Title:
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Dissecting the genetic control of grain : weight in UK wheat
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Wheat is one of the most economically important crop species in the world. It provides
twenty percent of calories to a global population of seven billion people. However, genetic
research of wheat is complicated as the genome is very large, full of repetitive sequences and
comprised of three similar sub-genomes. During the course of this project, the genetic
resources available for wheat drastically improved. The abundance of genome-specific SNP
markers increased considerably, and 2014 saw the release of a chromosome-based draft
sequence of the hexaploid wheat genome.
The wealth of publicly-available SNP genotype information was exploited, to identify
statistical associations between SNP markers and agronomically important traits, using two
experimental populations: the Avalon x Cadenza doubled haploid mapping population, and
the NIAB elite Multi-parent Advanced Generation Intercross (MAGIC) population. Genomewide
association, and QTL analyses identified regions of interest on chromosomes 3D, 4B
4D, 5A, 5B and 6A. These regions contained SNPs which had an association with either grain
yield; grain weight; grain width; grain length; grain surface area; or a combination of these
traits. Furthermore, regions of chromosomes IB, 2A, 5B, 5D and 6A were of particular
interest as they not only contained SNPs with a statistical association with a trait, they
contained a transcript that had differential expression between plants with high and low
thousand grain weight. These results suggest that although genetic diversity is limited, there
is still potential for the identification of yield-increasing genes within elite wheat.
Due to the lack of sequence information for wheat, few of the sequences of interest were
annotated with gene or protein function. However, a set of putative candidate genes have
been identified in both populations, which appear to be involved in plant growth and
development.
Of particular interest to the wheat breeding industry is the range of elite material studied.
Over 80% of allelic diversity seen in elite UK wheat was captured by the two experimental
populations, which, in total, represented 10 elite varieties. Therefore, there is a high chance
that the SNPs identified in these populations are segregating in elite breeding material.
Furthermore, a variety of hexaploid, tetraploid and diploid wheat material, including elite
varieties; wheat relatives; and wild landraces have previously been screened with the majority
of the SNPs used in this analysis. The SNP data is publicly available, making the results of
this study immediately available for validation or introduction into breeding programmes.
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