Intravarietal variation in satellites and C-banded chromosomes of Agropyron intermedium ssp. trichophorum cv....

A high amount of intravarietal variation in satellites and C-banded chromosomes was observed in the hexaploid wheatgrass synthetic cultivar 'Greenleaf' (Agropyron intermedium ssp. trichophorum (Link) A. &Gr., 2n = 6x = 42, genome E1E1E2E2SS). The cultivar is an open-pollinated perennial that shows extensive interplant polymorphism for many biological characters. Maximum number of satellites detected varied among plants from zero to six. In 61% of the plants, we observed two large satellites in association with zero, one, or two small ones. Chromosome constitution differed significantly among plants as revealed by analysis of variance based on the total number of banded chromosomes and the number of banded chromosomes with telomeric bands at either one or both ends. Heteromorphism in C-banding patterns between homologues was found in most of the chromosomes and was classified into four types: (i) difference in band size, (ii) difference in presence/absence of one or two bands, (iii) completely different banding patterns, and (iv) banded versus unbanded. Homologous chromosomes having types iii and iv heteromorphism could only be matched by their relative length and arm ratio instead of C-banding patterns. Deletions were detected in two chromosomes. Overall, C-banded chromosomes of this cultivar were characterized by the presence of large telomeric bands and were quite different from the previously reported karyotypes of the supposed diploid ancestor Agropyron elongatum (Host) P. Beauv. (genome EE) and an Ag. intermedium (Host) P. Beauv. accession (E1E1E2E2SS) The results suggest that dramatic chromosome modifications have occurred in this species during the course of evolution. The study sheds light on the extent of intrapopulation polymorphism present in the karyotypes of outcrossing polyploids and synthetic cultivars and has implications regarding strategies for chromosomal manipulation involving open-pollinated species.