Response of different intermediate-day onion hybrids to natural infestation by Phoma terrestris and Fusarium oxysporum f. sp. cepae in Ciudad Real, Spain with assessment of different soil disinfestation methods     

A. I. Nico  M. González Sánchez 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(4):783-793

Incidence and severity of Pink root caused by Phoma terrestris and Fusarium basal rot caused by Fusarium oxysporum f. sp. cepae were field-tested on factorial combinations of different soil fumigation treatments in five different intermediate-day onion hybrids widely adapted at the Bola?os de Calatrava area (Ciudad Real, Spain). The effect of Dazomet and virulence of the local isolates were then tested in trays under greenhouse conditions. When compared to Electric, the other four onion hybrids showed a certain degree of tolerance to Pink root and Fusarium basal rot with little difference among them. The field trial carried out in 2006 showed significant but negligible beneficial effects in medium bulb weight and Pink root severity due to Dazomet. The field trial carried out in 2007 showed significant beneficial effects of Metham-sodium on plant growth and Pink root and Fusarium basal rot severities. Sodium tetrathiocarbonate performed worse than the control. Greenhouse test showed that Dazomet performed nearly as well as sterilization under controlled conditions. Virulence of local isolates was lower than that of reference isolates.  相似文献   

The impact of quorum sensing on the virulence of Aeromonas hydrophila and Aeromonas salmonicida towards burbot (Lota lota L.) larvae     

Natrah FM  Alam MI  Pawar S  Harzevili AS  Nevejan N  Boon N  Sorgeloos P  Bossier P  Defoirdt T 《Veterinary microbiology》2012,159(1-2):77-82

In this study, the link between quorum sensing in Aeromonas spp. and its virulence towards burbot (Lota lota) was investigated. High mortality occurred in burbot juveniles challenged with Aeromonas salmonicida HN-00, but not in juveniles challenged with Aeromonas hydrophila AH-1N. Meanwhile, both A. hydrophila AH-1N and A. salmonicida HN-00 were virulent towards larvae. The effect of quorum sensing on the virulence of A. hydrophila AH-1N towards burbot larvae was further investigated using quorum sensing mutants (N-(butyryl)-L-homoserine lactone production and receptor mutants). Challenge with these mutants resulted in higher survival of burbot larvae when compared to challenge with the wild type, and the addition of the signal molecule N-butyryl-L-homoserine lactone restored the virulence of the quorum sensing production mutant. Moreover, quorum sensing inhibitors protected the burbot larvae from both Aeromonas strains. Finally, the freshwater micro-algae Chlorella saccharophila and Chlamydomonas reinhardtii, which are able to interfere with quorum sensing, also protected burbot from the pathogens. However, QS interference was unlikely to be the only mechanism. This study revealed that the virulence of Aeromonas spp. towards burbot is regulated by quorum sensing and that quorum sensing inhibitors and micro-algae are promising biocontrol agents.  相似文献   

Present and historical landscape structure shapes current species richness in Central European grasslands     

Scherreiks  Pascal  Gossner  Martin M.  Ambarl&#;  Didem  Ayasse  Manfred  Bl&#;thgen  Nico  Fischer  Markus  Klaus  Valentin H.  Kleinebecker  Till  Neff  Felix  Prati  Daniel  Seibold  Sebastian  Simons  Nadja K.  Weisser  Wolfgang W.  Wells  Konstans  Westphal  Catrin  Thiele  Jan 《Landscape Ecology》2022,37(3):745-762

Landscape Ecology - Current diversity and species composition of ecological communities can often not exclusively be explained by present land use and landscape structure. Historical land use may...  相似文献   

Invasion of a deciduous forest by earthworms: Changes in soil chemistry, microflora, microarthropods and vegetation     

Nico Eisenhauer  Stephan Partsch  Stefan Scheu 《Soil biology & biochemistry》2007,39(5):1099-1110

Ecosystems of northern North America existed without earthworm fauna until European settlers arrived and introduced European species. The current extent of invasion by some of these species, Lumbricus terrestris L., Octolasion tyrtaeum Savigny and Dendrobaena octaedra Savigny, into an aspen forest in the Canadian Rocky Mountains and the effects of the invasion on soil chemistry, microflora, soil microarthropods and vegetation were investigated. Densities of earthworm species, soil structure, plant coverage and abundance were determined along three transects starting at the edge of the forest. At locations with L. terrestris, litter was incorporated into the soil, and where O. tyrtaeum was present, organic layers were mixed with mineral soil layers. Organic layers disappeared almost entirely when both species occurred together. Carbon and nitrogen concentrations were reduced in organic layers in the presence of L. terrestris and O. tyrtaeum. Microbial biomass and basal respiration were reduced when L. terrestris and O. tyrtaeum were present, presumably due to resource competition and habitat destruction. Microarthropod densities and the number of microarthropod species were strongly reduced in the presence of O. tyrtaeum (−75% and −22%, respectively), probably through mechanical disturbances, increasing compactness of the soil and resource competition. The coverage of some plant species was correlated with earthworm abundance, but the coverage of others was not. Despite harsh climatic conditions, the invasion of boreal forest ecosystems by mineral soil dwelling earthworm species is proceeding and strongly impacts soil structure, soil chemistry, microorganisms, soil microarthropods and vegetation.  相似文献   

Rapid stakeholder and conflict assessment for natural resource management using cognitive mapping: The case of Damdoi Forest Enterprise,Vietnam     

Carsten?Nico?Hjorts?Email author  Stig?M?ller?Christensen  Peter?Tarp 《Agriculture and Human Values》2005,22(2):149-167

Understanding stakeholders perceptions and motivations is of significant importance in relation to conservation and protected area projects. The importance of stakeholder analysis is widely recognized as a necessary means for gaining insight into the complex systemic interactions between natural processes, management policies, and local people depending on the resource. Today, community and group-based participatory inquiry approaches are widely used for this purpose. Recently, participatory approaches have been critiqued for not considering power relations and conflict internal to the community. In this article, we suggest that the five-step Rapid Stakeholder and Conflict Assessment (RSCA) methodology addresses this critique. The objective of the methodology is to provide a facilitator with a comprehensive foundation on which to plan and conduct subsequent participatory project development. The RSCA integrates elements of soft systems and critical systems thinking. Qualitative research interviews and cognitive mapping of stakeholders mental models are used for collection of empirical material and analysis. The RSCA methodology is demonstrated in a case study concerning buffer zone management in the coastal wetlands of southern Vietnam. The case study shows that the RSCA methodology can provide an efficient way of obtaining a holistic and critical understanding of a complex resource management situation, thus potentially enhancing project performance in an instrumental as well as an ethical sense.  相似文献   

THE SCIENCE AND TECHNOLOGY BACKYARD AS A LOCAL LEVEL INNOVATION INTERMEDIARY IN RURAL CHINA     

Jinghan LI  Cees LEEUWIS  Nico HEERINK  Weifeng ZHANG 《农业科学与工程前沿(英文版)》2022,9(4):558

● Agricultural innovation is a coevolution process of hardware, software and orgware. ● Innovation intermediaries is important for the coevolution process of agricultural innovation. ● The roles of STBs have evolved from a knowledge broker to a broader innovation intermediary at the village level. ● Facilitating orgware is more effective than enabling software in promoting farmers’ adoption of improved tillage practice. ● Collaboration between individual STBs is needed to support the coevolution process of innovation at a larger scale. Agricultural innovation can be described as a coevolutionary process of technological innovation, symbolic change, and social or institutional innovation, which relies on the interactions and collaboration between multiple stakeholders. This view emphasizes the significance of innovation intermediaries in supporting the coevolution process of innovation. Many studies have provided evidence on how innovation intermediaries play roles in supporting the coevolution innovation process at a broader innovation system level. However, little emphasis has been given to the role of innovation intermediaries in supporting the coevolution process of innovation at the community level in rural China. To address this research gap, this paper offers a case study of a novel type of innovation support intervention designed to promote technical change at the community level, the Science and Technology Backyard (STB). The paper focuses on the efforts of a specific STB in Wangzhuang village to promote innovation in tillage methods in wheat production. The aims was to examine the role of this newly emerging innovation support intervention in supporting the coevolution process of innovation at the community level, and compare the outcome of the coevolution process in the village with an STB to that in villages without an STB. Innovation journey analysis is applied to understand the evolved intermediation roles in the innovation process, and multivariate regression analysis is employed to assess the outcome of the coevolution process in villages with and without an STB. The findings suggest that the roles of STBs have evolved from knowledge brokers to systemic innovation intermediaries that facilitate the coevolution process of innovation inside an STB village. It has led to a higher adoption rate of improved technology, a better enabling environment for learning, and more effective institutional support in STB villages than in non-STB villages. However, the effect of support provided by a single STB on the coevolution process outside the community was limited. This finding points to a need for collaboration mechanisms and for connecting single STBs to support the coevolution process of innovation at a larger scale.  相似文献   

Effect of infections with swine fever virus on immune functions II. Lymphocyte response to mitogens and enumeration of lymphocyte subpopulations     

Jan T. Van Oirschot  Dirk De Jong  Nico D.N.H.J. Huffels 《Veterinary microbiology》1983,8(1):81-95

Peripheral blood and spleen lymphocytes from pigs infected with a low-virulent strain of swine fever virus (SFV) were transiently hyporesponsive to the mitogenic action of PHA, PWM and Con A. The mitogenic reactivity of lymphocytes from lymph nodes from such pigs appeared to be enhanced rather than depressed at that time. In addition, hyperresponsiveness of peripheral blood lymphocytes (PBL) to these mitogens occurred in some pigs.PBL from pigs lethally infected with virulent SFV showed a persistent depression of the response to these mitogens, whereas lymphocytes from lymph nodes had a high responding capacity.A lymphocyte response to SFV antigens could not be demonstrated in infected pigs.These SFV infections did not markedly affect the percentage of lymphocytes in the blood and most lymphoid organs rosetting with sheep red blood cells. On the other hand, surface immunoglobulin-bearing lymphocytes were markedly increased in lymph nodes from pigs exposed to virulent SFV. The sum of both lymphocyte subpopulations in the lymph nodes from these pigs often considerably exceeded the 100% value, which strongly suggests the presence of cells bearing both surface immunoglobulin and receptors for dextran-treated sheep red blood cells.Possible correlations between these findings are discussed. The results suggest that infections with SFV induce systemic alterations in the process of lymphocyte recirculation in the pig.  相似文献   

土地细碎化对中国东南部水稻小农户技术效率的影响   总被引：22，自引：0，他引：22  

谭淑豪  Nico Heerink  曲福田 《中国农业科学》2006,39(12):2467-2473

【目的】水稻生产是中国广大稻区农民收入和减轻贫困的重要途径，而土地细碎化可能是目前进一步提高农业生产率和减轻农村贫困的主要瓶颈之一。【方法】采用详实的农户调查以及作物水平和地块层次的数据，用两阶段法分析了土地细碎化对中国东南部一个水稻主要产区农户技术效率的影响。【结果】研究区早稻的平均技术效率为0.85，晚稻为0.83，而单季稻为0.79。稻田平均地块大小对早、中、晚3种水稻的技术效率都有显著的正影响。此外，家庭规模和农地规模对3种水稻生产的技术效率也有显著影响。人口较多的家庭或规模较大的农场技术效率较小家庭或小农场要高。【结论】在现有技术状态下，水稻小农户的技术效率仍可得到可观的提高。研究揭示，减轻土地细碎度的项目如果能够与促进农村劳动力市场发育的措施结合起来，将是提高水稻生产技术效率行之有效的途径。  相似文献   

Growth performance and use of natural food by Oreochromis niloticus (L.) in polyculture systems with Barbodes gonionotus (Bleeker) and Cyprinus carpio (L.) in intensively cultivated rice fields     

Nico Vromant  C Q Nam  & F Ollevier 《Aquaculture Research》2002,33(12):969-978

In the freshwater area of Vietnam's Mekong Delta, Oreochromis niloticus (L.), Barbodes gonionotus (Bleeker) and Cyprinus carpio (L.) are often reared together in rice fields. In this study, we report the results of eight such polyculture experiments, examining variables affecting the specific growth rate and the average daily food energy consumption of individual O. niloticus. The standing biomass of O. niloticus and the wild fish biomass had a negative impact on the specific growth rate, whereas added pig manure, extra feed and inorganic fertilizer had a positive effect. The standing biomass of O. niloticus and C. carpio, and the wild fish biomass had a negative impact on the consumption of natural feed. We inferred that O. niloticus mainly lacks food in rice fields. This results in intraspecific competition. As in rice fields, C. carpio has basically the same feeding niche as O. niloticus; we found interspecific competition between the two species. O. niloticus consumed relatively more food in the vegetative phase of the rice crop, probably because of a higher abundance of phytoplankton. To get higher growth of O. niloticus, we recommend that farmers increase nutrient inputs and stock O. niloticus according to the size of the trench adjoining the rice field and not according to the size of trench plus field as is generally done.  相似文献   

Restoration of a small‐scale forest wetland in a Belgian nature reserve: a discussion of factors determining wetland vegetation establishment     

Gisle Weyembergh  Sandrine Godefroid  Nico Koedam 《水产资源保护:海洋与淡水生态系统》2004,14(4):381-394

• 1. The main aim of this restoration attempt within a nature reserve was to recreate sustainable conditions for wetland species, particularly aquatic plants.
• 2. In the process of restoration, two phases of activity were distinguished: a pre‐restoration phase, during which information on land‐use history and past vegetation was collected and used to establish clear restoration goals; and a restoration phase for stimulating germination and establishment of target species originating from the soil seed bank and species pool.
• 3. Within the first year of the study, pond digging allowed the establishment of extremely rare native species that react positively to mudflat creation and standing water availability. The results of this experiment indicate that pond digging can be a very suitable technique for re‐establishing aquatic and wetland vegetation, providing that the site is well chosen.
• 4. An essential prerequisite for successful restoration is a study of the past vegetation of the target site and its surroundings. This work illustrates the importance of past vegetation in affecting current restoration success and provides an example of how restoration projects benefit from knowledge and understanding of both historical and present conditions.

Copyright © 2004 John Wiley & Sons, Ltd.  相似文献