Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pollination”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed2003

A transformation method for obtaining marker-free plants of a cross-pollinating and vegetatively propagated crop.

It is generally thought that transformation of plant cells using Agrobacterium tumefaciens occurs at a very low frequency. Therefore, selection marker genes are used to identify the rare plants that have taken up foreign DNA. Genes encoding antibiotic and herbicide resistance are widely used for this purpose in plant transformation. Over the past several years, consumer and environmental groups have expressed concern about the use of antibiotic- and herbicide-resistance genes from an ecological and food safety perspective. Although no scientific basis has been determined for these concerns, generating marker-free plants would certainly contribute to the public acceptance of transgenic crops. Several methods have been reported to create marker gene-free transformed plants, for example co-transformation, transposable elements, site-specific recombination, or intrachromosomal recombination. Not only are most of these systems time-consuming and inefficient, but they are also employed on the assumption that isolation of transformants without a selective marker gene is not feasible. Here we present a method that permits the identification of transgenic plants without the use of selectable markers. This strategy relies on the transformation of tissue explants or cells with a virulent A. tumefaciens strain and selection of transformed cells or shoots after PCR analysis. Incubation of potato explants with A. tumefaciens strain AGL0 resulted in transformed shoots at an efficiency of 1-5% of the harvested shoots, depending on the potato genotype used. Because this system does not require genetic segregation or site-specific DNA-deletion systems to remove marker genes, it may provide a reliable and efficient tool for generating transgenic plants for commercial use, especially in vegetatively propagated species like potato and cassava.

Agriculture↗
PubMed2000

Effects of distance and pollen competition on gene flow in the wind-pollinated grass Festuca pratensis Huds.

Pollen dispersal and gene flow in the grass meadow fescue (Festuca pratensis Huds.) were studied using two populations which were homozygous for different allozymes at the Gpi-2 locus. The populations were established in a concentric donor-acceptor field experiment. Gene flow was found mainly to be affected by the distance between the donor and acceptor plants. Analysing 21 132 acceptor plant progenies, gene flow was shown to decrease rapidly with distance to the donor field up to 75 m, and beyond this distance much more slowly. The ability of donor pollen to fertilize acceptor plants depended very much on the density of the acceptor plants. Pairs of acceptor plants produced more compatible pollen locally, and captured significantly less donor pollen than single-plants. Despite the higher seed production of acceptor plants planted in pairs, the absolute number of heterozygous seeds carrying the donor allele was always lower than for single-plants. Wind direction had only a slight effect upon the type of pollen captured. Because of pollen production within the two plant populations being continuous and overlapping, the time when anthesis occurred had little effect on gene flow between the populations. Vigorous and tall acceptor plants with many panicles, high seed yield and high 1000-seed weight were able to capture more donor pollen than shorter plants. The results may be used to assess the risk of gene flow and to develop strategies for monitoring the spread of transgenes from genetically modified grasses.

Gene Frequency↗
PubMed1999

The population genetic structure of a large temperate pollinator species, Bombus pascuorum (Scopoli) (Hymenoptera: Apidae)

The genetic population structure of the bumble bee Bombus pascuorum was studied using six microsatellite loci and a partial sequence of the mitochondrial gene cytochrome b. Eighteen populations from central and northern Europe were included in the analysis. Observed levels of genetic variability and heterozygosity were high. Estimates of population differentiation based on F- and phi-statistics revealed significant genetic differentiation among B. pascuorum populations and suggest that two partially isolated gene pools, separated by the Alps, do exist. The distribution of mtDNA haplo-types supports this view and presents direct evidence for gene flow across the Alps. Estimates of the number of migrants exchanged among populations north of the Alps suggest that historical events may have left a strong imprint on population structure.

Journal Article↗
PubMed2002

Speciation in fig pollinators and parasites.

Here we draw on phylogenies of figs and fig wasps to suggest how modes of speciation may be affected by interspecific interactions. Mutualists appear to have cospeciated with their hosts to a greater extent than parasites, which showed evidence of host shifting. However, we also repeatedly encountered a pattern not explained by either cospeciation or host switching. Sister species of fig parasites often attack the same host in sympatry, and differences in ovipositor length suggest that parasite speciation could result from divergence in the timing of oviposition with respect to fig development. These observations on fig parasites are consistent with a neglected model of sympatric speciation.

Animals↗
PubMedDate not supplied

Sugar preferences and xylose metabolism of a mammal pollinator, the Namaqua rock mouse (Aethomys namaquensis).

The sugar preferences of 10 Namaqua rock mice, Aethomys namaquensis, were assessed using pairwise combinations of 30% (w/w) solutions of sucrose, glucose, fructose, xylose, and a mixture of equal parts of glucose and fructose. The tests were designed to control for side biases that were apparent in preliminary experiments. The mice preferred sucrose to fructose and glucose. Xylose, although the least preferred sugar, was willingly consumed by the rodents (up to 5.8 mL in 24 h). This contrasts with the strong rejection of xylose by nectarivorous birds on which similar preference tests were performed. The efficiency of xylose absorption and metabolism by A. namaquensis was investigated by measuring dietary intake, blood xylose levels, and urinary and fecal xylose output. Again in contrast to the birds, the apparent absorption efficiency of xylose was found to be very high at 97%, but exactly how the xylose is metabolized requires further study. Xylose is thought to be only slowly metabolized by mammals, and it is possible that intestinal bacteria may serve this purpose, like the ruminal bacteria that break down xylans in plant tissue.

Animals↗
PubMed2002

Genetic analysis of traits distinguishing outcrossing and self-pollinating forms of currant tomato, Lycopersicon pimpinellifolium (Jusl.) Mill.

The evolution of inbreeding is common throughout the angiosperms, although little is known about the developmental and genetic processes involved. Lycopersicon pimpinellifolium (currant tomato) is a self-compatible species with variation in outcrossing rate correlated with floral morphology. Mature flowers from inbreeding and outcrossing populations differ greatly in characters affecting mating behavior (petal, anther, and style lengths); other flower parts (sepals, ovaries) show minimal differences. Analysis of genetic behavior, including quantitative trait locus (QTL) mapping, was performed on representative selfing and outcrossing plants derived from two contrasting natural populations. Six morphological traits were analyzed: flowers per inflorescence; petal, anther, and style lengths; and lengths of the fertile and sterile portions of anthers. All traits were smaller in the selfing parent and had continuous patterns of segregation in the F(2). Phenotypic correlations among traits were all positive, but varied in strength. Quantitative trait locus mapping was done using 48 RFLP markers. Five QTL total were found involving four of the six traits: total anther length, anther sterile length, style length, and flowers per inflorescence. Each of these four traits had a QTL of major (>25%) effect on phenotypic variance.

Chromosome Mapping↗