The heterochromatin distribution and genome evolution in diploid species of Elymus and Agropyron

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Abstract
The acetocarmine–Giemsa C-banding technique was used to study heterochromatin distribution in somatic chromosomes of diploid Elymus junceus (= Psathyrostachys juncea) (2n = 14) (genome designation Ju = N) and nine diploid Agropyron species (2n = 14): A. cristatum (C = P), A. imbricatum (C = P), A. elongatum (= Elytrigia elongata = Thinopyrum elongatum) (E = J), A. junceum (= E. bessarabicum = T. bessarabicum) (J = E), A. spicatum (= Pseudoroegneria spicata) (S), A. libanoticum (= P. libanotica) (S), A. ferganense (S), A. stipifolium (= P. stipifolia) (S), and A. velutinum (V). With the exception of A. elongatum and A. velutinum, which were self-fertile, all species were cross-pollinating and self-sterile. The cross-pollinating species showed large terminal C-bands and a high level of C-band polymorphism. Agropyron elongatum, moderately self-fertile, showed small terminal and interstitial bands and a minimal C-band polymorphism. Agropyron velutinum, fully self-fertile, almost totally lacked C-bands. The Ju, C, E, and J genomes appeared to be distinctive and the equivalence of the E and J genomes was not supported from their C-banding patterns. Four species sharing the S genome, A. spicatum, A. libanoticum, A. ferganense, and A. stipifolium had C-band patterns similar to one another, although C-bands were less prominent in A. stipifolium than others.Key words: C-banding, karyotype, wheatgrass, cytology.