Clemson Peach Breeding Hones in on Disease Resistance, Flavor

According to Chalmers Carr of Titan Farms, the industry has improved packing shed technologies and commercial growers in the Southeast have done a good job of bringing up their quality and the maturity of the fruit. (Photo: Titan Farms)

Back in 2008, a peach breeding program was restarted at Clemson University, and it couldn’t have come at a better time. The focus of the program is on disease resistance and improving fruit quality and taste.

Specifically, the program is honing in on bacterial spot and brown rot because they are two of the most costly diseases in the Southeast, says Ksenija Gasic, Associate Professor of Horticulture, Peach Breeding and Genetics at Clemson. Fruit tree breeding typically has a long cycle, taking 15 to 20 years from the initial cross until the new variety is released, but that is now changing.

Ksenija Gasic

“Combining traditional and molecular techniques, we might be able to shorten this time or be more efficient in creating the right type of variability,” she says. “Therefore, I have not released varieties, but I have more than 400 promising selections that are being evaluated for their potential to be successful and worthy of testing in growers’ trials.”

Need to Increase Demand

Chalmers Carr

Chalmers Carr of Titan Farms in Ridge Spring, SC, says he is excited to see what the new breeding program will offer and what it will do to increase consumer demand for peaches.

“We need to make sure we have great tasting fruit for the consumer,” he says. “Consumer demand has been flat for peaches and we want them to have a great eating experience. Along with that the industry has improved packing shed technologies, and the remainder of the commercial growers in the Southeast have done a good job of bringing up their quality and the maturity of the fruit so it appeals to the consumer.”

Another quality growers will be looking for in peaches is cold hardiness. Carr cites the devastating freeze that occurred in March, when the temperature got down to 17°F, as a key reason this quality is important. The end result of the freeze is Carr and other growers in the area suffered huge crop losses. Carr says he is left with only about 20% of his peach crop to harvest.

“We were in full bloom on everything,” he recalls. “Some varieties are more cold hardy than others and our later ones have some peaches, so we are fortunate.”

The farm began running its packing shed the last week of June and plans to run it for only seven weeks, instead of the normal 16 weeks, and at a much slower pace than normal as a result of a significantly smaller crop, he says. The farm will be able to ship fruit beyond the state, but the peaches will be kept much closer to home than usual.

Consumer demand has been flat for peaches so growers need to have great tasting fruit, says Chalmers Carr or Titan Farms in South Carolina. (Photo: Titan Farms)

Freeze Fallout
When talking about breeding for cold hardiness, Carr says that trait would have had to have been in the breeding pipeline a while back and, to date, breeding for that trait hasn’t been a real driver for the industry.

“After a year like this, the industry is going to turn around and say [breeding for cold hardiness is what we need] but you can’t turn a breeding program around on a dime like that,” he explains. “Even then, there is a double-edged sword with cold hardiness.”

The double-edged sword he refers to involves how cold hardiness relates to a mild winter with reduced chill hours and dormancy.

“If you talk to any Georgia growers, their damage wasn’t so much from the freeze as it was from the mild winter and not enough dormancy. Usually the cold hardier the peach the more dormancy it requires,” he explains. “So it could be a double-edged sword if you start planting all high chillers that are more cold hardy and if you start having mild winters, you may not make the crop, either.”

In fact, Carr says growers in the Fort Valley region, which is where the Georgia commercial peach production is located — and not too far below on the longitude/latitude line below where he is growing — had significantly fewer chill hours this year.

“Where we had 750 chill hours this year, I think they were in the low 500s, so their late fruit didn’t develop,” he says. “In years past, we have typically mirrored each other as it relates to fruit harvesting and packing timeframes; however, they were able to pack early fruit for four or five weeks and we got completely wiped out on the early fruit. This is the first time I’ve ever seen that happen. It was a very fine line between the chill hours, crop development, and the timing of the freeze between Georgia and South Carolina this year. The result was partial crops for both states: Georgia with an early season crop and us with a mid- and late-season crop.”

Right Chill Requirements
According to Gasic, there are breeding programs in Florida and Texas that breed low-chill varieties. The Southeast easily has 500 chill hours every winter, but they want to avoid is early bloom or late spring frosts.

“To be sure that the blooming will happen late enough in spring to avoid the late spring frosts, we need cultivars that have chill requirements that we know would be satisfied (at the moment that is 500 to 600 chill hours) and high heat requirement or high base temperature when they start counting heat hours,” she explains. “That way, the trees will have their chilling satisfied and once they have enough heat they will bloom uniformly and in a short time (a few days).”

The good news is the region only sees a freeze like the one that occurred in March every 10 to 15 years, Carr says, and the growers in the area know which varieties came through for them this year. A similar weather event occurred in 2007 and there were varieties that prevailed during that freeze, as well.

Carr says those cold hardy varieties will have a place in growers’ planning going forward. “We will make some educated decisions on where to put those varieties that have been more proven to come through in events like this in some of our lower elevation spots,” he adds.

In the end, though, Carr says he would rather have Gasic and her team work on breeding for taste, fruit quality traits, and disease resistance rather than finding a variety that will make it in off years when a freeze event occurs.