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Abstract
Key messageMajor A1cytoplasm fertility restoration loci,Rf2andRf5, were found in the West African sorghum. A potential causative mutation forRf2was 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 A1 cytoplasmic male sterility system and to develop markers for a routine use in WA breeding programs. We genotyped by sequencing three F2 populations to map the Rf quantitative trait loci (QTL), validated the molecular KASP markers developed from those QTL in two F2:3 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 F2 populations. On chromosome SBI-05, we found a major fertility restorer locus (Rf5) 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, Rf2, explaining 31% of the phenotypic variation. Pentatricopeptide repeat genes in the Rf2 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 F2:3 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.
Highlights
Sorghum bicolor (L.) Moench is of vital importance for many smallholder farmers and their families in various regions of West Africa (WA)
In order to accelerate the development of hybrid parental lines for WA and facilitate broadening the genetic pool of WA sorghum females, this study aims to understand the underlying genetics of pollen fertility restoration in key WA hybrid parents, to develop diagnostic and cost-efficient molecular markers for fertility restoration that can be used in applied WA hybrid breeding programs, and to assess the potential utility of those markers
We report here (1) the evaluation of several pollen fertility restoration traits and relationships among them, (2) the identification of quantitative trait loci (QTL) for fertility restoration in the A1 cytoplasmic male sterility (CMS) system in WA germplasm and (3) molecular markers developed for further use in WA sorghum hybrid breeding programs
Summary
Sorghum bicolor (L.) Moench is of vital importance for many smallholder farmers and their families in various regions of West Africa (WA). Average grain yields for farmers in this zone are of 1 t/ha. A major challenge with the initial hybrids was their poor and unacceptable grain quality (Toure and Scheuring 1982). Recent work in WA to develop both male and female parents using the widely cultivated sorghum Guinea-race germplasm has resulted in hybrids with suitable grain quality combined with yield superiorities over farmer’s local varieties under diverse productivity conditions (Rattunde et al 2013; Kante et al 2017; Weltzien et al 2018). The positive results with these hybrids under on-farm farmer-managed testing, and indications that farmers are starting to adopt these new hybrids (Smale et al 2014) justify establishing a full-scale hybrid breeding pipeline to produce hybrids that meet farmers’ demands in this major sorghum producing zone
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