Growing Magazine - July, 2012

COLUMNS

Seed Research: Grape Returns to Its Wild Past

By Rebekah L. Fraser


NY95.0301.01 is a red wine grape with high disease resistance and potential to produce red wines of good quality.
PHOTO BY NEW YORK STATE AGRICULTURAL EXPERIMENT STATION.
If you're in viticulture, you probably spend a lot of time thinking about and fending off one or more of grape's three main pathogens: downy mildew, powdery mildew or black rot. If you're growing organically you may also have to fight Eutypa, Pierce's disease or Phomopsis, in addition to the other pathogens.

As food security becomes less stable worldwide many growers are turning to new methods and even to new crops to keep their businesses solvent. If you have already put 20 or 30 years into cultivating your vineyard, investing in a new crop, even within the grape family, may seem crazy. New plantings take three to four years to mature and fruit, and customers sometimes take longer than that to switch to a new varietal. The fact is, even if you did make the switch to another grape variety now, it might not solve your pathogen problems.

The common practice of cloning grapevines has left vineyards, and the entire grape industry, susceptible to disease. "Grape is incredibly diverse, but because growers have relied on clones, like pinot noir and chardonnay, probably 90 percent of the entire wine crop is now comprised of only a few varieties and their close relatives," says Dr. Ed Buckler, a USDA Agricultural Research Service (ARS) research geneticist at Cornell University's Institute for Genomic Diversity.

Buckler says consumer preference and labeling laws are preventing the crop from evolving to new threats. "It could be bred very effectively, but it just hasn't," he explains. In contrast, a crop like corn has more than 500 hybrids and many new varieties planted in the U.S. each year.

At Cornell and USDA's Geneva, N.Y., research station, breeders have been developing new grape varieties for over 125 years. Of the 56 varieties developed, Chardonel, Cayuga White, Noiret, Corot Noir and Valvin Muscat are some of the recent releases currently in commercial use in New York, Indiana, Ohio, Michigan, Arkansas and Missouri. Released in 1972, Cayuga White is now grown on over 400 acres of vineyard in New York state alone. Yet these diverse varieties all share some of the same lineage: Vitis vinifera.

With about 8 million hectares of vineyard worldwide, Vitis vinifera is the most valuable horticultural crop in the world. Consumers enjoy table grapes, raisins, nonalcoholic juice and wine. There are thousands of cultivars of Vitis vinifera. Cultivation of the domesticated grape, Vitis vinifera, began 6,000 to 8,000 years ago in the Near East. There may be enough diversity within V. vinifera to create a heartier variety, but most of the variation for resistance to the disease powdery mildew comes from wild species.

In 2006, when researchers in France and Italy finished sequencing the pinot noir genome, they opened the door for new research and breeding strategies. Not long after that, Dr. Sean Myles, a geneticist at Cornell, identified several regions of the genome involved in differentiating wild grape from domesticated grape. In grapevines, the primary domestication trait is the development of perfect flowers in cultivated grapes. Perfect flowers (rather than male plants and female plants) result in greatly improved efficiency of pollination and fruit development. "Imagine the first person who saw a grape cluster with hundreds of berries on a cluster, when most wild clusters may have approximately 20 berries per cluster, or for male vines no berries at all. That was the beginning of grape domestication, and we are now starting to understand what genes were responsible," explains Lance Cadle-Davidson, a plant pathologist with the USDA-ARS Grape Genetics Research Unit.

In 2011, Cornell grape breeder Dr. Bruce Reisch joined forces with Cadle-Davidson, Buckler and others to develop a project they expect will result in hybrid varieties that are better able to meet the needs of the industry. Twenty-five investigators across the U.S. and more than 10 different institutions are involved in this project, dubbed "VitisGen." Using a new technology involving direct DNA sequencing, the team has identified nearly 50,000 genetic markers.

One goal of the project is to develop new varieties of grape that don't require sprays. For the highest level of disease resistance, Reisch and his colleagues are using wild North American species that have co-evolved with downy mildew and powdery mildew. "They don't get sprayed in the wild. Wild grapes have natural or genetic resistance to those diseases, and they carry those resistance genes," Reisch reports.

The researchers are looking for progeny from the species that carry those resistance genes. It's best to identify them under no-spray conditions, but Reisch and his colleagues have needed to use a minimal amount of spray at times. Thanks to the technologies employed in the VitisGen project, Reisch is able to select the most disease-resistant seedlings just months after planting, based on the results of a DNA test.

An earlier breeding project incorporated some recently identified genes for disease resistance from Vitis cinerea and Vitis rupestris. One of the results is a red wine grape that Reisch and his colleagues are preparing to release next year. The selection, known as NY95, has a very high grade of downy mildew and powdery mildew resistance and very good red wine quality. "The wine quality is quite nice; suitable for blending at least and probably could be made into a very enjoyable varietal as well. I would liken it to a Beaujolais-style wine - light and fruity, but still has a nice dark color, has some cherry and berry characteristics to it. That's coming up as soon as next year," says Reisch.

Read more about the effects of grape's chief pathogens and the breeding methods and unique techniques Reisch, Cadle-Davidson and Buckler are employing in the SCRI VitisGen project in next month's column.

The author is a freelance writer based in Massachusetts and a monthly contributor to Growing.