- Author: Rika Fields
- Editor: David Alexander Foster
Breeding trees takes a long time, says Tom Gradziel, a geneticist at the University of California, Davis. He knows this because he's spent the last twenty years breeding almonds and peaches for California's booming fruit and nut industry. He's breeding a variety of peaches better-suited for mechanical harvest and a variety of self-pollinating almonds. He predicted the need for these varieties years ago because as a breeder, that's how Tom has to think. “The breeder has to be in tune with the industry in terms of what problems need solving and how to pragmatically go about finding those solutions,” he declares. He thinks ahead twenty years and selects traits to breed now based on what he thinks the industry needs in the future.
These days he's anticipating a need for trees that are less susceptible to January heat. He says that heat spells during the beginning stages of fruit development are already causing marginal issues such as bud failure or abnormal fruit development. His fear is that this will become more common, to the point where farmers will experience crop loss. The solution he finds most promising? Selecting for cultivars that are tolerant to a wider range of climatic conditions, ones that will not be derailed as easily by unexpected heat spells.
Tom tests cultivars on several plots under a variety of conditions before he releases them to growers. Long-term testing is an important aspect of what Tom does and is the reason why breeding takes such a long time. The process is long but it mitigates risks to growers by ensuring the trees grow well in whatever environment they're planted. There's always room for improvement, however, and Tom's greatest career accomplishment is his optimization of this process.
Building upon research conducted by Ted DeJong, a professor and pomologist at UC Davis, Tom improved the efficiency of his tree breeding program by mechanizing the pruning and flower-thinning of his trees. It allowed him to see uniform fruit on branches and allowed him to keep entire seedling blocks rather than eliminate imperfect trees. “You end up with something close to the true genetic potential,” Tom proclaims, “you're seeing what the maximum genetics can produce.” For his breeding program, Tom gets help from many outside sources, including the UC Cooperative Extension.
The cooperative extension system has been crucial to Tom's breeding endeavors because it has given him a large network to collaborate with. From the USDA to farm advisors, extensions specialists, nurseries, and growers themselves, Tom works with all these groups to test his trees. “We have a web of information going from the university to the growers and just as importantly from the growers and processors back to the university,” Tom states. Not only does this network help him in his experiments, they give him a reality check: nurseries and growers will tell him which solutions might work and what won't pass in the industry.
Tom wants to share with all growers this insight: tree selection is like a marriage. He calls it the Anna Karenina Principle, alluding to the first line of Leo Tolstoy's famous novel: “All happy families are alike; each unhappy family is unhappy in its own way.” Tom's point is that growers shouldn't choose a tree because it has one trait they really like. The tree they choose may be great for a few years but may be taken out by an especially strong gust of wind or a pathogen it's not resistant to. Instead, Tom says, growers should choose a tree that hasn't shown any flaws and will still be producing twenty years down the line.