Developing The Grapes Of The Future

(GP) - With a focus on disease resistance and hardiness, researchers are hard at work developing the grape cultivars of the future.

Through a multidisciplinary collaborative project called VitisGen, researchers are are working to decrease the time, effort, and cost of developing these new grapes.

According to the VitisGen website, the project “incorporates cutting-edge genomics technology and socioeconomic research into the traditional grape breeding and evaluation process, which will speed up the ability to identify important genes related consumer-valued traits like disease resistance, low temperature tolerance and enhanced fruit quality.”

Cornell University’s Bruce Reisch has been working as part of the VitisGen team since it first came together in 2010. He says the idea for the project came about from continuing dialogs between USDA researchers at Cornell’s New York State Agricultural Experiment Station in Geneva, NY, and other industry members, including those from the National Grape and Wine Initiative and South Dakota State University.

“For months in 2010, we put words to paper and signed up a total of about 25 colleagues to play a wide range of goals in aspects of improving genetic technology for grapevine improvement,” Reisch says. “The entire project also includes studies of industry needs, analyses of the potential benefits of new varieties from an economic standpoint, as well as Extension to communicate project goals and progress to the public.”

The project received funding in September 2011 and now involves more than 20 scientists who work as project directors, as well as additional faculty, staff and graduate students from 11 academic and governmental institutions across the country.

Cornell University Viticulture Extension Specialist, Hans Walter-Peterson, who is also part of the project, points out that the interdisciplinary nature of VitisGen is one of its greatest benefits.

“One of the unique aspects about VItisGen is that it brings individuals from different disciplines together to achieve its goals, including not just breeders and geneticists but also plant pathologists, food scientists, economists and social scientists,” he says. “Incorporating a broader set of skills and disciplines into the project helps to ensure that we are meeting not only our scientific and technical goals but also that the project is relevant to the needs and concerns of grape growers and those who use those grapes, including the end consumer.”

DNA Sequencing For Better Grapes
VitisGen is working to create maps of grapevine chromosomes and locate specific, desirable genes that breeders can then use to develop new varieties.

“Mapping populations,” which include between 100 and 500 seedlings from a cross of two vines, are used to begin the molecular portion of the project. DNA is extracted from the seedlings, and variations in the DNA sequence are mapped to each chromosome, Reisch explains.

“’Next Generation’ DNA sequencing is used to sequence very large amounts of the DNA of each seedling, and the final product, after much data processing, is a map of all 19 chromosomes of the two parent grapevines, with hundreds of DNA markers on each chromosome,” Reisch says. “These maps are much more powerful – much higher in marker density – than previous maps already available for grapevines.”

The next step of the process involves combining the power of these maps with DNA markers with the traits observed in each seedling.

“For instance, if we screen all 250 seedlings in a mapping population for powdery mildew resistance, we can then use the power of computing and our knowledge of genetics to scan these dense maps for chromosome locations controlling powdery mildew resistance,” Reisch explains. “The VitisGen project doesn’t deal with just a single mapping population and a single trait. In fact, breeders around the country are maintaining 16 mapping populations, and breeders, as well as VitisGen Trait Evaluation Centers, are characterizing the seedlings in each population for more than 100 traits.”

Finding The Right Genes
Reisch says one of the project’s biggest goals is to give breeders the ability to screen seedlings for the presence of desired genes before they even plant the vines.

Having the markers for important genes is key to the successful development of improved varieties, such as those resistant to powdery mildew.

“DNA technology can help us locate vines with three or more [powdery mildew] resistance genes,” Reisch says. “These vines should have stable, long-lasting resistance, which a pathogen like powdery mildew will have nearly no chance to overcome.”

The hope is that VitisGen will result in greatly improved, disease-resistant cultivars suited to various regions, “but without some of the negative aromas and flavors associated with the species carrying genes for disease resistance,” Reisch adds.

Walter-Peterson notes it’s important to emphasize that VitisGen is not using GMO techniques. “The primary goal of this phase of VitisGen has been to develop high-resolution chromosome maps to identify genetic markers within various species of grapes that are associated with certain traits,” he says. “This information can then be used by breeding programs around the world to improve their ability to rapidly screen seedlings to determine if they contain the desired traits.”

In addition to improving disease resistance, VitisGen is working to make sure new wine, table and raisin grape cultivars will be hardier and more resistant to spring frost damage. However, it will be some time before growers can plant these improved varieties. It takes anywhere from 10 to 25 years to develop and sufficiently field test a new variety, according to Reisch.