Identification of Closely Linked Flanking Markers to Rht8 in a Wheat Recombinant Inbred Line (RIL) Population.

Plant height (PH) is an important quantitative trait of wheat. It affects plant lodging, harvest index, disease resistance, and grain yield. To date, more than 20 reduced-height genes (Rht) have been reported on different chromosomes (Rht1 to Rht22). Among them, Rht1 (Rht-B1b), Rht2 (Rht-D1b), and Rht8 are frequently used Rht genes in breeding programs. Compared with Rht-B1b (Rht1) and Rht-D1b (Rht2), Rht8 on the short arm of chromosome 2D is a gibberellin (GA) sensitive gene and thus not associated with the GA pathway and does not reduce leaf area or coleoptile length. For this reason, Rht8 has been widely used in breeding programs worldwide, especially in moisture-limited situations where deep planting is essential. However, tightly linked markers are not available for high-throughput screening of Rht8, thus affecting selection efficiency. A simple sequence repeat (SSR) marker Gwm261 has been used for screening of Rht8, but recombinants are frequently observed between Rht8 and Gwm261. We conducted a genotyping-by-sequencing (GBS) assay and screened SSR markers on 2DS to identify markers linked to Rht8 in a recombinant inbred line (RIL) population derived from G97380A (Rht8) X G97252W (rht8). A total of 2,514 single nucleotide polymorphism (SNPs) and 3 SSRs (Gwm261, Xcfd53, PH2918-11) were used to construct a linkage map. The map contains 2,238 SNPs and 3 SSRs, covering all 21 chromosomes at a total length of 1474.278 cM with a marker density of 0.66 markers per cM. Using two seasons of plant height data, two SSR markers, Xcfd53 and PH2918-11, were found to flank Rht8 at 7.3 cM apart. Additionally, several SNPs closely linked to Rht8 were converted into KASP markers for high-throughput screening of Rht8. The flanking markers and KASP markers are all closer to Rht8 than Gwm261. Identification of the closer markers to Rht8 will significantly improve selection accuracy in developing new cultivars with Rht8.