Analysis of quantitative trait loci for fertility restoration in seven F2 populations derived from sorghum F1 hybrids bred in Japan.

To clarify the genetic mechanisms of fertility restoration in sorghum F1 hybrids produced in Japan ('Ryokuryu', 'Hazuki', 'Haretaka', 'Natsuibuki', 'Hanaaoba', 'Akidachi' and 'Kazetachi'), we analyzed QTLs for fertility restoration using seven F2 populations derived from those hybrids. By QTL mapping with a series of SSR markers, we detected three major QTLs for fertility restoration. These data and the results of haplotype analysis of known fertility restorer (Rf) genes showed that qRf5, corresponding to the Rf5 locus, was the most widely used Rf gene for fertility restoration of sorghum F1 hybrids among the lines tested. Other major Rf genes detected were qRf8, corresponding to Rf1, and qRf2, corresponding to Rf2. QTLs for grain weight also corresponded to these Rf loci. A minor QTL, qRf3, may also affect restoration of fertility. Our data show that three major Rfs-Rf1, Rf2, and Rf5-were used in F1 hybrid sorghum production in Japan. This knowledge can be used to improve the efficiency of the F1 sorghum breeding program.