Fine Mapping of Giberellin-Sensitive Dwarfism QTL in Winter Wheat

The major dwarfing alleles of wheat, Rht-B1b and Rht-D1b, reduce internode length by disrupting gibberellic acid perception. The reduced sensitivity to GA results in a significantly shortened coleoptile, which causes reduced emergence and uneven stand establishment with deep sewing. Efforts were made to map dwarfism QTL that act through alternative pathways, which do not carry the negative pleiotropy associated with Rht-B1b and Rht-D1b. A genetic map comprised of GBS and KASP markers was used to map dwarfism QTL in the MPV57 x Massey mapping population. Two QTL were discovered on chromosomes 6A and 6D, which were detected over two years and in multiple field locations. SNP associated with the QTL were used for fine mapping in a second population, MPV57 x LA95135. Heterogenous Inbred Families (HIFs) were developed from F4 plants heterozygous for the QTL regions on 6A or 6D. Individual F5 plants which were heterozygous recombinant in the 6A or 6D QTL regions were selected, and plant height will be measured on replicated head-rows of F7 HIFs. Comparisons will be made on highly replicated near-isogenic sister lines that contrast only for the QTL locus genotype, thereby controlling for genetic background effects and allowing for more precise estimates of the QTLs location.