Why We’re Breeding Apples For Climate Change
The Pacific Northwest tree fruit industry is ready for climate change. That is not saying we welcome its inevitable progress, just that we have some tools to deal with it, and perhaps even a reason to welcome slowly increasing temperatures, CO2 levels, and precipitation over the long run.
Why welcome it? That higher CO2 and temperature scenario may alter some microclimates here and there, bad news for certain wine grape varieties in the Willamette Valley, but across the Pacific Northwest as a region, it is also augurs higher yields and sufficient irrigation water.
But these are long-term issues. Short-term fluctuations in environmental (abiotic) factors like precipitation timing and amounts, temperature means and extremes, and solar radiation patterns, while often unexpected and dramatic, are not news nor subject to debate. Mother Nature and her weather events have been making and breaking farmers for centuries.
However, in perennial specialty crop industries like temperate tree fruit, we have for a long time been adapting to such fluctuations, investing heavily in research and Extension to develop, test, and implement improved horticultural practices while simultaneously employing better stewardship of our abundant natural resources.
Tricking Mother Nature
Mother Nature still has a powerful role to play, but we have a lot of tricks to mitigate her malicious intent: frost protection via wind, water, or heat, evaporative cooling, precision irrigation, overhead netting, reflective fabrics, training and pruning techniques, and so on.
Expensive though some of these measures may be, they more than pay their way on an acre of Honeycrisp apples or Rainier cherries. In fact, this sort of protected cropping is greatly increasing in importance across specialty crops and may ultimately be a globally significant approach to cope with climate change. However, right now, the proportion of such protected acres in temperate tree fruit is very small.
Annual crop producers, particularly in land-extensive field crops, face a bigger challenge and have fewer tools to mitigate abiotic stress. Of course, under irrigated conditions, a certain level of drought is not a disaster, but as we confront drought-related water shortages nationwide, commodity crops like corn, wheat, soybeans, cotton, etc., may find the water is simply unavailable in the required quantity and correct timing, or is just too expensive to pencil out.
Certain cultural practices, like conservation tillage or seeding techniques, especially in non-irrigated systems, do indeed offer a useful supplement in irrigated or dryland settings. Equally useful are varieties specifically bred to perform better on less water (or other inputs). In fact, this target trait is a high priority among many agronomic crop breeding programs.
Climate Defense In Genetics
While successful genetic solutions to crop stresses are being increasingly implemented, adopting such varieties is a lot easier for annual crop producers than for perennial crop producers, who often commit to a given genotype for decades.
Additionally, specialty crop breeding programs, while paying close attention to yield, must also meet and hopefully exceed threshold levels for product quality traits like size, flavor, and insect/disease resistance.
Adding a breeding effort to mitigate short-term abiotic stress by discovering and incorporating host plant resistance makes it a lot more difficult to develop a successful commercial cultivar in most specialty crops, certainly in temperate tree fruits. Such an effort requires more parents, more crosses, and more selections. In other words, more money! Those additional resources are difficult to come by in tree fruit breeding programs.
Private sector seed companies in large-scale crops like corn or wheat may be able to recover their investment in breeding cultivars for abiotic stress resistance, but at present that is an insurmountable challenge for the fewer and smaller specialty crop breeding programs with a smaller support base and more limited market potential.
Thus, in many agronomic crops, plant breeding to address the overall impact of climate change, and all those other traits producers require, is a viable option. I strongly believe that over time, as the revolution of DNA-informed breeding enhances specialty crop breeding programs, that producers of such crops as apples, beans, and carrots, among others, will have access to cultivars with a bundled package of priority traits. For example, see www.RosBREED.org.
Some Good News
A very hopeful glimmer on that horizon is the recently released apple Cosmic Crisp (WA38). Developed in the Washington State University breeding program by Kate Evans and Bruce Barritt, this cultivar has absolutely outstanding fruit quality characteristics and should do well in the hypercompetitive new apple cultivar marketplace.
Interestingly, in addition, Cosmic Crisp demonstrates tolerance to sunburn, a disorder of particular importance in Washington’s high desert tree fruit production areas and a predominant cause of reduced packouts pre- and postharvest. While not a primary target of the breeding program, this value-added trait demonstrates plant breeding for abiotic stress in specialty crops is doable.
However, as we wait for this and other breeding programs to develop cultivars that offer producers help dealing with short- and even long-term abiotic stress, it looks to me that our commitment to intensive horticultural intervention has a payback, and that our research and Extension activities to develop and implement those tools is a worthy investment.
That doesn’t mean climate change is a good thing for this planet. It does mean we should be thinking and investing in a number of ways to deal with its inevitable impact.