Evolutionary history of tall fescue morphotypes inferred from molecular phylogenetics of the Lolium-Festucaspecies complex

Abstract

BackgroundThe agriculturally important pasture grass tall fescue (Festuca arundinacea Schreb. syn. Lolium arundinaceum (Schreb.) Darbysh.) is an outbreeding allohexaploid, that may be more accurately described as a species complex consisting of three major (Continental, Mediterranean and rhizomatous) morphotypes. Observation of hybrid infertility in some crossing combinations between morphotypes suggests the possibility of independent origins from different diploid progenitors. This study aims to clarify the evolutionary relationships between each tall fescue morphotype through phylogenetic analysis using two low-copy nuclear genes (encoding plastid acetyl-CoA carboxylase [Acc1] and centroradialis [CEN]), the nuclear ribosomal DNA internal transcribed spacer (rDNA ITS) and the chloroplast DNA (cpDNA) genome-located matK gene. Other taxa within the closely related Lolium-Festuca species complex were also included in the study, to increase understanding of evolutionary processes in a taxonomic group characterised by multiple inter-specific hybridisation events.ResultsPutative homoeologous sequences from both nuclear genes were obtained from each polyploid species and compared to counterparts from 15 diploid taxa. Phylogenetic reconstruction confirmed F. pratensis and F. arundinacea var. glaucescens as probable progenitors to Continental tall fescue, and these species are also likely to be ancestral to the rhizomatous morphotype. However, these two morphotypes are sufficiently distinct to be located in separate clades based on the ITS-derived data set. All four of the generated data sets suggest independent evolution of the Mediterranean and Continental morphotypes, with minimal affinity between cognate sequence haplotypes. No obvious candidate progenitor species for Mediterranean tall fescues were identified, and only two putative sub-genome-specific haplotypes were identified for this morphotype.ConclusionsThis study describes the first phylogenetic analysis of the Festuca genus to include representatives of each tall fescue morphotype, and to use low copy nuclear gene-derived sequences to identify putative progenitors of the polyploid species. The demonstration of distinct tall fescue lineages has implications for both taxonomy and molecular breeding strategies, and may facilitate the generation of morphotype and/or sub-genome-specific molecular markers.

Genotypic and Chemotypic Diversity of Neotyphodium Endophytes in Tall Fescue from Greece

“…FaTG-2 isolates and Mediterranean-type tall fescue have been reported previously (12,14,42,49), but this is the first tall fescue endophyte population study to observe this correlation on a larger scale. Our findings, together with tall fescue interfertility data and cladogenic segregation based on grass gene sequences (26,27,30,50), suggest that these tall fescue races are likely different species. Furthermore, the mixture of both tall fescue races identified in this study suggests that Greece, particularly Crete, is a region with overlapping Continental and Mediterranean tall fescue populations and may be a region of considerable biodiversity for both plant and fungal germplasms.…”

“…Both Continental and Mediterranean tall fescue germplasm has been collected from Sardinia, indicating that the natural distributions of the two races overlap in the Mediterranean basin (27). However, crosses between Mediterranean germplasm and the other tall fescue races result in F 1 hybrids with low fertility (30,56), and phylogenetic analyses indicate that Mediterranean tall fescue is genetically distinct from Continental and rhizomatous races, possibly from an independent polyploid origin (26,50).…”

Cytogenetic relationships within the Maghrebian clade of <em>Festuca</em> subgen. <em>Schedonorus</em> (Poaceae), using flow cytometry and FISH

“…Moreover, the molecular analyses of cpDNA and mtDNA sequences suggest that F. arundinacea subsp. atlantigena serves as maternal progenitor (Hand & al., 2010;Inda & al., 2014). Based on the above mentioned findings and our FISH and genome size results, we hypothesize that this decaploid originated from the merge of an unreduced gamete -egg cell-of F. arundinacea subsp.…”

“…This results in the dispersal of the clade mostly in NW Africa and SW Europe (Inda & al., 2014). The speciation of the members of this clade was presumably associated with interspecific hybridization and several steps of polyploidization (Borrill & al., 1977;Inda & al., 2014 (Borrill & al., 1977;Catalán & al., 2004;Hand & al., 2010;Inda & al., 2008Inda & al., , 2014.…”

Insights into Seasonal Dormancy of Perennial Herbaceous Forages

“…Scientists believe that molecular mechanism of SD comprises several endogenously regulated pathways, which provide the plant genotypes better persistence in dry environment allowing the meristem to remain alive [29] [30] [37]. Molecular studies from three different morphotypes of tall fescue: Continental, Mediterranean, and rhizomatous show that the Mediterranean morphotype is evolutionarily distinct with both the Continental and rhizomatous types, and has different levels of summer dormancy [42] which lead us to believe that summer dormancy variability present in tall fescue germplasms has breeding value.…”