The limitations of petiole nitrate-N as a criteria for vine N status are widely recognized. The purpose of this study is to search for improved N tissue sampling and analytical methods which can be used for many wine cultivars under different growing conditions. Total-N and nitrate-N levels are being compared in leaf petiole and blade samples taken at bloom, veraison and harvest in 7 cultivars: French Colombard, Chenin Blanc, Ruby Cabernet, Barbera, Grenache, Chardonnay, and Cabernet Sauvignon. All of the trial blocks are located at the UC Kearney Agricultural Center except for Chardonnay and Cabernet Sauvignon which are on the Central Coast. A wide range of N fertilizer treatment is being imposed in order to establish large differences in vine N status and plant response. Fertilizer treatment was initiated one year ahead of the beginning of data collection to provide carryover N in the vines. Significant differences in N determinations for each cultivar, tissue, and sampling stage from N fertilizer treatment were found, with the exception of bloom blade total N. This tissue and stage was not significantly different for total-N in 3 cultivars ? Barbera, Grenache, and Chenin Blanc. Thus, so far, this tissue has shown the least promise as an indicator of differences in N status. There was a tendency for the veraison and harvest samples to show greater significant differences in N status as compared to bloom sampling. As expected, nitrate-N showed the greatest range in values from the low to the high N treatments. However, total-N showed as much statistical separation as nitrate-N by the Duncan’s Multiple Range Test. This suggests that there are good possibilities in developing useful critical values for total-N, as well as the traditional nitrate-N. Also, petioles tend to show as good, if not better, statistical separation for total-N as compared with blades. This is encouraging, as it would be very useful to be able to use petioles rather than blades because of value of petiole samples for other nutrient determinations. Some vine yield and fruit composition components showed significant differences due to fertilizer treatment. This should provide the opportunity to correlate vine response with leaf tissue N values. Correlation and regression analyses will be performed after 2 full years of vine and laboratory data. The goal is to develop some tentative critical values for total-N and/or nitrate-N for important wine cultivars.
The San Joaquin Valley wine cultivar clonal evaluation study was initiated in 1987. It is an ongoing study to evaluate the most promising, virus disease-free clonal material being held or introduced as potential FPMS source material. French Colombard, Chenin blanc, and Barbera were completed in 1994 and 1995. Trial blocks of 3 clones each of Grenache, Sangiovese, Muscat blanc and Muscat of Alexandria were established in 1993; data collection was initiated at harvest, 1995, in these new trials, except for Muscat blanc which had too much bunch rot for meaningful results. Significant clonal differences were measured in all of the cultivars as follow: Grenache. Clone 3 had heavier berries and a higher yield, but with lower fruit soluble solids, as compared to clone 1. These differences can be attributed to genetic clonal differences, as neither of these selections have indexed positive for virus nor have they been heat-treated. Clone 2 (a heat-treated selection of clone 1A) is not showing any important differences. Thus, there are no apparent effects from heat treatment to date. Sangiovese. This culitvar is showing rather distinct clonal differences, with clone 2 showing the greatest promise due to its smaller berry size, good fruit maturation, lowest fruit pH and bunch rot, while maintaining intermediate yields. Clone 3 had large berries but the lowest yields; clone 4 had the highest fruit pH and bunch rot, although it had the highest yields. Muscat of Alexandria. The California selection A3 out yielded both of its Australian counterparts ? J2 and G5 ? with comparable fruit composition. This data is very preliminary due to the relatively young vine age. More complete data collection, including cluster numbers and weight and berry phenols and anthocyanins, will be taken in 1996.
The Zinfandel clonal trial was terminated with only minor differences being found among certified Zinfandel clones. However Primitivo was different from the Zinfandels in having lower yield per vine due to smaller clusters, fewer berries/cluster and smaller berries. Sangiovese clones also differed significantly. Sangiovese 3 showed a trend towards lower yield and had significantly fewer berries per cluster. There was also a trend towards lighter clusters but it was non significant. Clone 3 also had slightly advanced maturity with 0.7 higher °Brix and 0.07 higher pH, although the acidity did not differ. Cabernet Sauvignon clones in the Napa hillside site show similar trends to previous AVF-funded work. FPMS 6 is the lowest yielding clone, with 2 and 5 being intermediate and 8 highest. Yield differences are due primarily to cluster wt. For Pinot noir, the range in yield was about 2-fold from 11.7 lbs/vine (5.1 tons/acre) for UCD1 to 22.3 lbs/vine (9.7 tons/acre) for UCD 31. Again in 1994, harvest date which stretched over 10 days, was correlated strongly with yield/vine. Yield differences were made up, again, of a complex combination of cluster number, berries/cluster and berry wt. Largest berries are seen in UCD 23 and 31, and ESP 374. Smallest berries were found in UCD 13 and the “Wente” selection. Clonal evaluation work in continuing on Zinfandel, Merlot and Malbec. Recently concluded and published clonal evaluation work can be found in Practical Winery & Vineyard, American Vineyard and the American Journal of Enology & Viticulture
Three clonal trials were reported on: Zinfandel/Primitivo/Sangiovese, Cabernet Sauvignon, and Pinot noir for sparkling. In the Zinfandel trial, the UCD materials remain indistinguishable with large, tight clusters and large berries; the Primitivo variety has consistently had looser clusters as a result of fewer berries/cluster. Sangiovese 3 continues to have fewer berries per cluster than Sangiovese 2. The Cabernet Sauvignon clones in the new hillside location are showing some of the same trends as in previous studies with one of the major differences being the fewer berries/cluster evident in clone 6. Differences in berry size which were generally not seen in previous studies must be followed for a few more years to establish a reliable trend. In Pinot noir for sparkling wine, differences were seen in most yield components, chemistry at harvest and duo-trio tests, despite the great influence of the cool weather at bloom and its effect on fruitset. Some year x clone interactions were seen indicating that clones were reacting with relative differences between the two years. Another year or two will be required to establish consistent trends.
A San Joaquin Valley wine cultivar clonal evaluation study was initiated in 1987. It utilizes 15 single-vine replicates in randomized complete blocks for each cultivar at the UC Kearney Ag Center. 1993 was the fifth year of comparison for three selections each of French Colombard and Chenin blanc. Each cultivar compares two different selections which are registered (indexed as virus free) but not heat treated. Additionally, each cultivar includes a heat treated selection. Thus, we are studying the possible influence of heat treatment on virus-free material of French Colombard and Chenin blanc. Barbera was in its third year of data taking. This compares an Italian selection, Rauscedo 6 (FPMS Clone 2), with Marshall (FPMS Clone 1). Barbera Clone 1 presently involves much of the present commercial acreage but was later found to contain mild leafroll. French Colombard. Clones 1 and 2 showed no significant differences in vine fruiting responses which is similar to the 1992 results. Thus, these two selections of the same genetic source but comparing no heat treatment (clone 1) vs. a 91 day heat treatment (clone 2) are now of similar performance. This is in contrast to the first two years (1990 and 1991) of data taking when clone 2 appeared to be the best selection due to more favorable fruit composition. In contrast, clone 5 had significantly lower soluble solids in 1993 and a trend toward smaller berries, heavier clusters, and higher yields as has been demonstrated in previous years. No differences in sensory analysis of the wines made from these selections in 1993 were shown. This trial will be summarized after the 1994 harvest. Chenin blanc. Clone 5 again produced the smallest berries and clusters of earliest maturity. However, the yields are lower and the bunch rot is higher with this selection. Clone 1 and 4 were similar in performance in 1993, although clone 4 has out-yielded clone 1 in the past. Sensory analysis comparisons of the wines showed no significant differences. A 6-year summary of this trial will be completed after the 1994 harvest. Barbera. Clone 2 (Rauscedo) would appear to be the recommended choice for future planting, given its virus-free status and higher yields as compared to clone 1 (Marshall). However, there is some delay in fruit maturation, a higher potential for rot, and possibly lower wine color with clone 2. Significant differences for wine taste and aroma of these selections were found but could not be consistently characterized. One more year of field data and wine quality comparison will enable us to make a more definitive recommendation. The problems with clone 2 point to the need for importation of additional clonal material for evaluation. Grenache. Sanqiovese, and Muscat blanc. Trials with 3 clones each were established in 1993 and are being trained in 1994.
Executive Summary: An on-going San Joaquin Valley wine cultivar clonal evaluation trial was initiated in 1986 and planted into the first trial block in 1987. Location is the University of California Kearney Agricultural Center, Parlier where cultural conditions and practices can be closely monitored. All of the selections are indexed FPMS sources, most of which are registered. None have ever been compared in clonal studies. Thus, industry would benefit from performance information on available selections. This study utilizes 15 single-vine replicates in randomized complete blocks for each cultivar. 1991 was the third year of comparison for three selections each of French Colombard and Chenin blanc. Each cultivar compares two different selections which are registered (indexed as virus free) but not heat treated. Additionally, each cultivar includes a heat treated selection. Thus, we are studying the possible influence of heat treatment on virus-free material of French Colombard and Chenin blanc. Barbera was in its first year of data taking. This compares an Italian selection, Rauscedo 6 (FPMS Clone 2), with Marshall (FPMS Clone 1). Barbera Clone 1 presently involves much of the present commercial acreage but was later found to contain mild leafroll. French Colombard. Clone 1 is the highest yielding, latest maturing, and most rot susceptible, possibly due to higher fruitfulness (cluster numbers and berries per cluster). Clone 5 tends to be the lowest yielding and earliest maturing selection over the three years of data taking. Presently, Clone 2 would appear to be the best overall selection. It is intermediate in yield and has favorable fruit composition characteristics. Interestingly, it is a heat treatment of Clone 1. Chenin blanc. Clone 5 produces the smallest berries and clusters of earliest maturity. However, yields are lowest and rot tends to be highest with this selection. Presently, Clone 4 would appear to be the best selection. It is the highest yielding and with the lowest rot incidence. This is a heat treatment of Clone 1 with more favorable vine yield characteristics. Barbera. These two selections were included to compare the widely planted Clone 1 (Marshall) with the only registered and recently introduced Clone 2 (Rauscedo 6). Because of its virus-free status, only Clone 2 should be recommended for planting at this time. However, its larger berry size and higher yields contribute to later fruit maturity and possibly lower anthocyanins per fruit weight. Further evaluation will be necessary to confirm this preliminary recommendation. Zinfandel was eliminated in 1991 due to inclusion of a misnamed selection. Grenache will be added with a comparison of three selections in 1993. Sanqiovese and Muscat blanc are also planned for future evaluation. Other cultivars will be added as promising selections become available. Wine samples will be made from French Colombard and Chenin blanc if full funding becomes available in 1992.
Five clonal trials were harvested in 1991, two Chardonnay, two Cabernet Sauvignon, and 1 combination of Zinfandel, Primitivo and Sangiovese. Clones were assessed for yield components and fruit maturity indices. Small-lot wines were made from only one trial (Jaeger Chardonnay) because of a shortfall of funds. The cane-pruned Jaeger Chardonnay clonal trial yielded less on average than the cordon-spur-pruned Beringer trial, although the trends bore some similarities. As in the past, clones 4 and 5 were among the highest yielding in both trials. Clone 14 at Jaeger and clones 6, 14 and 15 at Beringer were intermediate in yield. As has been the historical case, clone 16 yielded one-half to one-third of the highest yielding clones. It is interesting that the yield-pruning ratios varied from 1.5 to 7.8 at Jaeger and from 2.8 to 13.3 at Beringer. There has been a consistent trend for heavier pruning weights for clone 6 and 15, intermediate pruning weights for clones 4, 5, and 16 and low pruning weights for clone 14. The Cabernet clonal trial at Mondavi Woodbridge is showing that the highest yielding clones are 8 and 21, with clones 2, 4, 5, and 10 as intermediate and clone 6 as the lowest. The difference between the high and intermediate yielding clones is less than in past years. For the Zinfandel-Primitivo-Sangiovese trial, the 10-vine plots were split into thinned and not-thinned groups in 1991. Thinning of course reduced yield but did not result in larger vine size at dormant pruning in 1991-2. There were few differences among the Zinfandel selections. In many respects, Primitivo yield components were very similar to Zinfandel, although the formere seemed to ripen sooner. Sangiovese clones ripened sooner than either Zinfandel or Primitivo. Sangiovese 3 had fewer berries/cluster than Sangiovese 2, althoug the berries were somewhat heavier. Over the past two to three years additional trials have been established in Napa (Merlot, Cabernet Sauvignon), Sonoma (Chardonnay, Pinot noir – sparkling), Lake (Cabernet Sauvignon, Zinfandel) and Santa Barbara (Pinot noir – red and sparkling). Discussions are underway for Napa (Merlot, a second site) and Santa Barbara (Chardonnay).