Evaluation of Winegrape Clones

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.

Clonal Testing of Winegrapes in the San Joaquin Valley

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.

Breeding Grapevine Rootstocks for Resistance to Soil-Born Pests and Diseases

The development of new rootstocks is necessary to address viticulture’s current and future soil-bome problems such as: fanleaf degeneration; nematode complexes; armillaria root rot; drought tolerance; and salinity tolerance. Phylloxera is wide spread in the state, thus all new rootstocks must have dependable phylloxera resistance. Rootstocks are also needed for horticultural characters such as control of vigor and fruit maturity. This proposal primarily addresses the needs of wine grape growers. A similar proposal is funded jointly by the California Table Grape Commission and the California Raisin Advisory Board. I have worked hard to establish a Grapevine Nursery Commission that might also be a source of funds for rootstock breeding work, and I continue to pursue funding from private sources. Because of the need for many lab and field personnel, breeding is very expensive and combined funding is essential for progress. At present the departmental vineyard crew provides me with free labor for such things as planting, training, staking, trellising and grafting. This free labor source is not likely to continue as UC and Departmental budgets worsen. Additional field and lab help will be needed as the breeding program begins field testing and determinations of fruit and wine quality. Significant progress has been made in the lab and field evaluations are set to begin. We bench-grafted selected seedlings from the 1989 populations that have propagated well, been resistant to root knot nematode and should have high levels of phylloxera resistance. Replicated field trials of these grafted seedlings (we used both Chardonnay and Flame Seedless as scions) will begin at nematode and phylloxera infested sites this summer. Next year more cuttings of these seedlings will be available to establish trials at the Oakville Station and other select sites. Some of the seedlings that Lider produced in the 70’s have also been bench-grafted with the same scions. These were selected for possible broad-based nematode resistance (including dagger and root knot) and phylloxera resistance. Mike McKenry at the Kearney Ag Center will test additional selections from the 1989 populations in late June. He will infest the seedlings with 3 very aggressive strains of root knot nematode, the effects will be assessed in November. We have made 123 crosses thus far this year, more are expected as aestivalis, berlatidieri, cinerea, rotundifolia and rufotomentosa come into flower in June. Crosses were made to produce seedlings resistant to dagger and root knot nematodes and to combine these traits with phylloxera resistance and ease of propagation. Forty seven of the crosses were made to begin study of the evolutionary relationships between the Vitis species to allow us to better understand similarities in their resistance and horticultural characters. We also have many seedlings from the 1992 crosses that should be ready for field planting late this summer. Work has also progressed in the lab. While studying phylloxera DNA we found that many A’s and B’s exist in California, suggesting that B type is not spreading, but that it is selected for at a given AXR#1 site. This means that any site with AXR#1 and phylloxera is at risk, and that preventing B types from spreading to a given location is not likely to prevent decline. These discoveries would not have been possible without financial support for a post-doc from The Wine Group. We also succeeded in putting both the dagger nematode, Xiphinema index and phylloxera into tissue culture with grape. We are in the process of testing these in vitro systems to see if they can be used to reliably screen seedlings for resistance. If in vitro pest resistance reactions differ from whole plant reactions we will not be able to use in vitro techniques to screen seedlings, but they will still be valuable for studying pest biology. We identified new and strong sources of resistance to Meloidogyne incognita (root knot nematode) in various Vitis species and these were used in crosses this spring. We completed an isozyme study that allows identification of the rootstocks grown in California, and used the same technique to study variability in Vitis cordifolia, longii and riparia. Isozyme characterization of these species will help us define their range and taxonomic identity, and help choose northern selections that may have the potential to hasten fruit maturity and be useful in rootstock breeding.

Biotechnology for Grape Improvement

The goal of this research is to produce economically significant genetic improvements in existing grape varieties by using genetic engineering techniques to either 1) add new genes that confer traits such as insect or disease resistance or that enhance specific desirable fermentation or flavor properties, or 2) modify the function of existing genes so as to reduce or eliminate specific fruit components, such as browning enzymes, ethyl carbamate precursors, or seeds. Varietal characteristics other than the ones being deliberately engineered are expected to remain unchanged. We have continued to make progress toward the development of gene transfer technology for grape. We are able to introduce new genes into grape tissues, but have not yet produced whole vines that express new genes. The most successful gene transfer method for other plant species. Agrobacterium-mediated transformation of leaf explants, from which the regeneration of transgenic adventitious shoots is subsequently induced, has not been successful with grape. In order to develop better strategies for introducing economically significant genes into existing grape varieties, the cells in leaf explants that give rise to adventitious shoots were identified by histological analysis. The cells in leaf explants that are transformed by Agrobacterium were also identified in order to determine whether transformed cells could contribute to shoot meristems. Very few transformed cells were found in regions of the leaf explant that give rise to shoots, indicating that, although this method might produce occasional transgenic plants, it is unlikely to be a means by which this could be accomplished routinely. Other strategies that have been successfully employed with other plants, including Agrobacterium-mediated transformation of proliferating somatic embryo cultures and transformation of individual somatic embryos from which adventitious shoots can be induced, are now being pursued. A study of the biochemical interaction between grape tissues and several grape-specific Agrobacterium strains that we have isolated from California vineyards is underway in order to determine whether these strains might be engineered to introduce new genes more effectively than the laboratory strains in general use.

Clonal Testing of Winegrapes in the San Joaquin Valley

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.

Evaluation of Winegrape Clones

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).