameter of lateral branches as well as to the diameter of one-year-old shoots, enabling the branch/shoot biomass to be concentrated in a small volume (compact canopy).These are desirable characters for trees to be used in SHD olive orchards [13].
The average branch length along the central leader is an important parameter when planting olive trees at very high densities [22].In fact, long branches create problems in olive orchard systems with short distances between rows because the branches occupy too much inter-row space.Furthermore, they can interfere with straddle machine harvesting, as the long lateral branches, which exceed the limit compatible with the harvest tunnel width, can be broken or damage the machine [21][22][23].Therefore, for SHD olive orchards, it is preferable to have genotypes that develop lateral branches that are not excessively long.The average length of branches of the Arbequina cultivar was close to the average value across all genotypes.The genotype 'Fs-17 × Bouteillan' (A) had an average branch length much longer than all the other genotypes, on average 20 cm longer than those of 'Arbequina', while the genotype 'I-79 free pollinated' (G) had the shortest value, on average 9 cm less than Arbequina (Figure 1).
Rosati et al. [14] found that the branch insertion angle on the stem is not a relevant parameter in the characterization of 21 cultivars grown in a SHD olive orchard, but it gives an idea of the plant canopy habit.In the present study, 'I-79 free pollinated' (G), 'Nociara free pollinated 1' (H), and 'Nociara free pollinated 2' (I) had branch insertion angles around 50 degrees, which indicate an upright canopy habit, while all the other genotypes had higher angles, indicating an expanded canopy habit (Figure 3).In SHD olive orchards, narrow branch insertion angles could reduce light penetration into the internal parts of the canopy, with consequent reduction of the production efficiency and air circulation [23].The branch insertion angle, in addition to being genotype dependent, is also affected by the space between the trees, in turn affected by the plantation distances, with wider angles found in wider distance plantations [24].
The branching frequency and the branching density are the most relevant parameters to assess whether a genotype is suitable for planting density intensification [13].High was measured in relation to the central leader, thus placing the zero of the goniometer parallel to the central leader of the tree.
Lateral shoots (>5 cm in length) were also counted along each of these branches.Furthermore, the basal diameter of all branches inserted along the central leader was measured (at the first internode) as well as the diameter of the central leader just below the branch considered (at the first internode below the insertion).The ratio between these two diameters was calculated [13].The ratio between the length of the main branch and the diameter at the point of insertion with the central leader was calculated.The number of main branches is expressed as the number per bud or per cm of the central leader, as a measure, respectively, of branching frequency and branching density.
All the measurements were carried out in September 2022, except for the insertion angle, which was recorded in February 2023.
Data are presented as means ± standard errors.Genotype effects were analyzed by one-way analysis of variance (ANOVA) performed after normality and homoskedasticity tests.Averages were compared using Fisher's LSD test (probability level < 0.05).

Figure 2 .
Figure 2.Internode length in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
Figure 1.Length of the main branches in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 2 .
Figure 2.Internode length in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 2 .
Figure 2.Internode length in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 3 .
Figure3.Branch insertion angle on the central leader in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 4 .
Figure 4.Branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 3 .
Figure3.Branch insertion angle on the central leader in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 4 .
Figure 4. Branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 4 .
Figure 4. Branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 5 .
Figure 5.Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 5 .
Figure 5.Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 5 .
Figure 5.Branching density in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 6 .
Figure 6.Total branching density in ten new olive genotypes and the 'Arbequina' cultivar.In the y axis, we considered the main branches and the shoots inserted on the main branches.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 8 .
Figure8.Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between were compared using Fisher's LSD test (p < 0.05).

Figure 7 .
Figure 7.Diameter ratio (i.e., average ratio between main branch diameter and central leader diameter under the branch insertion) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 8 .
Figure8.Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 8
Figure8.Branch length to diameter ratio (i.e., average ratio between main branch length and the diameter of the same branch measured at the insertion with the central leader) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the x axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).

Figure 9 .
Figure 9. Correlation between the diameter ratio and the branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.Each point is one of the genotypes listed in Table1.

Figure 9 .
Figure 9. Correlation between the diameter ratio and the branching frequency in ten new olive genotypes and the 'Arbequina' cultivar.Each point is one of the genotypes listed in Table1.

Table 1 .
Identification letter of the genotypes under investigation.
in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).Branch insertion angle on the central leader in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).
Diameter ratio (i.e., average ratio between main branch diameter and central leader diameter under the branch insertion) in ten new olive genotypes and the 'Arbequina' cultivar.The letters on the X axis correspond to the breeds/genotypes listed in Table1.Data represent averages and standard errors (bars).Different letters above the columns indicate significant differences between genotypes.Averages were compared using Fisher's LSD test (p < 0.05).