The Clock Is Ticking: The Need for Precision Grape Breeding

By Margaret Leigh Worthington

On June 7, 2023, Margaret Leigh Worthington, Associate Professor of Horticulture and Director of the Fruit Breeding Program at the University of Arkansas System Division of Agriculture, testified at a hearing of the U.S. Senate Subcommittee on Food and Nutrition, Specialty Crops, Organics and Research on the Farm Bill’s Horticulture Title, which includes the authorization for the all-important Specialty Crop Research Initiative or SCRI. Margaret was speaking on behalf of the American Seed Trade Association (ASTA), but as a breeder of wine and table grapes and muscadine grapes, her excerpted and lightly edited remarks here illustrate the need for and value of innovation in grape breeding and biotechnology. Read the full transcript of her remarks.

Plant breeding dates back thousands of years to when people first domesticated wild plants. As the years have gone by, plant scientists’ understanding of agriculture has continued to progress. Building on the foundational principles that have been used for generations, new and evolving plant breeding innovations are allowing us to more efficiently and sustainably address the real and pressing challenges facing food and agriculture production. The continuous advancement in the understanding of plant genomes provides new opportunities to meet these challenges in a safe and sustainable way, both today and in the future.

Universities and companies alike are utilizing gene editing tools in research projects across all plant species for a range of needed applications benefiting farmers, consumers and the environment—from disease resistance and drought tolerance, to added nutritional benefits, better taste, and food safety. Importantly, this research includes critical applications in small-acreage, high-value specialty crops like grapes, which face unique challenges and have not previously been able to fully utilize the potential of the latest breeding tools due to the high cost and associated regulatory burdens. It is well documented that regulatory hurdles have contributed to limiting GM technology to only a few crops affordable by only multinationals, denying specialty crops an essential tool to meet global challenges. Unfortunately, investment in gene editing tools and trait targets in the specialty crop sector is similarly limited, due to uncertain regulatory outcomes in the U.S. and global inconsistency of regulatory policy.

I direct active cultivar development programs in blackberries, peaches, grapes and muscadine grapes at the University of Arkansas System Division of Agriculture. When I first started in my position in 2016, it was hard to envision how we would be able to make use of gene editing given our lack of understanding of fundamental genetics in these specialty crops. However, advances in genomics in the past seven years have enabled the discovery of genes associated with disease resistance, flowering time and consumer quality traits, even in relatively low-acreage crops like blackberries and muscadine grapes.

For example, elite wine and table grape varieties are susceptible to many diseases. In a typical growing season, growers can be expected to make 10 to 15 fungicide applications. This heavy spray schedule causes environmental impacts and financial burdens for growers. There are 45 known disease-resistance loci within the sexually compatible gene pool for grapes, many of which were discovered in part due to funding from the Farm Bill’s Specialty Crop Research Initiative, or SCRI. The process of backcrossing these resistance loci from wild relatives to elite germplasm is incredibly time-consuming, especially considering the long generation time in many perennial specialty crops. Traditionally, it has taken 20 to 80 years from making an initial cross to release of a new grape cultivar with a disease resistance locus. And, unfortunately, the market for new disease-resistant wine grape cultivars is limited as many consumers demand traditional wine grape varieties like Cabernet Sauvignon or Pinot Noir. However, gene editing could be used to develop a cultivar that is identical to Cabernet Sauvignon with stacked resistance loci for powdery and downy mildew resistance in a fraction of the time of traditional breeding methods. This technology would enable consumers to enjoy the same wines they love, while allowing growers to drastically reduce the number of fungicide applications they make each year.

I recently co-authored a paper in the journal, Nature Plants, that demonstrated how various breeding methods, including gene editing, can lead to the same seedless grape phenotype. The same can be said for pest-resistant phenotypes. In essence, precision tools like gene editing can allow us to reach the same outcome as could be achieved through more traditional breeding methods, or that could have happened in nature over time through natural mutation, but in a much more targeted, efficient and much faster way. This is critical as we’re up against the clock to address the very real and rapidly evolving threats facing the future of a secure and sustainable food and agriculture system. The tools of yesterday are simply too slow to address the challenges that are fast becoming reality today.

Precision breeding tools like gene editing are desperately needed to support the production of more resilient plants that can grow, for example, with less water, pesticides and other inputs, and result in fruits and vegetables that stay fresher longer. These are all important characteristics needed by U.S. farmers to address sustainable agriculture production and food security. Even if we can only explore these tools in experimental frameworks today, tomorrow will be too late to get started.

With the help of federal research funding since its founding in 1964, the University of Arkansas System Division of Agriculture Fruit Breeding Program that Margaret now leads has developed and released 66 fruit varieties that are now grown, not only in Arkansas but on six continents around the world.