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21.
Isotopic studies in temperate forest soils suggested that collembolans occupy a broad range of trophic niches. This notion is mainly based on the wide (up to 8-9‰) range of δ15N signatures of different species. The interpretation of these data depends strongly on the correct estimation of nitrogen isotope fractionation per trophic level. It is usually assumed that a consumer is on average enriched in 15N by about 3.4‰ relative to its diet. However, trophic fractionation is not uniform across different animal taxa and different tissues, and varies with a range of factors, including quality of the diet and the nutritional status of animals. We performed a laboratory experiment aiming to compare the trophic fractionation of nitrogen isotopes (Δ15N) in different Collembola species fed with three fungi of different palatability. Collembolans were fed with a single-species fungal diet for 75 days. There was a positive correlation between the whole body C:N ratio and reproduction rates of collembolans. We therefore used the C:N ratio as a proxy of nutritional status. In all species of collembolans, the trophic fractionation decreased with increased whole body C:N ratio, and this factor explained most of the within-species variation in Δ15N. The analysis of published data on the trophic fractionation of collembolans in laboratory experiments confirmed this conclusion. However, the mean trophic fractionation in most collembolan species studied in the laboratory was fairly similar. In contrast, field studies have documented a consistent difference in δ15N among different families of collembolans. In particular, in nearly all published cases Onychiuridae had δ15N higher than Isotomidae or Entomobryidae. A sharp contrast between laboratory-based estimates of the trophic fractionation (generally uniform in different species and families) and field data (which show a consistent difference in δ15N among different species and even families of collembolans) confirms that δ15N values of field-collected animals bear important information on the trophic position occupied by a particular species, and are not heavily affected by the species-specific differences in trophic fractionation. As the Δ15N in collembolans depends on their nutritional status, we suggest that the C:N values should be reported along with isotopic data to allow cross-study comparisons. 相似文献
22.
Konstantin Chekanov Elena Lobakova Irina Selyakh Larisa Semenova Roman Sidorov Alexei Solovchenko 《Marine drugs》2014,12(8):4504-4520
We report on a novel arctic strain BM1 of a carotenogenic chlorophyte from a coastal habitat with harsh environmental conditions (wide variations in solar irradiance, temperature, salinity and nutrient availability) identified as Haematococcus pluvialis Flotow. Increased (25‰) salinity exerted no adverse effect on the growth of the green BM1 cells. Under stressful conditions (high light, nitrogen and phosphorus deprivation), green vegetative cells of H. pluvialis BM1 grown in BG11 medium formed non-motile palmelloid cells and, eventually, hematocysts capable of a massive accumulation of the keto-carotenoid astaxanthin with a high nutraceutical and therapeutic potential. Routinely, astaxanthin was accumulated at the level of 4% of the cell dry weight (DW), reaching, under prolonged stress, 5.5% DW. Astaxanthin was predominantly accumulated in the form of mono- and diesters of fatty acids from C16 and C18 families. The palmelloids and hematocysts were characterized by the formation of red-colored cytoplasmic lipid droplets, increasingly large in size and number. The lipid droplets tended to merge and occupied almost the entire volume of the cell at the advanced stages of stress-induced carotenogenesis. The potential application of the new strain for the production of astaxanthin is discussed in comparison with the H. pluvialis strains currently employed in microalgal biotechnology. 相似文献
23.
Key weather parameters (monthly minimum and maximum temperature, precipitation) were extracted for 35 winter wheat breeding sites in central Asia, eastern Europe and Great Plains of USA from 1961 to 2009. Autumn and winter warming happened gradually, over a long period of time, but mostly before 1991. Climate changes after 1991 were mainly expressed through higher temperatures in spring, May, and June. Clear regional differences were observed for air temperature variation. Breeding sites in the USA seemed to be least subjected to climate change. There were no significant linear trends in yearly, seasonal, or monthly precipitation. Changing climates expressed through rising temperatures during critical stages of winter wheat development have already negatively affected yield gains in several countries, especially in eastern Europe. There are some positive changes associated with warmer winters, which may not require additional investment in traits associated with winter survival. Rising temperatures in spring are of particular concern since their effect on yield is negative in some regions. They certainly accelerate wheat development and shift heading to earlier dates. The interaction of higher temperatures in spring with the rate of crop development and yield is a fundamental issue which requires research. Rising temperatures in June are detrimental for grain development and filling and heat tolerance warrants high priority in breeding programs. 相似文献
24.
Madhav Bhatta Alexey Morgounov Vikas Belamkar Aysel Yorgancılar P. Stephen Baenziger 《Euphytica》2018,214(11):200
Genetic resistance to common bunt is a cost-effective, environmentally friendly, and sustainable approach to controlling the disease. To date, 16 race specific common bunt resistance genes (Bt1-Bt15 and Btp) have been reported in wheat. However, a limited number have been mapped and few markers have been identified, which limits the usage of molecular markers in a marker-assisted breeding program. A total of 125 synthetic hexaploid wheats (SHWs) were evaluated for reactions to a mixture of common bunt races under field conditions in Turkey in 2016 and 2017. The objectives of this study were to identify common bunt resistant genotypes, identify genomic regions conferring resistance to common bunt using 35,798 genotyping-by-sequencing derived single nucleotide polymorphisms (SNPs), and investigate the significant SNPs present within genes using the functional annotations of the underlying genes. We found 29 resistant SHWs that can be used in wheat breeding. The genome-wide association study identified 15 SNPs associated with common bunt resistance and a haplotype block comprising three SNPs in perfect linkage disequilibrium. Five of them were novel and were located on chromosomes 2A, 3D, and 4A. Furthermore, seven of the 15 SNPs were found within genes and had annotations suggesting potential role in disease resistance. This study identified several favorable alleles that decreased common bunt incidence up to 26% in SHWs. These resistant SHWs and candidate genomic regions controlling common bunt resistance will be useful for wheat genetic improvement and could assist in further understanding of the genetic architecture of common bunt resistance. 相似文献
25.
A. Morgounov V. Zykin I. Belan L. Roseeva Yu. Zelenskiy Hugo Ferney Gomez-Becerra H. Budak F. Bekes 《Field Crops Research》2010
Short season high latitude (50°N–56°N) spring wheat (Triticum aestivum L.) is grown on approximately 7 million ha in Western Siberia with average yield of 1.5–2.0 t/ha. A historical set of 47 varieties developed and grown in the region between 1900 and 2000 was evaluated at a trial in Siberian Research Institute of Agriculture (Omsk) in 2002–2008. The genetic gains for grain yield and associated changes in agronomic traits were analyzed for three maturity groups (early, medium and late) and four breeding periods (before 1930, 1950–1975, 1976–1985 and after 1985). The overall yield was 3.71 t/ha for modern varieties versus 2.18 t/ha for old varieties representing 0.7% increase per year in the course of 100 years. The genetic gains between the breeding periods indicated that the rate of progress for the early and medium maturity groups was more or less comparable from one breeding period to the other. For the late maturity group there was an obvious and sharp decline in genetic gain with time. Modern varieties were also characterized by average response to environmental mean and good grain yield stability evaluated according to Eberhart and Russell (1966). Thousand kernel weight and number of grains per unit area were linearly correlated with grain yield and genetic gain over time suggested their importance for breeding progress. Resistance to leaf rust in some modern varieties sustained and contributed to stability of genetic gains. The yield increase over time was not associated with plant height reduction and incorporation of Rht genes. The maturity range of the newer varieties is narrower compared to old germplasm as they tend to belong to medium maturity group. Translocation 1B.1R had limited contribution to Western Siberian germplasm being observed in only three varieties. The increase in adaptation, yield potential and its stability has been reached due to gradual accumulation of favorable genes through diverse crosses, robust selection and testing system. Resistance to leaf rust and other prevalent pathogens is of paramount importance for future progress. 相似文献
26.
Berger C Song Z Li X Wu X Brown N Naud C Mayou D Li T Hass J Marchenkov AN Conrad EH First PN de Heer WA 《Science (New York, N.Y.)》2006,312(5777):1191-1196
Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged. 相似文献
27.
Poinar HN Schwarz C Qi J Shapiro B Macphee RD Buigues B Tikhonov A Huson DH Tomsho LP Auch A Rampp M Miller W Schuster SC 《Science (New York, N.Y.)》2006,311(5759):392-394
We sequenced 28 million base pairs of DNA in a metagenomics approach, using a woolly mammoth (Mammuthus primigenius) sample from Siberia. As a result of exceptional sample preservation and the use of a recently developed emulsion polymerase chain reaction and pyrosequencing technique, 13 million base pairs (45.4%) of the sequencing reads were identified as mammoth DNA. Sequence identity between our data and African elephant (Loxodonta africana) was 98.55%, consistent with a paleontologically based divergence date of 5 to 6 million years. The sample includes a surprisingly small diversity of environmental DNAs. The high percentage of endogenous DNA recoverable from this single mammoth would allow for completion of its genome, unleashing the field of paleogenomics. 相似文献
28.
Alexei Morgounov Hugo Ferney Gómez-Becerra Aigul Abugalieva Mira Dzhunusova M. Yessimbekova Hafiz Muminjanov Yu Zelenskiy Levent Ozturk Ismail Cakmak 《Euphytica》2007,155(1-2):193-203
Sixty-six spring and winter common wheat genotypes from Central Asian breeding programs were evaluated for grain concentrations
of iron (Fe) and zinc (Zn). Iron showed large variation among genotypes, ranging from 25 mg kg−1 to 56 mg kg−1 (mean 38 mg kg−1). Similarly, Zn concentration varied among genotypes, ranging between 20 mg kg−1 and 39 mg kg−1 (mean 28 mg kg−1). Spring wheat cultivars possessed higher Fe-grain concentrations than winter wheats. By contrast, winter wheats showed higher
Zn-grain concentrations than spring genotypes. Within spring wheat, a strongly significant positive correlation was found
between Fe and Zn. Grain protein content was also significantly (P < 0.001) correlated with grain Zn and Fe content. There were strong significantly negative correlations between Fe and plant
height, and Fe and glutenin content. Similar correlation coefficients were found for Zn. In winter wheat, significant positive
correlations were found between Fe and Zn, and between Zn and sulfur (S). Manganese (Mn) and phosphorus (P) were negatively
correlated with both Fe and Zn. The additive main effects and multiplicative interactions (AMMI) analysis of genotype × environment
interactions for grain Fe and Zn concentrations showed that genotype effects largely controlled Fe concentration, whereas
Zn concentration was almost totally dependent on location effects. Spring wheat genotypes Lutescens 574, and Eritrospermum
78; and winter wheat genotypes Navruz, NA160/HEINEVII/BUC/3/F59.71//GHK, Tacika, DUCULA//VEE/MYNA, and JUP/4/CLLF/3/II14.53/ODIN//CI13431/WA00477,
are promising materials for increasing Fe and Zn concentrations in the grain, as well as enhancing the concentration of promoters
of Zn bioavailability, such as S-containing amino acids. 相似文献
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Mycetophilids is a species-rich insect group for which the ecological requirements in temperate forests are poorly understood. This study of mycetophilids was based on trap samples from 15 oak-dominated sites in the boreonemoral zone of southern Sweden. Species richness and composition were analysed in relation to environmental variables at a local and at larger scales (multiple regression), and compared to results from similar studies in spruce-dominated sites in the boreal zone of Norway (PCA and two-sample t tests). Regressions showing a dominance of regional factors over local in-site variables agree with species-richness models assuming that local communities most often are unsaturated. Precipitation (inter-correlated with elevation) was the strongest factor for explaining the variation in species-richness, which is consistent with previous results indicating that mycetophilids are disfavoured by drought. In addition to precipitation, the area of mixed forest with high biodiversity values (woodland key habitats and protected areas) was a positive factor for species-richness, probably because such habitats combine elements of both coniferous and deciduous forests. PCA ordination revealed a clear separation of the species composition between boreal and boreonemoral forests. Species-richness in boreal forest was significantly higher than in boreonemoral forest, indicating a preference for boreal habitats in many of the species. For mycetophilids and other drought-sensitive insects, it is suggested that (partial) cutting in some dense successional oak stands should be avoided, and that some invading spruces should be tolerated. 相似文献