Determine The Impact of Cluster Thinning and Cluster Zone Leaf Removal on the Hormone Content of Pinot Noir Grape Berry

During the past six months we have succeeded to reproduce the flower-to-berry monitoring procedure developed in our lab with similar outcomes. The justification of this procedure is to mitigate the extreme variability of flowering events in a cluster that is assumed to explain the berry variability. Using this procedure, we were able to distinguish “early” berries (emerging from early flowering events) from “late” berries (emerging from late flowering events). Previous observations in our group suggested that flowering time was not the major contributing factor of the ripeness variability at mid- véraison stage (50{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} of berries are green and 50{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} are colored) . This was confirmed again this year via the monitoring of several phenological parameters on “early” and “late” berries. We also confirmed that the seed weight relative to seed weight better explained the ripeness of individual berries at mid-véraison stage regardless of whether berries were categorized in the early or late berry groups. Interestingly, by monitoring berry size and berry weight, we also found that “early” and “late” berries rapidly overlapped their growing curves during the early stages of the growing season (week 3 to week 6 after bloom), which suggests a developmental mechanism to mitigate developmental variability among berries of a cluster.

On the other hand, ripeness variability at véraison was not associated with berries being “early” or “late” as both berry groups had a wide range of ripeness level at mid-véraison stage (sugar and pigment content). We also validated the effects of two viticulture practices (cluster thinned and fruit-zone leaf removal) on sugar and pigment contents regardless of whether berries were “early” or “late”. In vines with clusters thinned at 0.5/shoot, both accumulation of sugar and pigment contents were significantly higher in berries during the late stages of the ripening. For the fruit-zone leaf removed, only pigment content was significantly increased in sun-exposed clusters during weeks 12-15. The fine screening we performed to mitigate the developmental variability of berries has been successfully conducted and we are in the second phase of the project this year, which is the quantification of hormone and metabolite in control, cluster thinned, and fruit-zone leaf removed grapevines.

Comparison of Crop Load Management Systems and Differential Regulated Deficit Irrigation (RDI) on Vegetative Compensation, Whole-Canopy Photosynthesis, and Vine Performance in Procumbent Vitis vinifera L. in a Warm Climate

A traditionally managed head-trained, cane-pruned Merlot/Freedom vineyard planted on a California sprawl trellis was converted either to a bi-lateral cordon spur pruned (HP) or single high-wire bi-lateral cordon mechanically pruned (SHMP) crop load management system. Two irrigation treatments were applied. Vineyard was irrigated as follows A control treatment of sustained deficit irrigation (SDI) at 0.8 of estimated ETc was applied from anthesis until harvest (EL Stage 38) with a mid-day leaf water potential (¥[1]) threshold of -1.2 MPa. A regulated deficit irrigation (RDI) treatment was applied at 0.8 ETc from anthesis to fruit set (EL Stage 28) with a ¥[1]  threshold of -1.2 MPa, 0.5 ETc from fruit set to veraison (EL stage 35) with a ¥[1]  threshold of -1.4 MPa and at 0.8 ETc from veraison until harvest with a ¥[1]  at -1.2 MPa. Irrigation treatments were not initiated until ¥l reached -1.0MPa for vines in the 0.8 Etc treatments. It took one season to convert and establish canopies that can be cropped. In 2014 the  vineyard was cropped. The SHMP treatment irrigated with the SDI irrigation method generated the largest canopy earlier and was the most efficient user of applied water to fix carbohydrates. Furthermore, this canopy also yielded the greatest with acceptable canopy architecture and microclimate variables for the warm climate. There were few statistically significant effects of crop load management treatments or irrigation methods applied on seed and skin flavonoids. The total berry skin anthocyanins were most affected by the HP and SDI treatments in the initial year of data collection. The preliminary results suggest that it would take one full growing season to convert traditional California sprawl canopies to a SHMP trellis. The resultant canopy is a more efficient user of applied water amounts to fix carbon with greater yields with similar berry skin phenolics. The study is providing important science-based information for California wine[i] grape growers on how best to manage traditional California sprawl canopies to a SHMP trellis. The resultant canopy is a more efficient user of applied water amounts to fix carbon with greater yields with similar berry skin phenolics. The study is providing important science-based information for California wine grape growers on how best to manage traditional vineyards in times declining resources such as labor and water.

Defining Crop Load Metrics for Quality Pinot Noir Production in Oregon

A three year study began in 2013 to determine the impact of varying crop levels on vine growth and balance. The project involves two components: 1) a large grower collaborator crop load study and 2) a study that monitors vine growth, nutrition and physiology measures within four sites from the larger study. A total of 13 vineyard and winery collaborators have participated in the research and completed two full growing seasons of data collection and wine production for the study in 2013 and 2014. The 2013 season results from the large grower collaborative study indicates few differences in vine size (pruning weight), vine nutrient status, or fruit composition at harvest. Data from for the 2014 season are still being gathered from collaborators and will be analyzed statistically in spring/summer 2015. Data obtained from the four detail sites during 2013 and 2014 show no difference in vine nutrition at bloom or véraison, vine photoassimilation rates, nor differences in vine growth and leaf area when comparing full crop (non-thinned vines) with those cluster-thinned to one cluster/shoot. Despite very high yields in 2014, cluster thinning did not drastically change ripeness parameters measured. The differences in vine productivity among sites within the two projects are valuable in understanding how crop load may be influencing fruit composition and quality in vineyards with different yield capacity. The data obtained from the first two years of this research suggests that the Pinot noir vines in the Willamette Valley of Oregon may reach vine balance on their own and do not require cluster thinning to adjust for fruit ripeness or to maintain vine growth. Further seasons of research are required to better understand the role of vine balance.

Defining Crop Load Metrics for Quality Pinot Noir Production in Oregon

A three year study began in 2013 to determine the impact of varying crop levels on vine growth and vine balance. The project involves two components: 1) development of a large grower collaborator crop load study and 2) monitoring of vine growth, nutrition and physiology measures within four sites from the larger study. During 2013, the project included a total of 13 vineyard and winery businesses from across six AVAs in the Willamette Valley of Oregon. Collaborators successfully completed their first season of data collection as of this reporting, and results are being compiled and analyzed in winter 2014. The additional data from the four sites within the study are being analyzed in winter 2014, but preliminary data that shows no difference in vine photosynethetic assimilation or vine nutrition at bloom or véraison when comparing full crop (non-thinned vines) with those thinned to one cluster/shoot.

Improving Yield and Quality of Sauvignon Blanc

Clonal Trial: During the 2010 growing season, a trial containing 12 clones of Sauvignon blanc were grown and harvested. The vineyard is farmed organically, drip irrigated and planted in a Russian River loam soil in Hopland, Mendocino County, California. Clones include: UC FPS# 1, 6, 7, 14, 18, 20, 22, 23, 25, 26, and 27. The experimental design is a ANOVA Randomized Complete Block with 8 replications of 5 vine vines planted in 4 long east ?west rows. Replications are clearly marked with plastic cattle ear tags at the beginning and end of the plot containing the replication number and clone for easy identification. This is the fifth bearing year of the vineyard, and the vines were trained with two canes containing an average of 12 buds per cane on a vertical shoot positioned trellis (VSP). Vines were managed during the growing season to the cooperating grower?s commercial standards including trunk and cordon suckering and removal of sterile shoots, positioning shoots upright inside of fruiting wires, and a standard powdery mildew program utilizing stylet oil and wettable sulfur pre-bloom, and sulfur dust post bloom. No insecticides or miticides were applied. Nearly all vines are bearing at commercial levels, and we were able to sufficiently harvest enough fruit to make valid mean comparisons. This growing season was relatively cool and overcast. Consequently, the growing season was delayed by almost two weeks. Bud break occurred between April 1st and April 7th. Flowering occurred between June 15th to June 18th. Veraison was also late, between August 4th to August 12th. Harvest occurred on October 8th, and was scheduled to coincide with other Sauvignon blanc being crushed by the cooperator. In general, phenology was not significantly different between all of the clones. The exception is that veraison and ripeness were accelerated for UC FPS # 14 which generally has lighter crop loads ( Target fruit maturity was 22.5 to 23.5 {aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} brix.) Based on our data, these observations were concluded: ? The vines are becoming mature and are probably yielding within their commercial potential. Vine yield have a statistically significantly different range, from 3.7 kg to 9.9 kg, which would correspond from 3.2 to 8.5 tons per acre. Cluster counts are also significantly variable, from 31 to 65 clusters per vine. ? There are differences in cluster weights ranging from approximately 81g to 133 g. There is considerable variability in the clones in cluster size, looseness and yield potential. This allows growers some choice if they are in need of lighter crop loads to insure that fruit will ripen under cooler conditions. ? Fruit ripeness varied from around 21 {aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} brix to 24 {aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} brix. It appears that ripeness was affected by crop load. Clones that were carrying heavier crops were less ripe at harvest. ? The pH was higher than is typical for the cultivar in our region (ranging from around 3.5 to 3.7) and titratable acidity was moderate (ranging from .5 to .7 grams per 100 ml). Often fruit from our area has more acidity, but because of the large crop and the long hang time, acidity was lower than harvests that mature early and are lighter in size. ? UC FPS #1 is still an excellent clone, and yields consistently well from one season to the next. Trellis Trial: The trellis trial is in adjacent row to the variety trial. The experimental design is a randomized complete block, with 4 reps of 10 vines for each treatment. The trellis types were selected with the ability to be mechanically harvested. The following trellis types are being used: 1. Vertical Shoot Positioned Trellis (VSP), bilateral cordon, highway post, fruiting wire at 36 inches. 2. VSP, 4 canes, with 2 pairs stacked on fruiting wires at 36 inches and 44 inches. 3. VSP, bilateral cordon, fruiting wire at 36 inches, 12 inch cross arm at 48 inches, and 16 inch cross arm at 60 inches to create more pendant growth to help divigorate the vines (a modified California sprawl system). 4. VSP, modified cane pruning (continuous fruit curtain), cordon wire at 36 inches, 4 short canes are tied to fruit wire at 44 inches. 5. VSP, 4 canes tied to two parallel fruiting wires at 36 inches, two cross arms, one at 48 inches, and one at 66 inches. In 2009, we balance pruned the vines, meaning that we left 3 bud spurs, and tried to have an average of 40 buds per vine. Regardless, it is clear that the cane pruning systems are able to set larger crops than spur pruning systems.

Cultural Practices to Modify Berry Physical Properties and Susceptibility to Cracking

Ethrel sprays, irrigation regimes, and girdling all had a significant influence on Flame Seedless cracking in the 2010 field trials at Arvin, CA. Among the 64 treatment combinations of these factors, ethrel sprays had the largest effects, particularly the first ethrel spray, which increased cracking rate by six-fold compared to plots with no spray. This suggests that the dose and timing of the ethrel spray may be a key issue in balancing the advantages for color development with disadvantages of cracking. The four irrigation treatments, 0.6X, 1X (grower standard), 1.7X and 2.3X, caused clear differences in plant water status as measured by stem water potential (SWP), with berries from the higher irrigation treatments having significantly increased berry size, but also increased cracking, and berries from the lowest irrigation having decreased size, firmness, and cracking. Cell turgor was also well correlated with berry firmness. The correlation between irrigation and cracking justifies the prospect of future usage of SWP and other linked berry properties to monitor and minimize cracking, and we will continue research to resolve these factors in order to provide growers with information about threshold values for cracking. Girdling also significantly increased cracking with the late girdle having higher effects than the early girdle. Late girdle may not be as necessary for this field considering its negative impact on cracking but minor effects on color development.

Tracking of individual berry growth showed that berries at around veraison expanded with an average rate of about 2.5{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} per day, but most of the expansion occurred at night. A peak short-term rate equivalent to 6.4-8.5{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} per day was exhibited at 7-8am, but the monitored berries that showed these rates did not crack. Skin mechanical properties in the standard and frequent irrigation treatments were tested with custom equipment (berry balloon system, BBS), and in both treatments, pressure, stress and skin strain at failure (cracking) progressively decreased over berry development, indicating, as expected, that cracking susceptibility increases over time. In the scanning electron microscope (SEM) the surfaces of field-cracked, soaking-cracked, and BBS-cracked berries all showed clear evidence of failure by cell wall breaking and not cell separation, contrary to current scientific thinking. The BBS also detected varietal differences (Flame seedless vs Syrah) in skin mechanical properties, and given the strong impacts of ethrel spray on cracking, it will be important to quantify skin properties with BBS for the different ethrel treatments in 2011. Flame seedless berries were soaked in water with only the stylar end or the longitudinal side immersed, and berries cracked at the stylar end in the former case but remained intact in the latter. Soaking of entire flame seedless berries in water confirmed that berries crack at a fairly low strain (<5{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}). These results and our SEM images showing broken cell walls, indicate that cracking is most likely a local event that is initiated by failure of a few cells rather than a consequence of an overall expansion of the flesh, as previously believed.

The Determination of Crop Coefficients for Central Coast Vineyards

This project has further developed and applied a novel method for determining the site-specific irrigation crop coefficient, based on measurements of the midday canopy shaded areas using large solar panels. The canopy shaded areas were measured at eight vineyards throughout the growing season in San Luis Obispo County, and converted to crop coefficients. Together with local reference evapotranspiration and irrigation application data, the irrigation applications were expressed as a percentage of the full potential vine water use.

This technique makes it truly practical to fully utilize the equation developed by Williams and Ayers, which correlates the midday canopy shaded area to the irrigation crop coefficient. Prior to the development of this solar-panel method, the use of this equation was largely limited to research purposes, as the effort required for measuring the canopy shaded area using the existing manual or photographic techniques was impractical for commercial operations. The site-specific crop coefficients that a grower can collect with this method will allow one to apply climate-based irrigation scheduling with more confidence, less risk, and more consistency season after season. The large differences between the crop coefficients measured at sites that had similar trellis systems indicate that there is a value in measuring these coefficients locally.

With accurate crop coefficients it becomes possible to perform detailed evaluations of irrigation management at a given site, quantifying the season?s irrigation applications as percentages of the full potential vine water use. These results show, likely for the first time, just what degree of irrigation deficit the test plot vines were subjected to during the growing season.

Inception, Diagnosis, and Consequences of the Berry Shrivel Disorder

Berry shrivel (BS) is a disorder of unknown cause and sporadic appearance that has been increasingly observed in vineyards in Napa and Sonoma Counties. BS is commonly misdiagnosed as bunch stem necrosis (BSN), but we have found that the disorders can be clearly distinguished based on the presence of a healthy, green rachis in BS compared to a necrotic rachis in BSN-affected clusters, and the fact that BSN berries have normal to high Brix whereas BS berries have much lower Brix than normal berries. This was the second year of our study of BS development, and the first in which BS was prevalent enough to obtain a representative sample of BS berries over time. In order to determine whether BS is a berry, cluster, or vine level phenomenon, a substantial amount of over-sampling was required, and hence not all the 2005 samples of berry composition have been analyzed to date.

In both 2004 and 2005, around the time of veraison, and prior to any appearance of BS symptoms, BS berries were firmer than control berries, but the decline in firmness at veraison was faster in BS than in control berries, so that for most of the post-veraison period, BS berries were softer than controls. In 2004, BS fruit skin had a slightly increased mass of cell wall material compared to the skin of control berries, and a slightly reduced amount of cell wall material in the mesocarp, indicating that the disorder may be related to metabolic aberrations in cell wall metabolism in the mesocarp. In 2005, with a larger sample size, this was not the case. It is also unclear to what extent BS is associated with water stress. In Oakville, vines which historically have exhibited BS have been consistently less stressed than controls, but the opposite trend was observed in Sonoma County, and in nether location was the degree of BS associated with the level of water stress, as measured by leaf water potential.

In both 2004 and 2005, visual symptoms of shriveling, whether caused by BS, cluster girdling, or cluster excision, were always associated with a loss in mesocarp cell viability (as indicated by a fluorescent vital stain), and hence we can attribute the shriveling to cell death, rather than simply to berry desiccation. In both years there has been no apparent difference between BS and control berries in the xylem connection between the berry and the pedicle. For the 2005 berry composition data that is available, BS berries were similar to berries on girdled clusters, in that they both accumulated less soluble solids and had a lower pH than control berries. One key result from 2005 is that there is also evidence that BS symptoms, as measured by essentially all of the major indicators of berry development (Brix, pH, dry weight), are progressive over the season and are also expressed at the whole-vine level. Berries that show early symptoms of BS are the most affected, but lesser degrees of symptoms also occur in berries that are affected late, and still lesser, but measurable, symptoms occur on apparently healthy berries from affected vines. These results strongly suggest that, for a vineyard that is affected by the BS disorder, the effects of the disorder may not be limited only to clusters exhibiting shriveled berries.

Our current hypothesis is that BS is not a disorder related to xylem function and vine water relations, as thought previously, but rather a disorder either of phloem function and/or of vine photosynthesis. Wines were made from commercial Cabernet fruit (BV vineyard in Rutherford) that was either free from BS, or had varying levels of BS (5, 10, or 15{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} by weight), or BSN (40{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} by weight) fruit. In all cases, fermentation proceeded normally, and these wines will be subject to sensory and chemical analysis.

Effects of Berry Size and Crop Yield on Wine Composition and Sensory Quality

The effects of vine irrigation and crop yield on sensory quality of Cabernet Sauvignon wine from the 2000 harvest were investigated using descriptive analysis with a trained panel, quality ratings by members of the wine industry and tannin assays.Wines produced from vines with low irrigation regimes were rated highest in dried fruit/raisin, jam, and red/black berry aromas, fruity by mouth, and acidity and lowest in brown color. The high irrigation wines were rated lowest in bitterness, ethanol, body, and darkness. The medium irrigation wines were ranked highest in veggie aroma, astringency, brown, dark, body, ethanol, and bitterness and were ranked lowest in cherry aroma. Low irrigation wines received slightly higher quality ratings from members of the wine industry than high irrigation wines, but the difference was not significant, possibly because of differences among wine replicates.Lower crop yields tended to produce wines with high bell pepper and black pepper aromas, high astringency and bitterness, and high ethanol and veggie by mouth flavors, whereas the higher yields tended to result in wines with higher red/black berry, jam, and cherry aromas, red color, fruity by mouth, and acidic characters. Tannin concentration was significantly higher in the wines produced from low crop yields, consistent with the higher bitterness and astringency ratings given to those wines by descriptive analysis.We continued our investigation of the effects of crop yield on wine sensory quality using pruning and thinning trials on Cabernet Sauvignon grapes harvested in 2001.In the pruning trial, six treatments that left 12 to 48 buds/vine at pruning were imposed for the second consecutive season on the same vines. Vines were pruned to variations of 1 to 4 bud spurs and shoot thinned accordingly. These treatments resulted in 24 to 60 clusters/vine and produced yields that varied almost 2.5 times from lowest (3 tons/acre) to highest (8 tons/acre). In addition to yield components, a number of vegetative growth parameters were measured including budbreak, shoot diameter, and shoot length. There was only a slight decrease in shoot diameter, but shoot length was a strong inverse function of bud number, varying about 100{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} from highest to lowest bud number per vine. The cluster weight did not differ significantly among treatments. Although berry size was not constant among treatments, the differences were not greater than about 10{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} and did not show any clear relationship to the crop loads.In the thinning trial, vines were pruned to 2 or 4 bud spurs that were then cluster thinned at veraison to create 8 different crop load treatments. Crop load in this cluster thinning experiment was well distributed among the 8 thinning treatments, varying about 4-fold from 4 to over 16 lbs. per vine. These crop loads correspond to yields that vary from about 2 tons/acre to about 8 tons/acre. Thus, we were more successful in accomplishing low yield by cluster thinning than by severe pruning. There were 14 replicated yield treatments, six for the second year and eight for the first time in 2001. Wines were made from each treatment, and they are ready for bottling and subsequent sensory and chemical analysis this spring.

Effects of Berry Size and Crop Yield on Wine Composition and Sensory Quality

We draw these conclusions about the dependence of composition on size and irrigation:

  1. Imposing significant water deficits can decrease berry size and increase skin: juice ratio by approximately 25{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} compared to conventional irrigation regimes. From two separate yield experiments, it appears that smaller berries are not produced when yields are increased from 3.5 to over 10 tons/acre by leaving longer spurs at pruning.
  2. Berry size is highly correlated with seed mass/berry. However, berry growth did not keep pace with seed growth such that the amount of seed per unit berry mass increased with berry size. Low irrigation had less effect on seed growth than on mesocarp growth for any size of berry. Hence, Low irrigated fruit had greater relative seed mass, implying a greater concentration of seed tannin in the resultant wines.
  3. The mass of skin tissue bore a constant relation to berry size, i.e. the mass of skin per unit berry mass was relatively constant over the 3-fold range of berry sizes encountered. Low irrigated fruit had greater relative skin mass per berry. Low irrigation inhibited mesocarp growth more than skin growth such that the relative amount of skin per unit berry mass was always greater than for Control and High irrigated fruit.
  4. The amount of skin tannin per berry was a fairly constant fraction of berry size. Thus, the concentration of skin tannin in must was only slightly lower for large fruit than for small fruit (approximately 10{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}). However, the concentration of skin tannin was significantly greater in Low irrigation fruit of any size (approximately 30{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} greater in Low fruit).
  5. The amount of anthocyanin per berry increased with berry size, but was a slightly decreasing fraction of berry size. The resulting anthocyanin concentration was approximately 20{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23} less from the largest fruit compared to small fruit. Again, the concentration was significantly greater (approximately 30{aed9a53339cdfc54d53cc0c4af03c96668ab007d9c364a7466e3349a91bf0a23}) in Low irrigated fruit for all fruit sizes.

These results show that the amount of each skin solute is not a constant that is diluted to varying degrees dependent upon fruit growth. Accumulation of skin solute is coordinated with growth. Accordingly, oft observed changes in fruit composition caused by water deficits are not attributable simply to differences in berry growth. There is an independent effect of deficit irrigation on composition. Because deficit irrigation produces lower yield, it is important to evaluate whether there is an independent effect of yield on these quality parameters.

The fruit size and irrigation differences in fruit composition were carried through to the resulting wines.

The differences in wine composition were slightly less dependent upon fruit size than the juice composition, suggesting a possible difference in “extractability”. And, both fruit and wine composition were much less sensitive to fruit size than the theoretical dependence that is predicted from differences in surface: volume of the berries. A preliminary investigation found differences among the low, control and high irrigation wines in the intensities of green beans aroma, red fruit by mouth, bitterness and astringency as shown below. When wines were made from different sized berries that were irrigated similarly, small berry wines were more astringent than large berry wines.

PDF: Effects of Berry Size and Crop Yield on Wine Composition and Sensory Quality