Plant Genome II Conference
Town & Country Conference Center, San Diego, CA, January, 1994.
PG-II: BARLEY AND MODEL QTL SYSTEMS
BARLEY AND MODEL QTL SYSTEMS
Patrick Hayes. Department of Crop and Soil Science, Oregon State
University, Corvallis, OR 97331
Barley has proven to be a productive model system for
public-sector genome mapping and QTL analyses. The North
American Barley Genome Mapping Project has provided the
technology and data required for application of these techniques
to plant breeding. The intent of this presentation is to provide
a overview of three projects representing distinct approaches,
objectives, and targets in QTL application: (i) yield and malt
extract QTL selection and validation, (ii) development of a
catalog of mapped genes for resistance to barley stripe rust, and
(iii) mapping the components of winterhardiness. The QTL
validation project grew out of the extensive data set available
in the Steptoe X Morex mapping population. Multi-environment
agronomic and quality data were used to design a selection
response/QTL validation study. Three tines in the original
mapping population were crossed with the objective of generating
two sets of progeny that would, respectively, maximize the
probability of recovering an ideal genotype with all positive QTL
alleles, and maximize segregation at all possible QTLS. In
contrast to this 'ultimate phenotype' experiment, the barley
stripe rust project is representative of exotic germplasm
introgression. Barley stripe rust is simultaneously the worst
possible news and the greatest opportunity. This fungal pathogen
has arrived in the U.S. and virtually all barley cultivars are
susceptible. Sources of genetic resistance are available but
largely uncharacterized. We are proceeding to map resistance
loci in various accessions and to introgress resistance loci into
adapted germplasm. This will allow for the implementation of a
rational disease management strategy based on judicious use of
single and multiple resistance genes. Mapping the components of
winterhardiness is illustrative of the power of QTL analyses to
dissect complex phenotypes, validate classical epistatic models,
and relate known function genes to quantitative phenotypes. We
have mapped QTLs for cold tolerance, photoperiod response, and
vernalization response and related these to the classical
epistatic models for growth habit in barley. We have also mapped
a number of induced response clones, of which the Dehydrin loci
are particularly intriguing. The extensive classical and
molecular genetics mapping work in barley, coupled with the ease
of doubled haploid production and the economic value of this
public-sector crop, make it an ideal system for testing and
applying QTL theory.
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