The Karyotype of Elymus Mendodnus (Poaceae; Triticeae) from Argentina studied by Banding Techniques

Abstract

The karyotype of Elymus mendodnus (2n = 8x = 56) was investigated by Giemsa C-banding and N-banding, and AgNO3 staining. The chromosomes were large (7–13 μm). The chromosome complement consisted of 22 metacentric and 6 submetacentric pairs. Two metacentric and one submetacentric pairs had satellites on the short arms. One of the metacentric pairs had large satellites. The other satellites were small. The number of SAT-chromosomes was verified through AgNO3 staining confirming the presence of up to 6 nucleoli at interphase. The C-banding pattern comprised small to large C-bands at telomeric positions in all short arms except one and in most of the long arms. A few, mostly small bands were located at distal, intercalary positions. The small satellites were entirely heterochromatic. The amount of constitutive heterochromatin (14 %) was among the highest recorded in the Triticeae. Except in 12 chromosome pairs, incl. the 3 satellited ones, the overall similarity of the C-banding patterns of most chromosomes prevented a safe identification of homologues. Additionally, the level of identified banding pattern polymorphism was low, but supports an outbreeding nature of the species. N-banding produced no bands. A similar distribution of large C-bands and lack of N-banding have previously been observed in Psathyrostachys huashanica. This agrees with the presence of the Ns genome and the absence of the H genome in E. mendodnus (DUBCOVSKY et al. 1997), and suggests the absence of the pivotal St genome of Elymus. However, lacking further evidence we propose to retain the species in Elymus.