Cytogenetic insights into Festulolium

Climate change calls for new methods and plant materials to breed crops adapted to new environmental conditions. Sustainable forage and amenity grass production during periods of severe drought and heat waves during summer, and unequal distribution of precipitation over the year will require drought-tolerant genotypes. However, high-yielding ryegrasses (Lolium spp.), which are the most commonly used grass species, suffer during abiotic stresses. Introgression of drought and heat tolerance from closely related fescues (Festuca spp.) offers an opportunity to develop superior hybrid cultivars to mitigate the negative impact of climate change. Intergeneric cross-hybridization and the development of Festulolium (Festuca x Lolium) hybrids was initiated 100 years ago and resulted in registration of almost one hundred cultivars. For a long time, their genome composition was not known and was debated by breeders and geneticists. In the last three decades, molecular cytogenetic and genomic approaches have enabled their detailed characterization. These studies revealed a gradual replacement of Festuca chromosomes by those of Lolium in consecutive generations leading to an almost complete elimination of Festuca chromatin in the introgression forms. On the other hand, amphiploid cultivars seem to be more stable with the optimal proportions of the Lolium to Festuca genomes at about 2:1. In this mini review, we discuss recent advances in the analysis of the genome composition of Festulolium hybrids with a specific focus on genome (in)stability.