Reciprocal allopolyploid grasses (Festuca x Lolium) display stable patterns of genome dominance

Allopolyploidization entailing the merger of two distinct genomes in a single hybrid organism, is an important process in plant evolution and a valuable tool in breeding programs. Newly established hybrids often experience massive genomic perturbations, including karyotype reshuffling and gene expression modifications. These phenomena may be asymmetric with respect to the two progenitors, with one of the parental genomes being dominant. Such genome dominance can manifest in several ways, including biased homoeolog gene expression and expression level dominance. Here we employed a k-mer-based approach to study gene expression in reciprocal Festuca pratensis Huds. x Lolium multiflorum Lam. allopolyploid grasses. Our study revealed significantly more genes where expression mimicked that of the Lolium parent compared with the Festuca parent. This genome dominance was heritable to successive generation and its direction was only slightly modified by environmental conditions and plant age. Our results suggest that Lolium genome dominance was at least partially caused by its more efficient trans-acting gene expression regulatory factors. Unraveling the mechanisms responsible for propagation of parent-specific traits in hybrid crops contributes to our understanding of allopolyploid genome evolution and opens a way to targeted breeding strategies.

Automated summary

Allopolyploidization, involving the merger of two distinct genomes, is essential in plant evolution and breeding programs. Research on Festuca pratensis Huds. x Lolium multiflorum Lam. grasses found that the dominance of Lolium genome in gene expression is heritable and minimally affected by environmental conditions and plant age. This dominance may be partly attributed to more efficient trans-acting gene expression regulatory factors in Lolium.