Adam Kula

Cytotaxonomy and karyotype evolution inPhleum sect.Phleum (Poaceae) in Poland

Three taxa are distinguished in the sectionPhleumGriseb. in Poland:P. nodosum (2n = 14),P. pratense (2n = 42), and the third one unformally named hereP. “commutatum” (2n = 14). It corresponds morphologically toP. commutatumGaud. reported as a tetraploid taxon (2n = 28) from other geographic regions. Giemsa C-banded karyotypes of these three taxa help clarify the taxonomic status ofP. “commutatum” and the origin of the hexaploidP. pratense. It is suggested that changes in the amount of telomeric heterochromatin played an important role in the evolution ofPhleum karyotypes.

Karyotype structure and chromosome fragility in the grass Phleum echinatum Host

Phleum echinatum Host (2n = 2x = 10) is an annual Mediterranean species which differs from other representatives of the genus Phleum by reduced chromosome number, asymmetric karyotype and unusually high amount of DNA in the genome. Chromosomes of this plant were studied using conventional acetic-orcein staining and fluorescence in situ hybridization (FISH). FISH showed the major 35S ribosomal DNA (rDNA) site at the secondary constriction of satellite chromosome (3) and the minor 35S rDNA site near 5S rDNA cluster in the monobrachial chromosome 5. Telomeric repeats were detected at all chromosome ends within secondary constriction in satellited chromosome 3 and at the centromeric regions of chromosomes 1 and 2. Intrachromosomally located telomeric repeats are probably traces of chromosomal rearrangements that have shaped P.echinatum genome; they were prone to breakage which was manifested in chromosome fragmentation. The most distinct telomeric signals, suggesting massive amplification of interstitial telomeric sequences (ITRs), were observed at the nucleolar organizer region (NOR) of the third chromosome pair. Double FISH confirmed co-localization of telomeric and 35S rDNA repeats in this locus characterized by the biggest fragility in the karyotype. Fragile sites of P.echinatum, composed of amplified telomeric repeats, may bear a resemblance to metazoan rare fragile sites enriched in microsatellite repeats.

Karyosystematics of thePhleum alpinum polyploid complex (Poaceae)

The karyotypes of three taxa from thePhleum alpinum group of sect.Phleum (P. alpinum subsp.rhaeticum, 2n = 14,P. commutatum, 2n = 28, and informally namedP. “commutatum”, 2n = 14) were investigated by Giemsa C-banding. The overall similarity of diploid genomes suggests thatP. alpinum subsp.rhaeticum andP. “commutatum” are closely related — their karyotypes vary only with respect to their average amounts of telomeric heterochromatin. TheP. “commutatum” genome contains less telomeric heterochromatin than the genome ofP. alpinum subsp.rhaeticum, but in theP. alpinum group as a whole almost fluent transition between low (1.5%) and high (25.5%) amounts of telomeric heterochromatin was observed among populations. In the karyotype of tetraploidP. commutatum, seven distinguishable chromosome types were observed. Each of them is represented at somatic metaphase by four chromosomes. C-band structure of karyotype and average amount of telomeric heterochromatin suggest that this taxon has originated from hybridization between two related diploid forms of theP. “commutatum” — P. alpinum complex.

Karyotype and nuclear DNA content of hexa-, octo-, and duodecaploid lines of Bromus subgen. Ceratochloa

The subgenus Ceratochloa of the genus Bromus includes a number of closely related allopolyploid forms or species that present a difficult taxonomic problem. The present work combines data concerning chromosome length, heterochromatin distribution and nuclear genome size of different 6x, 8x and 12x accessions in this subgenus. Special attention is paid to the karyotype structure and genomic constitution of duodecaploid plants recently found in South America. Hexaploid lineages possess six almost indistinguishable genomes and a nuclear DNA content between 12.72 pg and 15.10 pg (mean 1Cx value = 2.32 pg), whereas octoploid lineages contain the same six genomes (AABBCC) plus two that are characterized by longer chromosomes and a greater DNA content (1Cx = 4.47 pg). Two duodecaploid accessions found in South America resemble each other and apparently differ from the North American duodecaploid B. arizonicus as regards chromosome size and nuclear DNA content (40.00 and 40.50 pg vs. 27.59 pg). These observations suggest that the South American duodecaploids represent a separate evolutionary lineage of the B. subgenus Ceratochloa, unrecognized heretofore.

Cytogenetic analysis of Miscanthus × giganteus and its parent forms

This study aimed at comparative karyotype analysis and measurement of the nuclear DNA amount in giant miscanthus, Miscanthus × giganteus, and its hypothetical ancestors: eulalia grass (M. sacchariflorus) and porcupine grass (M. sinensis). The triploid chromosome number 2n  =   57 in M. × giganteus and the diploid chromosome number 2n  =   38 in the other species were confirmed. In the karyotype of giant miscanthus three satellite chromosomes were observed, whereas in M. sinensis there were two and in M. sacchariflorus probably four chromosomes of this type. In the first species 1–4 B-chromosomes were evidenced. The highest proportion of the C-banding/DAPI (4’,6-diamidino-2-phenylindole) positive heterochromatin was found in M. sinensis cv. Gracillimus, and the least in the M. sinensis M07 genome. The banding patterns observed in M. × giganteus resembled those observed in M. sacchariflorus. The 2C nuclear DNA content in M. × giganteus was 7.47 pg and in M. sacchariflorus it was 5.14 pg; two analysed lines of M. sinensis differed in 2C DNA value (5.18 pg and 5.49 pg).