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Cane- and Spur-Pruned Pinot noir Results in Similar Fruitfulness, Yield, and Grape Ripeness under Cool Climate Conditions

Miranda R. Ulmer, Patricia A. Skinkis
Catalyst: Discovery into Practice  2020  4: 10-20  ; DOI: 10.5344/catalyst.2019.19004

Summary

Goals: Oregon Pinot noir growers prefer head training and cane pruning to cordon training and spur pruning, referred to herein as cane and spur pruning, respectively. With decreasing labor availability and increasing production costs, growers are interested in transitioning to spur pruning to improve vineyard economics because spur pruning requires less manual labor and is easier and more economical to mechanize than cane pruning. However, they are hesitant to adopt spur pruning because of fears of reduced and inconsistent yields, as they believe Pinot noir has unfruitful basal buds. We conducted a two-year field trial to compare Pinot noir cane- and spur-pruned vine productivity from dormancy to harvest in a vineyard trained to a unilateral Guyot training system where vines were head trained and cane pruned to one 10-node cane and one two-bud renewal spur or cordon trained and spur pruned to six spurs of two nodes per spur.

Key Findings:

  • Primary bud fruitfulness was no different between pruning methods.

  • Node position was important for dormant compound bud fruitfulness. The first, second, and third count nodes from the base of a cane or spur were fruitful, but node positions 4 and 5 had 11% higher fruitfulness.

  • There was higher compound bud fruitfulness and greater inflorescence primordia size in compound buds of dormant canes with greater weight and diameter, regardless of pruning method.

  • Pruning method did not affect vine phenology, yield, or harvest grape ripeness (Brix, pH, and titratable acidity [TA]).

Impact and Significance: Our study found no yield or grape ripeness differences between cane- and spur-pruned Pinot noir in a unilateral Guyot training system. Therefore, spur pruning is an option for producers who wish to reduce dormant pruning labor and who consider adopting mechanization for further cost savings. Additional shoot-thinning passes may be required in spur-pruned vineyards, since the older cordon wood resulted in greater growth of adventitious shoots in spring compared to cane-pruned vines.

Overview

Oregon is known for quality Pinot noir wine production. The majority of Oregon’s Pinot noir acreage (80%) is grown in the Willamette Valley1—a cool climate viticulture region characterized by cool seasonal temperatures and high winter rainfall. Vineyards in the region typically require intensive canopy management to control disease and fruit quality because of high vegetative vigor; however, yields tend to be low and variable across seasons.

Oregon’s cool climate has been purported as the cause of low yields as compared to warmer production regions. For example, the same Pinot noir clones grown in Oregon’s Willamette Valley had nearly two-fold higher yields reported in Sonoma, California.2,3 In addition, Oregon Pinot noir growers observe annual yield variation as reported in other cool climate winegrape regions.4 Grapevines have more seasonal yield variation than other crops, with 60 to 70% of this variability attributed to differences in the cluster number per vine.4 Multiple components comprise yield, including cluster number, cluster mass, berry size, and berries per cluster, but fruitfulness—defined as the number of inflorescences per shoot—is one of the most important contributors.5,6 Understanding Pinot noir fruitfulness may allow us to better manage yield quantity and consistency under cool climate conditions; however, few studies have addressed the effect of pruning on bud fruitfulness.

Pruning is essential to grapevine productivity because it reduces the number of fruiting buds, thereby allowing the vine to balance vegetative growth and yield relative to vine nutrient reserves.7 Pruning severity affects growth and yield because early shoot growth is dependent on stored carbohydrate and nutrient reserves.8 Studies have shown reduced shoot growth and cane-pruning weight with higher bud numbers left at pruning;9,10 larger vine size also has been reported with more severe pruning.11

Cane pruning involves selecting one or multiple one-year-old canes with six or more nodes at pruning and then removing all other one-year-old wood. Spur pruning involves pruning back one-year-old canes to one to three buds on spurs along a semipermanent extension of the trunk known as a cordon and then removing all other one-year-old wood. Oregon growers prefer cane pruning to spur pruning because they believe spur pruning results in low yields, reduced fruit quality, high-density canopies, and increased pest and disease pressures.12 However, a vineyard case study reported similar yields, cluster sizes, and fruit ripeness in cane- and spur-pruned Pinot noir vineyards in the region.12 Pruning accounts for 20 to 25% of annual canopy management costs, and 107 hr of manual labor/ha (43 hrs/acre) are required for pruning, brush removal, and cane tie-down in cane-pruned vineyards in Oregon.13 Fewer steps are required for spur pruning compared to cane pruning, and spur pruning has the potential for greater cost reduction due to fewer manual labor hours and the potential to mechanize.14,15,16 The spur-pruning process can be partially or completely mechanized and decrease labor demands by 50 to 90% with mechanical prepruners accompanied by manual labor follow-up.16,17 Spur pruning was effective in balancing vigor and yield and obtaining dependable budbreak and adequate fruit yield in California-grown Cabernet Sauvignon.18 If appropriately applied, spur pruning may be effective in achieving vine balance and desired yields with or without the use of mechanization in Pinot noir.

Grapegrowers are often not able to take on the risk associated with adopting new methods or increasing mechanization, especially those with small acreage and limited capital. This is of particular concern for many growers in Oregon and the Pacific Northwest because the majority are small producers.19 Therefore, we conducted a multiyear dormant pruning trial in a commercial vineyard in Oregon’s Willamette Valley to compare Pinot noir bud fruitfulness and harvest yields under cane and spur pruning. This was a first step in helping growers make changes toward vineyard practices that hold mechanization potential with the hope of improved economic viability.

Major Observations and Interpretations

We evaluated two dormant pruning methods, unilateral cane pruning and unilateral cordon-spur pruning in a 10-year-old commercial Pinot noir vineyard, which was planted to a spacing of 1.01 m between vines and 1.8 m between rows. Vines in both pruning treatments had 10 to 12 dormant buds left at pruning (cane = 10 buds per one cane and a two-bud renewal spur; spur = five to six, two-bud spurs per cordon). We measured dormant bud fruitfulness during three dormant periods (2017 to 2019) and yield during two crop years (2017 and 2018) to determine whether basal buds of Pinot noir lack fruitfulness and whether yields, ripeness, or phenology were altered by cane or spur pruning.

Seasonal weather and phenology

We evaluated three seasons of weather data (2016 to 2018), focusing on air temperature and heat unit accumulation during the seasons that would influence floral primordia development and bud fruitfulness the following year. The year prior to the onset of our study (2016) accumulated 268 GDD10 (where GDD is defined as growing degree days) during budbreak to bloom and 1440 GDD10 from budbreak to harvest. Years one (2017) and two (2018) of the study had similar seasonal heat unit accumulation, but the 2018 season was considerably drier, with 54 mm less rainfall than 2017 (Table 1). Both growing seasons were warmer than the long-term average of 1155 GDD10 calculated based on public weather data from 1894 to 2012 (Western Regional Climate Center, McMinnville, OR).20 The growing season rainfall accumulation was 11% higher in 2017 and 52% lower in 2018 than the long-term average of 285 mm (Western Regional Climate Center, McMinnville, OR).20 We monitored phenological development of cane- and spur-pruned vines over the two growing seasons and found no differences in key phenological development stages, including budbreak, bloom, and veraison.

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Table 1

North Willamette Valley weather dataa based on phenological stage for the 2017 and 2018 growing seasons.

Dormant measures

We first applied pruning treatments to unilateral Guyot-trained vines in February 2017; previously the entire block was spur pruned since 2013. Spur-pruned vines had 25% greater dormant pruning weights than cane-pruned vines at pruning the first year (February 2017) (p = 0.0014) (data not shown). The higher pruning weight in spur-pruned vines was due to having one more shoot per vine included in the pruned wood compared to the cane-pruned vines that had one shoot laid down at pruning. Cane weights did not differ at the outset of the study. Spur-pruned vines had 16 to 24% higher pruning weights than cane-pruned vines following the 2017 and 2018 growing seasons, and this was attributed to two to three additional shoots per vine. However, cane weights did not differ by pruning method (Table 2).

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Table 2

Pinot noir dormant whole vine pruning weight and average cane weight in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

Cane- and spur-pruned vines had similar dormant compound bud fruitfulness, defined as the inflorescence number per bud, during two of three dormancy periods (2017 and 2018) (Table 3). Regardless of the pruning method, primary buds contained approximately two inflorescence primordia, and secondary buds contained approximately one inflorescence primordia in 2017 and 2018, as is common for healthy Vitis vinifera dormant buds. In addition, there was no difference in the inflorescence primordia size (integrated fruitfulness index, which is a sum of all the primordia diameters within a bud) between the pruning methods in those years (Table 3). However, bud fertility was lower in 2019 than in the prior two years with respect to both the whole bud and the primary bud. Cane-pruned vines had 0.4 more inflorescences per bud than spur-pruned vines, and the inflorescence primordia were 0.2 mm larger in buds of cane-pruned vines. However, fruitfulness of the primary bud did not differ between treatments in 2019 (Table 3).

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Table 3

Pinot noir dormant bud fruitfulness components in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

Bud fruitfulness and inflorescence primordia size during dormancy was affected by node position and pruning method. In 2017, node 3 of spur-pruned vines had 0.7 more inflorescence primordia (Figure 1) and were 0.3 mm larger than node 3 of cane-pruned vines. In 2018, cane-pruned vines had 0.2 more inflorescence primordia at node 5 than the same node in spur-pruned vines, and in 2019, cane-pruned vines had 0.2 mm larger inflorescences at node 3 than spur-pruned vines at the same node position. There were no bud fruitfulness differences for other nodes when comparing pruning methods. Regardless of treatment and year, average whole bud fruitfulness at nodes 1 and 2 were 2.8 and 2.4, respectively, whereas the remainder of the buds averaged 2.9 inflorescences per bud. This seemingly small difference in bud fruitfulness could result in a 4 to 21% difference in vine yield. The first count bud position closest to the head of the vine or spur (node 1), was consistently more fruitful than node 2, and bud fruitfulness at node 2 was also lower than nodes 4 through 11 on cane-pruned vines.

Mean (+SE) dormant compound bud fruitfulness (number of inflorescence primordia per bud) at each node position (n = 50) in cane- and spur-pruned Pinot noir vines in (A) 2017, (B) 2018, and (C) 2019. Node 1 is the first count bud located proximal to the base of the cane or the spur of the cordon and each progressive node is distal on the cane (up to node 12) or spur (up to node 5). Statistical significance is denoted as *p < 0.05 and ** p < 0.01.
Figure 1

Mean (+SE) dormant compound bud fruitfulness (number of inflorescence primordia per bud) at each node position (n = 50) in cane- and spur-pruned Pinot noir vines in (A) 2017, (B) 2018, and (C) 2019. Node 1 is the first count bud located proximal to the base of the cane or the spur of the cordon and each progressive node is distal on the cane (up to node 12) or spur (up to node 5). Statistical significance is denoted as *p < 0.05 and ** p < 0.01.

Dormant canes used for bud dissections

There were no differences in dormant cane weights used for bud dissections at the outset of the study in 2017 (Table 4). However, canes from the plots destined for the spur-pruning treatments had larger internode diameters than plots destined for cane-pruning treatments in January 2017. Following the two experimental seasons, cane-pruned vines had greater cane weights than spur-pruned vines. Internode diameters of canes from the two pruning treatments did not differ in either year (Table 4). Bud fruitfulness components had a positive linear relationship with measures of cane size in all years of the study. Primary bud inflorescence primordia size was larger with greater internode diameter in 2017 (Figure 2), and whole bud fruitfulness was higher with greater cane weights in 2018 and 2019 (Figure 3). Additionally, we observed larger inflorescence primordia size with greater cane weights in 2019 (Figure 3).

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Table 4

Pinot noir dormant cane metrics used for compound bud dissections in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

Regression relationship between Pinot noir dormant cane diameter (mean diameter of nodes 1 to 12 in cane-pruned vines and nodes 1 to 5 in spur-pruned vines) and primary bud inflorescence primordia size, as measured by the integrated fruitfulness index, the sum diameters of all dormant bud inflorescence primordia (y = 0.1504x – 0.319, R2 = 0.521, p = 0.0184) in 2017. Each point represents plot means (n = 10 vines).
Figure 2

Regression relationship between Pinot noir dormant cane diameter (mean diameter of nodes 1 to 12 in cane-pruned vines and nodes 1 to 5 in spur-pruned vines) and primary bud inflorescence primordia size, as measured by the integrated fruitfulness index, the sum diameters of all dormant bud inflorescence primordia (y = 0.1504x – 0.319, R2 = 0.521, p = 0.0184) in 2017. Each point represents plot means (n = 10 vines).

Regression between dormant cane weight and bud fruitfulness parameters in an Oregon Pinot noir vineyard, shown as averages of all pruning treatments. (A) Positive linear regression between cane weight and bud fruitfulness (number of inflorescences per bud) in 2018 (y = 0.0129x + 1.5782, R2 = 0.4912, p = 0.024) and 2019 (y = 15.529x + 1.0561, R2 = 0.5495, p = 0.0142). (B) Positive linear regression between cane weight and inflorescence primordia size (integrated fruitfulness index) of the whole bud in 2019 (y = 8.2437x + 0.1917, R2 = 0.5009, p = 0.022). (C) Positive linear regression between cane weight and size of the primary inflorescence primordia in 2019 (y = 4.727x + 0.3004, R2 = 0.467, p = 0.0294). Each point represents plot means (n = 10).
Figure 3

Regression between dormant cane weight and bud fruitfulness parameters in an Oregon Pinot noir vineyard, shown as averages of all pruning treatments. (A) Positive linear regression between cane weight and bud fruitfulness (number of inflorescences per bud) in 2018 (y = 0.0129x + 1.5782, R2 = 0.4912, p = 0.024) and 2019 (y = 15.529x + 1.0561, R2 = 0.5495, p = 0.0142). (B) Positive linear regression between cane weight and inflorescence primordia size (integrated fruitfulness index) of the whole bud in 2019 (y = 8.2437x + 0.1917, R2 = 0.5009, p = 0.022). (C) Positive linear regression between cane weight and size of the primary inflorescence primordia in 2019 (y = 4.727x + 0.3004, R2 = 0.467, p = 0.0294). Each point represents plot means (n = 10).

Fruitfulness, fruit set, and yield

Fruitfulness, as measured by inflorescence number and size, was quantified at each node post-budbreak for buds retained on cane- and spur-pruned vines. Fruitfulness was measured on all data vines (10 per plot) by counting the number of shoots at each node when inflorescences were visible (five to seven leaf stage, BBCH 16) but before shoot-thinning was conducted by the commercial vineyard laborers. Cane-pruned vines had 0.6 more inflorescences per node than spur-pruned vines in 2017 (Table 3). However, spring fruitfulness did not differ in 2018 (Table 3). We quantified the number of flowers per inflorescence and percent fruit set to determine whether bud primordia size at dormancy related to inflorescence size and number of berries after fruit set. Cane-pruned vines had 37 to 47% more flowers per inflorescence prebloom and 24 to 33% more berries per cluster post-fruit set compared to spur-pruned vines (Table 5). Pruning method did not affect the percent fruit set in 2017 where both treatments achieved ∼50% set, but cane-pruned vines had 6% higher fruit set than spur-pruned vines in 2018 (Table 5).

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Table 5

Pinot noir inflorescence and fruit set components measured in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

Whole vine yields were higher in 2018 than 2017, but there were no differences by pruning method in either year (Table 6). Spur-pruned vines had four more clusters per vine than cane-pruned vines in 2017 and 2018. However, cane-pruned vines had 23 to 27% heavier clusters with 10 to 15% more berries than spur-pruned vines (Table 7). Although there were differences in cluster berry number, pruning method did not affect berry size or cluster compactness—a measure determined from the rachis length divided by the number of berries per cluster (Table 7). Regardless of treatment and year, cluster number per vine affected yield more than cluster weight. Additionally, cluster weight was influenced more by berry count than berry weight.

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Table 6

Pinot noir harvest yield and vine balance components in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

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Table 7

Pinot noir harvest grape cluster and berry parameters in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

We compared bud fruitfulness data with yield component data from 2017 and 2018 using multiple linear regression analyses to determine whether bud fruitfulness or floral primordia size could serve as a predictor of inflorescence size, cluster size, and harvest yields. However, we did not find any significant statistical relationships in either year.

Vine growth

We monitored shoot and canopy growth because growers were concerned about spur pruning leading to more dense canopies than cane pruning. Spur-pruned vines had six more shoots per vine compared to cane-pruned vines prior to shoot-thinning in spring 2018 (Table 8). Cane-pruned vines had longer shoots than spur-pruned vines when we measured them after shoot-thinning but before bloom in both years (Table 8). In 2017, cane-pruned vines had 24 cm longer shoots than spur-pruned vines at bloom time, but this difference did not exist in 2018 (Table 8). We observed more shoot length variability in cane-pruned vines than spur-pruned vines; however, growth rate was similar under both pruning treatments (data not shown). Cane-pruned vines had 12% less leaf area per vine at bloom in 2017 compared to spur-pruned vines, despite having longer shoots prebloom (Table 8). There were no leaf area differences at veraison in 2017, and there were no leaf area differences at bloom or veraison in 2018.

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Table 8

Pinot noir shoot and canopy growth and size in a vineyard study evaluating two dormant pruning methods in Dayton, Oregon.

Pruning weights were higher in 2017 than 2018, and spur-pruned vines had higher pruning weights than cane-pruned vines both years (Table 2). With the potential for different canopy density between the two pruning treatments, we monitored vine balance parameters. Cane-pruned vines had a higher yield-to-pruning weight ratio than spur-pruned vines in 2017 and 2018, but leaf area to yield was higher in spur-pruned vines only in 2017 (Table 6).

Grape ripeness

Grape ripeness was assessed prior to and at harvest. The pruning method did not affect basic grape ripening (total soluble solids [TSS], pH, TA) in the weeks prior to harvest. By harvest 2017, there were no differences in TSS or pH by pruning method; TSS ranged from 23.8 to 24.1 Brix, and pH was 3.3. However, TA was 7.5 and 8.0 g/L in cane- and spur-pruned vines, respectively (p = 0.0153). In 2018, there were no differences in grape ripeness; TSS ranged from 21.5 to 21.7 Brix, pH ranged from 3.1 to 3.2, and TA ranged from 6.7 to 6.8 g/L.

Broader Impact

Cane- and spur-pruned vines did not have either bud fruitfulness or inflorescence primordia size differences during the first two dormant periods of our study. By the final dormant period (2019), spur-pruned vines had fewer and smaller inflorescence primordia when considering all buds (primary and secondary) within a node. However, there were no differences in primary bud fruitfulness in 2019. Spring fruitfulness per node was lower in cane-pruned vines only in the first year of the study and did not differ by year two.

Each bud is subject to different physiological and environmental conditions as it develops along the shoot, and this may affect floral primordia development within the bud.4 Lower bud fruitfulness at basal buds has been reported for Pinot noir, Thompson Seedless/Sultana, and Sauvignon blanc.21,22,23,24,25 Bud fruitfulness of Sultana and Sauvignon blanc reportedly increase in a stepwise manner beginning proximal to the head of the vine.21,25 Basal buds were fruitful in our study; however, fruitfulness was lower at buds proximal to the head of the vine or cordon in cane- and spur-pruned vines, respectively. Inflorescence primordia size was also influenced by node position. Buds closer to the head of the vine were smaller than those more distal under both pruning methods.

Vine vigor affected bud fruitfulness parameters more than pruning method. There was greater fruitfulness and floral primordia size with greater cane size in all three years of our study. Other studies found greater grapevine bud fruitfulness components on shoots with larger internode diameters, larger cane cross-sectional area, and greater dormant cane weight.21,23,24 Cane mass and cross-sectional area are related to starch content within the cane, and sufficient carbohydrate reserves may play a role in fruitfulness and vine vegetative vigor the following year.21,23 Relationships reported in the literature between vine vigor and bud fertility likely contribute to the differences found between cane- and spur-pruned vines in our study, since increased vine vigor resulted in increased inflorescence number and size, regardless of pruning method. This suggests the ability of vines to achieve vegetative and reproductive balance.

Yield variation is typical for Oregon Pinot noir, and yield in this study varied 54% between 2017 and 2018. The higher yield and lower pruning weights in 2018 led to a nearly two-fold increase in the yield-to-pruning weight ratio, although vines were still within a healthy yield-to-pruning weight ratio of ≤5 often observed in Oregon.26 The reduced pruning weights in 2018 were likely due to the drier growing season, since the region received nearly half the in-season rainfall compared to 2017. Vines sustained canopy growth and fruit ripeness, and while there may not have been a carbohydrate resource limitation in-season, it may have led to greater resource competition with the developing buds. Other studies suggest a relationship between vine reserve carbohydrates on fruitfulness and yield the following year.23,27

Yield was similar between cane- and spur-pruned vines, but spur-pruned vines had smaller clusters as reported in other Pinot noir pruning studies.12,28 Yields were above typical target yields for Oregon Pinot noir, which are 4.5 to 6.2 t/ha (2 to 2.75 tons/acre).29 Cluster weight differences were a result of berry number per cluster, because berry weight was not different between pruning methods. Pinot noir berry weight appears relatively stable in different vineyard management studies conducted in Oregon.12,29,30,31 Pruning method did not affect basic ripeness at harvest, with no differences in TSS or pH, and the slightly higher TA (0.5 g/L) in cane-pruned vines in 2017 was likely too small to affect fermentation or wine quality. Similarly, others found harvest fruit ripeness unaffected by cane and spur pruning.12,32,33

Pruning method had little effect on vine vegetative vigor and growth. However, spur-pruned vines had shorter shoots before bloom than cane-pruned vines both years. This may be due to the growth of adventitious shoots along the cordon of spur-pruned vines in our study, and the grower confirmed greater adventitious shoot growth during manual shoot-thinning passes each spring. Others have reported more vegetative vine growth with spur-pruned vines, as reported by more shoots per vine, higher pruning weights, or more dense canopies in spur-pruned vines compared to cane-pruned vines.28,32 While some studies suggest that spur-pruned vines have greater carbohydrate reserves that could lead to vegetative growth differences,34 others have not been able to show this association.28 In our study, there was a minor difference in early season shoot length and leaf area between the two pruning methods. However, there were no leaf area differences by veraison and no effect on dormant cane weights; this was in part because the vines were managed with standard canopy practices for the region, including shoot-thinning to a uniform density and hedging. Furthermore, the timing of early stages of phenological development was not affected by pruning method as shown in another pruning study in a warm, humid region.32

The Oregon industry has typically preferred to use dormant cane pruning rather than spur pruning primarily because of concerns that low bud fruitfulness in Pinot noir would lead to very low and erratic yields if vineyards are spur pruned.12 The present study shows that basal buds of Pinot noir are fruitful and that cane or spur pruning may be used without reducing yields or basic fruit ripeness. Growers who use spur pruning may reduce dormant pruning costs and realize additional labor savings with the implementation of mechanization. While we found more early spring shoot growth that may require additional labor costs for shoot-thinning in spring, typical canopy management practices can be employed to achieve target shoot density, yield, and fruit quality for Oregon Pinot noir.

Experimental Design

We conducted a multiyear trial in a commercial vineyard in Dayton, Oregon (45°15′N, 123°02′W, 87 to 119 m asl). The block was planted in 2007 to Pinot noir (Pommard clone) grafted to 101-14 rootstock in Jory silty clay loam soils. Rows were oriented north-south on a hillside with 18% slope and a vine spacing of 1.01 m between vines, and 1.8 m between rows for a plant density of 5124 vines/ha. Vines were trained to a unilateral Guyot system with vertical shoot-positioning.

Two dormant pruning treatments were evaluated, including (1) Cane—vines were head trained and one cane selected to be tied down to the fruiting with 10 buds per vine with a two-bud renewal spur at the head of the vine, and (2) Spur—vines were cordon trained to one cordon along the fruiting wire with five to six spurs pruned to two buds per spur. Both cane- and spur-pruned vines retained one renewal spur per vine that contained two buds, and this was for the growth of a new cane for the cane system or as a replacement of the cordon if it would need to be replaced in the future. Treatment plots consisted of three consecutive whole vine rows, with each treatment replicated five times in a randomized complete block design. Pruning treatments were first applied to unilateral Guyot-trained vines in early February 2017; previously the entire block was spur pruned since 2013. Vines were subsequently pruned in the same way in early February 2018.

We collected all vineyard-related data from 10 randomly selected vines within the middle row of each plot. The commercial vineyard staff applied standard disease and canopy management practices during each growing season, including cluster-zone leaf removal to the eastern exposure of the canopy shortly after fruit set (done by hand) and mechanical hedging post-fruit set. Cluster thinning was not conducted per typical industry standards so that we could evaluate yield effects of the pruning treatments.

Bud fruitfulness

We collected dormant budwood prior to pruning during winter over three dormant periods (January 2017, 2018, and 2019). We selected one cane from each of 10 cane-pruned vines in each plot. These canes were selected near the head of cane-pruned vines because they were the best representation of the canes that would be selected at pruning to bear fruit the following season. For spur-pruned vines, we collected one cane arising from the proximal position from the cordon on any of the spur positions 2, 3, or 4 proximal to the trunk of the vine on a minimum of 10 vines per plot.

Canes were wrapped in plastic bags and stored at 4°C for no longer than one week before they were analyzed by bud dissection. We measured individual cane weights and internode diameter at the midpoint between each node along the cane using a caliper (0 to 150 mm Digital Caliper, Titan Professional Tools). Internode diameter was measured on nodes 1 to 12 in cane-pruned vines and nodes 1 to 5 for spur-pruned vines. These data were used to quantify cane size and were statistically analyzed with bud fruitfulness.

Dormant compound buds were measured for bud fruitfulness, which is the number of floral primordia present within both primary and secondary buds of the compound bud located at each node. “Node position one” was defined as the first count bud (from the head of the vine on cane-pruned vines or from the base of the spur) with at least 0.5 cm of cane below it, and each subsequent node is the bud distal to it along the cane or spur. Nodes 1 through 12 were analyzed on cane-pruned vines, and nodes 1 through 5 on spur-pruned vines. One person dissected all buds for this project by hand under a stereoscope (Nikon SMZ800N, Nikon Instruments Inc.). Thin, transverse cuts were made along the bud axis using a single-edged razor blade (3-Facet 0.23 mm Single Edge Blades, Personna GEM), and the number of inflorescence primordia was recorded. The width of each inflorescence primordia was measured with each sequential slice using a 10 mm microscale with 0.1 mm increments (Ted Pella, Inc.); but the widest measure was recorded. We calculated the integrated fruitfulness index (IFI, reported in millimeters) by taking the sum of the largest diameters of each inflorescence primordia within each bud of the compound bud; then we were able to determine IFI for the primary bud and the entire compound bud at each node.

Vine growth

We monitored phenology throughout the growing season using the BBCH scale.35 Two shoots per vine were tagged post-budbreak on 10 vines per plot and used for shoot growth measures, including shoot lengths and leaf area at bloom and veraison. Shoot lengths were measured at two dates (prebloom and bloom) using a flexible measuring tape, and the length recorded to the nearest 0.5 cm. No later shoot lengths were recorded because mechanical hedging ensued. We measured leaf area on the tagged shoots at bloom and veraison using a nondestructive template method.36 Briefly, the primary leaves on the two shoots per vine were measured against the template to determine leaf size at bloom and veraison, and the mean shoot leaf area was multiplied by the shoot number per vine. We collected dormant pruning weights by weighing the one-year-old wood removed after pruning following each growing season, making sure to include the shoot weight removed for bud dissections. This gave us an idea of possible vine vigor differences that may exist between pruning treatments.

Fruitfulness, fruit set, and yield

Once the inflorescences were visible (BBCH stage 16) and shoots were six to 10 inches tall, we counted the numbers of shoots and inflorescences at each node on the canes and spurs of all data vines (10 vines per plot) prior to shoot-thinning in spring. To understand the effect of pruning on another important component of yield, we determined fruit set by analyzing digital photographs of inflorescences preand postbloom.37 In short, we took a digital photograph of the basal cluster on each of the two tagged shoots per data vine (20 inflorescences per plot) before bloom when the flowers were separating (BBCH stage 57). Inflorescence photos were counted to determine the number of flowers per inflorescence. The same clusters were photographed ∼12 days postbloom when the berries were BB-sized (BBCH stage 73). At each time point, we randomly selected 30 basal clusters within buffer rows of each plot to be photographed and then removed them from the vine for manual counts to develop a standard curve comparing the number of flowers or berries in the photograph to actual counts. Regression analyses of the standard curve show a linear relationship, and equations were used to estimate the number of flowers and berries per inflorescence and percent fruit set (2017 prebloom: y = 1.6428x + 36.04, R2 = 0.77, p = <0.0001; 2017 post-bloom: y = 1.1973x + 25.816, R2 = 0.63, p = <0.0001; 2018 prebloom: y = 1.6798x − 23.878, R2 = 0.91, p = <0.0001; 2018 postbloom: y = 1.8813x − 19.843, R2 = 0.63, p = <0.0001). At the end of the season, whole vine cluster counts and yields were measured on 10 vines per plot within two to four days prior to commercial harvest.

Fruit composition

We collected a 10-cluster sample within each plot from nondata vines on a weekly basis beginning two to three weeks prior to harvest to track fruit ripening. We recorded cluster weight, number of berries per cluster, rachis weight, and berry weight. Fruit was pressed to juice (Welles Juice Press; Samson Life Inc.) and measured for TSS, pH, and TA. A digital temperature-compensating refractometer (Digital Refractometer 300051; Sper Scientific Ltd.) was used to measure TSS. The pH of the juice was measured with a temperature-compensating pH meter (Accumet AB15; Fisher Scientific). TA was determined using a 5 mL aliquot of juice diluted in 45 mL of distilled water and titrated to a pH endpoint of 8.2 with 0.1 N sodium hydroxide. TA is expressed in grams per liter (g/L) of tartaric acid equivalents.38

At harvest, we collected three fruit subsamples (five clusters each) from a total of 10 vines per plot for cluster architecture analysis and fruit ripeness. The methodology for preharvest samples was followed at harvest. In the laboratory, we recorded cluster weight, berry count per cluster, rachis weight, and rachis length. Berry weight was calculated after rachis weight was subtracted from cluster weight and divided by berry count per cluster. Cluster compactness was calculated by taking the rachis length and dividing it by the number of berries per cluster. Then we destemmed berries and pressed to juice, as described previously. Juice was analyzed for total TSS, pH, and TA, also described previously.

Statistical analysis

We performed statistical analyses with SAS Statistical Software 9.4 (SAS Institute, Inc.). PROC MIXED was used for analyses of variance with Tukey’s honest significant difference test with a mean separation at α = 0.05. Regressions were run using PROC REG for fruit set standard curves and for analysis of vine growth data with fruitfulness measures.

Acknowledgments

The authors thank Archery Summit Winery for the use of their vineyard for this research and Tim Scott, vineyard manager, for his research collaboration. This project is based on work that was funded by the American Vineyard Foundation and the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2016-38640-25383 through the Western Sustainable Agriculture Research and Education program under subaward number [GW18-027].

Footnotes

  • Received August 2019.
  • Revision received October 2019.
  • Accepted October 2019.
  • Published online June 2020

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Cane- and Spur-Pruned Pinot noir Results in Similar Fruitfulness, Yield, and Grape Ripeness under Cool Climate Conditions
Miranda R. Ulmer, Patricia A. Skinkis
Catalyst: Discovery into Practice  2020  4: 10-20  ; DOI: 10.5344/catalyst.2019.19004
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