The vast majority of commercial tall fescue cultivars are allohexaploid with 42 chromosomes (2n = 6x = 42). The genomic constitution of northern European and American hexaploid tall fescues consists of two groups of chromosomes originating from meadow fescue (L. pratensis [Huds.] Darbysh.), designated PP, and four groups (G1G1G2G2) from the tetraploid fescue Festuca arundinacea var. glaucescens Boiss (Humphreys et al., 1995; Sleper and West, 1996) (Note: For clarity, the nomenclature used in the original reference will be maintained in our discussion.) However, the genomic constitution of Mediterranean hexaploid tall fescues is potentially different and has not been determined. It is conceivable that other diploid [F. scariosa (Lag.) Asch. & Graebn.] and/or tetraploid (F. mairei St.-Yves) species contributed to the formation of these hexaploids. Taxonomy and polyploidy of tall fescue are reviewed thoroughly in Chapter 2. Tall fescue is closely related to the ryegrass (Lolium) genus and recently has been reclassified from Festuca arundinacea Schreb. to Lolium arundinaceum (Schreb.) Darbysh. (Darbyshire, 1993). However, evidence exists that may contradict this reclassification (Thomas et al., 1997) (see Chapter 27). In this chapter the two species names for tall fescue are used interchangeably. Lolium species have been used as a source of genes for improving traits of tall fescue, such as forage quality; ‘Kenhy' (Buckner et al., 1977) and ‘Johnstone' (Buckner et al., 1983) are examples of cultivars that were developed in this manner.
Tall fescue has a large genome, estimated at 5.27 to 5.83 × 106 kb (Seal, 1983), more than 12 times larger than the genome of rice (Oryza sativa L.). Tall fescue is a predominantly cross-pollinated species, with a high level of self-incompatibility. Individual plants are highly heterozygous, and normally each seed or plant in a population is genetically unique. A high level of genetic variation exists in tall fescue populations for several traits.
Although this chapter focuses on tall fescue, it should be noted that other Lolium and Festuca species are important forage and turf grasses. Meadow fescue (Festuca pratensis Huds.) is widely used in northern Europe for forage production, and several cultivars are available. Interest in meadow fescue for the northern United States has increased in recent years (Casler and van Santen, 2001). Festulolium refers to cultivars derived from crosses of Festuca and Lolium (Table 19-1) with the Lolium parent(s) having contributed the majority of the genome to many cultivars (Kopecký et al., 2006). Festulolium cultivars often are considered to be less persistent than tall fescue. Increased winter hardiness has become an important breeding objective in Festulolium and has led to the development of the cultivar Spring Green (Casler et al., 2002).
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Several cultivars of fine leaf fescues, including strong creeping red fescue (F. rubra L. ssp. rubra), sheep fescue [F. ovina L. ssp. hirtula (Hackel ex Travis) Wilkinson], hard fescue (F. brevipila Tracey), and chewings fescue [F. rubra ssp. fallax (Thiull.) Nyman] have been developed for turf use in the United States and other temperate climate areas.
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