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At least 1,351 records · Page 75Linked to original sources
PubMed2005

Bimodal distribution of flowering time in a natural hybrid population of daylily (Hemerocallis fulva) and nightlily (Hemerocallis citrina).

Time of flower anthesis in a day is thought to evolve in response to the time of pollinator activities. We studied blooming and withering time in natural populations of daylily (Hemerocallis fulva), nightlily (Hemerocallis citrina) and their hybrids, and also in an artificially obtained array of the F1 hybrids. Blooming time of H. fulva varied from 4:30 to 7:30 and H. citrina varied from 16:30 to 20:30. In a natural hybrid population, blooming time and withering time showed discontinuous bimodal distribution in spite that morphological traits of flowers showed continuous unimodal variation. Most F1 hybrids showed diurnal flowering. These findings indicate that only a few genes have strong phenotypic effect on the determination of flowering time in Hemerocallis, and suggest that the evolution from a H. fulva-like ancestor to H. citrina was not a continuous process by accumulation of minute mutations.

Circadian Rhythm↗
PubMed2006

Genetic diversity and mating system of the threatened plant Kirengeshoma palmata (Saxifragaceae) in Korea.

The endangered herb Kirengeshoma palmata, from eastern Asia, has had its population severely reduced in number through habitat loss and fragmentation. All of the individuals within five subgroups at Mt. Baek-un-san, in the southern part of Korea, were genetically surveyed by allozyme analysis. Genetic diversity levels within subgroups were relatively high, and a consistently high outcrossing rate as well as a negligible biparental mating rate were confirmed by this study. Several groups of visibly connected ramets were observed in a clustered distribution which suggested cloning. Absence of mating partner rather than pollinators decreased seed production in small mating groups. The present genetic structure of the five subgroups was probably the result of local extinction of intervening populations. Because K. palmata may be a self-incompatible species, populations with few genets face lowered seed set due to mate scarcity. Thus, this type of population may be at an increased risk of extinction as a result of inbreeding depression, loss of genetic variability, and reduced sexual reproduction. The small, genetically depauperate subgroups may need an input of seeds or plants from other populations in China or Japan in order to regenerate, but the possibility of outcrossing depression leads us to recommend outbreeding among the local subgroups of Mt. Baek-un-san to restore genetic variability.

Flowers↗
PubMed2002

Programmed cell death of Pinus nucellus in response to pollen tube penetration.

In ovules of Pinus densiflora, pollen tubes elongate and branch into the nucellar tissue in the direction of the female gametophyte. After pollination, nucellar cells located around the pollen grain and tube die off. We showed here that the nuclei of the nucellar cells were stained by TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end labeling). The number of TUNEL-positive cells increased during pollen tube growth. The tips of pollen tube branches protruded into the nucellar cells to form a convex-concave junction. At this junction, the cell membrane of nucellar cells was separated from the cell wall and the protoplast shrank. Small vesicles and amorphous materials were released from the protoplast into the space between the cell membrane and wall. Vacuoles were collapsed, chromatin was condensed, and mitochondria and plastids were deteriorated in the shrunken protoplast. Agarose gel analysis of DNA isolated from the ovules showed a DNA ladder, suggesting that the nuclear DNA had undergone internucleosomal cleavage. These results suggest that nucellar cells undergo programmed cell death in response to pollen tube penetration with some features resembling apoptosis and other features peculiar to nucellar cells.

Journal Article↗
PubMed2002

Differentiation in the status of self-incompatibility among Calibrachoa species (Solanaceae).

The overall status of self-incompatibility, as assessed by the rate of capsule-set after self-pollination, was investigated in the genus Calibrachoa (Solanaceae). Thirty-two species were surveyed using a total of 655 individuals collected in 102 different native populations in Argentina, Brazil, Mexico, and Uruguay. The rate of capsule-set in 278 voucher specimens collected from the same native habitats was also measured to obtain additional information to assess the degree of self-(in)compatibility. Only one species, Calibrachoa parviflora, was self-compatible (SC, autogamous) and the other 31 species were found to be self-incompatible (SI). A mixed population (SI and SC individuals in the same population) was not found. The differentiation of C. parviflora as an autogamous species is associated with a successful occupation of different (riparian) habitats within a larger range of geographic distribution compared to the rest of the species in the principally SI genus of Calibrachoa.

Journal Article↗
PubMed2005

Isoenzyme variation in Melipona rufiventris (Hymenoptera: Apidae, Meliponina) in Minas Gerais State, Brazil.

The stingless bee Melipona rufiventris is an important pollinator in several Brazilian ecosystems. Originally widely distributed in Minas Gerais (MG) state, this species is becoming very rare. Therefore this species was included in the endangered species list of MG. We used isoenzyme data for a better understanding of the genetic structure of several M. rufiventris colonies. Samples of 35 colonies were collected from 12 localities and evaluated by nine enzymatic systems, which yielded 17 loci. M. rufiventris genetic variation was found to be low, typical of an endangered species. The proportion of polymorphic loci was 5.88% in both ecosystems. Only Est-4 was polymorphic in colonies from the Forest and Mdh-1 in colonies from the Cerrado. The expected heterozygosity ranged from 0.0068 in the Cerrado to 0.0078 in the Forest. Despite this, enzyme electrophoretic analyses provided a good idea of the diversity between samples from Cerrado and Forest which reinforce the existence of two different "forms" of M. rufiventris in MG, one present in the Cerrado and the other in Forest. This information is of great importance for the conservation of M. rufiventris in MG.

Animals↗
PubMed2006

Genetic variation in Hippophae rhamnoides ssp. sinensis (Elaeagnaceae) revealed by RAPD markers.

Hippophae rhamnoides ssp. sinensis is endemic to China, and it is a dioecious, outcrossing plant. Although many studies have been undertaken mainly on its agricultural, nutritional, medical, and ornamental value, little is known about its population genetics. This study uses random amplified polymorphic DNA to investigate the genetic diversity and population genetic structure of 13 natural populations of the subspecies sinensis. Fifteen primers amplified 107 reproducible bands, with 95 (88.79%) being polymorphic. The gene diversity within population was 0.168, considerably lower than that of tree species and most perennial, outcrossing species, but higher than that of annual or short-lived, selfing species. The Gst value showed that 18.3% of the total genetic variation resided among populations, a little lower than that of outcrossing species. The present results are quite similar to those previously reported in another subspecies, H ssp. . rhamnoides rhamnoides. The low genetic differentiation among populations in ssp. sinensis may be attributed to the long-distance dispersal of seeds facilitated by birds, in addition to its characteristics of outcrossing, wind pollination, and widespread distribution. No association between genetic distance and geographical distribution was found. The population relationships revealed by the UPGMA dendrogram parallel this result, in that genetic distance did not increase with geographic separation. This pattern of population differentiation may imply the adaptation of ssp. s populations to the local environment, given that its habitats vary greatly across its distribution.

China↗
PubMed2005

Identification of self-incompatibility genotypes of apricot (Prunus armeniaca L.) by S-allele-specific PCR analysis.

A cDNA of 417 bp encoding an S-RNase gene, named PA S3, was isolated from apricot, Prunus aremeniaca. Nine S-alleles, S1-S9, were recognized by S-allele-specific PCR and confirmed by Southern blot analysis using PA S3 as probe. The S-genotypes of the six cultivars were determined and the results of self- and cross-pollination tests among the six cultivars were consistent with the predicted S-haplotypes by PCR analysis.

Alleles↗
PubMed2006

Temporal changes in the inequality of early growth of Cunninghamia lanceolata (Lamb.) Hook.: a novel application of the Gini coefficient and Lorenz asymmetry.

Growth within tree populations varies among individuals due to changes in biotic and abiotic factors. The degree of such variation, defined as growth inequality, serves as a useful indicator of the uniformity of growth within a population in response to the prevalent environmental conditions. By application of the Gini coefficient (G), an index for inequality, we characterized the early growth inequality of ninety crosses of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and their open-pollinated parental lines. Tree cumulative height was measured annually for 8 consecutive years. Both the crosses and parental lines exhibited temporal changes in growth inequality. The inequality of total height among the crosses decreased logarithmically with age by nearly 3-fold after 13 growing seasons, suggesting that tree height became less variable among the crosses as trees grew larger. Interestingly, the Lorenz asymmetry, an index reflecting the shape of the Lorenze curve from which G is derived, revealed that the inequality of annual height increment among the crosses resulted from an alternate contribution of the fast-growing and slow-growing trees. Among parental lines, two provenances with the smallest and the largest overall inequality in total height showed a similar pattern of changes in annual growth inequality, and the provenance differences were consistent over time. Compared to the other provinces, a local provenance exhibited less variation in total height among individual trees as reflected by a smaller value of inequality, and was better adapted to the field conditions. Our results demonstrated the sensitivity and usefulness of the Gini coefficient and Lorenz asymmetry for the analysis of growth inequality in non-natural populations. Growth inequality is a potentially useful evaluation criterion for early selection. Given comparable initial growth, provenances/families with lower growth inequality values would likely outperform those with higher growth inequality, and eventually tree size of the latter would be more variable due to greater variations among individual trees. Assessment of growth inequality at early ages will advance our understanding of variability of tree growth within a population, facilitate forest genetics improvement programs, and enhance the efficiency of tree breeding.

China↗
PubMed2006

Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland.

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.

Age Factors↗
PubMed2005

Genetic structure of wild rice Oryza glumaepatula populations in three Brazilian biomes using microsatellite markers.

The existence of Oryza glumaepatula is threatened by devastation and, thus, the implementation of conservation strategies is extremely relevant. This study aimed to characterize the genetic variability and estimate population parameters of 30 O. glumaepatula populations from three Brazilian biomes using 10 microsatellite markers. The levels of allelic variability for the SSR loci presented a mean of 10.3 alleles per locus and a value of 0.10 for the average allelic frequency value. The expected total heterozygosity (H(e)) ranged from 0.63 to 0.86. For the 30 populations tested, the mean observed (H(o)) and expected heterozygosities (H(e)) were 0.03 and 0.11 within population, respectively, indicating an excess of homozygotes resulting from the preferentially self-pollinating reproduction habit. The estimated fixation index ( (IS) ) was 0.79 that differed significantly from zero, indicating high inbreeding within each O. glumaepatula population. The total inbreeding of the species ((IT) ) was 0.98 and the genetic diversity indexes among populations, (ST) and (ST), were 0.85 and 0.90, respectively, indicating high genetic variability among them. Thus, especially for populations located in regions threatened with devastation, it is urgent that in situ preservation conditions should be created or that collections be made for ex situ preservation to prevent loss of the species genetic variability.

Alleles↗
PubMed2005

Synomone or kairomone?--Bulbophyllum apertum flower releases raspberry ketone to attract Bactrocera fruit flies.

Bulbophyllum apertum flower (Orchidaceae) releases raspberry ketone (RK) in its fragrance, which attracts males of several fruit fly species belonging to the genus Bactrocera. Besides RK as a major component, the flower contains smaller amounts of 4-(4-hydroxylphenyl)-2-butanol, plus two minor volatile components, veratryl alcohol and vanillyl alcohol. Within the flower, the lip (labellum) had the highest concentration of RK with much smaller quantities present in petals; other flower parts had no detectable RK. Male fruit flies attracted to the flower belong to RK-sensitive species--such as Bactrocera albistragata, B. caudatus, B. cucurbitae (melon fly), and B. tau. Removal and attachment of the pollinarium to a fly's thoracic dorsum occurred when a male of B. albistragata was toppled into the floral column cavity, due to an imbalance caused by it shifting its body weight while feeding on the see-saw lip, and then freeing itself after being momentarily trapped between the lip and column. During this process, the stiff hamulus (the pollinia stalk protruding prominently towards the lip) acted as a crowbar when it was brushed downwards by the toppled fly and lifted the pollinia out of the anther. If the fly was big or long for the small triangular lip, it would not be toppled into the column cavity and would just walk across the column, during which time the pollinarium could be accidentally removed by the fly's leg, resulting in a failed transport of the pollinarium. This suggests an unstable situation, where the orchid relies only on a particular pollinator species in the complex ecosystem where many RK-sensitive species inhabit. Wild males of B. caudatus (most common visitors) captured on Bulbophyllum apertum flowers were found to sequester RK in their bodies as a potential pheromonal and allomonal ingredient. Thus, RK can act either as a floral synomone (pollinarium transported) or kairomone (accidental removal of pollinarium leading to total pollen wastage), depending on the body size of the male fruit flies visiting the flowers.

Animals↗
PubMed2005

Cuticular hydrocarbons as sex pheromone of the bee Colletes cunicularius and the key to its mimicry by the sexually deceptive orchid, Ophrys exaltata.

Male Colletes cunicularius bees pollinate the orchid, Ophrys exaltata, after being sexually deceived by the orchid's odor-mimicry of the female bee's sex pheromone. We detected biologically active volatiles of C. cunicularius by using gas chromatographic-electroantennographic detection (GC-EAD) with simultaneous flame ionization detection. After identification of the target compounds by coupled gas chromatography mass spectrometry (GC-MS), we performed behavioral tests using synthetic blends of the active components. We detected 22 EAD active compounds in cuticular extracts of C. cunicularius females. Blends of straight chain, odd-numbered alkanes and (Z)-7-alkenes with 21-29 carbon atoms constituted the major biologically active compounds. Alkenes were the key compounds releasing mating behavior, especially those with (Z)-7 unsaturation. Comparison of patterns of bee volatiles with those of O. exaltata subsp. archipelagi revealed that all EAD-active compounds were also found in extracts of orchid labella. Previous studies of the mating behavior in C. cunicularius showed linalool to be an important attractant for patrolling males. We confirmed this with synthetic linalool but found that it rarely elicited copulatory behavior, in accordance with previous studies. A blend of active cuticular compounds with linalool elicited both attraction and copulation behavior in patrolling males. Thus, linalool appears to function as a long-range attractant, whereas cuticular hydrocarbons are necessary for inducing short-range mating behavior.

Animals↗
PubMed2006

Sex pheromone of the cranberry root grub Lichnanthe vulpina.

The cranberry root grub Lichnanthe vulpina (Hentz) (Coleoptera: Glaphyridae) is a pest of cranberries in Massachusetts, reducing yield and vine density. (Z)-7-Hexadecenol and (Z)-7-hexadecenal were identified from the female effluvia collection by gas chromatographic-electroantennographic detection and gas chromatography-mass spectrometry. The double-bond position was confirmed by dimethyl disulfide derivatization. Both compounds were tested in the field, each alone and as blends of the two. Each compound alone captured males; however, (Z)-7-hexadecenol alone captured significantly more males than did (Z)-7-hexadecenal alone. The addition of varying amounts of (Z)-7-hexadecenal to (Z)-7-hexadecenol did not statistically affect male capture. Flight activity of the cranberry root grub may be monitored with traps baited with rubber septa containing 300 microg of (Z)-7-hexadecenol. A test of trap vane colors indicated that traps with green or black vanes maximized target male catch while minimizing nontarget catch of important cranberry pollinators.

Animals↗
PubMed2004

Lipids stimulate spore germination in the entomopathogenic ascomycete Ascosphaera aggregata.

The alfalfa leafcutting bee (Megachile rotundata) is solitary and managed on a large scale for pollination of alfalfa seed crops. The bees nest in holes drilled in wood or polystyrene blocks, and their larvae are highly prone to a fungal disease called chalkbrood. The most prevalent form of chalkbrood is caused by Ascosphaera aggregata, but this ascomycete is difficult to culture. Hyphae will grow on standard fungal media, but spore germination is difficult to achieve and highly variable. We found that germination can be enhanced with oils. Lipids derived from plants and bee larvae increased germination from 50% (without oil) to 75-85% (with oil). Percent germination was significantly greater in the presence of lipids but germination was not significantly different when different oils, including mineral oil, were used. A. aggregata spores oriented along the oil-aqueous interface in the broth in a polar fashion, with swelling and germ tube formation always occurring into the aqueous portion of the broth. The other half of the spore tended to attach to a lipid droplet, where it remained, without swelling, during germ tube formation. The physical attachment of spores to the oil-aqueous interface is what most probably stimulates spore germination, as opposed to some nutritional stimulation. However, further research is needed to determine if and where the spores encounter such an interface when germinating in the host gut, where germination normally occurs.

Animals↗
PubMed2004

Chalcone synthase as a reporter in virus-induced gene silencing studies of flower senescence.

Agrobacterium-mediated infection of petunia (Petunia hybrida) plants with tobacco rattle virus (TRV) bearing fragments of Petunia genes resulted in systemic infection and virus-induced gene silencing (VIGS) of the homologous host genes. Infection with TRV containing a phytoene desaturase (PDS) fragment resulted in reduced abundance of PDS transcripts and typical photobleaching of photosynthetic tissues. Infection with TRV containing a chalcone synthase (CHS) fragment resulted in silencing of anthocyanin production in infected flowers. The silencing phenotype ranged from scattered white spots on the normal purple background to entirely white flowers. Symptoms in the V26 cultivar were a diffuse mosaic, but infection of some purple-flowered commercial cultivars resulted in large white sectors and even entirely white flowers. Abundance of CHS transcripts in the white flowers was less than 4% of that in purple flowers on the same plant. Infection with TRV containing a tandem construct of PDS and CHS resulted in leaf photobleaching and white patterns on the flowers. Transcripts of CHS and PDS were reduced both in leaves and in flowers confirming simultaneous silencing of both genes by the tandem construct. We tested the effects of infection with TRV containing CHS and a fragment of a petunia gene encoding for 1-aminocyclopropane-1-carboxylate oxidase (ACO4) Abundance of transcripts encoding ACO4 and ACO1 were reduced (by 5% and 20%, respectively) in infected flowers. Whether the flowers were treated with ACC or pollinated, the white (silenced) flowers or flower sectors produced less ethylene and senesced later than purple (non-silenced) tissues. These results indicate the value of VIGS with tandem constructs containing CHS as reporter and a target gene as a tool for examining the function of floral-associated genes.

Acyltransferases↗
PubMed2004

Cassava breeding: opportunities and challenges.

Although cassava is a major food crop, its scientific breeding began only recently compared with other crops. Significant progress has been achieved, particularly in Asia where cassava is used mainly for industrial processes and no major biotic constraints affect its productivity. Cassava breeding faces several limitations that need to be addressed. The heterozygous nature of the crop and parental lines used to generate new segregating progenies makes it difficult to identify parents with good breeding values. Breeding so far has been mainly based on a mass phenotypic recurrent selection. There is very little knowledge on the inheritance of traits of agronomic relevance. Several approaches have been taken to overcome the constraints in the current methodologies for the genetic improvement of cassava. Evaluations at early stages of selection allow for estimates of general combining ability effect or breeding values of parental lines. Inbreeding by sequential self-pollination facilitates the identification of useful recessive traits, either already present in the Manihot gene pool or induced by mutagenesis.

Breeding↗
PubMed2005

Comparative analysis of early embryonic sunflower cDNA libraries.

To gain information concerning cell functions and activities during sunflower embryogenesis, an expressed sequence tag (EST) approach was used to analyse gene expression in the early stages of sunflower embryos development. Confocal microscopy observations of whole-mounted embryos allowed us to identify precisely the major steps of the zygotic embryonic development. A time-course analysis was then employed to collect the embryonic material. Three cDNA libraries were constructed from microdissected embryos, and three other cDNA libraries were created using a classical day after pollination schedule. A total of 7106 ESTs were produced and assembled. The total number of putative different genes represents about 43.1 (3064 tentative contigs and singlets) of the analysed sequences. The unigenes that showed similarity to proteins with known or predicted functions (50.3) were classified into 15 different functional categories. The functional profiles were found to be quite similar for all studied embryo stages but statistical analysis revealed that successive and coordinate sets of genes are expressed at each embryonic stage. The analysis allowed us to identify abundant and differentially expressed genes at the early stages of embryos development as well as some putatively interesting genes, showing strong similarities with genes playing key roles in plant and animal embryogenesis. The data presented in this study not only provide a first global overview of the genes expression profile during sunflower embryogenesis but also represent an original and valuable tool for developmental genomics studies on exalbuminous dicots.

Cluster Analysis↗
PubMed2005

Stable plastid transformation in lettuce (Lactuca sativa L.).

Although plastid transformation in higher plants was first demonstrated in the early 1990s it is only recently that the technology is being extended to a broader range of species. To date, the production of fertile transplastomic plants has been reported for tobacco, tomato, petunia, soybean, cotton and Lesquerella fendleri (Brassicaceae). In this study we demonstrate a polyethylene glycol-mediated plastid transformation system for lettuce that generates fertile, homoplasmic, plastid-transformed lines. Transformation was achieved using a vector that targets genes to the trnA/trnI intergenic region of the lettuce plastid genome employing the aadA gene as a selectable marker against spectinomycin. Spectinomycin resistance and heterologous gene transcription were shown in T(1) plants derived from self-pollinated primary regenerants demonstrating transmission of the plastid-encoded transgene to the first seed generation. Crossing with male sterile wild-type lettuce showed that spectinomycin resistance was not transmitted via pollen. Constructs containing the gfp gene showed plastid-based expression of green fluorescent protein. The lettuce plastid could have potential both as a production and a delivery system for edible human therapeutic proteins.

Crosses, Genetic↗