Theor Appl Genet. 2025 Jun 09. 138(7): 141
Xiaoxia Yu,
Yupeng Feng,
Lulu Zhou,
Hongye Gao,
Hongbin Wang,
Yaru Chen,
Jiamai Liang,
Tianyu Meng,
Meng Li,
Yihan Yuan,
Junping Yu,
Hao Liu,
Aigen Fu,
Min Xu.
KEY MESSAGE: Two Restorer-of-fertility loci, Rf-m1 and Rf-m2, co-condition fertility restoration in ZD-type CMS soybean though complex genetic interactions in both gametophytic and sporophytic manners. In soybean (Glycine max), the genetic mechanisms underlying fertility restoration of ZD-type cytoplasmic male sterility (CMS-ZD) are not fully understood. By crossing the CMS-ZD line W931A with its strong restorer WR016, we elucidated the inheritance patterns of fertility restoration. We discovered that restoration by WR016 is primarily governed by two Restorer-of-fertility (Rf) loci, Rf-m1 and Rf-m2, located within ~ 220 kb on chromosome 16 and ~ 117 kb on chromosome 9, respectively. They exhibited two distinctive inheritance modes across genotype combinations. In plants with the genotype of -/rf-m1 -/rf-m2, such as F1 hybrids, gametophytic inheritance mode is predominant. In this case, Rf-m1 in haploid tissue is essential for pollen fertility restoration, and Rf-m2 is a modifier to enhance the effect. Correspondingly, plants displayed low pollen staining rates (sterile to ~ 50% depending on genotype). Conversely, in plants with one locus present as the homozygous Rf/Rf genotype, sporophytic inheritance mode is predominant. Plants exhibited high pollen staining rates (mostly > 80%), and the segregation of heterozygous loci in the next generation followed the Mendelian ratio. Notably, alleles rf-m1 and especially rf-m2 appear to suppress fertility. Further experiments revealed the best candidates of Rf-m1 and Rf-m2 are Glyma.16G139800 and Glyma.09G171200, encoding mitochondrial pentatricopeptide repeat (PPR) proteins GmPPR567 and GmPPR497. Haplotype analysis revealed that lines carrying homozygous Rf /Rf or rf /rf at both loci are rare among domesticated soybean germplasms. Using locus-specific markers and in silico haplotype screening, we identified two effective restorers and one maintainer line in elite germplasms, facilitating hybrid breeding in soybean.