High density mapping and haplotype analysis of the major stem-solidness locus SSt1 in durum and common wheat


Nilsen, K.T., N'Diaye, A., MacLachlan, P.R., Clarke, J.M., Ruan, Y., Cuthbert, R.D., Knox, R.E., Wiebe, K., Cory, A.T., Walkowiak, S., Beres, B.L., Graf, R.J., Clarke, F.R., Sharpe, A.G., Distelfeld, A., Pozniak, C.J. (2017). High density mapping and haplotype analysis of the major stem-solidness locus SSt1 in durum and common wheat. PLoS ONE, [online] 12(4), http://dx.doi.org/10.1371/journal.pone.0175285

Plain language summary

The wheat stem sawfly is an insect that reduces wheat yield which in turn reduces Canadian farmer profitability and contributes to limited production of wheat needed to feed an expanding world population. Resistance to the insect is available and breeding for resistance can be enhanced by the use of DNA markers associated with the genes for resistance. The closer the markers are to the resistance gene the more efficient breeding will be. This study identified markers very close to a gene that confers resistance to the wheat stem sawfly and will improve the rate of selection for resistance in breeding programs that use the markers.


Breeding for solid-stemmed durum (Triticum turgidum L. var durum) and common wheat (Triticum aestivum L.) cultivars is one strategy to minimize yield losses caused by the wheat stem sawfly (Cephus cinctus Norton). Major stem-solidness QTL have been localized to the long arm of chromosome 3B in both wheat species, but it is unclear if these QTL span a common genetic interval. In this study, we have improved the resolution of the QTL on chromosome 3B in a durum (Kofa/W9262-260D3) and common wheat (Lillian/Vesper) mapping population. Coincident QTL (LOD = 94-127, R2 = 78-92%) were localized near the telomere of chromosome 3BL in both mapping populations, which we designate SSt1. We further examined the SSt1 interval by using available consensus maps for durum and common wheat and compared genetic to physical intervals by anchoring markers to the current version of the wild emmer wheat (WEW) reference sequence. These results suggest that the SSt1 interval spans a physical distance of 1.6 Mb in WEW (positions 833.4-835.0 Mb). In addition, minor QTL were identified on chromosomes 2A, 2D, 4A, and 5A that were found to synergistically enhance expression of SSt1 to increase stem-solidness. These results suggest that developing new wheat cultivars with improved stem-solidness is possible by combining SSt1 with favorable alleles at minor loci within both wheat species.