Tall fescue is native to much of Europe, the Mediterranean region including North Africa, and parts of the Middle East, central Asia, and Siberia. Tall fescue germplasm is classified by taxonomists into five botanical varieties, [tetraploid glaucescens Boiss; hexaploid genuina Schreb.; octoploid atlantigena (St.-Yves) Auquier; decaploid cirtensis (St-Yves) J. Gamisans; letourneuxiana (St.-Yves) Torrecilla & Catalán]. Breeders classify it into two major germplasm pools, these being continental and Mediterranean, as well as two functional groups, forage (see Chapter 1) and turf (see Chapter 26) types.
Continental germplasm is characterized by populations and cultivars, such as ‘Kentucky 31' (KY-31), which are relatively winter hardy, summer active (i.e., have the potential to produce substantial amounts of forage from late spring to early autumn) and often have wide leaves. Continental types can be capable of supplying forage nearly year-round, either through active or stockpiled growth, in regions where they are well adapted, such as the lower Midwest and upper South of the United States. As a rule, Mediterranean germplasm is less winter hardy (Burner et al., 1988), more winter active (i.e., has the potential to produce substantial amounts of forage from mid-autumn to early spring), and often has narrower leaves than continental tall fescue. We have observed very stiff, wiry leaves during spring and summer growth in a number of tall fescue accessions originating from North Africa, although these may not all be hexaploids. At least one decaploid forage cultivar (Maris Kasba) has been developed for forage use on the basis of Moroccan germplasm of F. arundinacea.
Mediterranean germplasm, such as the cultivars Melik, Flecha, Fraydo, and Resolute, sometimes displays a high degree of summer dormancy, with plants ceasing growth and sometimes becoming senescent during this time, and then resuming growth in autumn. Summer dormancy has been found to confer increased persistence to tall fescue in dry environments such as western Texas (Malinowski et al., 2005b) and southern New South Wales, Australia (Hayes et al., 2006). The reader is referred to Volaire and Norton (2006) for a recent review of summer dormancy in cool season grasses. Continental tall fescue has been observed to be more resistant to ozone pollution (Johnston et al., 1983) and net blotch, incited by Drechslera dictyoides (Drechs.) Shoemaker (Burner et al., 1988), whereas Mediterranean germplasm is a potential source of resistance to Cochliobolus sativus (Ito and Kurib.), the causal agent of spot blotch (Linscombe et al., 1989) and crown rust, caused by Puccinia coronata Corda (Wofford and Watson, 1982).
Continental germplasm originates from central and northern Europe eastward through a portion of Asia and is the source germplasm for the vast majority of tall fescue in North America, whereas Mediterranean germplasm traces to southern Europe, the Middle East, and North Africa. Rhizomatous tall fescue, originating from northwest Spain and Portugal (Borrill et al., 1971), sometimes is considered a third germplasm pool. Plants of continental germplasm can form rhizomes (Jernstedt and Bouton, 1985; Bouton et al., 1989; Bouton et al., 1992). However, rhizomes are reported to be longer and more prevalent in rhizomatous germplasm originating from the Iberian peninsula (de Bruijn, 2004). Rhizomatous germplasm does not appear to be as winter hardy as continental types (Diesburg and Carlson, 1983).
Turf-type germplasm is characterized by finer leaves, an upright, short growth stature with generally darker color, and dense tillering. Turf types typically are continental germplasm that has evolved or been selected under turf management conditions, although the turf cultivars Torpedo (Stewart, 1997) and Labarinth were derived from rhizomatous germplasm of the Iberian peninsula.
A genetic barrier can exist between Mediterranean and continental types, particularly when crossing germplasm originating from North Africa with that from central or northern Europe, with meiotic irregularities being common among progeny of such crosses, despite uniform ploidy level of parents (Malik, 1967; Evans et al., 1973; Hunt and Sleper, 1981). Likewise, highly sterile hybrids can result from crossing rhizomatous germplasm with either continental or Mediterranean types (Carlson and Hurst, 1989). Meiotic irregularities in progeny resulting from crosses between different tall fescue germplasm pools are believed to be due to a breakdown in control of chromosome pairing (Jauhar, 1975, 1991), possibly resulting from different genomic constitutions. Sporophytic or genic factors have been suggested to contribute to sterility in meiotically regular progeny resulting from crosses between tall fescue genotypes of diverse geographic origins (Beuselink et al., 1983). However, it is possible that many of the differences are due to different genomic constitution, as most polyploid species are polyphyletic in origin, having formed recurrently from different diploid ancestors (Soltis and Soltis, 2000).
Fertility can be restored in hybrids between continental and Mediterranean types when the chromosome number is doubled to dodecaploid, although these amphiploid hybrids eventually form a chromosome number varying between 9x and 10x, as exemplified in the French cultivar Lunibelle. Fertility can be improved by backcrossing or topcrossing rhizomatous ´ continental F1 hybrids to continental germplasm (Carlson and Hurst, 1989) or by selecting for good seed set among such F1 hybrids, as was done in the breeding of the turf cultivar Labarinth.
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