Despite that close call, grape growers did not rush to breed disease resistance into their vines. One obstacle is that wine drinkers are attached to particular varieties, and if you cross a chardonnay grape with some other variety, it cannot be called chardonnay. In many wine-growing regions there are regulations that let only a specific variety be grown, lest the quality of the region’s wine be degraded. More than 90 percent of French vineyards are now planted with clones  genetically identical plants  certified to possess the standard qualities of the variety.

The consequence of this genetic conservatism is that a host of pests have caught up with the grape, obliging growers to protect their vines with a deluge of insecticides, fungicides and other powerful chemicals.

This situation cannot be sustained indefinitely, in Dr. Myles’s view. “Someday, regulatory agencies are going to say ‘No more,’ ” he said. “Europeans are gearing up for the day, which will come earlier there than in the U.S., for laws that reduce the amount of spray you can put on grapes.”

At that point growers will have three options. One is to add genes for pest resistance, risking consumer resistance to genetically modified crops. A second is to go organic, which may be difficult for a plant as vulnerable as the grape. A third is to breed sturdier varieties.

Breeding new grapes takes time and money. The grower has to plant a thousand seedlings, wait three years for them to mature, and then select the few progeny that have the desired traits. But a new kind of plant breeding now offers hopes of an efficient shortcut.

The new method depends on gene chips, like the one developed by Dr. Myles, that test young plants for the desired combination of traits. The breeder can thus discard 90 percent of seedlings from a cross, without waiting three years while they grow to maturity.

The new method, called marker-assisted breeding, or genomic selection, is already being used in breeding corn. “We can predict flowering within a couple of days by looking at the DNA,” said Edward S. Buckler, a leading corn geneticist at the Agriculture Department’s research lab at Cornell.