Of particular importance are the relationships between grasses in genus Lolium and those historically placed in a Festuca subg. Schedonorus. Grasses grouped in subg. Schedonorus include agronomically important species such as tall fescue, meadow fescue, and giant fescue [Lolium giganteum (L.) Darbysh. = F. gigantea (L.) Vill.].
Darbyshire (1993) proposed a more natural classification that incorporated Festuca subg. Schedonorus grasses within the genus Lolium. He noted the overemphasis placed on two morphological characters-paniculate inflorescence (Fig. 2-10) and presence of a lower glume-that were previously used to separate this subgenus from Lolium. Instead, Darbyshire focused on the ease of interspecific hybridization and the large number of other morphological characters that indicate the close evolutionary relationship of Lolium and subg. Schedonorus. Indeed, numerous studies of artificial hybrids indicate that reproductive barriers often are not appreciably greater for hybrids between Lolium and subg. Schedonorus than for many intraspecific crosses between species within subg. Schedonorus or within Lolium (Jenkin, 1933; Stace, 1975).
Morphological characters that serve to group Lolium spp. subg. Schedonorus spp. include wide, flat leaf blades and falcate leaf blade auricles not found in any related group (Darbyshire, 1993). Additionally, chloroplast restriction site variation (Darbyshire and Warwick, 1992; Lehväslaiho et al., 1987), chromosome synaptic ability (Jauhar, 1975), and electrophoretic mobilities of seed proteins (Bulinska-Rodomska and Lester, 1988) all support a congeneric grouping of Festuca subg. Schedonorus with Lolium.
Under this taxonomic scheme, the genus Lolium is expanded to include: L. pratense (= F. pratensis); L. arundinaceum (= F. arundinacea); Lolium giganteum (L.) Darbysh. (= F. gigantea); and Lolium mazzettianum (E. B. Alexeev) Darbysh. (= Festuca mazzettiana E.B. Alexeev) in the subg. Schedonorus. The tetraploid (4x) Festuca mairei and a number of subspecies and varieties of F. arundinacea of various ploidy levels have not been aligned formally yet with Lolium, although they have clear relationships with subg. Schedonorus.
Soreng et al. (2001) proposed that the name Schedonorus arundinaceus (Schreb.) Dumort. be conserved over the earlier Schedonorus arundinaceus Roem. & Schult. Before the 2006 acceptance of this proposal into the International Code of Botanical Nomenclature (ICBN) (http://www.ibot.sav.sk/icbn/main.htm, Appendix 4, verified 10 Jan. 2010), Schedonorus phoenix (Scop.) Holub was the correct name for tall fescue as a member of the genus Schedonorus. However, the name Schedonorus arundinaceus (Schreb.) Dumort. is now the correct name for tall fescue when it is placed in this genus. The preference of this publication to use L. arundinaceum follows from Darbyshire's 1993 reclassification and the analysis explained above. Furthermore, L. arundinaceum is considered equivalent to Schedonorus arundinaceus (Schreb.) Dumort. and is preferred over F. arundinacea.
|Fig. 2-10. Comparison of inflorescences of L. perenne (left) with 6x tall fescue (right).|
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