Identification of Candidate Genes for Fertility Restoration in Cytoplasmic Male Sterile Perennial Ryegrass (Lolium perenne L.)

Perennial ryegrass (Lolium perenne L.) is widely used for forage production in both permanent and temporary grassland systems. To increase yields in perennial ryegrass, recent breeding efforts have been focused on strategies to more efficiently exploit heterosis by hybrid breeding. Cytoplasmic male sterility (CMS) is a widely applied mechanism to control pollination for commercial hybrid seed production and although CMS systems have been identified in perennial ryegrass, they are yet to be fully characterised.

We have developed a bioinformatics pipeline for efficient identification of candidate restorer of fertility (Rf) genes for CMS. From a high-quality draft of the perennial ryegrass genome, 373 pentatricopeptide repeat (PPR) genes were identified and classified, further identifying 25 restorer of fertility-like PPR (RFL) genes through a combination of orthologous clustering and comparison to known Rf genes. These RFL genes were further investigated by phylogenetic analyses, identifying three groups of perennial ryegrass RFLs that likely represent conserved genomic regions of active RFL generation. To validate this hypothesis, a population of 576 plants segregating for fertility restoration has been genotyped by sequencing. This will allow us to functionally associate the candidate gene regions to the restoration phenotype.

Our work will allow the development of functional markers for PPR-Rf genes facilitating the use of CMS as an efficient tool to control pollination for hybrid crop production.

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