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Arkansas plant breeder John Clark.

Arkansas plant breeder John Clark.

Photos courtesy of John Clark, University of Arkansas

New nectarine varieties and a peach variety developed by fruit breeder Dr. John Clark at the University of Arkansas are high chill and should be adapted not only for Arkansas growers but for more northerly production areas of the United States.

Clark’s most recent releases are the nectarine varieties Bowden and Amoore Sweet, and a peach named Souvenirs. They are resistant to bacterial spot, an important trait to all growers in the more humid production areas of the eastern United States.

Clark has a track record not only in breeding stone fruit but also grapes and, especially, blackberries. He is one of the fruit breeders involved in the national RosBREED ­program.

Growers in Arkansas grow for local markets and for wholesale distribution. Clark has sought genetics that allow peaches to be firm at harvest, resistant to damage during handling and shipping, store well, and yet deliver the flavor, sweetness, juiciness, and melt-in-your mouth texture consumers like.

The discovery that a complex group of genes controls firmness and texture, and that firmness can be achieved without getting the rubbery texture often found in cling peach varieties, has given new avenues for peach improvement, Clark said.

The new nectarines, Bowden and Amoore Sweet, ripen in early July, have firm flesh, and can be stored up to three weeks, he said. These traits help extend marketing range and time.

Bowden is the first white-fleshed nectarine from the Arkansas Division of Agriculture breeding program.

“It has a really nice flavor in a very firm, nonmelting, cling nectarine with standard acidity,” Clark said. It ripens about July 4. This nectarine was named for Arkansas Extension horticultural agent Henry ­Bowden.
Amoore Sweet is the first low-acid nectarine from the Arkansas program, Clark said. It has yellow, nonmelting flesh, is very sweet, and ripens about July 6.

“It has an unusual flavor and its nonmelting flesh provides a novel eating experience, described as mango-like,” Clark said. “It expands the flavor profile of our nectarine varieties and is the sweetest of our nectarines and peaches.”

Amoore Sweet is named for James N. Moore, who started the university’s fruit breeding program in 1964. He retired in 1996, and Clark then took over as the program leader.

The new peach variety is Souvenirs, the first fresh-market yellow-fleshed peach from the Arkansas breeding program. The program’s first fresh-market peach was released

in 2000, but until Souvenirs, the program’s fresh-market peaches have been white-fleshed. Souvenirs ripens about July 6, Clark said, 105 days after bloom. It has low acidity and is semifreestone to freestone, depending on ripeness. It has exceptional skin color with 90 percent blush—the reddish color that consumers greatly desire.

It also has a slow-melting flesh that remains firm longer on the tree, but ultimately melts in the mouth. All the new varieties are self-fertile.

Clark said one of the goals of his fruit breeding program is to develop an abundant ­catalog of Arkansas-adapted plants with resistance to area pathogens and a diversity of colors, flavors, and other desirable traits for local markets.

Breeding and evaluation take place at the Clarksville Fruit Research Station in ­ west-central Arkansas, where winter temperatures fall to about 5°F, and it rains year round. Trees are grown in both open ­center and perpendicular-V training systems.

No bactericidal sprays are applied, since a key trait in the breeding program is bacterial-spot resistance. The new varieties were selected in 2004 and released last fall.

“An additional component to the peach and nectarine breeding program was added in 2011, that being cold storage of selections and cultivars for postharvest storage ­performance potential,” Clark said. “Previously, storage potential was only estimated for releases based on ­firmness of flesh at harvest.”

“Chilling requirement of these cultivars has not been determined but is probably near 800 hours,” Clark said. “These cultivars have not been tested in colder locations than Arkansas, thus ultimate bud hardiness has not been determined. However, good flower bud survival for all cultivars was experienced with lows of  3 to 5°F in 2010 and 2011, respectively.”

The Arkansas peach and nectarine cultivars are  by Cumberland Valley Nurseries, Inc., in McMinnville, Tennessee. Clark would welcome other propagators and hopes Arkansas-bred varieties will be tested and used in the Midwest, East, and Southeast, or even in the West.

Laying the groundwork

John Clark gives credit to his predecessors for laying the groundwork for his program, which has released several new peaches and nectarines since 2000.

When the program began in 1964, breeder Jim Moore focused on developing cling peaches growers could sell for processing to the Gerber baby food plant at Ft. Smith, Arkansas. Fred Hough, then the peach breeder at Rutgers University in New Jersey, provided germplasm in a low-acid white peach that turned out to carry genes for a unique kind of firmness, and that formed the basis for much of the breeding since, Clark said.

When Gerber quit purchasing Arkansas-grown processing peaches, the breeding program’s emphasis shifted in the fresh-market direction, he said, but the firmness genes remained.

Clark began releasing fresh-market peach varieties in 2002, coming out that year with White River, a large, sweet peach. It softens at ripening like other melting-flesh peaches. In 2004, he released White Rock and White County, the first low-acid white cultivars.

“White Rock appears to have two sources of firmness, one the processing cling type, and the other a unique type introduced in the program in the 1980s,” Clark said. “These sources appear to be possibly additive, providing for an exceptionally firm fruit that does not soften until fully ripe,” he said.

Three nectarines also came from the Arkansas program, one melting flesh and two nonmelting. The very early ripening Westbrook, a melting variety, was released as a local-market nectarine with good flavor but lacking firmness for shipping.

Westbrook is among the most bacterial-spot-resistant genotypes in the program, Clark said.

Arrington and Bradley nectarines both have nonmelting flesh. Flavor is a processing peach/nectarine mix, he said, and both hang well on the tree and allow for ripe fruits to be harvested and handled.