Genetic stability in interspecific hybridizations of wheat populations determined by meiotic index and pollen viability

The objective of this study was to evaluate genetic stability by determining the meiotic index (MI) and pollen viability in F1RC2 segregating populations, obtained by the crosses between wheat commercial cultivars and synthetic wheat, aimed at introgression/genetic resistance. For MI, three ears were collected per genotype, before anthesis, and they were fixed in Carnoy’s solution. The cytological slides were prepared by crushing the anthers and staining with 1% acetocarmine, and the normal tetrads and the ones with micronuclei were observed under a light microscope. For pollen viability, the ears were collected at the stage of mature pollen grain. The methodological procedure was similar to that of the tetrads, evaluating the pollen grains as viable, with little starch, with two pores, different sizes and non-viable. The pollen grain size was measured by the Axion Vision software. All the segregating populations with MI above 90% and high pollen viability (above 85%) reflected a stable meiotic behavior. About the variation in size, the CIGM90.909/BRS 179 cross showed pollen grains with 58.43 μm and CIGM93.298/BRS Guamirim, 47.15 μm. According to the results, wheat segregating populations were considered meiotically stable and suitable for use in wheat breeding programs and for incorporation of new important genes.

Palyno-morphology of Hedera L. (The ivy genus, araliaceae) and their systematics implications

The palynomorphological characteristics of 5 species belonging to Hedera of the Araliaceae family were studied in detail. These plant species were collected from various phytogeographical regions of Iran and Hungary. The palynological investigation was accomplished using Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). Pollen grains of the species are reticulate, prolate, sub-prolate, tricolporate, isopolar, radially symmetrical, and monad. The largest pollen grain was in the Hedera colchica species (72.24?1.6 ?m) and the smallest pollen grain was in Hedera helix (28.63?2.1 ?m). The research carried out by the TEM showed that the species were different in terms of exine thickness, tectum thickness, foot layer thickness, the diameter and length of the Columella, the thickness and shape of the Caput, the tectum to foot layer )T/F( ratio, the absence or presence of the Endexine and the thickness of the Intine layers. The main purpose of this study was the importance of the relationship between pollen grain size and the number of chromosomes and ploidy level in Hedera species.

Pollen grain size associated with pollinator feeding strategy

Angiosperm pollen grain diameter varies greatly from a few microns to over 100, but the selective forces driving the interspecific variation in pollen size remain unclear. Although both pre- and post-pollination hypotheses have been proposed, empirical evidence remains scarce. Here we propose that visits by pollen-foraging pollinators have selected against large pollen grains. An association between pollinator behaviour and pollen grain size was confirmed by field studies of 80 flowering species in natural communities, showing that pollinators positively collected pollen in those species with relatively smaller pollen grains but rarely did so in species with larger ones. Allowing for the confounding effects of pollinator type, flower size or style length and pollen grain number, we found a significant effect of pollen-foraging behaviour on variation in pollen grain size, particularly in bee-pollinated plants. While these results suggest that many plant species whose pollen is collected or consumed by pollinators produce small pollen grains, it remains unclear whether pollen grain size is directly affected by pollinator foraging habit or indirectly mediated by pollen number trade-offs.

Differences in stomatal and pollen grain dimensions and pollen viability between Paspalum rawitscheri populations

The objective of this study was to evaluate stomatal and pollen grain size and to estimate pollen viability of individuals from different populations of Paspalum rawitscheri (Parodi) Chase ex G.H. Rua Valls. To analyze stomatal size, slides were made of the adaxial leaf epidermis using the epidermal impression method. The height and width of 100 stomata per population were analyzed. Pollen was obtained from inflorescences to evaluate pollen grain size and pollen viability. Pollen grains were stained with 2% acetic orcein, 2% acetic carmine, or Alexander’s reactive stain. Per population, 1600 grains of pollen were observed for viability, and 50 grains of pollen were measured. There were significant differences between populations in stomatal height and pollen grain height and width. The populations also differed in pollen viability, with the Santa Maria population showing the lowest viability. The differences in stomatal and pollen grain size suggest genetic variability in the evaluated populations. Moreover, low pollen viability in one population indicates that its decline may be related to low fertility. Keywords: Grass. Ploidy. Fertility. Threatened species.

Asian paleoenvironments, paleogeography and paleobiodiversity interactions during the Greenhouse-Icehouse transition

<p>The ongoing surge of international research on Asian Climate and Tectonics enables to better assess interactions between forcing mechanisms (global climate, India-Asia collision, Tibetan Plateau growth) and paleoenvironmental changes (monsoons, aridification), land-sea distribution, surface processes, paleobiogeographic evolution and the global carbon cycle. We review here the progress of the ERC MAGIC project (Monsoons in Asia caused Greenhouse to Icehouse Change?) integrating regional geodynamic constraints, well-dated environmental / biodiversity records and climate modeling. MAGIC focuses on the Paleogene period that includes the global Greenhouse to Icehouse cooling, the early collision and plateau growth and associated regional development of monsoons and westerlies over the Proto-Paratethys sea. Our work focuses on three areas constraining Asian paleoenvironments. (1) In Myanmar, paleomagnetic results, new dating of magmatic rocks and sediments along with additional detrital geochronology and basin analysis of the Burmese subduction margin and implications for the history of India-Asia convergence. (2) Along the Northeastern Tibetan Plateau margin, the combination of multiple proxies (leaf wax stable isotope, pollen, grain size, etc…)  applied to an extended lacustrine Paleogene record enables to identify precisely Asian climate changes and their consequences on ecosystems. (3) In westernmost China and Tajikistan, the proto-Paratethys sea fluctuations and the sedimentary records of Pamir tectonic evolution are now precisely dated enabling to constrain driving mechanisms and paleoenvironmental consequences. Together these results are used to constrain climate modeling experiments which permit validation of hypotheses on interactions between paleogeography, paleoenvironments and paleobiodiversity at Asian and global scales in response to long-term and short-term events.</p>

A Cytotaxonomic study on Minuartia L. (Caryophyllaceae) in Iraq

Chromosome count, karyotypic character analysis, meiotic studies, monoploid karyograms and ideograms were performed in six taxa of Minuartia growing in Iraq (M. hamata, M. hybrida subsp. hybrida, M. intermedia, M. meyeri, M. picta and M. hybrida subsp. turcica). Species of M. hamata and M. meyeri showed 2n=2x=30 chromosome number, while M. hybrida subsp. hybrida and M. intermedia were diploid (26). The chromosome number (n=x) of six species was studied, and was found to be n=15 in M. hamata and M. meyeri, 13 in M. hybrida and M. intermedia, while in M. picta we recorded values of n= 11 and 14. Karyotype analysis of this species was first carried out in our study. Analysis of metaphases showed that the karyotype formula was mainly metacentric, submetacentric, and sub acrocentric. The sizes of the chromosomes were mainly small and very small. The course of meiosis varied from normal to abnormal. Abnormal microsporogenesis formation of two bridge chromosomes was detected in M. hamata and one bridge chromosome in M. intermedia and M. meyeri. Formation of laggard’s chromosomes was detected in M. hamata, M. meyeri and M. intermedia. As well as ring chromosome was showed in M. hybrida subsp. hybrida, also, some cells contain triad cell in metaphase stage instead four cells, as well as founded cell, contains two nuclei in same species which led to reduced pollen fertility and differences in pollen grain size.

The influence of urban environment on pollen grains of the silver birch (Betula pendula Roth) in conditions of Yakutsk

This paper studies variability of pollen grains of the silver birch in relation to the quality of urban environment. The material was collected in 12 sites. A total of 1,190 leaves and 24,000 pollen grains were examined and measured. The pollen fertility varied within 69-92%. Statistically significant decrease in fertility was observed in conditions of high-intensity traffic load, in the central area of the city, and where the road surface was in poor condition. Under the same conditions a statistically significant increase in percentage of relatively fertile pollen grains is observed. We found significant correlation between the level of fluctuating asymmetry (FA) and the share of fertile and half-fertile pollen grains. For fertility Spearmans rho was -0,71; and for half-fertility, r = 0,66, p 0,05. A similarly significant correlation (r = -0,7, p 0,05) was found between the diameter of pollen grains and traffic load, which indicates a consistent organism response to environment deterioration. From the above, it follows that for assessment of environmental condition such characteristics of pollen grains as fertility, half-fertility, and pollen grain size can be used.

Home at last III: Transferring Uechtritzia and Asian Gerbera species into Oreoseris (Compositae, Mutisieae)

Recently the Asian Gerbera species were shown to form a clade that was not the sister group of the African Gerbera. In this study, the position of the Asian Gerbera species was further assessed based on morphology and molecular phylogenetic analyses that included six Asian Gerbera and 26 other species from the Gerbera-complex. Morphological results showed that the six Asian Gerbera species, which were sampled, bear leaves with the adaxial epidermal surface lacking stomates, possess bracteate scapes and lack inner ray florets. These characters suggest that the Asian Gerbera species are most closely related to the species of Uechtritzia, which also share similar pollen grain size and shape with the Asian Gerbera, rather than to the African Gerbera. Furthermore, the phylogenetic results based on two nuclear (ITS and ETS) and three chloroplast (trnL–trnF, trnL–rpl32 and trnC–petN) sequences strongly support the Asian Gerbera and Uechtritzia forming a clade, with the latter nested within the Asian Gerbera species. Both morphological and molecular phylogenetic data thus confirmed the taxonomic identity of the Asian Gerbera and Uechtritzia. The authors herein formally treat the nine species of the Asian Gerbera and the three species of Uechtritzia as members of the genus Oreoseris, which is the earliest generic name of this lineage and has the nomenclatural priority.