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Fig. 2-1. Diagram of idealized tall fescue plant (D.M. Ball, C.S. Hoveland and G.D. Lacefield, with permission from Potash and Phosphate Institute and Foundation for Agronomic Research).

Taxonomists rely heavily on two main criteria for establishing species boundaries in the grasses: morphological characteristics and interfertility relationships. Morphological characters traditionally have involved gross anatomical features and growth habits (Fig. 2-1). More recently, a tremendous amount of insight has been gained through analysis of chromosome number and size, which also can be seen as morphological characters (see Morphological Characteristics section in this chapter). Interfertility among grasses also is considered an indication of close relations, and is used commonly to group grasses into biological species. While interfertility tends to be a more direct measure of the overall genetic similarity than morphology, the reverse is not always true, as fertility barriers can be induced by simple genetic mechanisms such as the S-Z incompatibility system or the emergence of polyploids (multiple chromosome sets).

Tall fescue (Fig. 2-2) [hexaploid (6x) Lolium arundinaceum (Schreb.) Darbysh. = Festuca arundinacea Schreb. var. arundinacea] (see Chapter 1) and its close relatives present an interesting classification problem because taxonomy based on morphological characters often conflicts with observed fertility relationships, as well as with many biochemical and molecular relationships. This group of grasses commonly is referred to as the Festuca-Lolium complex (Jauhar, 1993).

Lolium arundinaceum also is considered here as synonymous with Schedonorus arundinaceus (Schreb.) Dumort. nom. cons. (see Realignment of Schedonorus with Lolium section in this chapter).

Click Image to Expand Tall fescue plant at flower


Fig. 2-2. Tall fescue plant at flowering.
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