Canio G. Vosa

Heterochromatic patterns in Allium

SummaryThe karyotype of ten taxa in the cepa group of Allium and two allied species have been investigated using fluorochromes and Giemsa staining techniques. The chromosomes of all species have terminally located heterochromatic segments which show reduced Quinacrine-fluorescence and are deeply stained by the Giemsa technique. Together with morphological similarities these characteristics indicate a close relationship between the alliums of the cepa group and the two allied species A. schoenoprasum and A. ledebourianum. On the basis of chromosome morphology and C-band endowment the hybrid origin of the viviparous forms of the Onion: A. cepa var. viviparum, A. aobanum and A, wakegi is confirmed.

Chromosome banding patterns in cultivated and wild barleys ( Hordeum SPP).

SummaryAn investigation of seven species of wild barley and ten different forms of the cultivated species (H. vulgare) has revealed that all the species and cultivars have mostly procentric constitutive heterochromatin. Relatively smaller heterochromatic segments are found in intercalary and distal positions. Larger bands of varying sizes and reacting somewhat differently from the rest of the heterochromatin are generally found in association with the nucleolar constrictions.The amount and location of heterochromatin vary very little between the various species and cultivars. Extended studies are necessary to recognize the specificity of the banding patterns and their possible use in cytogenetic studies and in species recognition. The only criteria of discrimination between the species remain the number and morphology of the nucleolar chromosomes and the presence or absence of certain characteristic chromosomes. However, C-banding techniques allow the recognition of all different chromosome types, according to their heterochromatic patterns, within each species.

The basic karyotype of Rye ( Secale cereale ) analysed with Giemsa and fluorescence methods

SummaryThe basic karyotype of Rye (Secale cereale L.) has been analysed with several fluorochromes and with a Giemsa staining technique. Only the fluorochrome Hoechst 33258 and the Giemsa technique were successful in differentiating the heterochromatic segments.Five cultivated varieties were studied. In the haploid set there are 11 large and two small terminally located bands, four small intercalary bands and a variable band adjacent to the nucleolar constriction on chromosome VII which are constant for all varieties. Five more very small intercalary bands occur sporadically in all the varieties. All the chromosomes possess thin centromeric bands.

On the Quinacrine fluorescence and Giemsa staining patterns of the chromosomes of Vicia faba

Abstract A comparison has been made between the Quinacrine fluorescence bands and the bands obtained with a denaturating-reannealing-Giemsa technique in Vicia faba. The results show that some of the bands, particularly on the M and, proximally, on the S chromosomes are visible with both techniques. A complex pattern of bands on the S chromosomes is revealed with the Giemsa technique. Both the similarities and the differences between the banding patterns obtained with the two methods in Vicia faba may indicate various degrees of DNA repetitiousness and other physico-chemical properties in the chromosome segments involved.

Meiosis and B-Chromosomes in Listera Ovata (Orchidaceae)

SUMMARYIn Listera ovata the chiasma frequency is higher in embryo sac mother cells than in pollen mother cells. In both types of cell the chiasma frequency is raised by the presence of euchromatic B-chromosomes. The rise is not linear but zig-zag with odd numbers of the B-chromosome having a greater effect than even numbers. It is suggested that B-chromosomes prolong the time available for chiasma formation allowing the utilization of more sites for chiasma formation so accounting for the rise in chiasma frequency.

Two Track Heredity: Differentiation of Male and Female Meiosis in Tulbaghia

SUMMARYChiasma frequencies in male and female meiocytes in Tulbaghia follow the general rule and are higher in the female. A feature of female meiosis is a shift in the proximal localization, found in the male meiocyte, toward a more median and distal distribution of chiasmata.The results in Tulbaghia, together with the findings of other authors in many other organisms, indicate that there are two systems of recombination operating in any one species. The two systems tend in effect to stabilize favourable gene combinations and to facilitate their establishment in outbred species.

C-banding in maize II. Identification of somatic chromosomes

A biometrical analysis of C-banded and Feulgen stained somatic metaphases of maize stocks with different knob constitutions has shown that large bands alter arm lengths of mitotic chromosomes. A representative diagram of the knobless maize somatic karyotype and of a high knobbed stock are presented.

On chromosome uniformity, bimodality and evolution in the tribe Aloineae (Asphodelaceae)

Abstract Variable AC-segments (allocyclic chromosome segments) are present in all the species of the tribe Aloineae and are an indication of karyotype evolution and speciation in progress. In all species, the karyotype is very uniform and this uniformity may be the consequence of climatic stability and of similarity of habitat. All the species in the tribe possess a bimodal chromosome complement, a special character of ancient origin present in many organisms both vegetable and animal with a bearing on gene recombination and on evolution.

A revised cytotaxonomy of the genus Tulbaghia (Alliaceae)

Abstract A revision of Tulbaghia (Alliaceae) has been carried out. The genus includes twentyone species and one variety. On the basis of the different karyotypes, the genus can be subdivided into seven distinct Groups. Some species have poly-ploid forms but no true polyploid species has been found so far. A number of species possess heterochromatic segments which may be either mostly distally or proximally located. The heterochromatic segments of Tulbaghia are cold sensitive and specific fluorochrome staining shows that they are composed mainly of highly repetitive sequences of Guanine-Cytidine nucleotides. The possible evolutionary role of heterochromatin as well as that of the B-chromosomes, present in some species, is briefly discussed. The illustrations include micrographs of the mitotic chromosomes as well as colour photographs of the inflorescence of all the species. The typical habitat of two of the species is also illustrated in colour.

The cytogeographical distribution pattern ofAllium (Alliaceae) in the Greek Peninsula and Islands

Greece is considered as a secondary centre of evolution for the genusAllium since it possesses about 50% of the species known from the whole Flora Europaea area. In the present investigation 44 GreekAllium spp. have been studied and new chromosome counts are reported from 40 populations and 17 species. The distribution of the different cytotypes (x = 7, x = 8, x = 11 and 2n = 2x, 3x, 4x, 5x, 6x, 7x) in Greece is discussed. From the four phytogeographical subdivisions recognized, South continental Greece shows the greatest species and karyotype diversity. This phenomenon is probably due to the geographical position and to the geological history of this area which has received species and populations from different directions. Subsequently, hybridization apparently has been of evolutionary importance.