Mapping of QTLs Associated with Awn Length in Sorghum Recombinant Inbred Lines

Sorghum (Sorghum bicolor) is a useful crop for food source and bioethanol production, and is the world's fifth most important cereal crop after rice, wheat, maize and barley. The awn is a long needle-like structure derived from an extended lemma in a grass spikelet, and has roles in seed dispersal and burial, protection against animals. Despite its importance, little is known about the regulatory mechanism of sorghum awn formation. Here, we used recombinant inbred lines derived from the reference line, awnless BTx623 and Japanese landrace, awned NOG to detect quantitative trait loci (QTLs) for awn length by using genome-wide SNPs markers derived from RAD-seq. We detected four QTLs for awn length and found NOG alleles of all four QTLs have positive effect for awn length, and the most significant one was located on the long arm of chromosome 3 (qChr03). Interestingly, the awnless BTx623 allele is dominant in qChr03, while the awned NOG alleles are dominant in other three QTLs. Our results indicate there is a bizarre gene, Dominant Awn Inhibitor (DAI) on the long arm of chromosome 3. Future study about qChr03 may provide new insights into the molecular mechanism underlying awn development in sorghum.