Dynamic Changes in Genomes of Newly Developed Allopolyploid Grasses

Merging two genomes into a single organism via interspecific hybridization provides an opportunity to combine agriculturally important traits from biologically different species. Besides ancient allopolyploids such as cotton and wheat, interspecific hybridization might be employed in the targeted breeding programs to develop elite genotypes, which can be used instead of or in mixtures with parental species. This is a case of grass hybrid of fescues (Festuca L.) and ryegrasses (Lolium L.) called Festulolium combining high seed yield, rapid development and competitiveness from ryegrasses with abiotic stress tolerance from fescues. In most of the allopolyploids, exchanges between parental subgenomes via homoeologous recombination are highly supressed due to either high sequence divergence or establishment of regulatory mechanism permitting strict pairing of homologous chromosomes. However, this is not a case of Festulolium hybrids, where chromosomes of Festuca and Lolium pair freely and frequently recombine. In combination with the outcrossing status of these species, it results in the highly variable progeny with every single plant being unique. In the presentation, new insights into the structure, evolution and function of hybrid genomes including the shift in the genomic composition towards one of the parental genome, changes in allele-specific gene expression, identification of the chromosome pairing regulator and stabilization of genomic composition in advanced hybrid generations will be discussed.