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Abstract:
The "Green Revolution" dwarfing (Rht) alleles that increase
wheat yields under high input conditions are orthologues of the
Arabidopsis GAI gene and encode mutant DELLA proteins. DELLAs
are repressors of plant growth that are degraded in the presence
of gibberellin (GA) whereas the gai/Rht mutants are insensitive
to GA. Most UK wheat varieties carry the semi-dwarfing Rht2
(Rht-D1b) allele but variation in height between genotypes
suggests that other loci play a role in determining stature. We
aim to identify these loci through co-localisation of
quantitative stature traits identified in UK wheat germplasm
with genes in the GA-DELLA pathway. Additionally, TILLING will
be used to identify novel alleles of key genes from mutagenised
populations of wheat. Based on functional analyses in vitro and
performance in the field alleles will be selected for use in
wheat breeding. There are reports of Rht mutations affecting the
responses of wheat to stress, and a negative correlation between
GA content or responsiveness and stress tolerance has been
documented. Moreover, our recent work in Arabidopsis implicates
the GA-DELLA pathway as a central regulator linking GA, abscisic
acid and ethylene in a common stress- related network. It is
timely to translate these key discoveries into crop improvement
to enhance the tolerance of hexaploid wheat to environmental
stresses without compromising productivity. To this end, we will
take a knowledge-based approach to compare Arabidopsis and wheat
DELLA-mediated stress responses. We will use available genetic
stocks to determine whether existing, but relatively untested,
Rht alleles affect tolerance to salt, drought and heat stress.
Near-isogenic lines will be tested under controlled and field
conditions to select alleles that will be taken forward by
introgression into elite varieties. Novel alleles of GA-DELLA
alleles identified by TILLING will also be assessed for effects
on tolerance to drought, heat and other abiotic stresses.
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