Breeding cherries for hot climates
The largest sweet cherry breeding program is in California.
Bob Andersen retired as Cornell’s stone fruit breeder in 2004, when this picture was taken, and now works with David Cain at International Fruit Genetics.
When Dr. Bob Andersen retired as Cornell University’s stone fruit breeder in 2004, it took less than a year before he was back in the company of old friends and back at work breeding sweet cherries.
But instead of looking for cherries adapted to the cool, moist conditions of the Northeast, he’s evaluating cherry seedlings that will thrive in the Central Valley of southern California and other hot locations in Mexico, Australia, South Africa, and Chile. He’s looking for low-chill, heat-tolerant trees that will produce large, firm, sweet cherries without doubles, beaks, or sutures.
He’s working for Dr. David Cain at International Fruit Genetics in Delano, California, who is primarily known as a breeder of table grapes. It’s part-time work, Andersen said, and he’s evaluating some of the 60,000 seedlings that resulted from crosses Cain has made. The rest of the time, Andersen lives in the mountains near Asheville, North Carolina, where he goes on birding hikes, teaches wildlife classes to kids, and pursues an equine hobby with mules.
Andersen and David Cain go back a long way. Cain was Andersen’s first graduate student when Andersen was the cherry breeder at Michigan State University in the 1970s. Cain graduated to become a grape rootstock breeder for the U.S. Department of Agriculture in California and then moved to Clemson University in South Carolina to breed peaches.
While at Clemson, Cain influenced his mentor to come there in 1980 as department head, and Andersen left MSU to take that position. After five years there, both Andersen and Cain left—Cain going to Sun World in California as its stone fruit breeder, Andersen going to Cornell to breed sweet cherries.
Now, they’re back together in the California desert, with Andersen working for his former graduate student, who is now at International Fruit Genetics.
Andersen gives a lot of credit to Cain for his hard work, ambition, and keen insight that turns into entrepreneurship. Cain realized that buyers of table grapes are the same people who buy sweet cherries, and it made sense to have them available from the same sources. But sweet cherries don't produce well in the table grape country of California's southern San Joaquin Valley.
If sweet cherries could be reliably produced, growers there could grow both cherries and grapes. The cherries would be very early and would capture the season’s highest prices.
“Cain assembled cherry varieties from all over the world, especially going to Mediterranean countries like Greece, where cherries are grown in lower chill conditions,” Andersen said. “He gathered wild specimens, too.” He gathered material from other breeding programs and from the federal government’s repository at Davis, California, where sweet cherry breeding has been discontinued.
He began crossing them and planting the seedlings.
The work of evaluating sweet cherries in southern San Joaquin Valley conflicts head on with the grape bloom period, and Cain remains committed to table grapes, Andersen said. That’s the niche Andersen is now filling—evaluating sweet cherry seedlings when the fruit is ripe.
“He needs me because cherries ripen at the same time as grapes are blooming—so he can't devote more than about 10 percent of his time to cherries in May. I usually live in the San Joaquin Valley from about April 20 to Memorial Day and do all of the initial selection of cherries for Dr. Cain.
“So far, I’ve evaluated 9,000 seedlings, and there are another 50,000 in the field. It’s the largest collection in North America—and David started it as a hip pocket project. He has the largest sweet cherry breeding program in the world at this time. If my health stays good, I expect to help him for another ten years. It's nice income and interesting work.”
The two breeders have also established a connection with cherry breeder Nnadozie Oraguzie at Washington State University at Prosser and with several Oregon and Washington cherry firms who will be testing some of their higher chill cherries that are very early and would be of interest to growers in Washington and Oregon, he said.
There are two key issues with growing cherries in hot climates, Andersen said: Lack of chill hours and heat tolerance during flower bud initiation.
When sweet cherries don’t get enough hours of temperatures below 40˚F, they don’t grow or flower normally. “Leaves don’t emerge right, and trees come into bloom sporadically,” Andersen said. Varieties like Bing require 700 chill hours, and the southern San Joaquin Valley struggles some years to get 250. Chill hours requirement is a trait that breeders can select for. Andersen looks for signs of abnormal growth and flowering, and culls those seedlings that show no promise. But because of the interest in good early varieties in high chill areas, they are not automatically discarded. Some of them go to growers in higher chill areas for trials to compare them to varieties like Chelan.
Heat tolerance is a different trait. Trees that can’t tolerate heat during the critical time of flower formation, right after harvest in the hot San Joaquin Valley climate of early June, produce a high amount of cherries the next year that are either complete doubles or partial doubles, called beaks. Some also have sutures, a dimple from which a crack can develop.
Brooks has been the primary variety grown in California south of Fresno, Andersen said, but it’s a “dirty variety,” he said, meaning that it requires sorting to remove beaks and doubles. Developed by the University of California, Brooks is a large and firm cherry that ripens ahead of Bing. It is susceptible to cracking in rain. Bing can’t be grown there at all, he said.
In selecting, Andersen collects fruit from the south side of seedling trees, the hottest side, and technicians count the number of doubled or beaked fruit, looking for those lots having a low percentage of defective cherries.
All the other quality factors that sweet cherries need must be there in combination with good heat tolerance and/or low chill characteristics in the seedlings selected as potential varieties for International Fruit Genetics, Andersen said. Bitterness and small fruit are common traits, especially in some of the wild seedling material Cain used in the making the crosses. To evaluate these traits, taste buds still work, and Andersen has a wealth of experience looking for tasty cherries.
The cherries Andersen finds suitable for further development go to others in the proper climatic areas for field trials and evaluation.
When he’s not in California, Andersen does consulting work with some stone fruit growers on the East Coast, especially those trying high tunnel production. And he also works closely with Wally Heuser and Laura Heuser Gale at International Plant Management in Lawrence, Michigan. They have a contract to commercialize varieties Andersen had bred and was evaluating when he was at Cornell (see “Cherry breeding is slow work”).