Enjoyed a crisp white peach or a juicy plum this past summer?

Chances are that 85-year-old Floyd Zaiger was behind them in some way, through his disease-resistant root stocks, groundbreaking hybrids or commercial varieties that arrive in East Coast grocery stores unblemished.

“He eats, breathes and sleeps his trees, constantly thinking about their characteristics,” his daughter Leith Gardner said. “For my dad, it’s the love of his life, besides my mother.”

Zaiger’s 140-acre property on the outskirts of the California Central Valley city of Modesto is his laboratory. He and his family develop new varieties the old-fashioned way, by cross-pollinating his acres of leafy breeding stock and selecting for certain traits.

The painstaking process has paid off, with a hybrid plum-apricot he trademarked as the Pluot, and in Zaiger’s international reputation as a premiere developer of stone fruit, which are named for their hard pits.

Despite his age, Zaiger cruises the grove in a golf cart, working on new varieties that will be ready for market in several years.

“The Pluot was game-changing in my mind,” said Tom Gradziel, a pomologist at the University of California, Davis. “The plumcot cross-existed, but he saw potential in the plum’s sweetness and the apricot’s aromatics and crossed it back with the parent tree many times to bring out those characteristics — sweet but no bitter skin.”

Zaiger developed interspecies varieties like the aprium (part apricot and part plum), the peacotum (a hybrid of peach, apricot and plum) and the cherub (a cross between a cherry and a plum).

Gary Van Sickle, president of the California Tree Fruit growers organization, said Zaiger is the most prolific stone fruit breeder in the modern era.

“It takes somebody with vision to understand what the marketplace is going to want in a decade,” Van Sickle said.

What started as a hobby for Zaiger 55 years ago grew into an international business that is still family run. His daughter is the operation’s general manager. One son, Gary, runs the nursery and the other, Grant, tends the mature trees.

On a weekly field tasting tour with growers, Gardner squeezed a wedge of a fruit onto a handheld device that measures sugar in the juice.

Robert Woolley, the owner of Dave Wilson Nursery, plucked a plum from a high, sunny branch and took a bite.

“Whoa! That’s a sugar bomb,” he said. “It’s got everything except size.”

Even though researchers have made breakthroughs in fruit tree genome mapping recently — and despite the company’s name — Zaiger Genetics doesn’t splice genes or manipulate DNA to develop new plants.

It took researchers across the country and Europe 10 years to build a map of the peach genome, Gradziel said. But genomics has its limitations, he said. The field is in its infancy and might never duplicate Zaiger’s work.

“If you look at everything that Zaiger’s developed, none of those would be predictable with these new techniques,” Gradziel said. “Zaiger’s has a huge knowledge base and a huge germplasm to draw from. With linear breeding, we’ll lose his kind of out-of-the-box, creative, artistic, intuitive breeding.”

Zaiger and his staff make repeated and complex crosses in successive generations to make a bridge between two species. Their low-tech methods are painstaking and methodical.

He collects pollen with an eye shadow brush from a tree chosen for its flavor, then brushes it on the flower pistil of another tree chosen for its durability or resistance to disease.

Each of the 150,000 crosses currently in the orchard has a number to trace its lineage back to its great-great-grandparents or longer. Zaiger can track the expression of each characteristic in the progeny.

“The first thing I do when we see a tree with good characteristics and flavor is to open up the book and look at its pedigree,” Zaiger said.

These days, the book is a massive database of crosses.

“This is my bible,” he said, opening a three-ring binder in his office and pointing to the branches of an aprium hybrid’s family tree. “From here to here is six years work.”

From thousands of crosses, Zaiger and his children select a couple hundred to grow in a secondary plot. From those he chooses a few dozen to show off to growers every summer. With their feedback, he introduces a select few new varieties each year.

Each generation of trees takes three years to mature, and it can take decades for a successful variety to return a profit.

“We grew up with it, so we know you can’t be in a hurry,” Gardner said. “There’s always new material coming up the pipeline and we know that the next generation is going to bring new breakthroughs. We rely on the work we did 10 or 12 years ago.”

The Zaigers hold about 280 patents. Their best varieties, like the Pluot, are trademarked. Growers pay a royalty fee of $2.25 per tree, and 15 percent of the sales from their crop to Zaiger and marketers.

The company signed its first international contract in 1962 and now has contracts across Europe as well as New Zealand, South Africa, Australia, Argentina and Chile.

“Many breeders have successful varieties but Floyd’s contributions have been many and probably surpass everyone else for lifetime achievement,” said Eric Wuhl, director of research and development for Family Tree Farms in Reedley, Calif. “I don’t think a grower could grow from the beginning of the season to the end successfully without having Zaiger trees in the lineup.”