Cytogenetics and Plant Bleeding Cytogenet Genome Res 120:370–383 (2008) DOI: 10.1159/000121086 Cytogenetics of Festulolium ( Festuca ! Lolium hybrids) a b a D. Kopecký A.J. Lukaszewski J. Doležel a Laboratory of Molecular Cytogenetics and Cytometry, Institute of Experimental Botany, Olomouc b (Czech Republic); Department of Botany and Plant Sciences, University of California, Riverside, CA (USA) Accepted in revised form for publication by M. Schmid, 29 September 2007. Abstract. Grasses are the most important and widely cul- ted detailed studies of intergeneric chromosome recombi- tivated crops. Among them, ryegrasses (Lolium spp.) and nation and karyotyping of Festulolium cultivars. These fescues ( Festuca spp.) provide high quality fodder for live- tools were also invaluable in revealing the origin of poly- stock, are used for turf and amenity purposes, and play a ploid fescues, and facilitated the development of chromo- fundamental role in environment protection. Species from some substitution and introgression lines and physical map- the two genera display complementary agronomic charac- ping of traits of interest. Further progress in this area will teristics and are often grown in mixtures. Breeding efforts require the development of a larger set of cytogenetic mark- to combine desired features in single entities culminated ers and high-resolution cytogenetic maps. It is expected that with the production of Festuca ! Lolium hybrids. The so the Lolium – Festuca complex will continue providing op- called Festuloliums enjoy a considerable commercial suc- portunities for breeding superior grass cultivars and the cess with numerous cultivars registered all over the world. complex will remain an attractive platform for fundamental They are also very intriguing from a strictly cytogenetic research of the early steps of hybrid speciation and interac- point of view as the parental chromosomes recombine free- tion of parental genomes, as well as the processes of chro- ly in hybrids. Until a decade ago this phenomenon was only mosome pairing, elimination and recombination. known in general quantitative terms. The introduction of Copyright © 2008 S. Karger AG, Basel molecular cytogenetic tools such as FISH and GISH permit- Open landscape is usually covered by grasses, and by nity purposes, in sport and urban contexts where their aes- learning that their color is green, humans are aware of their thetic value cannot be overestimated. Last but not least, existence since early childhood. Not many people know, grasses play a fundamental role in soil conservation and en- however, that grasses are one of the most important culti- vironment protection (Wang and Ge, 2006). vated plants on Earth, with the total area of grassland esti- Due to their value, grasses are often preferred over other mated to be twice that of cropland (Jauhar, 1993). There are crops. For example, in spite of environmental conditions many important uses of grasses: they are widely used for amenable to production of cereals, corn, sugar beet and po- pasture and play a key role in providing high quality fodder tato, nearly 40% of the total acreage in the Czech Republic for livestock. Some grass species are used for turf and ame- is covered by grassland (Černoch et al., 2003) while in the United Kingdom, 75% of the total agricultural land is de- voted to grass production (Thomas et al., 2003). Out of many grass species, ryegrasses ( Lolium spp.) and fescues This work was supported in part by the Czech Science Foundation (grant award ( Festuca spp.) predominate. In Europe, 23% of the grassland 521/07/P479). area (52 million ha) is covered by just two ryegrass species, Request reprints from D. Kopecký Lolium multiflorum Lam. and Lolium perenne L. The an- Institute of Experimental Botany, Sokolovská 6 nual production of ryegrass seed in Europe exceeds 45,000 CZ–772 00 Olomouc (Czech Republic) telephone: +420 585 205 857; fax: +420 585 205 853 tons with the value of 160 million € (Lübberstedt et al., e-mail: [email protected] 2003). Fax +41 61 306 12 34 © 2008 S. Karger AG, Basel Accessible online at: E-Mail [email protected] 1424–8581/08/1204–0370$24.50/0 www.karger.com/cgr www.karger.com Table 1. Chromosome number and DNA content of some ryegrass and fescue species Species Common name Chromosome number/genome 1C DNA contenta pg DNA Referenceb Lolium perenne Perennial ryegrass 2n = 2x = 14 2.08 1 Lolium multiflorum Italian ryegrass 2n = 2x = 14 4.10 2 Festuca pratensis Meadow fescue 2n = 2x = 14; AA 2.20 3 Festuca scariosa 2n = 2x = 14; BB 2.68 4 Festuca glaucescensc 2n = 4x = 28; BBCCe 4.28 5 Festuca mairei 2n = 4x = 28; BBDDe 3.95 5 Festuca arundinacea Tall fescue 2n = 6x = 42; AABBCCe 6.05 6 Festuca gigantead Giant fescue 2n = 8x = 56; AAXXYYZZe 7.23 5 a DNA content of one non-replicated chromosome complement (holoploid genome size). For the terminology on ge- nome size see Greilhuber et al. (2005). b Key to references: 1 = Evans et al. (1972), 2 = Schifino and Winge (1985), 3 = Olszewska and Osiecka (1982), 4 = Harper et al. (2004), 5 = Seal AG. (pers. comm. 1979 in: Bennett et al. 1982), 6 = Ceccarelli et al. (1992). c Sometimes referred as F. arundinacea var. glaucescens and F. arundinacea var. fenas. d Hexaploid cytotypes were reported by some authors (i.e. Morgan et al., 1988). e Genomic constitution of allopolyploid species has only been considered by Bowman and Thomas (1976), Thomas et al. (1997) and Harper et al. (2004); further analyses are needed to prove it. Whereas the genus Lolium consists of eight species, the Chromosome number and morphology genus Festuca is diverse and comprises almost 500 species (Clayton and Renvoize, 1986). The genus has been subdi- While all eight species comprising genus Lolium are dip- vided into six sections: Ovinae , Bovinae , Sub-bulbosae , loid (2n = 2x = 14), ploidy levels vary greatly in the genus Variae , Scariosae and Montanae (Hackel, 1882). In a recent Festuca ( Table 1 ), ranging from diploid (i.e. F. pratensis ; classification, Clayton and Renvoize (1986) divide the genus 2n = 2x = 14), through tetraploid (i.e. F. arundinacea var. Festuca into nine subgenera: Hesperochloa , Xanthochloa , glaucescens (= F. glaucescens ); 2n = 4x = 28), hexaploid (i.e. Drymanthele , Schedonorus , Subulatae , Subuliflorae , Obtu- F. arundinacea var. genuina (= F. arundinacea ); 2n = 6x = sae , Festuca and Helleria . Of this plethora of species mainly 42), octoploid (i.e. F. arundinacea var . atlantigena forma F. pratensis and F. arundinacea , which belong to the Bovinae pseudo-mairei Lit. and Maire; 2n = 8x = 56), decaploid (i.e. section (subgenus Schedonorus ), are used in agricultural F. arundinacea var . letourneuxiana St. Yves; 2n = 10x = 70) production. to dodecaploid (i.e. F. summilusitana ; 2n = 12x = 84). Only P e r e n n i a l r y e g r a s s ( L. perenne ) is the single most impor- a few studies dealt with the origin of polyploids (i.e. Hum- tant grass species and is used for grazing, hay and turf. This phreys et al., 1995). Nevertheless, all polyploid Festuca spe- species is native to Central and South Europe, North-West cies described herein are believed to be allopolyploid ( Ta- Africa and South-West Asia, and comprises annual and bi- ble 1 ). Based on the widespread occurrence of polyploidy, ennial types. It is widespread in most temperate regions, Malik and Thomas (1966) considered Festuca more ancient including Australia and New Zealand, where it was intro- than Lolium . duced by the first settlers. Italian ryegrass ( L. multiflorum ) Malik and Thomas (1966) were among the first to is a close relative of perennial ryegrass with similar geo- karyotype Festuca and Lolium . In ryegrasses (including graphic distribution, and is widely used as fodder plant for L. perenne and L. multiflorum ), they identified three pairs hay and grazing. Meadow fescue (Festuca pratensis Huds.) of submedian chromosomes with secondary constrictions is a perennial grass of Europe and South-West Asia, which (sites of the nucleolar organizing regions, NORs), one large has been introduced into North America. Tall fescue ( Fes- median pair and three smaller pairs of submedian chro- tuca arundinacea Schreb.) is a perennial widely distributed mosomes. More recently, Thomas et al. (1996) confirmed over Europe, North-West Africa and temperate Asia and the presence of NORs on three pairs of L. multiflorum was also introduced into North America. The present re- chromosomes after fluorescence in situ hybridization view focuses on cytogenetics of grass species which are used (FISH) with the 45S rDNA probe. They also detected an in breeding of improved cultivars, including interspecific additional seventh site of 45S rDNA in L. perenne . This and intergeneric hybrids, and the main attention is given to site co-localized with a Giemsa band located proximally Festuca ! Lolium hybrids. Only scant attention is given to on the long arm of chromosome 5 (Thomas, 1981; Thomas other species belonging to both genera. et al., 1996). Interestingly, this seventh site of 45S rDNA was undetectable in our analyses (Kopecký et al., unpub- lished). Cytogenet Genome Res 120:370–383 (2008) 371 In contrast to the similarity of karyotypes in various spe- in F. arundinacea and speculated on a role of L. multiflorum cies of Lolium , Festuca species display larger karyotypic in the evolution of F. arundinacea after allopolyploidization variation. By analyzing karyotypes in 12 fescue species after and diversification from its progenitors. orcein staining, Malik and Thomas (1966) identified four Other phylogeny studies in polyploid species were based pairs of chromosomes with secondary constrictions in F. on FISH with probes for rDNA. Theoretically, an autotetra- pratensis and six pairs of such chromosomes in F. glauces- ploid should have two pairs of chromosomes with the same cens . However, lower numbers of NORs were detected by chromosomal distribution of rDNA loci as its diploid par- silver staining (Carnide et al., 1986) and by FISH with 45S ent.