Twenty red wine varieties were studied for the first year of data in 2006. Harvest began on 12 September and concluded 11 October in 2006. Harvest date for each variety is presented in table 4. Harvest date was determined by maturity with a harvest goal of 23 Brix.

Two measures of yield are presented because many of the varieties had a substantial number of shriveled and rotten clusters. We measured good clusters and estimated the weight of unusual clusters. Yield potential ranged from 23.3 tons for Cinsaut to 3.6 for Tinta Francisca. Potential yield was not correlated with harvest date (r2 = 0.06). The two varieties with potential yield above 20 tons, Cinsaut and Montepulciano, were harvest on the last day, Malbec with 4.1 tons was also harvested that day.

The difference between potential and harvest yield varied widely. More than 76%of the Souzao crop was lost while less than 1%of Tinto Cao was lost. Crop was lost either because it was shriveled or rotten. Observations of several of the varieties merit mention. Durif, Tannat and Souzao were both afflicted by shrivel close to harvest. The onset of shrivel for both these varieties was dramatic with the fruit looking normal in one week and shriveled the next. In both these cases the shriveling occurred within a week or two of harvest. We are rather alarmed at the large amount of rotten and shriveled fruit and certainly large amounts of rotten or shriveled fruit cannot be tolerated. Data collected in future years will be important in understanding the rot potential of these varieties.

We were more or less successful in our goal of harvesting each variety at 23 Brix (Table 7). Malbec and Tinta Amarella were harvest on the last harvest date because they had stopped accumulating sugar at previous sample dates. Excluding Malbec and Tinta Amarella mean Brix was 23.6 and the range was from 25.4 to 22.4. As previously described the trial is in a warm climate and grapes grown under this condition are often low in titratable acidity and have high pH. We are therefore, interested in varieties that have relatively high titratable acidity and low pH at harvest. At this early point in the trial, Petite Verdot, Freisa, Refosco, Montepulciano and Aglianico show some promise to fulfill these criteria.

Interestingly, thanks to work by Larry Williams, we can report that the some of the varieties had significantly different water status measures, despite being on the same rootstock and growth with the same irrigation regime. A more in-depth look at variety influence on water status is proposed for 2007.

In the 2001 growing season, we successfully harvested 20 Mediterranean wine grape cultivars planted in an experimental vineyard at the UC Hopland Research and Extension Center (UCHREC). Small lots of experimental wine have also been made, and are in process. Phenological data (budbreak, bloom, veraison and harvest) were taken. Harvest data included yield per vine, number of clusters per vine, and average cluster weight. Fruit measurements included average berry weight, total acidity, pH, and sugar expressed in percent brix. Most cultivars ripened adequately, but it is still difficult to fully ripen Montepulciano and Aglianico under our conditions.

Comprehensive final reports were written for the Lake County Mediterranean Wine Grape Cultivar plots (see attached). In general, the cultivars being evaluated in Lake County did well in the trial at Red Hills, where the soils limited the vines to more modest yields, and there was sufficient heat to ripen everything. In the Highland Springs plot, few of the cultivars were able to adequately ripen due to large crops and cooler weather conditions. Data were presented at the Lake County Annual Wine Grape Day on December 7th, 2001. Sample wines made from the plots were also tasted, and it is clear that there is potential for high quality wine to be made from these selections, especially Syrah, Sangiovese, Barbera and Dolcetto.1

PDF: Evaluation of Selected Mediterranean Wine Grape Cultivars and Clones in Lake and Mendocino Counties

The limitations of petiole nitrate-N as a criteria for vine N status are widely recognized. The purpose of this study was 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 (NO3-N) levels were compared with 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 were located at the UC Kearney Agricultural Center except for Chardonnay and Cabernet Sauvignon that were on the Central Coast. A wide range of N fertilizer rates was imposed in order to establish large differences in vine N status and potential plant response. Fertilizer treatment was initiated one year ahead of the beginning of data collection to provide carry-over N in the vines. Significant differences in N determinations for each tissue and sampling stage from N fertilizer treatment were found in 5 cultivars at Kearney, with the exception of bloom blade total-N. This tissue and stage was not significantly different for total-N in 4 cultivars ? Barbera, Grenache, French Colombard and Chenin blanc. Bloom blades showed the least promise as an indicator of differences in N status in these trials. There was a tendency for the veraison and harvest samples to show greater significant differences in total-N status as compared to bloom sampling. Nitrate-N most often showed the greatest range in values from the low to the high N treatments. However, total-N showed as much statistical separation as NO3-N by the Duncan’s Multiple Range Test. This indicates the possibility of developing useful critical values for total-N, as well as the traditional NO3-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. Over half of the vine yield and fruit composition components showed significant differences due to fertilizer treatment. This provides the opportunity to correlate vine response with leaf tissue N values. Correlation and regression analyses are being conducted on all of the data with goals to determine the best timing and tissue-type for N status and to develop tentative critical values for total-N and/or NO3-N for each cultivar. Four years (1996-99) of N fertilizer treatment with 3 years (1997-99) of data collection from the Chardonnay and Cabernet Sauvignon trials have shown minor or no differences. The Chardonnay vineyard was unresponsive in all measurements, indicating adequacy in N status ans/or lack of vine N uptake. The Cabernet Sauvignon vineyard showed no vine growth or fruiting response, but demonstrated significant differences in vine N status due to treatment. This included leaf petiole and blade levels of NO3-N and total N at the various vine stages.

A San Joaquin Valley wine grape trial block was established in 1992 at the UC Kearney Agricultural Center to evaluate potential Italian and Rhone regional cultivars of limited experience to the San Joaquin Valley. A collection of the most promising selections from Fay Triplett’s wine cultivar breeding program was included in another trial, as well as a collection of Muscat cultivars for premium dessert wine production. The second year of field data collection in 1997 is summarized as follows: Rhone and Italian Cultivars ? Shiraz, Nebbiolo, Sangiovese, and Mouvedre showed the most promising characteristics of the black cultivars. Cinsault and Dolcetto were the least promising. Grenache and Barbera served as standard comparisons. Shiraz and Nebbiolo were comparatively early ripening, moderate yielding, small-berried, free of bunch rot, and of good fruit composition. Conversely, Cinsault had large berries of poor composition (high pH and low TA); Dolcetto had excessive cluster numbers which developed poorly (berry shrivel and drop) with the sparse vine canopy. Delayed fruit maturation with a high yield in Sangiovese demonstrates the need to adjust crop load in this large-clustered cultivar. Mouvedre was less promising than Sangiovese due to more bunch rot and poorer fruit composition. Viognier showed the most promise of the non-standard white cultivars tested, with early ripening small berries, low bunch rot, and satisfactory yields. Sauvignon blanc performed well except that it had a higher rot potential than Viognier. Marsanne again had heavy clusters with high rot and the poorest fruit composition. French Colombard, the standard, had the highest yield of the most balanced fruit composition, as might be expected. Muscat Cultivars ? Muscat blanc and Orange Muscat were again early-ripening. Malvasia Bianca and Aleatico were the highest and lowest yielding, respectively. The opposite was true in 1996, suggesting an >alternate bearing= response. Bunch rot was again high in Aleatico. Orange Muscat, Muscat blanc, Malvasia Bianca and Muscat Hamburg show the most promise but with a need to manage potential bunch rot. Aleatico has been the least suitable of the cultivars Fay Triplett Wine Cultivar Selection ? Sixteen black selections were in full production for data collection in 1997. Four had a high bunch rot incidence while the others were low-moderate to rot-free. Eleven cultivars ripened in mid September; four ripened exceptionally late and may not have ever achieved full-ripeness. Most of the selections had very favorable titratable acidity levels for the San Joaquin Valley. Nine of the selections were above 0.80 g/100 ml at harvest. Most of the fruit pH=s were also very favorable, with 8 selections showing pH levels below 3.5. Some of the selections showed excellent viticultural characteristics such as open canopies, small berries and loose clusters, good fruit color, and varietal flavor characteristics. One more year of fruiting data will be collected in order to determine the best selections for wine making evaluation.