In established vineyards, node number retention at winter pruning is the first step to achieving and maintaining vine balance. Balanced vines exhibit timely and quasiuniform 100 percent budburst. To understand how vine capacity and balance are expressed before flowering, mature Sauvignon blanc vines were pruned according to a 5 [total node numbers on canes: 10, 20, 30, 40, 50] x 3 [total node numbers on spurs: 1, 2, 3] factorial design in one site, and in two other sites according to a 5 [total node numbers on canes: 10, 20, 30, 40, 50] x 2 [total node numbers on spurs: 1, 2] factorial design. Two spurs of one, two or three nodes each were retained on either side of the vine. The number of canes laid down per vine was one, two, three and four canes each of 10 nodes for the 10, 20, 30 and 40node treatments, and four canes averaging 12.5 nodes for the 50node treatment. The budburst percentage was calculated on the whole vine, canes, and spurs. Blind nodes, count shoots, noncount shoots and double shoots were counted and mapped along canes and spurs. Many noncount shoots were measured on the vine head of 10node vines (29.5 ± 3.0 shoots,
Key words: blind node, budburst, correlative inhibition, development, double shoot, vine balance
Retaining the requisite number of nodes after pruning is one of the most costeffective means of achieving an equilibrium between vegetative and reproductive growth (
The location, distribution and proportion of blind nodes is generally reported on frost damaged vines or on dormant vines.
The proportion and distribution of blind nodes along canes and spurs is especially critical for the management of canepruned vines. Blind nodes at the proximal section of fruiting canes can drastically limit the number of candidate dormant shoots to retain at winter cane pruning to form fruiting canes or renewal spurs (
It has been observed that on cane pruned grapevines, budburst and early shoot growth is irregular, with budburst beginning on nodes at the most distal positions to the vine head, resulting in vigorous and rapidly growing shoots at distal positions compared to shoots located in the middle or proximal positions to the head (
Understanding the physiological changes pruning induces on mature grapevines, such as the development and distribution of double shoots, blind nodes and percent budburst, are crucial for minimising withinvine shoot growth variability and promoting adequate dormant shoot selection at pruning, thus ensuring sustained grapevine management and productivity. A previous study on the characterisation of dormant shoot attributes found that changing the node number affects the attributes of retained dormant shoots at cane pruning (
The research was conducted in two commercial vineyard blocks, one in Awatere Valley, Marlborough, New Zealand (GPS: 41°39'43.3"S, 173°59'59.9"E; masl: 140 m), and the other in Waipara, Canterbury, New Zealand (GPS: 43°06'17.4"S 172°42'26.1"E; masl: < 100 m). Across all three sites, the rows and vines were selected based on their vigour (weak vines rejected), age (replants avoided) and health condition (disease and pest free).
Awatere Valley: Site 1 and Site 2. A detailed description of the Awatere Valley vineyard block, including trellis systems, grapevines genotypes, vineyard management and prevailing weather conditions during the experiment, is given in a previous paper (
In 2020, 50 new vines were selected in the middle part of the row, hereafter referred to as Site 2. Site 2 represented a seasonal repeat of the 2019 experiment at Site 1, which excluded the carryover effect of the previous year’s pruning treatments. These vines had, on average, 62.2 ± 1.2 mm trunk diameter, 30.4 ± 0.06 dormant shoots per vine, 1118 ± 3.7 g cane weight per vine, and 1395 ± 4.3 g total pruning weight per vine.
Waipara vineyard block: Site 3. A vineyard block in Waipara was selected as Site 3 in 2020. It was established in 2006 and planted with
In 2019 at Site 1, vines were pruned according to a 5 (cane node load) x 3 (spur node number) factorial design. The number of canes was set to one, two, three and four each of 10 nodes for N10 to N40 treatments, and four canes averaging 12.5 nodes for N50 treatments. Spur node number was set at one, two and three nodes per spur (on two spurs per vine). Each treatment was replicated five times to give a total of 75 experimental units (vines). The factorial design generated 15 total vine node load treatments (i.e., cane node load plus spur node number) ranging from 12 to 56 nodes at Site 1 and from 14 to 56 nodes at Site 2 and Site 3, as presented in Table S1. Cane and spur nodes were counted starting 10 mm from the junction of the cane/spur with the perennial wood, clearly distinguishing basal nodes from the first separate node at position one. Budburst occurred on 22 October 2019 and was determined when the first green tip was visible on over 50 % of vines. Fifteen days following budburst at growth stage EL 9 – two to three separate leaves (Modified Eichhorn and Lorenz grapevine growth stages (
Blind node number was obtained by counting all count nodes that failed to burst bud. To determine where blind nodes and double shoots occurred, each cane was divided into four cane sections from its point of attachment on the vine head (cane origin) to its extremity (cane tip). Part one (the proximal section to the head – P1) contained nodes one to three, with node one being the closest to the cane origin and head of the vine; part two (the first middle section – P2) included nodes four to six; part three (the second middle section – P3) corresponded to nodes seven to nine; and finally, part four (the distal section – P4) contained nodes 10 to 13. This division was made to account for the differential growth response of these cane sections (
In winter 2020 at Site 2, 50 vines were selected and pruned for a 5 (cane node load) x 2 (spur node number) factorial experiment, with five replicates and with the same five node loads as at Site 1, in combination with two node numbers for spurs (two and three node spurs). The factorial design resulted in 10 total vine node load treatments (Table S1). The same measurements were collected as for Site 1.
Waipara site, Site 3. Fifty vines were selected along a south/northoriented 550vine row and pruned in winter 2020 with the same node treatments as Awatere Site 2. Measurements were the same as at the Awatere sites, except that budburst was also monitored on four dates at regular intervals from 24 September to 8 October 2020.
All measured variables (count shoots, double shoots, basal shoots, blind nodes, growth stage and percent budburst) were compared using the Analysis of Variance (ANOVA) and the protected Fisher's Least Significant Difference Test (LSD). Before running ANOVA, Levene's test was conducted to check the homogeneity of variances and the ShapiroWilk test was applied to check data were normally distributed. The ANOVA assumptions were met for all measured variables and the interaction between cane node load and spur node numbers was not significant; consequently, only the main effects were analysed. The significance for all tests was defined at
The vine budburst percentage significantly increased with decreasing cane node loads and total node load across all three sites (Table 1; Figure S1). At Site 1 in spring 2019, all treatments had a vine budburst well above 100 %, with N10 vines recording the highest and N50 vines the lowest percentages (
titre du tableau
Cane node loads
Site 1
Site1
Site 2
Site 3
Vine budburst percentage (%)*
N10
262 ± 18 aA
232 ± 15 aB
211 ± 23 a
310 ± 19 a
< 0.05
N20
182 ± 8.2 bA
155 ± 6.2 bB
141 ± 7.2 b
152 ± 15 b
< 0.01
N30
141 ± 5.0 cA
123 ± 5.7 cB
118 ± 4.3 bc
120 ± 9.0 bc
< 0.01
N40
124 ± 4.7 cdA
110 ± 2.7 cB
101 ± 2.5 c
120 ± 4.2 bc
< 0.01
N50
114 ± 4.2 dA
105 ± 2.5 cA
104 ± 1.6 c
104 ± 5.3 c
ns
< 0.001
< 0.001
< 0.001
< 0.001
N10, N20, N30, N40, and N50 refer to total node number on vine canes (N) equal to 10, 20, 30, 40 and 50 nodes respectively. Values are mean ± standard error of the Mean of 15 vines at Site 1 and 10 vines at Site 2 and 3. Means sharing the same lowercase letter in a column (cane node load comparison) or the same uppercase letter in a row (2019 and 2020 seasons comparison at Site 1) are not significantly different (Fisher’s protected LSD test,
The budburst percentage on canes decreased with increasing node numbers, being significantly high on N10 vines but low on N50 (Table 2). The reduction in the vine budburst observed at Site 1 between 2019 and 2020 was also reflected in the cane budburst. Contrary to vine budburst that was always greater than 100 % regardless of the node treatments and sites, cane budburst was always below 100 % on N50 vines, and in the 2020 spring none of the treatments reached 100 % at Site 1 and Site 2 (Table 2). At Site 3, the cane budburst was statistically similar for all node treatments. The very high vine budburst measured on N10 vines was caused by the great number of noncount shoots on the vine head, and the cane budburst of around 100 % on those same N10 vines was the result of the very small number of blind nodes that appeared on canes, as will be discussed below.
titre du tableau
Cane node loads
Site 1
Site 1
Site 2
Site 3
Cane budburst percentage (%) ^{*}
N10
119 ± 1.0 aA
96 ± 1.8 aB
90 ± 2.7 a
107 ± 5.1 a
< 0.05
N20
106 ± 4.0 abA
94 ± 2.1 abB
87 ± 3 ab
108 ± 3.3 a
< 0.01
N30
98 ± 4.0 bcA
90 ± 2.2 bcB
86 ± 0.8 ab
106 ± 2.2 a
< 0.01
N40
95 ± 3.0 bcA
87 ± 1.7 cB
86 ± 0.8 ab
105 ± 1.7 a
< 0.01
N50
90 ± 2.0 cA
86 ± 1.5 cA
81 ± 1.8 b
98.6 ± 2.2 a
ns
< 0.01
< 0.001
< 0.05
ns
Spur node number
Spur budburst percentage ( %) ^{#}
S1
224 ± 12 aA
200 ± 14 aB


< 0.01
S2
130 ± 10 bA
113 ± 3.5 bB
109 ± 3.6 a
128 ± 6.5 a
< 0.01
S3
108 ± 6 bA
102 ± 2.7 bB
105 ± 2.5 a
87.9 ± 6.6 b
< 0.05
< 0.001
< 0.001
ns
< 0.001
N10, N20, N30, N40, and N50 refer to total node number on vine canes (N) equal to 10, 20, 30, 40 and 50 nodes respectively and S1 = spurs with one node, S2 = spurs with 2 nodes, S3= spurs with 3 nodes. For cane node load treatments, values are mean ± standard error of the Mean of 15 vines at Site 1 and 10 vines at Site 2 and 3. For Spur node number treatments, values are mean ± standard error of the Mean of 25 vines at all three sites. Means sharing the same lowercase letter in a column (cane node loads or spur node load comparison) or the same uppercase letter in a row (2019 and 2020 seasons comparison at Site 1) are not significantly different (Fisher’s protected LSD test,
The budburst on spurs also increased with decreasing spur node numbers and always exceeded 100 %, except at Site 3 for threenode spurs (Table 2). At Site 1 for instance, onenode spurs had the highest percentage (224 ± 12 %) and threenode spurs the lowest (108 ± 6 %) (
titre du tableau
Cane node loads
24 Sept. 2020
28 Sept. 2020
2 Oct. 2020
8 Oct. 2020
Cane budburst percentage (%)^{*}
N10
5.0 ± 3.4 a
33.3 ± 5.7 a
78.8 ± 4.7 a
107 ± 5.1 a
N20
2.5 ± 2.5 a
37.1 ± 4.1 a
74.2 ± 5.4 a
108 ± 3.3 a
N30
6.0 ± 2.2 a
38.4 ± 3.8 a
79.8 ± 3.7 a
106 ± 2.2 a
N40
3.2 ± 1.7 a
38.6 ± 4.0 a
75.0 ± 2.1 a
105 ± 1.7 a
N50
2.2 ± 0.8 a
32.1 ± 4.1 a
69.7 ± 3.9 a
98.6 ± 2.2 a
ns
ns
ns
ns
Spur node numbers
Spur budburst percentage ( %) ^{#}
S2
10 ± 3.5 a
44 ± 6.1 a
89 ± 2.9 a
128 ± 6.5 a
S3
8.6 ± 3.3 a
48 ± 5.2 a
78 ± 3.4 b
87.9 ± 6.6 b
ns
ns
< 0.05
< 0.001
N10, N20, N30, N40, and N50 refer to total node number on vine canes equals 10, 20, 30, 40 and 50 nodes respectively and S2 = spurs with 2 nodes, S3= spurs with 3 nodes. For cane node load treatments, values are mean ± standard error of the Mean of 15 vines at Site 1 and 10 vines at Site 2 and 3. For Spur node number treatments, values are mean ± standard error of the Mean of 25 vines at all three sites. Means sharing the same letter in a column are not significantly different (Fisher’s protected LSD test,
When the total vine node load was considered, the trends observed on the vine budburst and cane budburst percentage were confirmed, with V12 to V16 vines having the highest percentages and V52 to V56 the lowest (Figure S1 and S2).
The average number of blind nodes at all three sites increased with increasing cane node loads (
titre du tableau
Cane node loads
Site 1
Site 1
Site 2
Site 3
Average number of cane blind nodes per vine
N10
1.0 ± 0.2 dA
1.1 ± 0.2 dA
0.9 ± 0.2 d
1.0 ± 0.2 c
ns
N20
2.0 ± 0.3 cdA
1.8 ± 0.3 dA
2.4 ± 0.6 c
2.0 ± 0.4 c
ns
N30
2.6 ± 0.3 bcB
3.6 ± 0.5 cA
4.2 ± 0.2 b
2.3 ± 0.5 c
< 0.05
N40
3.4 ± 0.4 bB
5.5 ± 0.5 bA
7.2 ± 0.7 a
4.5 ± 0.5 b
< 0.01
N50
6.6 ± 0.6 aB
7.6 ± 0.3 aA
7.6 ± 0.3 a
6.3 ± 0.6 a
< 0.05
< 0.001
< 0.001
< 0.001
< 0.001
Average number of cane double shoots per vine
N10
0.6 ± 0.3 bA
0.7 ± 0.2 aA
0.0 ± 0.0 b
0.8 ± 0.5 b
ns
N20
1.1 ± 0.4 abA
0.7 ± 0.3 aA
0.0 ± 0.0 b
1.7 ± 0.7 ab
ns
N30
1.4 ± 0.3 aAB
0.7 ± 0.3 aBC
0.4 ± 0.1 b
2.1 ± 0.5 ab
< 0.05
N40
1.7 ± 0.6 aAB
0.7 ± 0.2 aB
0.5 ± 0.2 b
2.5 ± 0.6 ab
< 0.05
N50
1.7 ± 0.5 aA
0.9 ± 0.2 aA
1.1 ± 0.3 a
2.6 ± 0.7 ab
ns
< 0.05
ns
< 0.01
< 0.05
Average number of shoots per vine head
N10
13.5 ± 1.7 aB
17.8 ± 1.8 aB
16.8 ± 3.2 a
29.5 ± 3.0 a
ns
N20
13.8 ± 1.5 abA
14.1 ± 1.7 aA
12.5 ± 1.8 ab
11.3 ± 3.5 b
ns
N30
10.6 ± 1.1 abcA
10.0 ± 1.2 bA
10.5 ± 1.4 b
6.1 ± 3.1 bc
ns
N40
9.3 ± 1.6 bcA
8.8 ± 0.7 bA
7.3 ± 1.1 b
6.8 ± 1.8 bc
ns
N50
9.1 ± 1.2 bB
8.1 ± 0.8 bB
9.4 ± 0.9 b
2.8 ± 1.9 c
ns
< 0.05
< 0.001
< 0.01
< 0.001
N10, N20, N30, N40, and N50 refer to total node number on vine canes (N) equal to 10, 20, 30, 40 and 50 nodes respectively. Values are mean ± Standard Error of the Mean of 15 vines at Site 1 and 10 vines at Site 2 and 3. Means sharing the same lower case letter in a column (cane node loads comparison) or the same upper case letter in a row (seasons and sites comparison) are not significantly different (Fisher’s protected LSD test,
At Site 1, between the 2019 and 2020 seasons, the average number of blind nodes per vine rose significantly for N30, N40 and N50 vines (from 2.6 ± 0.3, 3.4 ± 0.4 and 6.6 ± 0.6 up to 3.6 ± 0.5, 5.5 ± 0.5 and 7.6 ± 0.3 respectively). This increase in the number of blind nodes explains why the vine budburst and cane budburst decreased for these vines, given that their average number of head shoots and double shoots remained fairly stable over the same period (Table 4). Blind nodes were present on all four cane parts but with greater numbers at proximal parts and the least at distal parts regardless of sites, seasons and node loads (Figure 1). The middle sections had similar, intermediate numbers of blind nodes.
N10, N20, N30, N40, and N50 refer to total node number on vine canes (N) equal to 10, 20, 30, 40 and 50 nodes respectively and p1, p2, p3 and p4 to the cane’s Proximal, First middle, Second middle and Distal parts relative to the head of the vine. Points and bars represent mean ± standard error of the mean of 15 vines for Site 1 and 10 vines for Site 2 and Site 3. Means sharing the same letter across cane sections over one season are not significantly different (Fisher’s protected LSD test, p ≤ 0.05).
N10, N20, N30, N40, and N50 refer to total node number on vine canes (N) equal to 10, 20, 30, 40 and 50 nodes respectively and p1, p2, p3 and p4 to the cane’s Proximal, First middle, Second middle and Distal parts relative to the head of the vine. Points and bars represent mean ± standard error of the mean of 15 vines for Site 1 and 10 vines for Site 2 and Site 3. Means sharing the same letter across cane sections over one season are not significantly different (Fisher’s protected LSD test, p ≤ 0.05).
In spring 2019 at Site 1, double shoots were more frequent on highnode vines (N40 and N50; 1.7 ± 0.5 and 1.7 ± 0.6 double shoots respectively) than on lownode vines (N10; 0.6 ± 0.3 double shoots,
In the spring of 2020, all vines had statistically the same number of double shoots (
At all three sites, there were greater numbers of blind nodes on threenode spurs than on two and onenode spurs (Figure 2; Table 5). At Site 1 in both 2019 and 2020, one and twonode spurs had similar but fewer blind nodes than threenode spurs (
S1 = spurs with one node, S2 = spurs with 2 nodes, S3 = spurs with 3 nodes and 1, 2 and 3 to spur node positions from proximal to distal. Points and bars represent mean ± Standard error of the mean with n = 25 vines per treatment for Site 1 and n = 10 vines per spur node treatment for Site 2 and 3. Means sharing the same letter across node positions over one season are not significantly different (Fisher’s protected LSD test,
S1 = spurs with one node, S2 = spurs with 2 nodes, S3 = spurs with 3 nodes and 1, 2 and 3 to spur node positions from proximal to distal. Points and bars represent mean ± Standard error of the mean with n = 25 vines per treatment for Site 1 and n = 10 vines per spur node treatment for Site 2 and 3. Means sharing the same letter across node positions over one season are not significantly different (Fisher’s protected LSD test,
titre du tableau
Spur node numbers
Site 1
Site 1
Site 2
Site 3
Average number of spur blind nodes
S1
0.12 ± 0.001 b
0.25 ± 0.001 b


S2
0.35 ± 0.001 b
0.85 ± 0.001 a
0.10 ± 0.001 b
0.12 ± 0.001 b
S3
1.0 ± 0.1 a
0.88 ± 0.1 a
0.84 ± 0.1 a
1.04 ± 0.2 a
< 0.001
< 0.001
< 0.001
< 0.001
Average number of spur basal shoots
S1
2.2 ± 0.1 a
1.8 ± 0.2 a


S2
1.2 ± 0.3 b
0.5 ± 0.1 b
0.4 ± 0.1 a
1.1 ± 0.2 a
S3
0.5 ± 0.1 c
0.1 ± 0.001 c
0.2 ± 0.1 a
0.2 ± 0.1 b
< 0.001
< 0.001
ns
< 0.001
S1 = spurs with one node, S2 = spurs with 2 nodes, S3 = spurs with 3 nodes. Values represent mean ± Standard error of the Mean of 25 vines at all three sites. Means sharing the same letter in a column are not significantly different (Fisher’s protected LSD test,
The average leaf appearance on shoots on 5 October 2020 at Site 1 was statistically similar on all vine node loads, except on 10node vines, which were one EL unit behind compared to the other vines (
The average leaf appearance on spurs at Site 1 was significantly more advanced on onenode and twonode spurs compared with threenode spurs (
At Site 1 and Site 2, and regardless of cane node loads, shoots at the distal cane section (last nodes of the cane or terminal nodes) were at a more advanced leaf appearance stage than shoots at the proximal and middle cane sections (
N10, N20, N30, N40, and N50 refer to the total node load on vine’s canes being equal to 10, 20, 30, 40 and 50 nodes respectively. Points represent mean ± standard error of the mean with n = 15 vines at Site 1 and n = 10 vines at Site 2. Means sharing the same letter are not significantly different (Fisher’s protected LSD test,
N10, N20, N30, N40, and N50 refer to the total node load on vine’s canes being equal to 10, 20, 30, 40 and 50 nodes respectively. Points represent mean ± standard error of the mean with n = 15 vines at Site 1 and n = 10 vines at Site 2. Means sharing the same letter are not significantly different (Fisher’s protected LSD test,
N10, N20, N30, N40, and N50 refer to the total node load on vine canes being equal to 10, 20, 30, 40 and 50 nodes respectively. Points represent mean ± standard error of the mean with n = 10 vines for each cane node treatment. For a given date means sharing the same letter are not significantly different (Fisher’s protected LSD test,
N10, N20, N30, N40, and N50 refer to the total node load on vine canes being equal to 10, 20, 30, 40 and 50 nodes respectively. Points represent mean ± standard error of the mean with n = 10 vines for each cane node treatment. For a given date means sharing the same letter are not significantly different (Fisher’s protected LSD test,
As with the canes, the number of leaves at Site 1 and Site 2 was significantly higher on spur terminal shoots (node position 2 for twonode spurs and node position 3 for threenode spurs) than on proximal shoots (spur node position 1) (Figure 5 a, b). At Site 3, from 24 September 2020 to 8 October 2020, terminal shoots were significantly more advanced in the EL stages than proximal shoots for both spur node numbers (
S1 = spurs with one node, S2 = spurs with 2 nodes, S3 = spurs with 3 nodes and 1, 2 and 3 mean spur node positions from proximal to distal. Points and bars represent mean ± standard error of the mean with n = 25 vines per treatment for Site 1 and n = 10 vines per spur node treatment for Site 2 and 3. For a given date means sharing the same letter are not significantly different (Fisher’s protected LSD test,
S1 = spurs with one node, S2 = spurs with 2 nodes, S3 = spurs with 3 nodes and 1, 2 and 3 mean spur node positions from proximal to distal. Points and bars represent mean ± standard error of the mean with n = 25 vines per treatment for Site 1 and n = 10 vines per spur node treatment for Site 2 and 3. For a given date means sharing the same letter are not significantly different (Fisher’s protected LSD test,
A vine budburst percentage at or around 100 % is often an indication that a vine has been pruned to its capacity, with higher values suggesting that the vine had potential to support more growth, and lower values the opposite scenario (i.e., potential to support less growth) (
Previous literature reports that the higher budburst percentage observed on severely pruned vines is caused by double shoots and latent buds bursting, producing water shoots and suckers (
The dormancy of the secondary and tertiary bud of the compound bud is controlled not by vine vigour (higher carbohydrate reserves induced by low node numbers or severe pruning) but rather by chilling duration and phytohormones, such as Abscisic Acid (
Blind nodes were conspicuous on high node vines and were mainly located at the cane proximal part to the vine head (Table 4, Figure 1). A blind node contains one or more buds that failed to burst, either because they developed inside the canopy under shaded conditions or because the vine lacked sufficient carbohydrates to stimulate growth (
The formation of blind nodes at the proximal part to the head of fruiting canes of highnode vines can be caused by correlative inhibition. Correlative inhibition and apical dominance are two intimately connected phenomena. Correlative inhibition is expressed in spring when distal nodes break dormancy first and grow more vigorous shoots than middle and proximal nodes (
The effect of node loading in the expression of correlative inhibition on New Zealand Sauvignon blanc grapevines had not been considered before. The most recently published research on Sauvignon blanc response to increasing node loads focused on longterm response at the scale of the whole vine; it reported the presence of blind nodes in the middle section of canes, but did not address the withinvine changes in growth along canes, spurs and the vine head (
Between 2019 and 2020 (Site 1), the number of blind nodes rose significantly on high node vines possibly due to the conjunction of correlative inhibition and bud necrosis. Bud necrosis is a physiological disorder characterised by the abortion and death of buds developing inside a compound bud within each node (
The location of blind nodes at the proximal section to the head of fruiting canes could have serious consequences for the management of canepruned vines. At winter pruning, the dormant shoots that form fruiting canes and renewal spurs are selected from the shoots located near or on the vine head (
Increasing cane node load had little or no effect on the start of budburst and its progression over the first two weeks following budburst (Figure S10 a; Table 3). This result confirms similar observations reported on young vines by
When comparing individual nodes on canes and spurs, there were strong differences in leaf appearance stages among node positions, with distal buds bursting earlier and developing faster than buds in proximal node positions (Figure 3 and Figure 5). As already discussed, this was caused by correlative inhibition. The consequences of correlative inhibition are nonuniform budburst and shoot growth along the cane. The variability observed in shoot growth became more pronounced over time regardless of node loading. Thus, even appropriate node loading cannot offset the negative effects of correlative inhibition on canepruned vines. Therefore, existing methods, such as cane cracking, bending/arching or the application of hydrogen cyanimide could be used to control correlative inhibition (
The response mechanism of mature Sauvignon blanc grapevines to increasing node loads in the first two weeks following winter rest is complex. Vines responded to lower node loading by developing a large number of noncount shoots on the head, resulting in the vine budburst percentage reaching 1.5 to three times the optimal threshold of 100 %. Higher node loading inhibited shoot development, resulting in more blind nodes on canes, particularly at proximal positions of the head, and fewer shoots, if any, on the vine head. There were no changes to double shoots in response to the higher node loads. The imbalance caused by lower node loads was well captured by the vine budburst percentage. On the other hand, the imbalance resulting from higher node loads was poorly captured by the vine budburst percentage alone, because noncount shoots may have masked the presence of blind nodes. Cane percent budburst, together with blind node and noncount shoot measurements, provided a more accurate assessment of vine response to node loading and balance status. Vines responded to high node loads by producing more blind nodes, which were mostly located at the proximal section of the cane. The presence of double shoots was not in itself a sign of vine imbalance. Threenode spurs developed more blind nodes than onenode and twonode spurs. Cane node loads had no significant effect on the start of budburst and its progression during the first two weeks following budburst at vine scale. However, budburst along the canes and spurs started at the most distal node. This research enhances our understanding of withingrapevine physiological response to increased node number, and identifies a composite metric (cane percent budburst, cane blind node, head shoot count) for monitoring grapevine vegetative growth, capacity and balance at preflowering. It also justifies the practice of retaining onenode or twonode spurs at winter cane pruning.
This publication is supported by Lincoln University, Villa Maria New Zealand, Tiki Wine and predominantly the MaaraTech Human‐Assist project funded by the New Zealand Ministry of Business, Innovation and Employment (MBIE; GrantUOAX1810). Several institutions contribute to the MaaraTech project: University of Auckland (lead), University of Waikato, University of Canterbury, University of Otago, Lincoln Agritech, and Plant and Food Research.