Identification of QTL associated with shattering in two spring wheat (Triticum aestivum L.) populations using high-density SNP markers

Spike shattering can cause severe grain yield loss in wheat. Wheat varieties with reduced shattering but having easy threshability is the target of variety developers. The objective of this study was to determine and map QTL conferring shattering resistance in two Canadian spring wheat doubled haploid populations – Carberry/AC Cadillac and Carberry/Thatcher. Both populations were evaluated for shattering near Swift Current. The Carberry/AC Cadillac population (n=812 lines) was evaluated in five environments between 2012 and 2014. The Carberry/Thatcher population (n=297) was evaluated at one location in 2016 and two locations in 2018 comprising three environments. Shattering was scored on a scale of 1 - 9, with 1 being no shattering within the plot and 9 being 100% shattering. For the Carberry/AC Cadillac population, one environment in 2014 showed little differential among lines. The populations were genotyped and mapped with SNP markers and quantitative trait locus (QTL) analysis was performed. The parents, AC Cadillac and Thatcher, had reduced shattering compared to Carberry in the majority of environments. The distributions of shattering scores were typically continuous and skewed with a preponderance of low shattering types. Two low shattering QTL contributed by Carberry on chromosomes 4B and 5A were consistent in both populations. No other QTL segregated in the Carberry/Thatcher population. In contrast, five other QTL were identified in the Carberry/AC Cadillac population on chromosomes 1A, 3A, 3D, 7A and 7D. Resistance alleles were contributed by Carberry on chromosome 7A and by AC Cadillac on 1A, 3A, 3D and 7D. Although Carberry is more susceptible to shattering relative to AC Cadillac and Thatcher, it contributed two of the most consistently and strongly expressed resistance QTL. The markers for the shattering resistance QTL can be used to improve selection in wheat.