Moctar Kante, Henry Frederick W. Rattunde, Baloua Nébié, Eva Weltzien, Bettina I. G. Haussmann, Willmar L. Leiser

Theoretical and Applied Genetics; November 2018, Volume 131, Issue 11, pp 2397–2412

Key message: Major A₁ cytoplasm fertility restoration loci, Rf ₂ and Rf ₅ , were found in the West African sorghum. A potential causative mutation for Rf ₂ was identified. KASP markers were validated on independent material.

Abstract

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 F_2:3 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 F_2:3 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.

See: https://link.springer.com/article/10.1007/s00122-018-3161-z

Fig. 3

Scan of QTL for male fertility reaction (A₁ cytoplasm) in sorghum POP_FL for chromosome SBI-02, and a high-resolution genome map showing the selected and sequenced PPR genes and their positions (indicated with arrows) among the SNPs within this region. The heatmap shows the R² among the different SNPs, delimiting three major linkage blocks, whereas the QTL peak falls within the middle one