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Down on wheat drought

By Ed Haag

Any farmer can tell you that
dry and wet periods run in cycles. Despite periodic droughts, as in the 1930s,
the last 100 years have been mainly damp.

In many areas of the Corn
Belt, a soaking wet 2010 shows wet conditions still persist. In some areas,
though, there’s evidence the wet trend is shifting.

“I don’t think we are ever
going to return to the precipitation we saw in the 1980s and 1990s, because we
have already shifted out of that wet phase,” says Richard Seager, senior
researcher from Columbia University’s Lamont-Doherty Earth Observatory.

Seager and his associates
have collected historic data from sources that include tree ring samples. These
accurately reflect a continuum of growing conditions dating back as far as 1200
A.D., he says.

Research conducted by Mark
Svoboda, a climatologist with the National Drought Mitigation Center,
University of Nebraska, supports Seager’s conclusions. His analysis of historic
records clearly shows periods of extended drought happening more frequently
than they have over the last 200 years. Svoboda notes some of these droughts
lasted several decades and fundamentally changed the ecology of impacted areas.

“Regardless of where you
stand on the global warming issue, it just makes sense that we should be
prepared for these events,” he says.

These warnings have not gone
unheeded. Some regional grower associations, working with their respective
land-grant universities, actively support expanding breeding programs for
drought-resistant crops. Washington State University’s (WSU) wheat breeding
program is a beneficiary of such efforts.

“In low-precipitation areas,
even small incremental gains in drought hardiness can make a difference,” says
Scot Hulbert, who holds the Cook Endowed Chair in Cropping Systems Pathology
position at WSU.


International Cooperation,
Local Focus

The Washington Grain
Commission (WGC) established the R. James Cook Endowed Chair in Wheat Research
at WSU in 1998, with a $1.5 million endowment. This chair was created to
strengthen research and graduate education in the plant, soil, and
microbiological sciences.

Advances already made by
Hulbert and his wheat breeding team include crossing globally recognized
drought-tolerant germplasm with established regional wheat varieties. “We are
doing a lot of crosses with Australian wheat varieties selected for water-use
efficiency like Drysdale and Rees,” says Hulbert. “We also work with CIMMYT germplasm.”

CIMMYT is a Mexican-based
international wheat and maize breeding center. WSU wheat breeders and WGC
members have visited CIMMYT facilities and met with scientists.

Hulbert notes WSU wheat
breeders are focusing on developing regionally adapted drought-tolerant
varieties to be used in new erosion-slicing cropping systems.

“Roughly two thirds of the
wheat acreage in Washington currently has summer fallow in its rotation,” says
Hulbert. “While it might work financially for producers, it is just not
sustainable. Their top soil is literally blowing away.”

Introducing wheat varieties
with higher water-use efficiency could transform acreage that is fallowed every
other year into annually cropped acreage.

Choosing Suitable Germplasm

Before any of this is
possible, though, Hulbert and his team must determine which introduced
germplasm is best suited for crossing to local strains and which plant traits
are relevant to drought hardiness in the Pacific Northwest. 

“At this point, we don’t
know for sure which are the most important traits for our region,” says
Hulbert. He concludes these drought-resistant traits should include a plant’s
ability to do the following:

  • Reach and extract water at
    the desired depth.
  • Produce early ground cover
    and biomass. This translates directly into better competitiveness against
  • Maintain photosynthesis
    while minimizing moisture loss through transpiration. This also aids a plant’s
    tolerance for conditions that would otherwise precipitate plant dehydration and
    system collapse.

Hulbert says another group
of characteristics that are likely to make the Northwest Pacific drought short
list are avoidance traits – those characteristics favorable to a plant’s
survival in a specific growth environment. These include traits such as early
flowering prior to annual heat events and winter growth habits that allow a
plant to take optimal advantage of seasonal precipitation.

Another land-grant
university involved in drought research is Colorado State University (CSU).
Like their Washington counterparts, Colorado wheat growers have proactively
supported university drought research.

“The wheat growers in our
state increased the checkoff from 1¢ to 2¢ a bushel,” says Patrick Byrne, CSU
professor of soil and crop sciences. “A lot of that money comes to CSU for
research and helps support our drought-tolerance breeding program.”

Working with USDA, CSU’s
drought scientists have successfully established a managed drought research
site in an area that receives 12 inches of precipitation a year.

“This is a research farm in
Greeley, Colorado, that has many acres of drip irrigation. It allows us to
precisely control and monitor the amount of water applied,” says Byrne. “We
typically grow materials for a study side by side – one under well-watered
conditions and the other under drought-stressed conditions.” 

Byrne’s personal expertise
and interest are in identifying genetic markers associated with drought

“Knowing which parts of
chromosomes affect the traits of interest is one of our goals,” he says. 

Meanwhile, CSU plant
breeders, working with University of Nebraska breeders, are crossing Middle
East wild wheat cultivars with local varieties. “This spring and summer, we
will be looking at these crosses to see if we have any indications of drought
tolerance,” says Byrne.

He notes the pace of
developing new local varieties with desirable traits, such as drought
hardiness, can be excruciatingly slow. But considering the potential stakes in
play, for Byrne and others in the agricultural research community, it is well
worth the effort.

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