New wrinkle on California's raisins.

California produces 425,000 tons of raisins -- 99 percent of the nation's annual yield -- with a market value of $560 million. A big business, producing raisins is also an unpredictable one. Early rains can rot the grapes as they dry on trays in the field for up to 4 weeks. And growers find it increasingly difficult to locate enough handpickers.

To get around these problems, David W. Ramming and his coworkers at the U.S. Department of Agriculture's Horticultural Crops Research Laboratory in Fresno -- raisin country -- have spent the past 12 years developing DOVine. Named for its ability to dry on the vine, it's the first commercial grape resulting from a cross between two seedless varieties.

Growers can mechanically harvest DOVine's raisins off trellised canes. Moreover, Ramming notes, dried-on-the-vine raisins (such as the predecessor of DOVine pictured at right) are less vulnerable to rot and to the burned flavor that can develop when unseasonable heat caramelizes the sugar in tray-dried grapes.

Because vine drying takes longer than tray drying under equivalent sunlight, grapes to be vine-dried must ripen earlier to beat the fall rains. DOVine does. And Ramming's team reports that the quality of its raisins "is the same as or better than [that of] Thompson Seedless" -- the variety now used for 99 percent of California raisins.

Key to producing the new grape was a technique known as "embryo rescue," developed in Ramming's laboratory. Seedless grapes initially develop a seed that later aborts. His team excised that seed from 6-week-old grapes and nurtured its embryo. This shaved 5 years off DOVine's development time, Ramming says, and eliminated the unwanted traits a true-seeded parent would have contributed.