Centromeres in Arabidopsis thaliana evolve through frequent insertions and deletions of repeat units and increased rates of point mutations driven by homology-directed repair, a mutation spectrum that...

The European potato germplasm originated from a few founding genotypes, and its narrow genetic base has since been broadened through introgressions from wild relatives. We combined pedigree records an...

Meiotic recombination ensures accurate chromosome segregation and promotes genetic diversity by generating crossovers between homologous chromosomes. While essential in most sexually reproducing organisms, recombination is variably regulated and can be absent in some lineages, a condition known as achiasmy. However, obligate achiasmy in both sexes of a sexual species has not been previously documented. Here, we investigate the beak-sedge Rhynchospora tenuis, a holocentric plant with the lowest known chromosome number among flowering plants (n = 2) and inverted meiosis. Using chromosome-scale genome assemblies from nine accessions, molecular cytogenetics, immunocytochemistry, high-throughput single-gamete sequencing and whole-genome sequencing of controlled crosses, we show that R. tenuis undergoes obligate, genome-wide achiasmy in both male and female meiosis. Despite normal early meiotic axis formation, synapsis fails, crossovers are not detected cytologically or genetically, and univalents persist at metaphase I. Extensive haplotype-specific accumulation of transposable elements (TEs) generates segregation distortion (e.g. meiotic drive), favouring the transmission of larger, TE-rich chromosomes. Remarkably, sexual reproduction is retained with fertilisation producing viable seeds only when translocation-compatible gametes meet, indicating strong post-meiotic selection that eliminates incompatible homozygous combinations. As a result, all surviving offspring are genetically identical to the maternal genotype, effectively restoring heterozygosity each generation and mimicking clonal reproduction. We propose that the combined effects of recombination loss, low chromosome number, holocentricity, inverted meiosis, and selective transmission of longer chromosomes enable faithful segregation and clonal-like inheritance despite sexual reproduction. These findings challenge the boundary between sex and clonality, revealing a unique evolutionary strategy linking genome architecture, recombination loss, and transmission bias. ### Competing Interest Statement The authors have declared no competing interest.

A haplotype-resolved pan-genome of autotetraploid European potato founder lines shows high nucleotide diversity at remarkably low haplotype diversity, which is probably the result of hybridization eve...