Agriculture Reference
In-Depth Information
program in the Great Plains started to develop
HW wheat by the early 1990s. Hard white wheat
cultivars released in the region to date, and the
respective developing party, include 'Intrada',
'Guymon' and 'OK Rising' (Oklahoma State
University and USDA-ARS); Arlin, Betty,
Heyne, 'Trego', 'Lakin', and 'Danby' (KSU);
'Nuplains', 'Antelope', 'Arrowsmith', and 'Anton'
(USDA-ARS and University of Nebraska-
Lincoln); 'Alice' (South Dakota State Univer-
sity); 'Avalanche' (Colorado State University);
and Rio Blanco, Oro Blanco, 'Platte', 'NuFron-
tier', 'NuGrain', 'NuHorizon', 'NuHills', and
'NuDakota' (AgriPro-Coker).
Red grain color is inherited as a dominant trait
in wheat and conferred by three genetic loci des-
ignated R1 , R2 , and R3 (McIntosh et al., 2005).
Presence of a dominant allele at any one of these
loci will condition the red-grained phenotype.
Intermatings of red wheats can yield white-
grained progeny if the red wheat parents carry
recessive alleles at complementary R loci. Many
white-grained cultivars have been developed by
intermatings of red-grained parents. Arlin was
derived via selection of white-grained progeny
from a bulk population of HRW and hard red
spring parents that were intercrossed in 1981
(Sears et al., 1993). Alice descended from the
cross of two red wheat parents, 'Abilene' and
'Karl'.
While the existing red wheat gene pool could
provide genes for agronomic adaptation and
disease resistance, introduction of genes for novel
quality traits (see below) must be incorporated
into HW wheat breeding efforts. Current efforts
typically involve either intermatings of adapted
white wheat breeding lines or matings between
previously released HW wheats and adapted red
wheats. For example, Antelope was derived from
the mating of 'Pronghorn', a Nebraska-developed
HRW wheat, and Arlin, a HW wheat (Graybosch
et al., 2005). Because the Great Plains white wheat
gene pool is small while the North American
HRW gene pool is a large product of a 75-year
breeding effort, matings with adapted red wheats
are essential.
Red wheat will continue to provide parentage
for development of new HW winter wheat culti-
vars. Segregation ratios in progeny of crosses
(matings) of red-grained and white-grained
parents will differ depending on the genotype of
the red-grained parent. For example, matings of
a red wheat parent possessing homozygous domi-
nant alleles at R1 , R2 , and R3 and any white
wheat will yield white-grained progeny at a fre-
quency of 1 : 64. The 1 : 64 ratio is the “worst-
case” scenario. In a survey of 90 UK wheats,
Flintham and Humphray (1993) found 41%
carried a single dominant R allele, 41% carried
two dominant R alleles, and only 18% had domi-
nant alleles for all three loci. If results from the
UK are representative of most wheat breeding
pools, more favorable segregation ratios of 1/4 or
1/16 will be more often encountered. A red-
grained parent of the genotype R1R1r2r2r3r3 will
yield white-grained progeny at a frequency of
1/4, after mating with a white wheat.
Still, wheat breeding progress requires the
evaluation of large numbers of selected progeny,
and the low frequency of white-grained progeny
in matings derived from red wheat is an impedi-
ment to breeding progress. The process has,
however, been greatly expedited by the develop-
ment of automated seed sorting technology
(Dowell et al., 2006). Such systems are capable of
rapidly extracting white seed from early-genera-
tion segregating or mixed populations, allowing
breeders to seed nearly pure white-grained popu-
lations, even after red wheat matings. Although
color-sorting technology is available, breeding
programs will rarely target only one wheat class.
Great Plains wheat breeders likely will continue
to develop and intermate both red and white
wheat parents and use sorting technology to
derive various gene pools to meet regional
needs.
Late-season rainfall, especially if it occurs as
wheat plants approach physiological maturity,
can result in the initiation of germination in situ
(i.e., preharvest sprouting), with a concomitant
release of amylase enzymes. High amylase activity
leads to starch digestion, resulting in a loss of test
weight and diminished processing quality. In
general, red wheat is more resistant to preharvest
sprouting than white wheat (Morris and Paulsen
1992); but in typical years, preharvest sprouting
Search WWH ::




Custom Search