May 22, 2023Texas A&M releases low-, medium-chill peaches
Whether served in pies or cobblers, shakes and ice cream or eaten straight from a roadside fruit stand, peach lovers in Texas owe much of their delight to Texas A&M AgriLife’s Stone Fruit Breeding and Genetic program.
The peach and nectarine breeding program, established in 1935, is a product of researchers in the Department of Horticultural Sciences at the Texas A&M College of Agriculture and Life Sciences and Texas A&M AgriLife Research.
To date, the program is responsible for 40 stone fruit varieties that perform well in climate zones across Texas and the southern U.S. The dozens of resulting new varieties expanded the growing options for backyard and commercial producers and added sensory characteristics consumers could choose based on personal preference or use.
Since 1983, the program has been led by David Byrne, Ph.D., professor and Basye Endowed Chair in Rose Genetics in the department. Over the last 40 years, his program has released 40 varieties of peaches and nectarines, with another dozen or so getting close to release.
His work has resulted in the release of low- and medium-chill peach and nectarine varieties bred for qualities that appeal to fruit consumers, like taste, color, shape and firmness. Varieties were bred to have white or yellow flesh with low to traditional acidity, respectively.
“There is a lot of history here, but when I started, there was one medium-chill variety available to commercial growers and maybe one for the low-chill zone, but very, very little was available, and they were traditional acidity, yellow-fleshed,” he said. “And in the time I’ve been here, we’ve released about 35 peach varieties available to backyard and commercial producers.”
Peach program adds low-, medium-chill varieties
The first objective was to develop more peaches and nectarines adapted to mild winter regions because there were only a few commercially useful low- to medium-chill varieties when Byrne started.
Peach varieties require a minimum of chill hours – hours with temperatures under 45 degrees – to set fruit properly. Cloudy, wintery days with temperatures between 32-44 degrees are ideal for promoting the hormones that dilute growth inhibitors within the tree throughout winter.
Too few chill hours can lead to poorly developed buds and flowers that can have a cascading effect, leading to stunted or misshaped fruit to no fruit at all. Multiple seasons without reaching proper chill hours can kill trees.
Byrne said medium- and low-chill options have been critical to the evolution of peach production in Texas and other warmer climates throughout the U.S. and worldwide.
Low-chill varieties require less than 250 chill hours, whereas medium-chill varieties require 350-650 hours for optimal fruit production, Byrne said. By contrast, many traditional peach varieties require 800 or more chill hours to set fruit properly.
Low- and medium-chill requirement characteristics are better adapted for Central and South Texas’ warmer, sunnier climate, Byrne said. The program has produced peach and nectarine cultivars that can be grown from the Lower Rio Grande Valley to North Texas.
The program began with the goal of providing more options for Texas backyard and commercial peach and nectarine growers, Byrne said. The adapted hybrids allow commercial growers to diversify their fruit crop and potentially capitalize on early-season fruit production. They also provide consumers with a range of colors, tastes and shapes.
Among the recent medium-chill releases are several series of peaches and nectarines that include both white and yellow flesh, subacid and traditional acidity types, and flat, or donut shaped, and standard shaped.
The series are named by their respective characteristics, Byrne said.
Zest fruit have a traditional acidity-sweet flavor profile, while Delight fruit are subacid varieties with a very sweet flavor. Golden Zest has a golden skin color, yellow flesh and traditional acidity, whereas White Zest also has an acid-sweet taste but white flesh. White Delight has white flesh and a very sweet flavor profile. Flat Delight has white flesh, is very sweet and donut shaped.
“Diversity of varieties is important for commercial producers because crops can be hit or miss each year based on weather and chill hours,” he said. “When the weather cooperates, low-chill and medium-chill varieties also allow growers to extend the growing season and market peaches earlier – late-April and May – which means better prices for their fruit.”
Hybridization takes time, collaboration
Breeding stone fruits takes time, Byrne said. It takes researchers at least eight years to release a new variety from the original cross. A new release could take 15-20 years to develop if several cycles of tree breeding are needed to accomplish a specific goal.
Many of the newer releases fall into this category, Byrne said. Peach varieties were bred over years of cyclical evaluations and hybridization to select phenotypical characteristics Byrne and his research team chose.
These characteristics centered around chill hours and early ripening but also included taste, shape, size and increased post-harvest life by incorporating non-melting flesh and resistance to internal browning.
Byrne has collaborated with a range of private and public organizations and companies over the years to efficiently accomplish the program’s breeding work. He has also been heavily involved in international collaborations with researchers and breeders in China, Japan, Argentina, Morocco, Egypt, France, Italy, Spain, Brazil, Uruguay, Mexico, Israel, Thailand, Australia and South Africa.
These collaborations have been key in the breeding program with respect to germplasm acquisition/interchange, the development of the breeding populations needed for the selection process, and the locations in various ecological sites for both primary seedling selection and advanced selection evaluation trials.
Second-stage evaluation trials in collaboration with commercial producers in Texas, Arizona, South Carolina, California and Mexico have also been critical to the program’s success in identifying peach varieties with characteristics ideal for low- to medium-chill zones.
“The medium- and low-chill zone in the U.S. is only so big, but when you go international, it gets much bigger,” he said. “The program benefits us by providing trial data, but it also benefits the researchers, the breeders and ultimately the producers and consumers in those nations.”
More varieties to come
It’s taken 40 years to release 35 peach varieties, but Byrne said a bevy of peach releases is just around the corner. He has 15 or so that should be ready for release over the next three years.
These releases will include more varieties in the existing variety series Royal Zest, White Zest, Smooth Zest, White Delight, Flat Delight and Smooth Delight that improve fruit size and quality and expand the ripening and adaptation range of each. In addition, Byrne said he will be releasing a new series of subacid yellow peaches that have spectacular flavors.
Breeders typically license propagation rights to produce trees for commercial or backyard demand, Byrne said.
“I am proud of the work and the results, but I am most proud of the collaborations and relationships built over the years that got the program to this point,” he said. “It’s developed into something that has positively impacted many people and fruit production in Texas and beyond.”
Photos by Michael Miller, Texas A&M AgriIife