• WSU Horticulture and Landscape Architecture
• WSU Mount Vernon NWREC

Annual Report 2003

Evaluation of Wine Grape Cultivars and Selections for a Cool Maritime Climate

G.A. Moulton, G.H. Spitler, J. King, L.J. Price, R.S. Darland and T.R. Bronkema
 

Summary

In 2003 the weather provided excellent conditions for evaluating the full range of cultivars on trial, with 1965 AHU at the Mount Vernon site and 2147 AHU at Everson (to October 31, 2003). The wines produced this year should prove to be a benchmark for comparison with future seasons. A full crop was produced from most of the trial plots at Mount Vernon, and from many of the main cultivar and rootstock plots at Everson. In some cases where wines were made from cultivars in the pretest plots with only 3 plants per cultivar, juice from both sites were combined to yield enough for a 3 or 5 gallon carboy. Cultivars vinified at Mount Vernon in 2003 included 14 red wine cultivars and 15 white wine cultivars. This includes the wine from the Pinot Noir rootstock trial, in which fruit from each rootstock was vinified separately.

New planting in 2003 included additions to the pretest and an advanced cultivar trial grafted to selected rootstocks. After seeing results of the rootstock trials in 2002 , it was decided to graft certain promising cultivars that had showed good performance onto the best performing rootstocks. This advanced cultivar trial includes standards like Madeleine Angevine, Siegerrebe and Leon Millot along with promising cultivars from the pretest and main trial. Most of these will be planted in spring 2004 and begin fruiting in 2005-2006.

Collecting and analyzing harvest data and producing wines for evaluation continued in 2003. Cooperation of area winemakers is engaged in the post-harvest evaluation of varieties suitable for wine production (see Discussion & Recommendations, below.) Individual wines are being made from grapes of Pinot Noir 2A from each of the 8 rootstocks harvested separately. Wine is also being made from several of the varieties, as well as a blend from the varieties with a partial crop. Evaluation of the 2003 wine crop is estimated for spring-summer of 2004.

After seeing results of the rootstock trials in 2002 and 2003, new planting in 2004 included additions to the pretest and an advanced (replicated) cultivar trial grafted to one of the 3 promising rootstocks. This trial includes standards like Madeleine Angevine, Siegerrebe and Pinot Noir along with promising cultivars from the pretest and main trial. Most of these were planted in spring 2004 and should begin fruiting in 2005-2006, if funding is maintained. Aim of this trial is to see whether the rootstock effects observed in Pinot Noir 2A will also carry over to other varieties.
 

Methods

Data collection in this trial consists primarily of weekly sampling of fruit as harvest season approaches, and laboratory analysis of the juice to determine brix, pH and titratable acid. Berry sampling is done by taking 10 berries from each plant for a sample of 50 berries from each 5-plant replicated plot in the rootstock and cultivar trials. Each plot in the cultivar trial is replicated 3 times, and in the rootstock block 5 times. (In the pretest plots with only 3 plants/cultivar, berry samples are collected from the 3 plants at random, depending on the amount of fruit available.)

At harvest, yield of each plot is weighed, a bunch count is made of a sample bin to determine bunch weight (an aid for preparing yield estimates), and juice samples are collected for analysis as the grapes are being crushed.

Project categories

1. Cultivar Trials

The trial initiated in 2000 presently consists of about 20 cultivars, selections, and clones (see Appendix B, Table 1). Plot design is a randomized block of 3 replications, with 5 plants per replication. At the Mount Vernon site, row spacing is 10' rows with 6' between plants. At Everson the spacing is 9' rows with 5' between plants.

In 2003 an advanced cultivar trial on selected rootstocks was begun at Mount Vernon (to be completed in 2004), consisting of 3 replications, with 5 plants per replication, spaced in 10' rows with 6' between plants: Rootstocks are Millardet et de Grasset 101-14 and Couderc 3309. Cultivars are Garanoir, Leon Millot, Madeleine Angevine, Optima, Ortega, Pinot Gris (Ruhlander clone), Pinot Noir 777, Regent, Reichensteiner, Schonburger, Siegerrebe and Sylvaner, all of which have performed well at the trial sites.

2. Pretest

The pretest (see Appendix, Table 2) screens potential cultivars, to determine if they should be added to the main replicated trial, from which varietal wines can be produced for evaluation. The pretest consists of 3 plants per cultivar, replicated once. Promising grapes from the pretest will be multiplied, replicated and added to the main trial. Some promising cultivars or clones advanced to the main trial in 2004 are Optima, Ortega, Pinot Gris [Ruhlander] and Reichensteiner.

3. Rootstock Trial

The rootstock trial consists of Pinot Noir 2A grafted on 7 rootstocks plus a self rooted control (see Appendix B, Table 3). Each rootstock is evaluated for its effect in terms of maturity, yield, and quality compared with self rooted plants. Replications consist of five plants on each rootstock, replicated three times at the Everson plot and five times at the Mount Vernon plot. At Mount Vernon the two additional replications have been used for conducting cultural studies in comparison of the standard cultural treatment in the rootstock block.

4. Cultural Studies

A. Cluster thinning – In one row, fruit was thinned to 1 cluster per shoot, and compared with 2 clusters per shoot which was the standard for the rest of the plot.

B. Plastic row shield – A 3' wide sheet of clear plastic was hung on the west side of the trial row in April and retained until harvest. The sheet extended 1 ½' above and 1 ½' below the lateral canes (fruiting area.) Fruit from this row was compared with the control (no plastic) to examine possible effect in advancing ripeness.

C. Fruit harvest timing – On October 8, 2003 fruit samples were taken from all plots in the Pinot Noir rootstock trial, at which time several of the plots met standard criteria for harvest. However, it was decided to keep the fruit hanging and monitor the plants for any disease (rot). Because of good canopy management, vine structure was open to air circulation. This combined with careful monitoring of disease and timely application of fungicides, allowed harvest to be delayed until October 27. Comparison was made between juice samples taken at harvest with those taken earlier to see what changes occurred over time in brix, pH and titratable acid.

D. Spacing – In 2003, a vine spacing trial was initiated, consisting of replicated plots at 8' spacing between rows, with in-row spacing at 4', 6', 8' and 10' to evaluate the effect of various spacings and rootstock on vine vigor, canopy management, production efficiency and overall vine balance. Cultivars included in the trial are: Agria, Dornfelder, Dunkelfelder, Pinot Noir 777 and Zweigelt.
 

Results

1. Cultivar trials

Harvest data from 2003 are shown below. Data from the trial at Everson are shown in Appendix A.

Table 1. Cultivar trial, Mount Vernon – Harvest date, average pH, brix, titratable acid and fruit yield (in harvest order)

2. Pretest

Harvest data from the pretest (3 plants/plot) 2003 are shown below.
Table 2. Pretest cultivars, Mount Vernon - Harvest date, brix, titratable acid and fruit yield
(in harvest order, R = red wine cultivar)

Most of the cultivars and selections in the pretest produced enough fruit for evaluation in 2003, and several of them yielded enough for wine making in either single varietals or blends, when crops from Mount Vernon and Everson plots were combined. Cultivars were evaluated for their performance in an exceptionally good year such as this, and those that did not do well were scheduled for discard (see Appendix B.)

3. Rootstock Trial

Samples of 10 berries per plant/50 berries per plot were taken on October 8, 2003 and the juice extracted and analyzed. Results of juice analysis for selected rootstocks are shown below.
Table 3. Average pH, brix, titratable acid, cluster size and fruit yield of selected rootstocks (10/08/2003)

The entire Pinot Noir trial was harvested on October 27, 2003 and the juice analyzed with results shown below.

Table 4. Rootstock trial - Mount Vernon 10/27/03 - Average fruit yield, cluster size, brix, pH and titratable acid
(in ascending order by titratable acid)

All rootstocks had lower levels of titratable acid than self rooted; Table 4 above shows those where differences were statistically significant. All had higher pH than self rooted but differences did not reach 5% level of significance except for 5BB. All had higher brix readings than self rooted but did not reach 5% level of significant difference. Cluster weight varied and some differences were significant. The biggest difference was between C3309 and 5C. Both 101-14 and 420A had lower titratable acid and higher brix than self rooted, though yields were statistically the same.

In comparing the rootstocks overall, those that were most successful in promoting earlier ripening were Millardet et de Grasset 101-14, Millardet et de Grasset 420A and Couderc 3309.

4. Cultural Studies

A. Cluster Thinning - Analysis of juice from vines with 1 cluster/shoot vs. 2 clusters/shoot is shown below.
Table 5. Cluster Thinning Trial 2003

Data from juice analysis showed significant differences in yield and cluster weight between the plants where clusters were thinned to 1 cluster/shoot, compared to 2 clusters/shoot. Yield of vines with 2 clusters/shoot was 38% higher than with 1 cluster/shoot. No significant difference was found between the treatments in the measurement of brix, pH and titratable acid.

B. Plastic row shield – Analysis of juice from vines with plastic shield vs. no plastic is shown below.
Table 6. Plastic shield trial 2003

Application of plastic row shield advanced bloom by approximately 2 weeks, and bunches in the shielded row were noticeably earlier to color. Yield in tons/acre at 10 X 6 plots was 4.0 T/A for plots with no plastic and 3.4 for plots with plastic shield. Both treatments were trained at 2 clusters/shoot.

C.Fruit harvest timing - Analysis of juice from the Pinot Noir plot sampled on October 8, 2003 was compared with juice sampled from the same plots at harvest on October 27, 2003.. Data were averaged for all plots harvested on each date and results are shown below.
Table 7. Fruit samples 10/08/2003 and 10/27/2003

Data averaged for all Pinot Noir plots tested on October 8 and harvested on October 27 showed no significant change in total acids. However, brix continued to rise in the 3 weeks between sample and harvest date from 18.9 to 20.5. This indicates that fruit maturity will continue to advance as long as healthy green leaves remain on the plants.
 

Discussion

Results of the trials to date have clearly shown that high quality wine grapes can be grown in western Washington, given careful choice of the appropriate varieties and rootstocks, and selection of a good site. After selecting a suitable area for establishing the vineyard, take soil tests and amend the soil as needed. Many soils tend to be low in potash, magnesium and calcium. Monitor heat unit accumulation from April 1 - October 31, using an Avatel, Hobo or similar recording device.

Most of the plots in the trial produced sufficient fruit both for sample tests and for wine making. Evaluating their performance in 2003 resulted in several promising cultivars.

Recommended varieties with high potential are early clones of Pinot Noir and Pinot Gris, grafted onto a rootstock (preferably Millardet et de Grasset 101-14, Couderc 3309 or Millardet et de Grasset 420A.) On a site with marginal heat units, it may be necessary to concentrate on the earlier varietals such as Siegerrebe, preferably grafted on a rootstock. Some of the promising newer German varietals may also be worth trying, also grafted on rootstock, either as varietals or for blending (see list of promising cultivars, above.)

Good cultural practices can do much to enhance fruit maturity. Cluster thinning, plastic row shields, good canopy management and attention to nutrition and disease sprays in a timely manner all help to maximize fruit quality.

Acknowledgements

Support for this project in 2003 was provided by the Washington State Wine Advisory Board and the Northwest Center for Small Fruit Research. The help and participation of our cooperators in harvesting and winemaking is gratefully acknowledged.

Appendix A – Results of Everson Trial

Table 1. Red wine cultivars vinified in 2003, Everson (AHU 2127)

Table 2. Rootstock trial 2003, Everson

Appendix B – Cultivars/Selections and Rootstocks on trial

Table 1. Main variety evaluation 2003 (* = Everson only)

Discards 2002-2003

Table 2. Pretest, 2003 (* = Everson only)

Discards 2003

Table 3. Rootstock Trial (Pinot Noir 2A)

Discards 2003
Kober 5BB – better than own root plants but inferior to best
Malegue 44-53 – same
Riparia Gloire – same
Teleki 5C – same