To clarify the genetic mechanisms of fertility restoration in sorghum F 1 hybrids produced in Japan ('Ryokuryu', 'Hazuki', 'Haretaka', 'Natsuibuki', 'Hanaaoba', 'Akidachi' and 'Kazetachi'), we analyzed QTLs for fertility restoration using seven F 2 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 F 1 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 F 1 hybrid sorghum production in Japan. This knowledge can be used to improve the efficiency of the F 1 sorghum breeding program.

Purple corn is a maize variety (Zea mays L.) with high anthocyanin content. When purple corn is used as forage, its anthocyanins may mitigate oxidative stresses causing lower milk production in dairy cows. In this study, we analyzed quantitative trait loci (QTLs) for anthocyanin pigmentation of maize organs in an F2 population derived from a cross between the Peruvian cultivar ‘JC072A’ (purple) and the inbred line ‘Ki68’ (yellowish) belonged to Japanese flint. We detected 17 significant QTLs on chromosomes 1–3, 6, and 10. Because the cob accounts for most of the fresh weight of the plant ear, we focused on a significant QTL for purple cob on chromosome 6. This QTL also conferred pigmentation of anther, spikelet, leaf sheath, culm, and bract leaf, and was confirmed by using two F3 populations. The gene Pl1 (purple plant 1) is the most likely candidate gene in this QTL region because the amino acid sequence encoded by Pl1-JC072A is similar to that of an Andean allele, Pl-bol3, which is responsible for anthocyanin production. The markers designed for the Pl1 alleles will be useful for the breeding of F1 lines with anthocyanin pigmentation in cobs.

DNA markers for the genes for flowering time (Ma1/SbPRR37, Ma2/SbEHD1, Ma3/SbPhyB, Ma4/SbCO, Ma5/SbPhyC, and Ma6/SbGHD7), semi‐dwarfism (dw1 and dw2), fertility restorers (Rf1, Rf2, Rf5, and partial A1 mitochondrial sequence) and cytoplasmic–nuclear male sterile (CMS), and brown midrib (bmr‐2, bmr‐6, and bmr‐18) were developed in this study. These markers and previously published DNA markers for dw3 were used to analyze sorghum cultivars used in breeding programs in Japan and traditional landraces from the National Institute of Agricultural Sciences (NIAS) sorghum core collection. Agronomically useful mutations were effectively detected in the cultivars by the DNA markers. Most of the mutation types for flowering and semi‐dwarfism were detected in sorghum cultivars, but only the dominant‐type allele of SbEHD1 and SbPhyB for flowering was detected in the NIAS collection. Fertility restorers and CMS were rarely detected in NIAS collection. Agronomically useful traits such as early flowering and semi‐dwarfism became combined in the modern cultivars by phenotypic evaluation for the adaptation of harvesting to the temperate zones. Fertility restorers and CMS were introduced for F1 hybrid breeding. These phenotypes are often recessive, so information on the alleles responsible would be helpful for sorghum breeding. We expect these DNA markers to facilitate and improve the efficiency of F1 sorghum breeding programs.

Cytoplasmic male sterility (CMS) is widely used to control pollination in the production of commercial F 1 hybrid seed in sorghum. So far, 6 major fertility restorer genes, Rf1 to Rf6, have been reported in sorghum.Here, we fine-mapped the Rf5 locus on sorghum chromosome 5 using descendant populations of a 'Nakei MS-3A' × 'JN43' cross. The Rf5 locus was narrowed to a 140-kb region in BTx623 genome (161-kb in JN43) with 16 predicted genes, including 6 homologous to the rice fertility restorer Rf1 (PPR.1 to PPR.6). These 6 homologs have tandem pentatricopeptide repeat (PPR) motifs. Many Rf genes encode PPR proteins, which bind RNA transcripts and modulate gene expression at the RNA level. No PPR genes were detected at the Rf5 locus on the corresponding homologous chromosome of rice, foxtail millet, or maize, so this gene cluster may have originated by chromosome translocation and duplication after the divergence of sorghum from these species. Comparison of the sequences of these genes between fertile and CMS lines identified PPR.4 as the most plausible candidate gene for Rf5.

To compare the seed productivity of germplasm in India (Tamil Nadu) and Japan (Tsukuba), a total of 105 accessions from the Japanese National Agriculture and Food Research Organization (NARO) sorghum core collection were cultivated. The comparative cultivation studies were conducted at two locations in India and one in Japan. Differences in cultivation environments, including day length, temperature, and rainfall were evident in all the studies, and accordingly, seed production varied. The accessions grown in Japan yielded the highest number of grains per panicle. However, 11 accessions cultivated in Japan produced no harvest. Conversely, all accessions grown in parts of India, such as in Coimbatore, produced seeds. Therefore, although seed production in Japan was superior, there were benefits to cultivating the crops in India, including longer cultivation periods and the ability to overcome difficulties with seed multiplication found in Japan. Comparative cultivation projects involving international collaborative research are essential to reveal seed productivity in genetically diverse resources of sorghum. This study provides data about international sorghum production and information about differences in available accessions.