Claus Baden

Comparison of the Giemsa C-banded karyotypes of the three subspecies ofPsathyrostachys fragilis, subspp.villosus (2x),secaliformis (2x, 4x), andfragilis (2x) (Poaceae), with notes on chromosome pairing

The karyotypes of diploidP. fragilis subsp.villosus (2n = 2x = 14) and tetraploid subsp.secaliformis (2n = 4x = 28) were studied by Giemsa C- and N-banding, and AgNO3 staining and compared with the karyotype of subsp.fragilis (2x). The complements of subsp.villosus and subsp.fragilis were similar, with 8 metacentric and 6 SAT-chromosomes, one metacentric and two submetacentric pairs, with small to minute, polymorphic, heterochromatic satellites. The complement of subsp.secaliformis on the whole agreed with a doubling of the complement of diploidP. fragilis, suggesting autopolyploidy. Only the presence of 12 nucleoli in interphases identified 6 SAT-chromosome pairs. In subsp.villosus one or two extra micronucleoli indicated a chromosome pair with very low nucleolusforming activity, bringing the number of SAT-chromosome pairs to 4. This number may be a characteristc ofPsathyrostachys. Besides very small, inconsistently observed bands, the C-banding pattern consisted of 0–3 small bands per chromosome at intercalary and terminal locations, and at NORs. The level of banding pattern polymorphism was low, but enough to indicate that the taxa are outbreeders. Similarities in chromosome morphology and C-banding patterns identified homology of all chromosomes of subsp.villosus, but for 12 pairs only in subsp.secaliformis. Between plants, reliable identification of homology and homoeology (subsp.secaliformis) was possible only for the SAT-chromosomes and the shortest metacentrics. Chromocentres were very small and the amount of constitutive heterochromatin was low. N-banding stained chromosomes uniformly. The basic karyotypes of theP. fragilis taxa were similar to those ofP. juncea, P. lanuginosa, andP. stoloniformis supporting a close relationship and the presence of a common genome, N. NORs had different nucleolus-forming activities. Meiotic analysis demonstrated a high level of bivalent pairing in the three taxa. A chromosomal rearrangement was suggested in subsp.villosus. The low multivalent frequency in subsp.secaliformis indicates the presence of a pairing regulation mechanism. The majority of chiasmata were interstitial. Pollen grain size discriminated between diploid and tetraploid taxa. The existence of a diploid cytotype of subsp.secaliformis is supported by pollen measurements of herbarium material.

The karyotype ofFestucopsis serpentini (Poaceae Triticeae) from Albania studied by banding techniques and in situ hybridization

The karyotypes of two populations ofFestucopsis serpentini (2n = 2x = 14) endemic to Albania were investigated in detail by Giemsa C- and N-banding, AgNO3 staining, and in situ hybridization with an rDNA probe. The complements consisted of 14 large chromosomes, 10 metacentric and 4 SAT-chromosomes, a metacentric and a submetacentric pair. SAT-chromosomes from one population carried exclusively minute satellites, whereas SAT-chromosomes from another population also carried larger polymorphic satellites, suggesting a geographical differentiation. The existence of four chromosomes with nucleolus forming activity was established through AgNO3 staining; however, the rDNA probe additionally hybridized to intercalary positions in the short arms of two metacentric chromosomes revealing two inactive rDNA sites. C-banding patterns comprised from zero and up to four very small to larger, generally telomeric bands per chromosome giving low levels of constitutive heterochromatin. Similarities in chromosome morphology and C-banding patterns identified the homologous relationships of all chromosomes in one population, but of three pairs only in the other. Reliable identification of homologous chromosomes between plants was only possible for the SAT-chromosomes. A comparison between the C-banded karyotypes ofF. serpentini andPeridictyon sanctum supports their position in two genera.

An Ecogeographical Study of the Genus Hordeum

An Ecogeographical study of the genus Hordeum , An Ecogeographical study of the genus Hordeum , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی