Cytological understanding is an important parameter to understand the genetic architecture of yam bean. The ploidy level and genome size of two cultivated species of yam bean (Pachyrhizus erosus and P. tuberosus) were estimated using flow cytometric analysis of young leaf tissue, with propidium iodide as a fluorescent dye. Six genotypes of P. erosus and three genotypes of P. tuberosus were analysed. Rice (Oryza sativa cv. Nipponbare) and Mung bean (Vigna radiata cv Berken) were used as internal reference standards. Variation of 2C nuclear DNA content among the six P. erousus lines was 4.18%, ranging from 1.17 to 1.22 pg, whereas only 1.8% variation was observed among the three P. tuberosus lines, which ranged from 1.07 to 1.09 pg. Moreover, it was found that the nuclear DNA content of P. tuberosus was lower than that of P. erosus. The result of the flow cytometric analysis showed that all the species were diploid (2n = 2x) and coefficient of variation (CV%) of all the accessions of the two species was less than 3.5%. This is the first report of ploidy analysis and genome size estimation of the leguminous underutilized tuber crop yam bean using flow cytometry. This result will be helpful for yam bean genome sequencing and crop improvement programmes.

Prior research indicated that analysis of nuclear DNA content by flow cytometry could be used to distinguish smooth pigweed × tall waterhemp hybrids when the parent lines are known. Flow cytometry was performed on nuclei isolated from several Illinois populations of smooth pigweed and tall waterhemp. The smooth pigweed and tall waterhemp analyzed had nonoverlapping 2C nuclear DNA content values, with mean values of 1.04 and 1.34 pg, respectively. The consistent difference in DNA content observed between the two species indicates that DNA content analysis can be used to distinguish their hybrid progeny in natural populations.

Genetic diversity of 30 common vetch (Vicia sativa L.) lines and cultivars obtained from various resources or collected from natural flora of Turkey was evaluated by using 55 sequence-related amplified polymorphism (SRAP) and five inter-simple sequence repeat (ISSR) primer sets, and their nuclear DNA contents were determined by flow cytometer. A total of 188 polymorphic loci were detected, with an average of 3.62 loci per primer. The percentage of polymorphic loci was 82.1%. The polymorphism information content values ranged from 0.12 to 0.96, with an average of 0.63. The genetic distance coefficients were in the range of 0.112–0.627. Cluster analysis revealed that the 27 lines and three cultivars could be divided into two main groups. No polyploidy was detected within any vetch lines tested while significant (P< 0.0001) nuclear DNA content differences were determined. The present study revealed that fast and accurate fingerprinting analysis could be done using SRAP and ISSR markers, which indicated existing significant variation among common vetch lines and cultivars.

A technique was developed for dissection and isolation of male germ cells in the oyster Crassostrea gigas. This procedure can provide cells for the exploration of processes involved in the reproductive physiology of bivalves. Spermatogonia were chosen because of their essential role in spermatogenesis and the impact of gonia proliferation on reproductive effort. A non lethal method for determining sex and reproductive cycle stage was first validated in oysters. This first step was essential in order to constitute a homogeneous pool of oysters at the same stages of gametogenesis. Germ cell fractions were then obtained from a density gradient, and enrichment of each fraction was ratified by electron microscopy and by means of a 2-parameter flow cytometry procedure (DNA and mitochondrial staining). A significant enrichment in spermatogonia and spermatocytes was confirmed by the increased expression of markers of proliferative cells (proliferative cell nuclear antigen, PCNA) and early germ cells (oyster vasa-like gene). A preliminary cell sorting procedure is also reported, which was applied to fractions enriched in spermatogonia.

In Scutigera coleoptrata, double spermatogenesis (macro and micro germinal cells) was reinvesti gted by means of both image analysis and electron microscopy. Image analysis of the cell-lines showed no differences in DNA content between the two types of spermatogesis.The only difference found, with the exception of the size and the related number of organelles, was that in the macro-cell line the chromatin was well dispersed and no condensed, which is the opposite of what was observed in the macro-cell line. It is asumed that the level of activity related to this condensation process is at the origin of the two pathways of development.

The desiccation sensitivity of seeds of Inga vera Willd. subsp. affinis, a recalcitrant-seeded tree from Brazil, was analysed, focusing on water relations and cell-cycle aspects, including DNA content and the microtubular cytoskeleton. Seeds were collected at four developmental stages, dried to different moisture contents (MCs), assessed regarding water activity and set to germinate. Samples of fresh (non-dried) developing and mature seeds were used for assessment of DNA content by flow cytometry. Immunohistochemical detection of microtubules (MTs) was done in mature seeds at different MCs. Slight desiccation of immature seeds increased germination, but further drying resulted in a quick decline of germinability. During seed development the desiccation sensitivity decreased slightly, but DNA content of the embryonic axis cells remained constant, suggesting no relation between those two parameters. Embryonic axis cells of mature seeds showed abundant cortical microtubule arrays, which were not affected by mild desiccation, but broken down by further drying. It appeared that, upon rehydration, damaged cells were not able to reconstitute the microtubular cytoskeleton. The failure of germination of Inga vera seeds after drying could not be attributed to cellular damage to DNA synthesis and mitosis, since the radicle protruded by means of cell elongation, without a need for cell division. However, the breakdown of MTs during desiccation, and their subsequent inability to reassemble upon rehydration, may be related to the decreased germination, since MTs are required for cell elongation.

Seeds of sugar beet (Beta vulgaris L.) were collected at weekly intervals from 3 weeks before to 1 week after commercial harvest time, dried and stored at room temperature (18–22°C). Laboratory germination tests and flow cytometric analyses were performed immediately after harvest (fresh seeds) and five times at weekly intervals during storage (dry seeds). After 6 months of storage, seeds were exposed to a controlled deterioration treatment (CD). The proportion of G2 nuclei in the embryo was constant in the fresh seeds, regardless of their maturity. It decreased, however, after drying and CD, especially in those seeds harvested before maturation drying had commenced. The proportion of endosperm cells in the seed decreased with maturation, and a further decrease was observed after drying and CD. These observations suggest that nuclei with a higher nuclear DNA content were more sensitive to water stress caused by premature desiccation and to deterioration than nuclei with a lower DNA content. Fresh seeds exhibited some germination, but this increased after drying, suggesting that desiccation induced a switch from the developmental to the germination mode. Germination percentages were the highest in dry seeds collected at the commercial harvest time and a week after. This high germinability coincided with the highest proportion of G2 cells in the embryo. It is concluded that flow cytometry provides information about the status of sugarbeet seed maturation, seed quality and storage potential, and can be used for estimation of optimal harvest time.

The nuclear DNA content in Dicentrarchus labrax, Sparus aurata, Liza ramada, and Anguilla anguilla, was measured by flow cytometric analysis. Male human leukocytes were used as internal reference cells. Nucleated fish erythrocytes were stained simultaneously to human leukocytes with a staining buffer containing propidium iodide (PI). Nuclear DNA contents of target species were estimated in relation to an assigned value of 7.0 pg DNA for male human leukocytes. The DNA content/nucleus (±CI) was 1.55 ± 0.02 pg for D. labrax, 1.90 ± 0.03 pg for S. aurata, 1.57 ± 0.02 pg for L. ramada, and 2.43 ± 0.04 pg for A. anguilla. Intraspecific DNA content variations ranged from 0-9% and averaged around 4% in all taxa. The results did not evidence significant differences in genome size between males and females in either D. labrax or L. ramada. / Anguilla anguilla

An image analysis system was used to count and measure acetoorcein-stained mitotic chromosomes of the acidothermophilic unicellular red algae Galdieria maxima, G. partita, G. sulphuraria and Cyanidium caldarium (Cyanidiophyceae). Chromosome numbers fell into two groups: n = 2 for all three species of Galdieria and n = 5(7) for C. caldarium. It seems that a separation of C. caldarium from Galdieria is karyologically justified. A chromosome number of 2 appears to be indicative of the genus Galdieria and could be used as a marker to distinguish this taxon from Cyanidium. The two smaller chromosomes in the karyotype of C. caldarium were about 0·4 μm long whereas the other three were 0·5–0·7 μm long. In karyotypes of Galdieria species, the two chromosomes differed in length, the smaller chromosome ranging from 0·8 to 1·8 μm and the larger one from 1·2 to 2·3 μm. The visualization of these extremely small chromosomes was possible due to pretreatment of the cells with the DNA intercalator 9-aminoacridine. The mean absolute length of each chromosome of the three members of Galdieria had statistically significant interspecies differences. Nuclear 1C DNA contents were estimated in the algal cells by the Feulgen technique. All species investigated had genome sizes of 1·50–2·25×10−2 pg. Thus it seems that the members of Cyanidiophyceae have the smallest known genomes of all photosynthetic eukaryotes.

The ability of 16 calcareous grassland species to establish in competition with adult neighbours of two different growth forms was assessed in a glasshouse experiment. The questions asked were: (1) how well is establishment ability related to plant traits such as seed mass, DNA content, relative growth rate and adult height; and (2) are the results consistent across different neighbours? Two measures of establishment ability were calculated, survival relative yield and biomass relative yield, for seedlings grown with a dicot. (Leontodon hispidus) and with a graminoid (Festuca ovina). The results depended on which measure of establishment ability was used. When establishment ability was measured in terms of biomass relative yield, seed mass was a good predictive trait, accounting for 38–55% of variation. However, when establishment ability was measured as survival relative yield, adult height was found to be the best predictor, capable of accounting for 20% of variation, although this was not consistent across neighbours. Thus, no clear relationship between plant traits and establishment ability was found: results depended on the measure of establishment ability used, and in the case of adult height, on the identity of the neighbour species. Survival relative yield was strongly associated with target and neighbour species growth form type, with stronger suppression of like than of non-like growth forms. The lack of strong relationships between plant traits and establishment ability, and the dependence on neighbour identity, suggests that the links between plant traits and establishment might be context-dependent; thus an understanding of the mechanisms underlying any such links is essential.