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排序方式: 共有282条查询结果,搜索用时 281 毫秒
61.
62.
Buch LH Sørensen MK Lassen J Berg P Jakobsen JH Johansson K Sørensen AC 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2011,128(3):174-182
Genetic parameters were estimated for protein yield (PY), clinical mastitis (CM), somatic cell score, number of inseminations (NI) and days from calving to first insemination (CFI) in first‐parity Swedish Red cows by series of tri‐variate linear animal models. The heritability of PY was moderate (0.34 ± 0.004), and the heritabilities of the functional traits were all low (0.014 ± 0.001–0.14 ± 0.004). The genetic correlation between CM and CFI (0.38 ± 0.05) was stronger than the correlation between CM and NI (0.05 ± 0.06), perhaps because CM and CFI usually are observed in early lactation when the cow is likely to be in negative energy balance, whereas NI generally is recorded when the cow is not in negative energy balance any more. The genetic correlation between NI and CFI was very close to zero (?0.002 ± 0.05), indicating that these two fertility traits have different genetic backgrounds. All genetic correlations between PY and the functional traits were moderate and unfavourable, ranging from 0.22 ± 0.02 to 0.47 ± 0.03. In addition, the effect of including genetic and phenotypic correlations between the trait groups milk production, udder health and female fertility on the accuracy of the selection index was quantified for a heifer, a cow and a proven bull. The difference between the accuracy obtained by multi‐trait and single‐trait evaluations was largest for the cow (0.012) and small for the heifer and the bull (0.006 and 0.004) because the phenotype of the cow for one trait could assist in predicting the Mendelian sampling term for a correlated trait. 相似文献
63.
Hooshang Majdi Laimi Truus Ulf Johansson Jan-Erik Nylund Håkan Wallander 《Forest Ecology and Management》2008
In the study reported here we examined the short-term effects (1–3 years) of slash retention (SR) and the long-term effects (13–15 years) of wood-ash application (A) on fine roots and mycorrhizae in a 40-year-old Norway spruce forest in southwest Sweden. Soil cores were used to obtain estimates of the biomass (g m−2) of roots in three diameter classes (<0.5, 0.5–1 and 1–2 mm), root length density (RLD), specific root length (SRL) and mycorrhizal root tip density (RTD). Fine root (<1 mm) length production and mortality, and mycelium production, were estimated using minirhizotron and mesh bag techniques, respectively. Compared with the control plots (C), the biomass of fine roots in diameter classes <0.5 mm and 0.5–1 mm was significantly higher in A plots, but lower in SR plots. In addition, RLD was significantly lower in the humus layer of SR plots than in the humus layers of C and A plots, but not in the other layers. None of the treatments affected the SRL. In all soil layers, the SR treatment resulted in significant reductions in the number of ectomycorrhizal root tips, and the mycelia production of fungi in mesh bags, relative to the C treatment, but the C and A treatments induced no significant changes in these variables. Fine root length production in the C, A and SR plots amounted to 94, 87 and 70 mm tube−1 during the 2003 growing season, respectively. Fine root mortality in treated plots did not change over the course of the study. We suggest that leaving logging residues on fertile sites may result in nitrogen mineralisation, which may in turn induce reductions in root biomass, and both root and mycelium production, and consequently affect nutrient uptake and the accumulation of organic carbon in soil derived from roots and mycorrhizae. 相似文献
64.
The methanol extractives from western red cedar mechanical pulps were found to be radically different in composition to the
extractives obtained from the heartwood. The major heartwood extractive components, the tropolones and lignans, were not present
in the extractives from the pulps. However, the proportion of a brown polymer doubled. The low and high molecular weight methanol
extractives components from the pulps were separated using methyl tert-butyl ether. The low molecular fraction contained mostly
guaiacyl-based compounds with dihydroquercetin, thujic acid, 3-hydroxy-1-(4′-hydroxy-3′-methoxyphenyl)-2-oxopropane and 4-ethyl-2-methoxy-6-hydroxyphenol
being positively identified. The brown polymeric portion had molecular weights ranging from 1,000 to 10,000. Infrared analysis
indicated that the polymers were formed from lignans. Examination of the changes in diffuse reflectance UV-visible and infra
red spectra of the pulps on extraction with methanol, suggested that the colour resides in insoluble polymers formed from
plicatic acid/plicatin during refining.
Received 18 December 1998 相似文献
65.
Anna M. Johansson Maulik Upadhyay Erling Strandberg Susanne Eriksson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2020,69(1-2):39-46
ABSTRACTThe Swedish Mountain (Fjäll) cattle and the subpopulation Fjällnära originates from northern Sweden. They are differentiated from both traditional and commercial cattle from southern Sweden. We analysed data from the GGP HD150k SNP array and investigated genetic diversity and differences between Fjäll and Fjällnära, and between different groups of Fjällnära. We found that the Fjällnära can be divided into four groups, which are differentiated from each other and from the other Fjäll cattle. We also compared allele frequencies between different groups of Fjäll and Fjällnära for some of the functional SNPs included in the SNP array. Interestingly, the B allele of Beta lactoglobulin has a very high frequency (94%) in the Fjällnära cattle, which is significantly different from the frequency in the Fjäll cattle (60%). Comparing older samples of Fjäll cattle with more recent samples, we found a significant increase in the frequency of the B allele in Fjäll cattle. 相似文献
66.
Abstract. The influence of intensively fertilized short-rotation forest plantations on nitrogen concentrations in groundwater was studied by piezometer readings and water sampling over a two-year period in a sandy field growing willow ( Salix spp.) and other species. The mineral-N content of the unsaturated zone was measured in soil samples collected to 0.9 m depth. Although piezometer readings suggested that deep groundwater could be affected, the concentrations of nitrate-N and ammonium-N were usually less than 1 mg per litre. There was also little mineral-N in the unsaturated zone, except for occasional peaks in the topsoil (0–30 cm) after application of fertilizer. We conclude that there is little risk of nitrogen contamination of groundwater in intensively cultured tree stands receiving up to 150 kg N/ha/yr as fertilizer. This is probably because willow can take up water and nitrogen from deep parts of the soil profile. 相似文献
67.
M. Kacprzak F.O. Asiegbu G. Daniel J. Stenlid M. Mañka M. Johansson 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(2):191-207
Three conifer species (European larch, Norway spruce, Scots pine) were investigated for their resistance to five damping-off pathogens (Rhizoctonia solani, Fusarium solani, F. oxysporum, F. culmorum, F. avenaceum). Inoculation of the primary roots of seedlings with these pathogens caused host cell death which did not prevent the invasive growth of these fungi; seedlings that had formed secondary and tertiary roots could overcome the infection to a significant degree. Infections with R. solani caused significant mortality to all the conifer species. In contrast, the tree species expressed different levels of resistance when challenged with the Fusarium isolates, with Norway spruce being the most resistant compared to uninoculated controls. Some of the Fusarium isolates were more pathogenic to certain hosts than others; F. oxysporum for European larch, F. avenaceum for Scots pine, F. solani for European larch; only F. culmorum was significantly pathogenic to Norway spruce. No significant differences in disease severity were observed at different soil pH (4.3–7.5). Disease progression was delayed at lower (10–15°C) rather than higher temperatures (20–25°C). 相似文献
68.
Aziz-ul-Rahman Jonas Johansson Wensman Muhammad Abubakar Muhammad Zubair Shabbir Paul Rossiter 《Tropical animal health and production》2018,50(8):1815-1819
Peste des petits ruminants (PPR) is a contagious viral disease of domestic small ruminants. It also affects wild ungulates but there are comparatively few studies of the incidence of natural infection, clinical signs and pathology, and confirmation of the virus, and in these species. In this article, we list the wild ungulates in which PPRV infection has been confirmed and summarize available information about the presentation of the disease, its identification, and impact of virus on wildlife populations. Considering recent reports of outbreaks by the World Organization for Animal Health (OIE), it is important to understand the transmission of this disease within wildlife populations in PPR endemic regions. 相似文献
69.
Alphonsine Mukamuhirwa Helena Persson Hovmalm Rodomiro Ortiz Obedi Nyamangyoku Maria Luisa Prieto–Linde Anders Ekholm Eva Johansson 《Journal of Agronomy and Crop Science》2020,206(2):252-262
The climate change will contribute drought and temperature extremes to rice growing systems, especially when cultivated in equatorial regions. To evaluate opportunities to cultivate and breed drought-tolerant rice, seven rice cultivars were evaluated in Rwanda for recurring morphological drought scores, grain yield and components, and quality characteristics. The cultivation conditions, that is site and drought treatment, impacted morphological drought scores, growth and yield attributes, while cultivar affected quality attributes. Thus, site showed a higher impact on grain yield and components than drought and cultivar, with generally a reduced grain yield at the low-temperature site, as a result of low spikelet fertility. Morphological drought scores were generally increased by drought, while drought at the reproductive stage at the high-temperature site was negative for yield and its components. The cultivars “Intsindagirabigega” and “Jyambere” were adapted to high-temperature site conditions. The cultivar “Intsindagirabigega” had the highest amylose content, and “Mpembuke,” the highest antioxidant capacity. Thus, climate change with increased temperature and drought extremes may increase rice productivity in cool areas, while especially drought at reproductive stage will be detrimental in low altitude areas with high temperature. Cultivar variation indicated opportunities for selection and breeding of climate change tolerant rice cultivars which should be of immediate priority. 相似文献
70.
Dick R. Johansson 《Biological conservation》1978,14(1):45-62
Several species of the genus Saintpaulia, popularly known as Usambara violets, have become a remarkable success as indoor plants in Europe and the USA. Their ancestors, some twenty species in total, live in mountains and near the coast in Tanzania and Kenya. The Saintpaulias require a very special environment since they are sensitive to drought and to competition from other plants. Thus, most species live on steep rock surfaces in dense shade where few other plants thrive. The Usambara violets in cultivation are mostly referred to as Saintpaulia ionantha. Previous records of this species refere to a restricted area near Tanga in Tanzania where today it is very rare because of changes in the environment. Tree-felling to create farmland or to obtain firewood has exposed the previously shaded limestone cliffs, making them unsuitable as habitat for Saintpaulia ionantha.Generally speaking, disturbance of the environment by clearance of trees and bushes is the main threat to the survival of most species, particularly those which occur in the lowlands. 相似文献