Genetic and physical analysis of a single Festuca pratensis chromosome segment substitution in Lolium perenne

The economic and ecological importance of forest trees, as well as their unique biological features, has recently raised the level of interest in studies on their genomes, including sequencing of the entire poplar genome. However, cytogenetic studies have not moved in parallel with developments in genomics. This is especially true for hardwood species characterized by small genomes and relatively high numbers of small chromosomes. Molecular cytogenetic studies have mainly been focused on coniferous species, owing to the larger size of their chromosomes, and have been applied exclusively for chromosome identification and comparative karyotyping in an attempt to understand genome evolution and phylogenetic relationships. In this context, rRNA genes physical mapped by FISH reveal particularly useful chromosomal landmarks with variable distribution patterns between species. Here we present a contribution of DNA markers used for chromosome analysis, which already allowed a deeper characterization and understanding of the processes underlying genome diversity of forest trees. The use of advanced cytogenetic techniques and other potential important methods for genome analysis of forest trees is also discussed.

Section: Future Prospectsmentioning

confidence: 99%

Molecular cytogenetics of forest trees

Ribeiro

Barão

Viegas³

et al. 2008

“…By analyzing meiosis in triploid L. multiflorum plants, Thomas (1995) determined chromosome 2 to have fewer partner exchanges than other chromosomes. Armstead et al (2001) explained different recombination frequencies of two different chromosomes of F. pratensis substituted into diploid L. perenne by differences in chromosome affinity, different innate recombination frequencies, by the sampling effect, or environmental and/or genetic factors.…”

Section: Molecular Cytogeneticsmentioning

confidence: 99%

“…Hotspots of recombination were described in diploid L. perenne ! F. pratensis (Armstead et al, 2001) and in triploid L. multiflorum ! F. pratensis (Zwierzykowski et al, 1999a) hybrids.…”

Section: Molecular Cytogeneticsmentioning

confidence: 99%

“…The availability of a full set of single chromosome substitution lines would permit comprehensive studies of the genetic control of desirable agronomic characters and the localization of the genes on genetic and physical maps. Such a linkage between physical and genetic maps in grasses has been demonstrated by Armstead et al (2001), who developed a powerful approach for studying genetic recombination and high resolution mapping for dissection of specific characters. In their study they make use of two monosomic substitutions of F. pratensis chromosomes into diploid L. perenne and their recombinant derivatives, and demonstrate that the relationships between physical and genetic distances vary along the length of a chromosome arm and the presence of recombination hot-spots.…”

Section: Analyses Of Individual Chromosomesmentioning

confidence: 99%

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Cytogenetics of Festulolium (Festuca × Lolium hybrids)

Kopecký

Lukaszewski

Doležel

2008

Grasses are the most important and widely cultivated crops. Among them, ryegrasses (Lolium spp.) and fescues (Festuca spp.) provide high quality fodder for livestock, are used for turf and amenity purposes, and play a fundamental role in environment protection. Species from the two genera display complementary agronomic characteristics and are often grown in mixtures. Breeding efforts to combine desired features in single entities culminated with the production of Festuca × Lolium hybrids. The so called Festuloliums enjoy a considerable commercial success with numerous cultivars registered all over the world. They are also very intriguing from a strictly cytogenetic point of view as the parental chromosomes recombine freely in hybrids. Until a decade ago this phenomenon was only known in general quantitative terms. The introduction of molecular cytogenetic tools such as FISH and GISH permitted detailed studies of intergeneric chromosome recombination and karyotyping of Festulolium cultivars. These tools were also invaluable in revealing the origin of polyploid fescues, and facilitated the development of chromosome substitution and introgression lines and physical mapping of traits of interest. Further progress in this area will require the development of a larger set of cytogenetic markers and high-resolution cytogenetic maps. It is expected that the Lolium – Festuca complex will continue providing opportunities for breeding superior grass cultivars and the complex will remain an attractive platform for fundamental research of the early steps of hybrid speciation and interaction of parental genomes, as well as the processes of chromosome pairing, elimination and recombination.

“…GISH allows us to see introgressed chromatin, and to use this convenience of the L-F system for the purpose of physical mapping (Armstead et al, 2001;King et al, 2002b). A single chromosome of Fp is introgressed into Lp and substitutes for its Lp homolog, giving a plant 13 Lp plus 1 Fp chromosome (i.e.…”

Section: Mapping a Single Chromosomementioning

confidence: 99%

A decade of “chromosome painting” in Lolium and Festuca

Pašakinskiené

Jones²

2005

GISH has been a particularly useful technique for studying the Lolium-Festuca species complex of forage grasses. The reason for this utility is two-fold: (i) the complex is unique amongst crop plants in which fertile hybrids, and backcross progenies, can be produced which recombine genomes and promiscuously exchange their genes through homoeologous recombination; (ii) dispersed repetitive DNAs differ between species, and this allows tracking of the identity of chromosomes and chromosome segments. This tracking property has enabled several fruitful lines of research to produce a harvest of new information for both fundamental and practical purposes. We review this first decade of GISH (genomic in situ hybridization) in Lolium-Festuca, and discuss and summarize the achievements which have accrued.