Howdy! Welcome to grape breeding in Texas
By Andrej Svyantek, Ph.D., Department of Horticultural Sciences, Texas A&M University, AgriLife Research
Grapevine improvement is a numbers game. One metric ton of fresh wine grapes likely contains more than one million grape seeds (after accounting for variation in berry mass, seed set, rachis mass, and other factors). That’s a lot of potential grapevines. In the wild, grapes play this number game to their advantage, using their sweet sugars, colorful pigments, and delicate aromas to conscript birds and beasts to pick their berries and spread their seeds. When dropped to grow, grape seeds are deposited with a little bit of fecal fertilizer on their way to becoming the latest vine to try their hand against Mother Nature’s Phylloxera, freezes, and foliar diseases. Of all the many billions of seeds sprouting forth each year from compost piles and spread by bird splat, few may have what it takes to shape the growth of our anthropocentric grape and wine industries.
Intentional crossing, imposed environmental constraints, and an applied breeder’s eye can help improve the odds of finding a vine worthy of training, naming, and growing as a new cultivar. These odds are further increased through the addition of tools that either enhance a breeder’s data collection process, boost selection accuracy, or expand the genetic variation in a meaningful manner.
As a breeder, my goal is to reduce the amount of time and money spent on developing new grapevines by refining methodologies and technologies. As a grape grower, my goal is to create vines that are productive, durable, and simultaneously both easier and more economical for our farmers to grow. As a parent, my goal is to develop vines that are a delicious component of healthy eating habits. Finally, as a new Texan serving our farmers, my goal is to develop vines that are suited to the needs of our state so we can put food on the table and drink in the glass for our families and friends.
Texas is graced with a rich and growing viticultural history. Early grapevine introductions date back to the 17th century Spanish missions that brought Vitis vinifera from Europe. This was followed by reciprocity with the exchange of North American Vitis to Europe for use as rootstocks, courtesy of the work of Thomas Volney Munson of Denison, TX. Cumulatively, our state is gifted with just about 171.9 million acres; it is home to many distinct viticultural regions and eight established AVAs. However, growing grapevines in Texas is not without challenges. We can lump our obstacles into abiotic (think drought, heat, and soil or water conditions), biotic (think Pierce’s disease, Black Rot, Grasshoppers or Phylloxera), and chaotic (think hurricanes and tornadoes, extreme temperature swings, and hail). As a grapevine breeder, each obstacle is a new opportunity for work. The open communication of farmers’ struggles helps breeders identify new targets and traits so that future cultivars are better adapted to the on-farm needs of our growers.
Genetic Variation, the Basis of Breeding
As a diploid organism, bunch grapes (Vitis) have two copies of each of their nineteen chromosomes (one from each parent). Each chromosome contains unique sequences with genetic variation built up through chromosomal aberrations (structural changes to chromosomes) and point mutations (shifts in specific base pairs or their order). These genetic variations are shuffled through the process of meiosis when gametes are formed (pollen and ovules); the combined shuffling and inherent variation from both the seed and pollen parents give rise to seedlings, each drastically different from the next.
Taking this variation into account, breeding a new grapevine variety is kind of like buying a winning lottery ticket several thousand times in a row. Each individual DNA base pair in a plant’s genome is what drives variation; they can be viewed as individual balls of the lottery where the winning alignment is a desirable expression of a trait contributing to a new cultivar. The genomes of our grapevines are composed of only about 500 million base pairs. This complexity leads to a considerable number of possible lottery tickets. When there is a difference at a single DNA base pair, we call it a single-nucleotide polymorphism (SNP). These SNP differences can shift the state of alleles (think of alleles as the varying forms of a given gene); when alleles differ, it drives shifts in the plant’s phenotype (observable traits associated with things like resistance, resilience, production, and quality).
As plant breeders, we are playing the lottery with each specific cross we make. After emasculation and pollination, we are gambling that our new seedlings’ DNA will contain impactful SNPs that shape a majority of “winning” alleles across the approximately 30,000 genes of the Vitis genome. More “winning” alleles contribute to a more desirable phenotype for our growers, processors, and consumers. Plant breeders are playing the odds in attempting to align favorable parents, select favorable seedlings, and win the lottery for our growers with the goal of transforming meaningful genetic SNPs into industry shaping sips with each new grape cultivar released.
Fortunately, we are not gambling blindly like a bird plucking and plopping berries along a fence row. After crossing, the tools a plant breeder utilizes on the path to a new cultivar are phenotypic selection, marker-assisted selection, and genomic selection. These tools are critical, and their useful application is dependent on the presence of genetic variation within our crop plant.
Tools of the Trade
Genetic Variation: For all crops in the U.S. (including grapevines), the genetic variation that allows breeders to serve growers is housed in the USDA Germplasm Repositories. These repositories are our most valuable resource for viticulture’s present and future success. They are our first ingredients when we start cooking up a new cultivar and they are our last line of defense as we battle against pests, diseases, and environmental challenges. Without these repositories’ collections of plant biodiversity, all breeding would be incapacitated and incapable of forging a better future for U.S. farmers.
Phenotypic Selection: As breeders, phenotyping (measurement of a trait) is the single most important factor in selection and cultivar release. This process is critical for identifying plants that will perform for growers because it is an observation of the plant’s actual performance. For grapes, we have multiple phenotypes of interest. To serve our growers, we need environmental stress tolerance, biotic stress resistance, and yield. However, with grapes we are often as interested in improving chemistry and end-product quality, such as wines. Phenotypic selection is expensive and challenging for many traits due to the cost and time associated with data collection, the time required to wait for that trait to expose itself, the inherent sources of variation that impact plant performance, and the required environmental or biotic constraints for selection of certain traits (we cannot test for drought tolerance during a deluge). Traits that require mature plants (like wine chemistry), traits that require pest and disease pressure, and traits that require extreme climate events (like Winter Storm Uri to test the hardiness of vines in Texas) all can benefit from marker assisted and genomic selection techniques.
Marker Assisted Selection:
Researchers merge phenotype with genetic markers to develop molecular maps for breeders to follow on the path of grapevine creation. This process of associating traits with regions along chromosomes is called Quantitative Trait Loci mapping. The knowledge of which chunks of DNA explain variation in plant response become very important for breeders hoping to use this information for marker assisted selection (MAS). MAS allows a breeder to screen seedlings for things like disease resistance (without exposing them to pathogens) and wine color (without waiting for their fruit). MAS tools require a substantial investment of researchers’ time and effort, but they have a massive time saving impact for breeders in selection.
Genomic Selection: For crops with many target traits (like grapes) that are under control of many genomic regions (like grapes) where farmers demand whole-plant improvement and high-quality cultivars (like grapes) a technique called genomic selection is necessary to address these highly quantitative traits. Developing an integrated genomic prediction platform for Texas and other grapevine breeding programs is essential to making the most of researchers’ efforts past, present, and future.
In 2025, Texas A&M University launched a Grapevine Breeding Program into the turbulent waters of viticulture, research, and cultivar development. As a new program, our efforts are geared towards developing methods to rapidly screen promising progeny. This is geared towards increasing the odds of winning the lottery for Texas farmers using Vitis’ natural variation, informative markers, and genomic and phenomic selection procedures so we can deliver environmentally durable grapevines with rugged resistance for our growers. Starting a new grapevine breeding program at Texas A&M University is a challenge, but it is a numbers game that we can win for our farmers if we keep the numbers on our side.
Adiós For Now!
My name is Andrej Svyantek. You can reach me at andrej.svyantek@ag.tamu.edu for collaborations, discussions, or just to describe your dream grapevine.
