Genetic mapping and comparative analysis of heading date in hexaploid oat

Heading date is a critical developmental transition in the life cycle of an oat plant. The objectives of this study were to identify DNA markers associated with quantitative trait loci (QTL) affecting heading date in hexaploid oat, and to locate and characterize heading date QTL by comparative analysis using an oat reference genome. Genetic linkage maps were constructed using single nucleotide polymorphism (SNP) markers in recombinant inbred lines (RILs) from the oat populations FL0206B-S-B-S1 × UFRGS 078030-1 and URS Taura × Leggett. Days to heading were collected in field trials, and QTLs for heading date were identified in several genomic regions of the two maps. The oat loci with the most significant additive effects were associated with the linkage groups Mrg02, Mrg06 and Mrg05 in the FL0206B-S-B-S1 × UFRGS 078030-1 population and with the linkage groups Mrg12, Mrg24 and Mrg11 in the URS Taura × Leggett population. Major QTLs affecting heading date were mapped to locations consistent with known QTLs and genes that play critical roles in regulating flowering. These genes include HD3a and FT, which are orthologs of the VRN3 gene in small grains and integrate the vernalization and photoperiod response pathways, PRR37 (= PPD1), the main gene determining photoperiod sensitivity in wheat, and COL13 and GI, which are involved in the regulation of flowering by photoperiod. In addition, novel heading date QTLs were identified that will be valuable for molecular selection in oat breeding programs aimed at developing new and improved oat cultivars adapted to specific growing conditions.