QTL mapping and validation of fertility restoration in West African sorghum A cytoplasm and identification of a potential causative mutation for Rf.

Key message Major A cytoplasm fertility restoration loci, Rf and Rf , were found in the West African sorghum. A potential causative mutation for Rf was identified. KASP markers were validated on independent material. To accelerate the identification and development of hybrid parental lines in West African (WA) sorghum, this study aimed to understand the genetics underlying the fertility restoration (Rf) in WA A cytoplasmic male sterility system and to develop markers for a routine use in WA breeding programs. We genotyped by sequencing three F populations to map the Rf quantitative trait loci (QTL), validated the molecular KASP markers developed from those QTL in two F populations, and assessed the most promising markers on a set of 95 R- and B-lines from WA breeding programs. Seven QTL were found across the three F populations. On chromosome SBI-05, we found a major fertility restorer locus (Rf) for two populations with the same male parent, explaining 19 and 14% of the phenotypic variation in either population. Minor QTL were detected in these two populations on chromosomes SBI-02, SBI-03, SBI-04 and SBI-10. In the third population, we identified one major fertility restorer locus on chromosome SBI-02, Rf, explaining 31% of the phenotypic variation. Pentatricopeptide repeat genes in the Rf QTL region were sequenced, and we detected in Sobic.002G057050 a missense mutation in the first exon, explaining 81% of the phenotypic variation in a F population and clearly separating B- from R-lines. The KASP marker developed from this mutation stands as a promising tool for routine use in WA breeding programs.