Page 197 - PC2019 Program & Proceedings

PLANT CANADA 2019

S179. Cultivar classification, major genes, and chromosomal position explain the distribution of
genetic diversity in a sample of Canadian bread wheat
*1
2
Hargreaves, W. ; C. Pozniak ; L. Lukens ; A. N'Daiye
2
1
1 University of Guelph
2 University of Saskatchewan
Understanding the distribution of genetic diversity and linkage disequilibrium within Canadian bread
wheat illuminates past effects of selection and enables an increased rate of improvement. Here, population
structure and genetic diversity of a sample of Canadian bread wheat was investigated in a sample of 365
cultivars using 14,074 SNPs. Cultivars were classified by year of release, phenotypic group, market class,
and breeding program. All classifications partitioned genetic diversity; phenotype captured the most at
22.7% with the other factors dividing more within phenotypes. A single dominant
allele is sufficient to switch type for three phenotypic traits. Two of these, however, have homoeologous
genes with dominant alleles leading to genetically heterogenous but
phenotypically similar cultivars. Despite this, markers linked to a number of these genes are
differentiated between contrasting trait groups. Finally, recombination is repressed in large chromosomal
regions proximal to centromeres potentially resulting in highly reduced variation due to drift in effectively
small breeding populations. Within chromosomes 1A, 2A, 6A, 6B and 7A large haplotypes 100s of Mb
long were observed proximal to the centromeres. We potentially observed similar large haplotypes on 3A,
3B, 4A, 4B, 5A, 5B, and 7B based on sparse polymorphic markers usually in high LD. In conclusion,
although attributes and major genes affect allelic diversity, we view that these very large, non-
recombining, haplotypes is a major stumbling block for generating diversity within Canadian bread
wheat.

William Hargreaves (whargrea@uoguelph.ca)

S180. Tackling pre-harvest sprouting in small grain cereals
*
Chen, W-Y ; S.K. Kadoll; J. Singh
McGill University

Pre-harvest sprouting (PHS) is the premature germination of grains while head is still maturing in the
field. Breeding PHS resistance is challenging due to genetic complexity and phenotyping difficulties. We
have recently discovered specific set of Argonaute (AGO) genes, which associates with PHS resistance in
both wheat and barley. This novel AGO/ PHS association could lead to provide efficient and reliable
biomarkers for the development and selection of PHS tolerant wheat and barley varieties. Moreover, the
AGO4_9 is a member of RNA-directed DNA methylation (RdDM) pathway, which is involved in DNA
methylation process. The current efforts are, first, identifying the RdDM pathway gene families and other
genes associated with germination process such as pullulanases in small grain cereals. Data indicates that
barley has 14 AGO related genes. In addition, 17 Pol subunit1 like, 10 methyltransferase, 7 RDR, 5 DCL,
1 pullulunase, 2 pullulunase inhibitors and only one HEN1 genes were identified. Their spatiotemporal
expression of key genes was also studied in barley. Efforts are being made to functionally characterize
sprouting specific AGO4_9 and pullulunase genes in barley. These results will allow us to devise new
tools for improvement in grain quality and quantity, nutritional value and farm economy of cereal grains
production in Canada.

Wei-Yuan Chen (wei-yuan.chen@mail.mcgill.ca)

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