A genetic linkage map has been constructed for meadow fescue ( Festuca pratensis Huds.) (2n=2 x=14) using a full-sib family of a cross between a genotype from a Norwegian population (HF2) and a genotype from a Yugoslavian cultivar (B14). The two-way pseudo-testcross procedure has been used to develop separate maps for each parent, as well as a combined map. A total number of 550 loci have been mapped using homologous and heterologous RFLPs, AFLPs, isozymes and SSRs. The combined map consists of 466 markers, has a total length of 658.8 cM with an average marker density of 1.4 cM/marker. A high degree of orthology and colinearity was observed between meadow fescue and the Triticeae genome(s) for all linkage groups, and the individual linkage groups were designated 1F-7F in accordance with the orthologous Triticeae chromosomes. As expected, the meadow fescue linkage groups were highly orthologous and co-linear with Lolium, and with oat, maize and sorghum, generally in the same manner as the Triticeae chromosomes. It was shown that the evolutionary 4AL/5AL translocation, which characterises some of the Triticeae species, is not present in the meadow fescue genome. A putative insertion of a segment orthologous to Triticeae 2 at the top of 6F, similar to the rearrangement found in the wheat B and the rye R genome, was also observed. In addition, chromosome 4F is completely orthologous to rice chromosome 3 in contrast to the Triticeae where this rice chromosome is distributed over homoeologous group 4 and 5 chromosomes. The meadow fescue genome thus has a more ancestral configuration than any of the Triticeae genomes. The extended meadow fescue map reported here provides the opportunity for beneficial cross-species transfer of genetic knowledge, particularly from the complete genome sequence of rice.

A linkage map of meadow fescue (Festuca pratensis Huds.) and comparative mapping with other Poaceae species

Three widely used cultivars of each of the species Festuca pratensis Huds, Lolium perenne L, and Dactylis glomerata L were investigated by means of randomly amplified polymorphic DNA (RAPD) markers and vegetative growth traits in order to investigate genetic variability within each cultivar and to compare the level of diversity among cultivars and species RAPD markers allowed a clear separation of the three species Genetic variability based on RAPD markers was considerably lower for F pratensis cultivars than for L perenne and D glomerata cultivars which showed similar levels of variability The proportion of variability due to variation within cultivars, determined by an analysis of molecular variance, was lower in F pratensis (646%) than in L perenne (824%) and D glomerata (851%) A comparison of F pratensis and L perenne, based on vegetative growth traits, confirmed the differences in genetic variability within cultivars F pratensis showed lower coefficients of genetic variation for eight of ten traits when compared to L perenne This study demonstrates considerable differences in genetic variability which may have consequences for the adaptability and persistency of individual cultivars

Genetic variability of forage grass cultivars: A comparison of Festuca pratensis Huds., Lolium perenne L., and Dactylis glomerata L.

Tall fescue (Festuca arundinacea Schreb.) is commonly grown as forage and turf grass in the temperate regions of the world. Here, we report the first genetic map of tall fescue constructed with PCR-based markers. A combination of amplified fragment length polymorphisms (AFLPs) and expressed sequence tag-simple sequence repeats (EST-SSRs) of both tall fescue and those conserved in grass species was used for map construction. Genomic SSRs developed from Festuca x Lolium hybrids were also mapped. Two parental maps were initially constructed using a two-way pseudo-testcross mapping strategy. The female (HD28-56) map included 558 loci placed in 22 linkage groups (LGs) and covered 2,013 cM of the genome. In the male (R43-64) map, 579 loci were grouped in 22 LGs with a total map length of 1,722 cM. The marker density in the two maps varied from 3.61 cM (female parent) to 2.97 (male parent) cM per marker. These differences in map length indicated a reduced level of recombination in the male parent. Markers that revealed polymorphism within both parents and showed 3:1 segregation ratios were used as bridging loci to integrate the two parental maps as a bi-parental consensus. The integrated map covers 1,841 cM on 17 LGs, with an average of 54 loci per LG, and has an average marker density of 2.0 cM per marker. Homoeologous relationships among linkage groups of six of the seven predicted homeologous groups were identified. Three small groups from the HD28-56 map and four from the R43-64 map are yet to be integrated. Homoeologues of four of those groups were detected. Except for a few gaps, markers are well distributed throughout the genome. Clustering of those markers showing significant segregation distortion (23% of total) was observed in four of the LGs of the integrated map.

An SSR- and AFLP-based genetic linkage map of tall fescue (Festuca arundinacea Schreb.).

Referee: Dr. Ian Ray, Plant Breeding and Genetics, Department of Agronomy & Horticulture, New Mexico State University, MSC 3Q, P.O. Box 30003, Las Cruces, NM 88003-8003 Forage and turf grasses are the backbone of sustainable agriculture and contribute extensively to the world economy. They play a major role in providing high quality and economical meat, milk, and fiber products and are important in soil conservation, environmental protection, and outdoor recreation. Conventional breeding contributed substantially to the genetic improvement of forage and turf grasses in the last century. The relatively new developments in genetic manipulation of these species open up opportunities for incorporating cellular and molecular techniques into grass improvement programs. For some commonly used forage and turf species, significant advances have been achieved in the following areas: (1) establishment of a tissue culture basis for the efficient regeneration of fertile and genetically stable plants, (2) generation of...

Forage and Turf Grass Biotechnology

Restriction fragment length polymorphism was assessed in wild and cultivated populations of Hevea brasiliensis using random probes from an Hevea nuclear library. One-hundred-and-sixty-four individuals were surveyed, and the results discussed in the light of previous work performed on isozyme variation. Both studies show that germplasm collections have led to an effective enrichment of the genetic resources available for Hevea breeding, and that cultivated clones have conserved a relatively high level of polymorphism, despite their narrow genetic base and their high level of inbreeding. An equivalent level of polymorphism is revealed by random nuclear probes and isozymes. However, the genetic structuring of the diversity appears more striking using RFLP markers. Wild accessions can be divided into three genetic groups according to their geographical origin. The present results are an essential guide to the incorporation of wild material in breeding schemes.

Genetic diversity among wild and cultivated populations of Hevea brasiliensis assessed by nuclear RFLP analysis.

Restriction fragment length polymorphisms (RFLPs) have several advantages over conventional genetic markers and as a result have received increased attention from plant breeders and geneticists. Th...

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A survey of restriction fragment length polymorphisms in tall fescue and its relatives

Intergeneric hybridizations have been made between species of Lolium and Festuca. It has been demon- strated, largely through conventional cytogenetic analysis, that the genomes of the two genera are related, however, much information is lacking on exactly how closely related the genomes are between the two species. We applied genomic in situ hybridization (GISH) techniques to the F1 hybrids of tetraploid Festuca mairei with a genomic consti- tution of M1M1M2M2 and diploid Lolium perenne with a genomic constitution of LL. It was shown in the triploid hy- brids (LM1M2) that the chromosomes of M1 and M2 from F. mairei could pair with each other, and it was further discovered that L chromosomes of L. perenne paired with M1 and M2 chromosomes. Our results showed that meiocytes of Lolium-Festuca are amenable to GISH analysis, and provided direct evidence for the hypothesis that the chromosomes of Lolium and Festuca may be genetically equivalent and that reciprocal mixing of the genomes may be possible. Resume : Des hybrides intergeneriques entre des especes appartenant aux genres Lolium et Festuca ont ete produits. Il a ete demontre, principalement au moyen d'analyses cytogenetiques conventionnelles, que les genomes des deux genres sont apparentes. Cependant, il manque encore beaucoup d'information sur le degre veritable de parente des genomes de ces deux especes. Les auteurs ont employe l'hybridation genomique in situ (GISH) sur des hybrides F1 provenant du croisement entre un Festuca mairei tetraploide (formule genomique M1M1M2M2 )e t unLolium perenne diploide (for- mule genomique LL). Il a ete montre, dans les hybrides F1 triploides (LM1M2), que les chromosomes M1 et M2 du F. mairei s'appariaient les uns avec les autres et il a ete observe que les chromosomes L du L. perenne s'appariaient egalement avec les chromosomes M1 et M2. Ces resultats ont montre que les meiocytes de l'hybride Lolium-Festuca se pretent a l'analyse GISH et ont procure des evidences a l'effet que les chromosomes des genres Lolium et Festuca pourraient etre genetiquement equivalents et que le brassage reciproque des genomes pourrait etre possible. Mots cles : Lolium, Festuca, hybridation in situ, meiose. (Traduit par la Redaction) Cao et al. 403

Genomic in situ hybridization (GISH) reveals high chromosome pairing affinity between Lolium perenne and Festuca mairei.

A model is constructed for chromosome association at meiotic metaphase I in tetraploids. Probabilities are estimated for each pachytene configuration and for subsequent formation of at least one chiasma in each combination of chromosome arms. Long and short arms can differ but are related through an effective arm ratio so as to maintain the same pattern of genomic affinity for both arms. No other a priori assumptions are made about the pattern of genomic affinity, but the same basic assumptions are made as in our preceding model for triploids. The model is statistically overparameterized and therefore has multiple solutions whose range can be found through repeated optimization from different starting points. In some cases the same expected meiotic analysis can arise from quite different genomic structures, which therefore cannot be distinguished on the basis of unmarked chromosomes. Solutions to the model are conveniently expressed in terms of the proportion of metaphase I association due to each pairwis...

A model of meiotic chromosome association in triploids

This study considered the effects of three continuous growth temperatures (14, 21, and 28 °C) on apparent genomic structure, apparent chromosome arm ratio, pollen abortion, and meiotic nonreduction...

David A. Sleper

Papers

A survey of restriction fragment length polymorphisms in tall fescue and its relatives

Genomic in situ hybridization (GISH) reveals high chromosome pairing affinity between Lolium perenne and Festuca mairei.

A model of meiotic chromosome association in triploids

Effect of temperature on meiosis and fertility in Festuca mairei × Festuca arundinacea var. glaucescens