Uncovering the mechanism of female restitution in sugarcane hybrids.
basic_science · Level V
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- Record sourced from PubMed, PMID 42557324.
- Also identified by DOI 10.1038/s41586-026-10863-3.
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Abstract
Variations of meiosis, which normally halve genetic complements prior to fertilization, can have profound consequences. For example, whole-genome duplications (polyploidy) have shaped the evolution and diversification of most angiosperm lineages. The century-long success of sugarcane interspecific hybrids has been attributed to unusual female restitution-an unreduced maternal gamete fusing with a normal haploid paternal gamete<sup>1,2</sup>. Here we generated haplotype-resolved genomes of octoploid Saccharum officinarum LA Purple and decaploid Saccharum spontaneum US56-14-4. Eight F<sub>1</sub> hybrids between these species exhibited 2:1 maternal to paternal genomic ratios, with 2 assemblies revealing canonical haploid sets of approximately 40 paternal and approximately 80 maternal chromosomes. The maternal chromosomes comprise 40 pairs of duplicated, partially recombined sister chromatids that retain around 62.5% of maternal genetic diversity, characteristic of second division restitution. Using single-molecule long-read sequencing and a novel algorithm that is broadly applicable to polyploid genomes, we identified two classes of recombination breakpoints, including a previously unrecognized configuration supported by both recombinant and non-recombinant reads, across all hybrids and diagnostic of second division restitution. These findings resolve a century-old cytological debate, add new insights into meiotic variations, and offer a genomic approach to accelerate genetic gain in this globally critical sugar and bioenergy crop.