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151.
There are several hurdles to ensure sustainable seed production and consistent flow of improved legume varieties in sub‐Saharan Africa (SSA) and South Asia (SA). The unreliable demand, autogamous nature of most of the grain legumes, and slow variety replacement rate by smallholder farmers do not provide strong incentive for private seed companies to invest in legume seed business. Unless a well thought‐out and comprehensive approach to legume seed delivery is developed, current seed shortages will continue, eroding emerging market opportunities. The experiences reported here are collated through a 10‐year partnership project, the Tropical Legumes in SSA and SA. It fostered innovative public–private partnerships in joint testing of innovative market‐led seed systems, skills and knowledge enhancement, de‐risking private sector initiatives that introduced in new approaches and previously overlooked entities in technology delivery. As new public and private seed companies, individual seed entrepreneurs and farmer organizations emerged, the existing ones enhanced their capacities. This resulted in significant rise in production, availability and accessibility of various seed grades of newly improved and farmer demanded legume varieties in the target countries.  相似文献   
152.
Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. The International Centre for Tropical Agriculture (CIAT) and its national partners in Africa aim to overcome production constraints of common bean and address the food, nutrition needs and market demands through development of multitrait bean varieties. Breeding is guided by principles of market‐driven approaches to develop client‐demanded varieties. Germplasm accessions from especially two sister species, P. coccineus and P. acutifolius, have been utilized as sources of resistance to major production constraints and interspecific lines deployed. Elucidation of plant mechanisms governing pest and disease resistance, abiotic stress tolerance and grain nutritional quality guides the selection methods used by the breeders. Molecular markers are used to select for resistance to key diseases and insect pests. Efforts have been made to utilize modern genomic tools to increase scale, efficiency, accuracy and speed of breeding. Through gender‐responsive participatory variety selection, market‐demanded varieties have been released in several African countries. These new bean varieties are a key component of sustainable food systems in the tropics.  相似文献   
153.
Effect of Li, Al, Cd, Cu(II), Mn(II), Pb(II), Se(IV) and Zn on entomopathogenic nematodes S. carpocapsae and H. bacteriophora mortality, pathogenicity, and productivity was studied under laboratory conditions. These ions were administered as the sole ions as well as in the Li-Al, Li-Cd, Li-Cu(II), Li-Mn(II), Li-Pb(II), Li-Se(IV) and Li-Zn pairs. Lithium as the sole acting ion exhibited a weak lethal effect on the nematodes. In combinations with other metal ions under study lithium used to inhibit their harmful effects.  相似文献   
154.
Metapopulation and optimal foraging theories predict the presence of animals and their duration, respectively, in foraging patches. This paper examines use of these two theories to describe the movements and patterns of foraging in patches used by Caspian gulls (Larus cachinnans) at inland reservoirs during the chick-rearing period. We assumed that birds would move differently across diverse habitats, with some types of land cover less permeable than others, and some landscape features acting as corridors. We also expected larger and less isolated patches, and patches that were close to corridors, to have a higher probability of the presence of foraging birds, and that they would be more abundant, forage for a shorter time, and hunt smaller prey than in small, more isolated patches surrounded by barriers. Forests seem to be a much less permeable type of land cover, whereas rivers became corridors for Caspian gulls during foraging trips. Probability of bird presence was positively related to the size of foraging patches and negatively linked with distance to the nearest river, distance to the nearest foraging patch, and the presence of forests in the vicinity. The same factors significantly affected bird abundance. Contrary to expectations, the duration and success of foraging were not influenced by any variable we measured, suggesting that although larger patches contain a higher abundance of fish, their density and the probability of capturing prey were relatively stable among the various patches. However, gulls that foraged in more isolated ponds that were located further from the river and the colony, and also surrounded by forest, captured larger fish more often than birds that foraged near the colony in less-isolated patches. Pooling metapopulation and optimal foraging concepts seems to be valuable in describing patch use by foraging animals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
155.
Purpose

The purpose of the study was to determine the levels of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran (PCDD/F), two types of persistent organic pollutant (POP), in an urban retention reservoir located in an industrial zone within a coal-mining region. It also assesses the potential ecological risk of the PCDDs/Fs present in bottom sediments and the relationship between their content and the fraction of organic matter.

Materials and methods

The sediment samples were collected from Rybnik Reservoir, located in the centre of the Rybnik Coal Region, Silesia, one of Poland’s major industrial centres. Seventeen PCDD/F congeners in the surface of the sediments were analysed using high-resolution gas chromatography and high-resolution mass spectrometry (HRGC/HRMS).

Results and discussion

The toxic equivalency (TEQ) of the PCDDs/Fs in the sediments ranged from 1.65 to 32.68 pg TEQ g?1. PCDDs constituted 59–78% of the total PCDDs/Fs, while the PCDFs accounted for 22–41%. The pattern of PCDD/F congeners in the sediments was dominated by OCDD. However, the second-most prevalent constituents were OCDF and ∑HpCDFs in the low TOC sediment (< 10 g TOC kg?1), but HpCDD in the rich TOC samples (> 10 g TOC kg?1). PCDD/F concentrations in the sediment samples were 2- to 38-fold higher than the sediment quality guidelines limit, indicating high ecological risk potential. Although a considerable proportion of PCDDs/Fs in the bottom sediments from the Rybnik Reservoir were derived from combustion processes, they were also obtained via transport, wastewater discharge, high-temperature processes and thermal electricity generation. The PCDD/F concentrations were significantly correlated with all fractions of organic matter; however, the strongest correlation coefficients were found between PCDDs/Fs and humic substances. Besides organic matter, the proportions of silt/clay fractions within sediments played an important role in the transport of PCDDs/Fs in bottom sediments.

Conclusions

The silt/clay fraction of the bottom sediments plays a dominant role in the movement of PCDDs/Fs, while the organic matter fraction affects their sorption. The results indicate that the environmental behaviour of PCDDs/Fs is affected by the quantity and quality of organic matter and the texture of sediments.

  相似文献   
156.
Skin biopsies were taken from female dogs, the primary hair follicles isolated and the dermal papilla dissected. After incubation in supplemented Amniomax complete C100 medium in 24-well culture plates, the dermal papilla cells (DPC) grew to confluence within 3 weeks. Thereafter, they were subcultivated every 7 days. Dermal fibroblast (DFB) cultures were established by explant culture of interfollicular dermis in serum-free medium, where they reached confluence in 10 days. They were subcultivated every 5 days. For immunohistochemistry, cells were grown on cover slips for 24 h, fixed and stained with antibodies against collagen IV and laminin. DPC showed an aggregative growth pattern and formation of pseudopapillae. Intensive staining for collagen IV and laminin could be observed until the sixth passage. DFB grew as branching, parallel lines and showed only weak staining for collagen IV and laminin.  相似文献   
157.
Interleukin (IL)-8 and its receptors, CXCR1 and CXCR2, are key regulators of inflammation. However, knowledge of these receptors at the genomic level is limiting or absent in cattle. Therefore, our objective was to identify bovine orthologs of human CXCR1 and CXCR2. Alignment of bovine CXCR2 reference mRNA to the bovine genome revealed two regions of similarity on BTA2 approximately 20 kb apart and on opposite strands. Comparison with the human genome suggested the more centromeric region to be CXCR2 and the more telomeric region to be CXCR1 which contradicts the current annotation of the bovine CXCR2 reference mRNA. This observation was verified by sequencing RT-PCR products of specific regions within each predicted IL-8 receptor and comparing with human sequences using ClustalW. Further examination of coding and non-coding regions within the IL-8 receptor genome complex revealed that both bovine and canine CXCR1 and CXCR2 genes had more conserved sequences in common with the human genes than either mouse or rat, and may offer more suitable animal models for certain applications. This molecular information provides a stepping stone for greater understanding of the role each IL-8 receptor plays in inflammation and will enhance our ability to develop strategies against inflammatory based diseases.  相似文献   
158.
Objective-To evaluate antimicrobial susceptibility of commensal Escherichia coli strains isolated from the feces of horses and investigate relationships with hospitalization and antimicrobial drug (AMD) administration. Design-Observational study. Animals-68 hospitalized horses that had been treated with AMDs for at least 3 days (HOSP-AMD group), 63 hospitalized horses that had not received AMDs for at least 4 days (HOSP-NOAMD group), and 85 healthy horses that had not been hospitalized or treated with AMDs (community group). Procedures-Fecal samples were submitted for bacterial culture, and up to 3 E coli colonies were recovered from each sample. Antimicrobial susceptibility of 724 isolates was evaluated. Prevalence of resistance was compared among groups by use of log-linear modeling. Results-For 12 of the 15 AMDs evaluated, prevalence of antimicrobial resistance differed significantly among groups, with prevalence being highest among isolates from the HOSP-AMD group and lowest among isolates from the community group. Isolates recovered from the HOSP-AMD and HOSP-NOAMD groups were also significantly more likely to be resistant to multiple AMDs. Resistance to sulfamethoxazole and resistance to trimethoprim-sulfamethoxazole were most common, followed by resistance to gentamicin and resistance to tetracycline. Use of a potentiated sulfonamide, aminoglycosides, cephalosporins, or metronidazole was positively associated with resistance to 1 or more AMDs, but use of penicillins was not associated with increased risk of resistance to AMDs. Conclusion and Clinical Relevance-Results suggest that both hospitalization and AMD administration were associated with prevalence of antimicrobial resistance among E coli strains isolated from the feces of horses.  相似文献   
159.
In organic apple orcharding there is a continuous need for natural fungicides effective against Venturia inaequalis (Cooke) Winter, the causal agent of apple scab. In this study an in vitro assay is presented for determining the germination inhibitory potential of extracts and pure compounds. From a screening of plant extracts, the methanol extract of Morus root bark revealed distinct V. inaequalis inhibiting qualities, which were subjected to a bioguided fractionation. Among the isolated metabolites [moracins M (1), O/P (2), kuwanon L (3), and sanggenons D (4), B (5), G (6), O (7), E (8), and C (9)] all the Diels-Alder adducts (3-9) showed an antifungal activity with IC50 values between 10 and 123 microM. The in vitro activity of the most active fraction (A5, IC50 39.0 +/- 4.2 microg/mL) was evaluated in vivo, confirming a distinct antifungal activity against V. inaequalis for the tested natural material.  相似文献   
160.
The hippocampus and entorhinal cortex play a pivotal role in spatial learning and memory. The two forebrain regions are highly interconnected via excitatory pathways. Using optogenetic tools, we identified and characterized long-range γ-aminobutyric acid-releasing (GABAergic) neurons that provide a bidirectional hippocampal-entorhinal inhibitory connectivity and preferentially target GABAergic interneurons. Activation of long-range GABAergic axons enhances sub- and suprathreshold rhythmic theta activity of postsynaptic neurons in the target areas.  相似文献   
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