|dc.description.abstract||Semi-dwarf wheat has historically resulted in reduced stem lodging, increased harvest index, and in some areas, improved yields. The Rht18 gene is known to reduce height in wheat, but there are currently no commercial varieties in Western Canada that contain this gene. In Western Canada the two main sources of dwarfing in wheat, Rht-B1b and Rht-D1b, have negative agronomic effects, such as a reduced coleoptile length, reduced emergence, and varietal off-types. Therefore, it is favorable to investigate the introduction of Rht18 for use in Canadian varieties. This was carried out by measuring the agronomic and quality differences between two set of near-isogenic lines with the same genetic background, but one carrying the gene and the other not. The Rht18 gene resulted in dwarfing by approximately 16.2 cm compared to the regular height NILs. It showed the expected benefits of reduced stem lodging and increased harvest index. There was an increase in days to flowering and maturity, spikes per unit area, protein percentage, and Falling Number, as well as a minor reduction in yield, test weight, and thousand kernel weight in the Rht18-carrying NILs. There was also reduced coleoptile length but no reduction in emergence compared to NILs that did not carry the gene. Compared to check varieties, these agronomic measurements were within a normal range for Canada Western Red Spring wheat varieties.
The location of Rht18 was identified and markers were validated to ensure the most efficient breeding and introduction of the gene into the breeding program. The SNPs IWB52666, IWB39455, and IWA1813 were linked to Rht18 on chromosome 6A of wheat. They were also validated and are appropriate for use in a hexaploid wheat breeding program. Having the availability of these SNPs as molecular markers and knowing the effects of Rht18 introduction into a hexaploid wheat background will allow for increased breeding potential in the future and the possibility of a new dwarfing source in varieties in Western Canada. Semi-dwarf wheat containing Rht18 can been grown with higher resistance to stem lodging and harvest index without major linkage drag of agronomic and quality traits.||