MODESTO, Calif. — 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.