Triticum aestivum, bread wheat, belongs to the order Poales (Glumiflorae), family Poaceae (Gramineae), tribe Triticeae, genus Triticum. The tribe Triticeae consists of 18 genera which are divided into two sub-groups, the Triticinae and the Hordeinae. The major genera in the sub-group Triticinae are Triticum, Aegilops, Secale, Agropyron and Haynaldia (Odenbach 1985, Zeller 1985, Körber-Grohne 1988).