Avenue Vine

Salinity Studies:
For the last two decades, my research has focused on salinity stress. The inhibition of plant growth by salinity involves two components. Initially, the plant experiences a water stress, but with time salts accumulate in the plant creating an additional ionic stress. In my laboratory, we are currently focusing on how salinity inhibits plant growth by these two components.

The water stress component has been investigated by studying the immediate effects of salinity on the growth parameters regulating leaf elongation. We found that salinity increases the apparent yield threshold of the cell walls in the growing region of the leaf, which results in lower growth rates. We have interesting correlations of the plant response to the plant growth regulator, abscisic acid with salinity stress, particularly the effects on growth, cell wall yield threshold and cytosolic calcium.

The identification and characterization of the mechanisms regulating plant growth under saline conditions is leading to the molecular characterization and manipulation of proteins associated with salt-tolerance in plants. Currently we are taking a functional genomic approach by screening 70,000 line of Arabidopsis mutants for salt tolerance in order to identify which genes are involved in salt tolerance.

Wine Grape Studies (Drought, salinity and cold stresses)

Northern Nevada appears to have a good climate for growing grapes (Vitis vinifera). My lab has been investigating the feasibility of growing grapes in Nevada (see Nevada Grapes BELOW). Nevada's climate is very stressfull and includes drought, salinity, cold and high temperatures.

Recent advances in genomics have led to improved strategies for engineering stress tolerance in plants. Drought, salinity and cold stress alter gene expression in plants with considerable overlap among these stresses. This fact is exemplified by the observation that over-expression of a single Arabidopsis transcription factor enhances the expression of multiple gene products involved in drought, salinity and cold tolerance responses. My current research program on wine grapes will lead to a better understanding of the genetic mechanisms for cold, drought and salinity tolerance in V. vinifera. Ultimately this research will improve wine grape production efficiency in colder and drier regions of the world and a better understanding of the factors that contribute to improved wine quality under abiotic stress conditions.

Impacts of drought, salinity and cold on grapevines:

1. Water deficit:
The influence of plant water status on grape productivity and fruit composition had a priority rank of 2.57 (7th most important issue) in the 1999 AVF California Viticulture Research Survey Summary. Water usage is a major concern to many growers, particularly those in NV and CA, from both an economic and quality point of view. Controlled irrigation can not only save water, but also have a positive impact on the quality of wine made from grapes grown in semi-arid regions.

At the UNR vineyard in Reno, NV, (summer of 2000) we applied water at 75 % of crop evapotranspiration, once plants reached a water potential of -10 bars. Only 9 applications of water were needed for the entire season resulting in an 80% reduction in water use from the previous year. This represents 0.25-acre feet of water &endash;a very low rate of water application. This water saving is extremely significant in arid Nevada. By comparison, Churchill County farmers produce quality alfalfa hay with an average application of 3.5 acre feet of water (14 times more water than our grapes). As water rights have become limiting in this and other areas throughout NV and CA, the use of alternative crops using less water has become a high priority.

Regulated deficit irrigation can improve grape quality, affecting wine aroma and taste by altering metabolite and glucan composition, with little, if any, loss in production. This was true in the UNR controlled irrigation study described above, where water deficit balanced vegetative to fruit growth resulting in higher quality fruit and a better quality wine.

2. Salinity stress:
Irrigation can have an important impact on grapevines in semi-arid regions because of salt build-up. Saline soils make up 23% of the world's cultivated soils and are seriously threatening irrigated crops in semi-arid regions. Saline soils make up approximately 30 and 50% of the irrigated soils in CA and NV, respectively. Grapevines are considered moderately sensitive to salinity. They are particularly sensitive to chloride and different rootstocks can give important chloride exclusion properties to the scion.

3. Cold stress:
Vine damage due to freezing is an important constraint and economic cost to growers in the northern regions of North America and Europe. Occasionally, entire vineyards of V. vinifera must be replaced because of extensive freezing damage at very low temperatures (-10 to -15°F). Native North American species of Vitis can survive temperatures down to -25°F. In Nevada, these temperatures are occasionally observed in Reno and Fallon. The record lows for these areas are -19°F (1890) and -27°F (1989), respectively, providing strong justification for improving cold tolerance traits if vineyard expansion in desirable arid areas like NV is to proceed.

Strategies for improving stress tolerance in grapevine:
There are several different approaches to developing more stress tolerant V. vinifera plants including: a) adapting cultural practices, b) selecting for more tolerant germplasm, c) making hybrids of V. vinifera with more tolerant native North American species, and d) using genetic engineering technology to develop more hardy genotypes.

Breeding for stress tolerance has proven difficult and has not provided desirable outcomes. Breeding specific characteristics takes considerable time for V. vinifera. Consequently, clones are vegetatively propagated to prevent loss of desirable grape and wine qualities. Hybrids that are more cold tolerant than V. vinifera have been developed at Cornell University, but wine made from these grapes is inferior to premium quality wines made from V. vinifera grapes grown in the major wine producing regions of the world. Thus, the genetic modification of specific premium quality V. vinifera clones by recombinant DNA technology is viewed as the most attractive option for improving stress tolerance.

A potential limitation of recombinant DNA technology is that stress tolerance is complex, requiring the response of many genes. A genetic engineering strategy we are pursuing, namely the over-expression of transcriptional activators such as the CBF/DRE family has a much higher potential for success than strategies relying on single stress adaptive transgenes because multiple adaptive genes would be overexpressed.

CBF/DRE transcriptional activators:
The CBF/DRE transcriptional activators, CBF1 (DREB1B), CBF2 (DREB1C) and CBF3 (DREB1A) are some of the master switches for drought, salinity and cold tolerance. Over-expression of CBF1 in Arabidopsis increased cold tolerance by 3.3° C. Over-expression of CBF3 also increased the freezing, drought and salinity tolerance of Arabidopsis, and rice. Constitutive over-expression of each of the CBFs in Brassica napus increased the freezing tolerance of both cold acclimated and non-acclimated plants without any detrimental effects.

My Objectives for Wine Grape Research at UNR are:
1) To enhance drought, salinity and cold tolerance in grapevine by the over-expression of CBF/DREs

2) To develop cDNA libraries from drought, salinity, and cold stressed leaves, roots and fruits of V. vinifera.

3) To discover other genetic tools for engineering improved stress tolerance.

4) To conduct comparative metabolite profiling in grapes from well-watered and water-deficit treated vines and work towards determining the genetic basis of the factors responsible for improving the quality of wine produced from drought-stressed plants.

The long-term goal of our research is to understand and enhance the cold, drought, and salinity stress tolerance mechanisms in V. vinifera. This research will not only have immediate practical benefit by producing V. vinifera with improved stress tolerance, but also provide important insights into the molecular basis of stress tolerance and underlying mechanisms of how abiotic stress improves wine quality. Investing now in the development of comprehensive molecular genetic resources for V. vinifera, will greatly facilitate future gene discovery efforts of novel stress tolerance mechanisms and lead to improvements in both production efficiency and wine quality under adverse growing conditions.

NEVADA GRAPES:
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I. Wine Grapes are a Low Water-Use High-Value Crop in High Demand

For a typical vineyard in Colorado, it takes three years to start producing grapes. In the 4th year a vineyard produces enough grapes to become profitable. In the 6th year, establishment costs will be paid off (not including equipment and land costs). Thereafter, a grower averages a net return of $5,134 per acre per year at 1999 prices. A typical vineyard will last at least 20 years and may last 60 years if it is well maintained.

Our Vision for the State of Nevada:
We anticipate that research conducted by the College of Agriculture, Biotechnology and Natural Resources at the University of Nevada, Reno will lead to a successful wine industry within the State of Nevada. The wine industry in the USA and the world is growing very rapidly. In 1998, the California wine industry generated $12.6 billion in retail sales in the United States and had a $33 billion economic impact on the state. In less than 40 years, Washington State has created a wine industry that produces $250 million in wine retail sales per year. By the year 2000, Washington had over 20,000 acres of vineyards and the number of wineries has increased from 19 to 145 in 20 years. Colorado has some of the highest vineyards in the world, ranging between 4000 and 6,400 ft above sea level. In 2000, Colorado had 80 vineyards (the first one was established in 1968) producing 563 tons of grapes on 400 acres with a wine retail value of over 4 million dollars. In the last 10 years, Colorado wineries have multiplied from 5 to 24. It is notable that vineyards in both Washington State and Colorado have climates similar to Northern Nevada.

UNR Vineyard Results

UNR Valley Road Vineyard, July 2001

In 1995, the University of Nevada, Reno (UNR) and Tahoe Ridge Vineyards and Winery teamed-up to establish a 1,080 vine experimental vineyard comprising 12 varieties of Vitis vinifera wine grapes in Reno, Nevada. These grape varieties were selected based upon their ability to produce quality wines in other regions that have similar climates to the Reno-Minden area (Bonn, Germany; Reims, France; Christchurch, New Zealand; Yakima, Washington). Some of these grape varieties have adapted better than others at the UNR vineyard.

Winter dieback has had a major impact on survival and productivity over the past five years. We have replanted 15 to 20 percent of the vineyard yearly. Of the 12 varieties, we have removed two, Muscat Blanc and Muller Thurgau, in the spring of 2001 and replaced them with Syrah and Merlot. The Muscat Blanc and Muller Thurgau have been the most sensitive varieties to cold and have not produced any grapes. The most promising varieties are three white grapes and one red grape. They are Semillon, Chardonnay, White Riesling, and Lemberger, respectively. Some of these results were not expected based upon past performance of these varieties in other similar regions (Washington and Colorado). This points out that it is important to conduct variety trials in each region of interest, because they will perform differently (unpredictably) in different areas.

Irrigation can have an important impact on grapevines in semi-arid regions. In the summer of 2000, we applied water at 75 percent of crop Et (evapotranspiration), once plants reached a water potential of minus 10 bars. This resulted in a total of 9 applications for the entire season resulting in an eighty percent reduction in water use from the previous year. This represents 0.25 acre feet of water per acre for the season (a very low level of water application). Overall vine quality was improved with this watering schedule. We intend to pursue this type of irrigation regime in the following years. This water savings is extremely significant in arid Nevada. For example, Churchill County farmers produce quality alfalfa hay with an average application of 3.5 acre feet of water per acre per season (14 times more water than our application to grapes). Thus, it would seem that this area may have its own unique set of conditions which favor varieties not previously predicted. Further variety trials are warranted.

Northern Nevada can produce excellent quality wines. The sugar to acid ratio of the grape musts for many of the varieties reached the optimum quality value of 30 over the first two growing seasons we have had so far. A 1999 White Riesling made from grapes at UNR by Tahoe Ridge Vineyard and Winery won a silver medal at the Nevada State Fair. Due to the young age of most of the other wines, they have not yet been properly evaluated. This pilot study along with previous work done by Tahoe Ridge Vineyard and Winery has led to the conclusion that wine grapes can be successfully grown in Northern Nevada and that it is possible to produce excellent quality wines.

II. Churchill County Has Great Potential for Growing Premium Quality Wine Grapes

Frey Ranch Vineyard, July 2001, a cooperative research collaboration between the College of Agriculture, Biotechnology, and Natural Resources (CABNR) at the University of Nevada, Reno and the Churchill County Grape Growers, Inc.

Frey Ranch, July 2001

More photos--(LEFT CLICK HERE)

The initial success of the UNR vineyard has generated considerable interest in nearby areas. One of these areas is Fallon in Churchill County, seventy miles east of Reno. This region contains approximately 50,000 acres of farmland (mostly alfalfa) with approximately 2,300 small family farmers, many who have been working the soil for four generations. More than 95% of these farmers own less than 100 acres. The climate is milder and the growing season is longer compared to Minden and Reno. Water is an important issue for these farmers.

Fallon and other Nevada areas have climates equal to or better than some Napa regions for growing premium grapes. See the table below for Growing Degree Day (GDD) calculations.

Temperature comparisons indicate that Churchill County has very similar temperatures to the Napa's Carneros region (if not more favorable). The best premium wines are made from grapes grown in regions with a GDD between 2500 and 3000. One of the most interesting temperature statistics is that Churchill County had a 30 degree diurnal temperature differential, between the high and low during the growing season, while Napa had a 26 degree temperature differential. These large daily temperature fluctuations between high and lows create a very desirable "sugar to acid ratio" for high quality wines. Thus, there is good potential to establish vineyards in Churchill County. However, a variety trial is needed along with an irrigation study to determine the minimum amounts of water needed to produce premium quality grapes for wine.

A 3 acre experimental vineyard has been established at the Frey Ranch in Fallon. This research project is a joint venture by the Churchill County Growers, Inc. and CABNR at the University of Nevada, Reno. V. vinifera grapes (10 varieties) were planted at the beginning of July, 2001.

III. Why Aren't Wine Grapes a Sure Thing?

There is a lot of variation in the way wine grape varieties respond to different climatic and soil conditions. The French have spent several centuries determining which particular varieties do best in a specific appellation. Therefore, varietal trials are needed at each particular region to accurately assess their potential.

The biggest dangers to vines in Northern Nevada are very low winter temperatures (below minus 10°F), fluctuating temperatures (false springs) which could cause premature spring growth, and alkaline or saline soils. V. vinifera grapes are adapted to Mediterranean-type climates. This species can be substantially damaged in the colder regions of the world. Native North American species of Vitis are more cold tolerant in these colder regions. Therefore, the genetic potential is there to improve cold tolerance. We have a very active research programt to improve the cold tolerance of V. vinifera varieties.

Source: “Hybrids that are more cold tolerant than V. vinifera have been developed at Cornell University, but wine made from these grapes is inferior to premium ...,“ Grant R. Cramer
Professor, Department of Biochemistry, University of Nevada, Reno, NV 89557, January 15, 2006

Additional Articles:
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“Cornell Grape Research Expansion Supports Lake Erie Growers,” January 15, 2007

“Genetic Answers to Ancient Headaches Sought by Wine Researchers,” June 14, 2006