LOS ANGELES – It's not easy peddling fresh fruit to a nation of junk-food addicts. But in rural Kern County, Calif., David Cain is working to win the stomachs and wallets of U.S. grocery shoppers.

Cain is a fruit breeder. His latest invention is called the Cotton Candy grape. Bite into one of these green globes and the taste triggers the unmistakable sensation of eating a puffy, pink ball of spun sugar.

By marrying select traits across thousands of nameless trial grapes, Cain and other breeders have developed patented varieties that pack enough sugar they may as well be Skittles on the vine. That's no accident.

"We're competing against candy bars and cookies," said Cain, 62, a former scientist at the U.S. Department of Agriculture who now heads research at privately owned International Fruit Genetics in Bakersfield, Calif.

In an intensely competitive marketplace, breeding and branding have become almost as valuable to farmers as sun and soil. Producers are constantly tinkering, hoping to come up with the next Cuties Clementine orange or Honeycrisp apple — distinct products that stand out in the crowded fruit aisle.

"People are looking for more flavor," said Mark Carroll, senior director for produce and floral at Gelson's Markets, which will carry the Cotton Candy grape. "Once they get hooked, they want more no matter what."

Angelica Ayala removed seeds from grapes and placed them in a petri dish in a lab at International Fruit Genetics.

Cain's company, in the heart of California's $1.1 billion table grape industry, specializes in bold flavors and exotic shapes. Purple-hued Funny Fingers are long and thin like chili peppers. A variety named Sweet Sapphire come as round and fat as D batteries. Like the Cotton Candy, the special varieties are patented, then licensed to growers. The Funny Fingers are marketed as Witch Fingers and are available at high-end supermarkets. The Cotton Candy will be available this month.

Ordinary grapes like the red Flame Seedless can cost as little as 88 cents a pound. The Cotton Candy could fetch around $6 a pound, though prices would come down if enough growers cultivate the grape.

The U.S. designer-fruit craze kicked into high gear in the late 1980s. That's when a Californian plum-apricot hybrid called the pluot hit the market. The crispy stone fruit, which took 20 years to develop, proved such a hit with consumers that it inspired more farmers to invest in breeding programs to boost sales.

California is now churning out other sweet inventions, including apriums (a pluot but with more apricot), peacharines (peach and nectarine) and cherums (cherry and plum).

Not to be confused with GMO engineering, cross-breeding techniques employed by fruit breeders are centuries old. In the case of grapes, pollen from male grape flowers is extracted and then carefully brushed onto the female clusters of the target plant. Then comes a lot of waiting. Then replanting. Then repeating the process — for years, even decades.

"It's a bit like fishing. You never know when you're going to get the big one," said Cain, a soft-spoken man who would look every bit the lab coat-clad scientist if it weren't for the soil under his nails.

Fruit breeders have made California No. 1 when it comes to grapes. Almost all the table grapes commercially grown in the U.S. come from the Golden State, which shipped a record 100 million boxes last year.

Still, to stay competitive in the nation's lunchboxes, growers must keep developing new tastes.