21.09.2011 18:02 Age: 3 yrs

New and improved stone fruits

   

Left, Bergarouge apricot from the INRA breeding program. Top right, Bloody flesh nectarines. Bottom right, Favel apricot.

Apricot breeder works to extend the French season into September.

Bloody-fleshed nectarines, plum pox–resistant stone fruit, and super-sweet apricots are a few examples of the products being developed at a government-supported stone-fruit–breeding program in southeastern France.

While France is not the biggest European producer of peaches, nectarines, and apricots, stone fruit play an important role in the country's tree fruit industry. France ranks third in the European Union for peach production, behind Italy and Spain, with an average annual production of 400,000 tons. Annual apricot production averages 180,000 tons, about 6 percent of the world's apricot production of 2.7 million tons.

Stone fruit cultivar and rootstock breeding programs are a main focus of the National Institute for Agricultural Research (INRA) in Avignon, France, located in the center of France's stone fruit production. Peach breeder Thierry Pascal and apricot breeder Jean-Marc Audergon look for varieties with production regularity, improved fruit quality, and attractiveness. Additionally, they are breeding for pest and disease resistance, targeting plum pox, green peach aphid, powdery mildew, and brown rot. They use molecular markers and genetic mapping to help them select for specific traits.

Apricot diversity

A large problem for apricot growers in Europe is that most cultivars are specific to one location, Audergon said. "In peaches, most varieties come from the same germplasm, and the same peach can be grown in California, South Africa, and southern France. But with apricots, only a few can be grown in different locations.

" Audergon has traced the apricot's highway of cultivation—dating back more than 2,000 years—that has shaped the genetic diversity of apricot germplasm. While the fruit originated in China, genetic diversification occurred as it moved along cultivation routes that took it through European, Asian, African, and North and South American continents.

"Plant material from the southern route that followed the Mediterranean Sea is very different than material that followed the two northern routes," he said. Cultivars that originated from the northern routes are all self-fertile, require high chilling hours, and are orange to deep orange, Audergon noted. While some cultivars from the southern route are self-fertile, most are self-incompatible, have white flesh, and require low chilling hours.

The wide diversity of apricot germplasm poses challenges in a breeding program, he said, adding that molecular markers are completely different among the groups of apricots that adapted to the different routes. In addition to working with genetic diversity, breeding new and improved apricot cultivars has its own set of hurdles, he added.

Fruit quality is always an issue because apricots have a natural tendency to degrade quickly after picking. Some varieties are sensitive to cold-storage temperatures.

The short harvest window is another area that needs improvement. Audergon is working to expand the apricot harvest window in France that currently runs from mid-May to July 20. The new selection A2821, bred by INRA, would stretch harvest to the first few days of August, but several more varieties are needed to extend harvest into September.

Red and white

Audergon is crossing white apricots with red and orange varieties in hopes of finding new, super-sweet, colored varieties. White apricots, with Brix of up to 24 percent, are not very attractive because of their pale color, he said. "But their taste is where all the interest is.

" He sees opportunity to develop completely red apricot cultivars by using white, blushy red, and deep orange varieties as parents. While the first cross from these colored fruit do not have red flesh, the next line of crossing has resulted in some red-fleshed apricots.

Examples of new apricot varieties developed by INRA are Soledane, an early variety for the Mediterranean region; Florilege, a blushy, midseason apricot grown in the Rhone Valley; and, Bergarouge, a large, tasty, and deep blush, late-season fruit that is a big producer and can be grown in all French production areas. 


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