AgBioResearch

The year 2050 is expected to reach an important milestone in global agriculture: the world population is expected to top 9 billion people, a one-third increase over the current population. Much of this growth will take place in less developed, already food-insecure regions of the world such as Africa. And rising life expectancies are exacerbating the problem. To meet the essential needs of a population this size, global food production will need to rise by an estimated 70 percent.  And climate research indicates that much of the world will experience unprecedented shifts in temperature, precipitation and humidity and increasingly extreme weather by 2050.

Fortunately, researchers from Michigan State University (MSU) are acting on these projections now to enable farmers around the world to produce food in an uncertain future.

Potatoes for a changing climate

When conducting research on plant biology and physiology for her Ph.D. at the University of Illinois, Urbana-Champaign, Courtney Leisner was able to study the effects of altered climate conditions on a variety of crops, such as corn and soybeans. In 2014, when she joined the lab of MSU AgBioResearch plant biologist C. Robin Buell as a visiting research associate, she found new opportunities to pursue that interest.

“When I joined Robin’s lab, I was really interested in incorporating some kind of climate change work into our projects,” Leisner said. “When she told me about the possibility of a new potato project coming up, I saw an opportunity to tackle an issue that all of our growers are going to be wrestling with in the coming years.”

With funding from Project GREEEN (Generating Research and Extension to meet Economic and Environmental Needs, a collaboration between MSU, the Michigan Department of Agriculture and Rural Development and Michigan’s plant agriculture industries to fund plant agriculture research in the state), Leisner and Buell created a team with MSU AgBioResearch potato breeder Dave Douches and MSU climate scientist Julie Winkler. Their mission: to discover how potatoes would react to the climate of the future.

Using weather data recorded from 1980-2000 and climate change simulations from the North American Regional Climate Change Assessment Program, Winkler developed a suite of local climate change projections for Michigan between the years 2040 and 2070. This range was selected because the models would retain a high degree of accuracy, as an ensemble of climate simulations for the region was already available, and would give Douches enough time to begin developing entirely new potato cultivars.

Douches has been studying potatoes since joining MSU in 1988. As leader of the MSU potato breeding and genetics program and faculty coordinator at the MSU Montcalm Research Center, where the university has pioneered potato research for the past 50 years, Douches’ understanding of the importance and complexity of the tuber is pretty unrivaled. The development of new potato varieties to help Michigan growers face new challenges in the field is the cornerstone of his research.

“It takes between 10 and 15 years to create a new potato variety from start to finish, so we need to be proactive about identifying the challenges the future could bring,” said Douches, professor in the MSU Department of Plant, Soil and Microbial Sciences. “You can’t simply change your varieties year-to-year to react to last season’s issues -- you have to look ahead as best you can.”

New stresses from a new climate

The team turned to the latest high-tech tools. Using growth chambers, they grew multiple potato cultivars under the climate projections for Michigan’s potato region. They took careful physiological measurements of the plants, including the rate at which photosynthesis occurred and the level of gas exchange between the leaves and the atmosphere.

The potato plants were subjected to several experiments. In the first, potatoes were grown under a flat temperature increase of 2.7 degrees Celsius above current field temperatures – the average temperature increase predicted for the climate of 2050.

The other two incorporated seasonal temperature changes: one in which temperatures in the growth chamber rose until they peaked during the potatoes’ bulking period, and the other in which the temperature peaked early in the season, when the plants were developing aboveground vegetation.

All of the experiments were treated with an increase in carbon dioxide levels as well -- with 563 parts per million compared with the approximately 400 ppm present in today’s atmosphere.

The temperature and photosynthetic period in each growth chamber were altered every two weeks to mimic changes throughout the season.

“We wanted to simulate what the plants would experience in the field,” Leisner said. “Not just in terms of the climate, but the entirety of the growing season. It makes our findings that much more accurate to what farmers are going to see in reality.”

At the end of the growing season, the potatoes were harvested and final measurements taken of their color, biomass, weight and specific gravity – the estimate of dry matter, as opposed to water. All are significant factors in determining the market value of a potato crop.

While data analysis continues, the experiments have revealed that a changing climate will bring new stresses.

“Every time we did the experiment, you could tell within four to six weeks that the plants looked different,” Buell said. “While we’re not certain if the changes are caused by the higher temperatures, the higher carbon dioxide levels or both, it’s clear to me that something substantial is going on.”

Of the three iterations of the experiment, the team found that the climate conditions that saw temperatures peak during the bulking phase resulted in a significantly different harvest than the other two. Each individual tuber was slightly larger but showed a lower specific gravity, which reduces market value. Additionally, some potato cultivars produced fewer tubers than those under the control conditions.

The impact of climate change also varied greatly depending on the potato cultivar. Manistee, a cultivar released by Douches in 2013, proved significantly more resilient to the effects of climate change than the older varieties widely grown in Michigan -- Atlantic and Snowden.

Though changes to the potato in the field would be highly significant, that is not where the journey ends. Most potatoes harvested in Michigan are ultimately moved into long-term storage, where they can be preserved for months and provide processors and retailers with product nearly year round. Examining the impact of climate change on the potatoes’ ability to retain their quality in storage was also of paramount concern.

“The tuber is still alive in storage, it’s still respiring, and so you have to keep them under the right conditions so they don’t start germinating and sprouting,” Buell said. “That means keeping them dormant by keeping them cool.”

Thanks to Michigan’s relatively cool climate, current potato storage facilities do not experience significantly high costs to refrigerate during the five to six months of storage. Rising temperatures could mean change, however. The team is currently testing the storage viability of various cultivars under different climate projections, with Manistee, again, showing more resilience than others.

Breeding a more climate-proof potato

As shown with the growth chamber experiments, the right potato varieties are key. Douches, armed with new data and the 30-year advance warning, is working to incorporate climate resiliency into the MSU potato breeding portfolio.

“The climate models and the experiments we’re doing here are telling us that we’re going to see new stresses on potatoes, and that tells me, as a breeder, that we need to develop new varieties that can withstand that type of environment,” Douches said. “And this will go beyond Michigan -- it’s going to affect all of the potato-growing states across the northern U.S., which together feed a lot of our country. If we can’t figure this out, things are going to change in a really negative way.”

Originating in the Andes Mountains of South America, potatoes are grown throughout the world, including regions with climates already close to Winkler’s projections for Michigan. Douches aims to look to the heat-tolerant cultivars grown in equatorial regions as a starting point, though even that brings challenges.

“Closer to the equator, they have a much shorter day length, which means those varieties are used to significantly less photosynthesis activity,” Douches said. “So we can’t directly take those varieties and plant them in Montcalm County. We can, however, study their germ plasm and cross them with our current varieties to try to take advantage of their characteristics.”

Rising temperatures and carbon dioxide levels also suggest that growers will see increases in pest and disease pressures, also subjects of future experiments.

Beyond potatoes

The impact of climate change will extend to every aspect of agriculture in Michigan. In fact, in some respects, Michigan growers are already experiencing it.

MSU AgBioResearch plant pathologist George Sundin has been working with Michigan apple growers since he came to MSU in 2002.

“We know from the past 50 years that the date the apple trees bloom and when they break dormancy has been moving up,” said Sundin, professor in the MSU Department of Plant, Soil and Microbial Sciences. “We were early again this year, and every time that happens we run the risk of frost damage.”

Those same higher temperatures, along with wetter conditions, also stand to exacerbate the two major apple diseases -- apple scab and fire blight. Together, these diseases already present significant challenges. In 2000, for example, a fire blight epidemic wiped out nearly 400,000 apple trees in southwestern Michigan and caused over $42 million in losses. As periods with temperatures exceeding 70 degrees Fahrenheit during bloom have increased the past few years, incidences of fire blight outbreaks have risen.

Breeding new apple cultivars takes many years. New varieties better adapted to a changing climate remain a distant prospect, Sundin said. Instead, he sees the adoption of a variety of cultural practices as the answer to fighting diseases -- for example, providing information to growers on removing fire blight cankers and hastening the decomposition of dead leaves, in which the apple scab fungus overwinters, with fertilizers.

“Climate is an important issue that goes beyond sea levels and ice caps,” Sundin said. “Most diseases are favored by warm, wet weather, and climate change is going to bring us more of both. It’s critical for all of agriculture.”

Michigan’s cherry crops have also been hard hit by an already changing climate. Like apples, cherry trees have blossomed early because of warming weather, occasionally with devastating consequences. MSU AgBioResearch plant breeder Amy Iezzoni has seen the impact firsthand.

“Many growers in the state have already lost significantly to climate change,” said Iezzoni, professor in the MSU Department of Horticulture. “In 2002, a spring frost wiped out all but about 8 percent of the cherry crop. A lot of growers had no income from cherries that year. It was a horrific event that we thought would happen once in a lifetime. But then it happened again in 2012.”

Iezzoni is breeding new cherry cultivars that bloom later in the spring, allowing them to miss most of the late frosts. But again, it takes time to develop new varieties. In the interim, Iezzoni recommends that growers seek out orchard sites with good air drainage, such as those near Lake Michigan, which affords a buffer against extreme weather conditions. She also advises using wind machines to raise the temperature around the cherry trees by mixing warmer air at the top of an inversion layer with colder air near the ground.

The new difficulties that climate change will bring and, in some cases, already has brought to Michigan agriculture underline the importance of such proactive research.

“Everything is affected by climate,” Douches said. “We grow crops where we do because that’s what the current climate dictates. While we can change where we grow them, we can also work to adapt them to new conditions, given enough time.”