Genome constitution and evolution in Lolium × Festuca hybrid cultivars (Festulolium)

Abstract

Festulolium hybrids are being increasingly used worldwide as forage grasses. This is due to their superior agronomic characteristics, which combine yield performance of ryegrasses (Lolium multiflorum and L. perenne) and tolerance against abiotic stress of fescues (Festuca pratensis, F. arundinacea and F. arundinacea var. glaucescens). Despite the widespread use, only fragmentary information exists on their genomic constitution. We used genomic in situ hybridization (GISH) to analyze genomic constitution of over 600 plants from almost all commercially available cultivars of Festulolium. Our results revealed a surprisingly large range of variation in the proportions of parental genomes and in the extent of intergenomic recombination. Using fluorescence in situ hybridization (FISH) with probes for ribosomal DNA, we assessed the frequency of recombination and elimination of particular chromosomes and chromosome groups in three contrasting Festulolium cultivars. This study provides novel information that will aid in understanding the relationship between a genetic make-up and the phenotype of Festulolium hybrids. Our results indicate that GISH might be a useful tool to aid in Festulolium breeding and provide data for a more detailed description of registered cultivars.

An Increasing Need for Productive and Stress Resilient Festulolium Amphiploids: What Can Be Learnt from the Stable Genomic Composition of Festuca pratensis subsp. apennina (De Not.) Hegi?

“…One example where Festulolium amphiploids were required was reported recently where in order to assist efficient ruminant nutrition, the maintenance of complete and balanced Lolium and Festuca genome complements was seen as an essential prerequisite in order to combat plant-mediated proteolysis within ingested fodder (Humphreys et al, 2014). Unfortunately, for such a breeding approach the outcome reported from all cytogenetic studies that involved amphiploid Festulolium varieties was that unbalanced genome complements had arisen over generations of seed multiplication which had resulted in a shift toward a Lolium genome, accompanied by loss of Festuca chromosomes (Canter et al, 1999;Kopecký et al, 2006;Zwierzykowski et al, 2006). This outcome was aided by frequent homoeologous pairing and recombination between Festuca and Lolium chromosomes and possibly by the self-incompatibility of the species involved (Kopecký et al, 2008a(Kopecký et al, , 2010Harper et al, 2011).…”

Cytogenetics of Festulolium (<i>Festuca </i>×<i> Lolium</i> hybrids)

“…'Kemal', 'Duo' and 'Matrix'), GISH failed to detect any Festuca chromatin and only a few segments were found in several plants of Festulolium cv. 'Bečva' and 'Lofa' (Kopecký et al, 2005a(Kopecký et al, , 2006. As these cultivars display morphological characters intermediate to the parents, it may well be that the intergenomic introgressions in these cultivars are below the resolution limit of GISH.…”

“…Our more recent studies (Kopecký et al, 2005a(Kopecký et al, , 2006) revealed larger differences in the proportions of parental chromatin present in various types of Festulolium cultivars. While cultivars originating from the L. multiflorum !…”

“…Whereas the original protocols for GISH and FISH were time-consuming and laborious (Schwarzacher and Heslop-Harrison, 2000), a simplified GISH protocol developed by MasoudiNejad et al (2002) is suitable for large-scale studies. Kopecký et al (2005aKopecký et al ( , 2006 demonstrated its utility in Festuca ! Lolium hybrids.…”

“…However, duplications or other structural differences between the Festuca and Lolium genomes could potentially account for quadrivalent formation in F1. Using GISH and FISH on mitotic chromosome spreads, Kopecký et al (2006) demonstrated recombination between non-homoeologous chromosomes in six out of 28 euploid individuals of L. multiflorum ! F. pratensis cultivars.…”