Fruit of the earth

Climate change is not likely going to be gentle with California’s ag industry, according to experts with the U.S. Department of Agriculture. As things grow warmer and drier, many cultivars of fruits and nuts currently grown in the Napa, Sonoma, Sacramento and San Joaquin valleys may wane in productivity, and plant breeders will likely have plenty of work to do in the years coming as they hustle to replace obsolete edibles.

The USDA’s National Clonal Germplasm Repository at UC Davis already carries a huge collection of fruits, including 302 varieties of figs, 491 of walnuts, more than 3,140 of grapes and many more. Much of this botanical library grows near Winters at Wolfskill Experimental Orchard, owned by the college and leased in part to the government.

But Dr. Malli Aradhya, a USDA geneticist who works in the repository, knows that better fruits remain uncollected—and we need them sooner than later, he says. In the past three decades, says Aradhya, California’s winters have warmed perceptibly, and the trend is expected to accelerate. Stone fruits, figs, pistachios and other plants that require just a kiss of the cold each season may experience reduced flowering and lower yields. Insects and diseases could also become a problem as temperatures climb, says Aradhya.

The surest fix for the problem is to build a broader collection of cultivars—especially drought-resistant ones—for the use of breeders in building hardier plants, and to this end Aradhya’s eyes are locked on Central Asia and the Caucasus. Here, in what was once the cradle of agriculture, grows a greater diversity of figs, apricots, pomegranates, grapes and apples than any place else on the globe.

Specifically, Aradhya is looking at Azerbaijan, a small nation tucked between the Caspian and Black seas, just a hop north of Iran and a skip east of Turkey. He has been here twice before on government collecting trips. Last fall he brought home 145 new fruit varieties to add to the UC Davis collection, including walnuts, almonds, olives, mulberries, prunes, other stone fruits, and pistachios. The latter is a major point of weakness in California. An industry worth almost $600 million, 90 percent of it is precariously based on one single cultivar, says Aradhya, and just a few degrees change in temperature or a nasty pest could wreak havoc on California’s pistachio business unless the industry is bolstered by a wider, more genetically diverse base.

On August 27, Aradhya leaves for his next trip, a 30-day expedition into the remoter corners of Azerbaijan followed immediately by a stop in Kyrgyzstan, home to vast forests of wild walnuts. Upon arrival in Azerbaijan’s capital of Baku, several guides and interpreters will meet the geneticist at the airport and lead him to sites of interest. Besides pistachios, Aradhya aims to collect figs, pomegranates and walnuts. Each of these will be fruiting during his journey, making it easy to identify premium specimens. The team will likely spend some time exploring the wilderness for figs and pomegranates, but mostly, the collectors will be peddling the doorsteps of villagers.

“That’s where you find the best fruits,” explained Aradhya. “They find them, take cuttings and grow them in their yards.”

From the very finest fruits that they find, the team will take bud wood, to be used in grafting onto rootstock or for direct rooting in the soil—the only ways to make exact clones of promising cultivars. Aradhya will also bring back seeds. Planted and brought to maturity, it’s anyone’s guess just what properties these seedlings will sport, and it may be five to eight years, said Aradhya, before such experimental trees provide fruit.

Azerbaijan’s government operates several fruit collections of its own, but these libraries, established during the days of Soviet rule, have since suffered neglect, and Aradhya and the USDA hope to salvage what’s left of them. In return, the UC Davis repository, which serves as a botanical toolbox for local as well as international breeders, may be used to replant Azerbaijan with its own indigenous cultivars. Afghanistan and Iraq too have suffered great losses of tree-fruit diversity through years of war and could eventually use assistance in replanting.

But global warming, meanwhile, is certain to intensify. Less clearly understood is how California’s almonds, figs and pistachios will weather the heat.