Tom Gradziel

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.

Happy 2016 from the Fruit and Nut Research and Information Center!

We want to take a moment to remind you that the FNRIC website is fully formatted to be compatible with mobile browsing from cell phones and tablets. This includes all of our pages and links, such as the chill calculators, fruit and nut information and the research databases. By being mobile compatible you can access all of our information from anywhere you are be it traveling, in the field or simply away from a computer.

To access our website from your phone or tablet all you need to do is open your favorite browser and type in fruitsandnuts.ucdavis.edu. Once our homepage is loaded you can browse our information and follow the links just as you would from your computer. Below are some screenshots of what you will see when accessing our website from a mobile device.

If you encounter any issues or have questions please email us at fruitsandnuts@ucdavis.edu.

Winter dormancy is the annual life stage of a deciduous tree between leaf drop and bud break. It is initiated by a factor within the plant bud itself, and it takes a certain amount of cool temperature--the chilling requirement -- to break this rest and start growing again in response to warm temperatures.

The simplest models developed to estimate chill accumulation use a simple count of the number of hours in which the temperature is below 45°F (Chill Hours). However, there is a concern with the chill hour models, particularly under mild winter conditions, such as last year. From the perspective of tree physiology, when cold winter nights (below 45°F) are immediately followed by warm winter days (above 75°F), some of the accumulated chill can be cancelled out, and the Chill Hour model does not account for this. The Dynamic Model was developed to respond to these conditions. It counts chill accumulation (Chill Portions) during hours below a temperature threshold, but then eliminates that accumulation if cold temperatures are followed by warm temperatures within a 24 hour time span.

Regardless of which model you are watching, the current season is chilly, so far. Both Chill Portions and Chill Hours are higher than 5-year averages (tables below). Does this mean we will meet the chilling requirement for your trees? It is too early to say for sure but we are off to a great start!

For excellent references for the chilling requirements of various crops, including variety-specific details, see: Fruit & Nut Crop Chill Portion Requirements by UCCE Orchard Advisor Katherine Pope and the table at the bottom of the webpage: Prune Chilling Prediction Model by UCCE Orchard Advisor Franz Niederholzer.

 

As summer continues to heat up, keep in mind that regulations remain in effect to reduce the volatile organic compounds (VOCs) that can be emitted into the atmosphere by pesticides and other harmful chemicals and contribute to the amount of ozone or smog in the environment.  

Calculators from the Department of Pesticide Regulation (DPR) that determine the VOC emissions from fumigant and non-fumigant pesticides before application are available to help growers, pest control advisers, and pesticide applicators comply with the regulations.  The UC Statewide Integrated Pest Management (IPM) Program provides a link to these calculators from each of the treatment tables in the UC Pest Management Guidelines and click on the Air Quality – Calculate emissions button.

Take steps to reduce VOCs.  Avoid emulsifiable concentrate (EC) formulations as they release the highest VOC emissions.  Pesticide control advisers and growers can also reduce VOC emissions by employing IPM practices such as using resistant varieties, traps, exclusion, and biological control.  When using pesticides, spot-treat and seek low-emission materials.  Solid formulations, such as granules or powders, are best.

Check the fact sheet on the DPR web site for the most up-to-date-information on VOC restrictions and regulations.