Duarte Nursery of Hughson, Calif., has introduced its Clean Plant system that produces disease- and pest-free rootstocks and nursery trees and vines.

"We have a whole new generation of grape rootstocks that are ultra-clean," says nursery President John Duarte.

For walnut growers, the nursery offers trees free of Agrobacterium, the organism that causes crown gall.

Among the trees being offered through the program are Prunus, walnuts, pistachios, citrus, kiwi, figs, olives, blueberries and grape elite rootstock.

Because all of the plants are grown in containers and never touch the soil, they also are nematode free.

The system is based on tissue culture and micropropagation, where plants are essentially cloned in a laboratory.

The result is similar to sets of identical twins rather than brothers and sisters, which can vary greatly in genetic traits.

"Everything is identical to the mother plant," Duarte says.

This leads to more uniform plants, more even growth habits and more uniform orchard or vineyard establishment, Duarte says.