| Several tests for so Over the past several years, research conducted
at Colorado State University (CSU) has resulted in successful development
and release of improved winter wheat cultivars for producers in Colorado.
A large component of the overall breeding effort has been directed toward
rapid deployment of genetic resistance to the Russian wheat aphid (RWA),
an introduced insect pest against which resistance was previously unavailable
in adapted cultivars.
Since 1994, five improved cultivars carrying resistance to the RWA have
been released by CSU through the partnership with the Colorado Wheat Administrative
Committee (CWAC) and Colorado Wheat Research Foundation (CWRF). These
cultivars (‘Halt’, ‘Yumar’, ‘Prowers’, ‘Prairie Red’, and ‘Prowers 99’)
each carry a single resistance gene called “Dn4”, a gene proven in both
greenhouse and field studies to be highly effective in minimizing the adverse
effects of the RWA in infested wheat. Within our current germplasm
base (often called “the breeding pipeline”), the vast majority of RWA-resistant
breeding lines carry the Dn4 resistance gene. Because there exists
concern (albeit slight) over development or introduction of RWA biotypes
against which Dn4 is ineffective, we continue to work with several other
resistance genes. Experimental lines carrying some of these other
resistance genes have reached advanced stages of testing and one of these
lines is currently under consideration for potential release.
In addition to advanced experimental lines with “new” sources of RWA-resistance,
we have also been working to develop a RWA-resistant version of ‘Akron’,
a cultivar released by CSU in 1994. Akron is susceptible to the RWA
yet has shown exceptional field performance in variety trials and farmers'
fields throughout Colorado and the west central Great Plains. In
development of the RWA-resistant version of Akron, 85 experimental lines
were tested at three locations during the 2000 field season. From
these 85 lines, a group of five has been identified and will be entered
in the 2001 Uniform Variety Performance Trial (UVPT). With statewide
and regional yield trials during the 2001 and 2002 field seasons, and simultaneous
increase and purification for RWA resistance, we hope to be able to release
a RWA-resistant version of Akron in fall 2002. While the release
date for one of these lines is a couple of years away, we have already
brought this material into our crossing program to broaden our efforts
in combining RWA resistance with the adaptive features that have made Akron
so popular in Colorado.
While RWA resistance will continue to be a primary focus of wheat breeding
efforts at CSU, other objectives have recently received increased attention.
The first of these is the development of Clearfield™ (imidazolinone-resistant)
winter wheat cultivars adapted for production in Colorado and the west
central Great Plains. The Clearfield™ trait, developed by BASF
(formerly American Cyanamid) without the use of recombinant DNA technologies
(e.g., is “non-GMO”), would allow selective control of several winter annual
grass weeds (e.g., jointed goatgrass, downy brome, cheatgrass, Japanese
brome and feral rye) that are problematic in Colorado. Through a
partnership between CSU, the CWAC, and BASF, an ambitious inter-disciplinary
research program was initiated in 1997 to develop adapted Clearfield™ wheat
cultivars and appropriate management strategies for deployment of this
technology. Six promising experimental lines were entered for statewide
testing in the 2000 UVPT. Two of these (coded CO980894 and CO980889)
performed exceptionally well and have been retained for further yield testing
and foundation seed increase to enable potential release in fall 2001.
A large number of experimental lines developed through parallel, accelerated
breeding schemes are also currently under field evaluation and are positioned
to provide potential cultivar releases in 2002 and 2003. In addition
to carrying the Clearfield™ trait, many of these lines also carry
the Dn4 RWA resistance gene.
Development of hard white winter wheat (HWW) cultivars has also received
significant attention at CSU over the last few years. From the standpoint
of end-use markets, the growing interest in HWW can be attributed to the
following factors: slightly greater milling yield; product development
for a more health-conscious and ethnically-diverse society (e.g., whole
wheat white bread, flat tortillas, and noodles); and rapidly-increasing
demand in overseas markets, most notably in Southeast Asia (for a multitude
of different types of noodle products). While HWW breeding research
began in the Great Plains many years ago, it hasn’t been until the last
couple of years that HWW cultivars yield-competitive with the best hard
red winter wheat (HRW) cultivars were made available. Since 1997,
we’ve seen the release of several new cultivars (e.g., ‘Betty’, ‘Heyne’,
‘Nuplains’, and ‘Trego’) that promise to capture a significant portion
of the acreage in their primary areas of adaptation. Within each
of the programs that have released new HWW cultivars, a steady stream of
improved HWW cultivars is expected for years to come.
Within the CSU wheat breeding program, we currently have one experimental
HWW line under foundation seed increase for potential release in 2001.
This experimental line (coded CO940611) originated from a germplasm exchange
with the Kansas State University breeding program in western Kansas (Hays)
in 1995. While this line lacks RWA resistance, it has shown exceptional
performance in Colorado Variety Performance tests since 1997, yielding
slightly less than Alliance but superior to other cultivars commonly grown
in Colorado. This experimental line has shown great promise, but
development of HWW cultivars with RWA resistance is a major priority.
To this end, roughly 50% of the experimental lines that were in their first
year of field testing in 2000 are HWW originating from crosses with RWA-resistant
parents. Selection for RWA resistance and continued statewide yield
testing will hopefully provide a RWA-resistant HWW cultivar release by
2004.
Without a doubt, the most daunting challenges for HWW breeding are those
that arise from the fact that we are most likely in a transition period
between large-scale HRW production and large-scale HWW production in the
west central Great Plains. Until a breeding program is capable of
making adapted HWW x HWW crosses (which yield 100% HWW segregates), efforts
necessarily revolve around isolating HWW lines from mixed samples of HRW
x HWW crosses. While this is relatively straightforward in the absence
of rain-induced weathering, the genetics of bran color are such that white
segregates from HRW x HWW crosses are quite rare – often only 6% at best.
Of greater importance, however, is the fact that HWW cultivar development
requires additional evaluation efforts for traits that are generally less
important within the HRW market class. The first of these, that of
the tendency of HWW to sprout in the head under wet conditions at harvest
(known as “preharvest sprouting”), is a problem that presents a definite
concern to the industry. Fortunately, sprout-tolerant germplasm is
available and manageable screening techniques may be readily implemented
within the framework of existing programs. Furthermore, preharvest
sprouting is expected to be of lesser concern for HWW production in Colorado
and the west central Great Plains where environmental conditions that promote
sprouting in the head prior to harvest are much less prevalent.
End-use quality evaluation also presents a unique and significant set
of challenges. Because the Asian noodle market represents an attractive
export market opportunity for Colorado-produced HWW, our quality evaluation
in the breeding program must be geared toward providing wheat cultivars
that are desirable for both bread and noodle production. While we
have a much greater understanding today of both domestic and export quality
requirements, time and patience will likely be required to successfully
integrate “dual-purpose” quality performance criteria into germplasm adapted
for production in Colorado and the west central Great Plains.
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