Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2015
Abstract
A survey of nematodes associated with terrestrial slugs was conducted for the first time in Norway. A total of 611 terrestrial slugs were collected from 32 sample sites. Slugs were identified by means of morphological examination, dissection of genitalia and molecular analysis using mitochondrial DNA. Twelve slug species were identified, representing four different slug families. Internal nematodes were identified by means of morphological analysis and the sequencing of the 18S rRNA gene. Of the sample sites studied, 62.5% were found to be positive for nematode parasites, with 18.7% of all slugs discovered being infected. Five nematode species were identified in this study: Alloionema appendiculatum, Agfa flexilis, Angiostoma limacis, Angiostoma sp. and Phasmarhabditis hermaphrodita. Of these species, only one nematode was previously undescribed (Angiostoma sp.). This is the first record of the presence of A. appendiculatum, A. flexilis and A. limacis in Norway.
2014
Authors
Zhibo Hamborg Sissel Haugslien Jihong Liu Clarke Carl Jonas Jorge Spetz Dag-Ragnar Blystad Qing Wang YeonKyeong Lee Astrid H Sivertsen Gry SkjesethAbstract
Chrysanthemum stunt viroid (CSVd) was first reported in US in the 1940s and is widespread in the world wherever chrysanthemum is grown. Cryotherapy of shoot tips, a new biotechnology developed in the recent years, is a novel application of plant cryopreservation techniques that allows pathogen eradication at a high frequency. Existing studies have proven that this technique can efficiently eradicate pathogens such as virus, phytoplasma and bacterium. However, up to now, there has been no report on viroid eradication. In the present study, we attempted to establish a droplet vitrification cryotherapy method for Argyranthemum and to apply it to eradicate CSVd. Results obtained so far demonstrated that cryotherapy of shoot tips alone failed to eradicate CSVd from the infected shoot tips of Argyranthemum maderense ‘Yellow Empire’. Using in situ hybridization of CSVd and histological analysis, we found that CSVd can invade meristematic cells and at the same time, these cells were able to survive following cryotherapy. These findings explained why cryotherapy of shoot tips alone could not be efficient enough to eradicate CSVd from the diseased materials. Further studies combining cold treatment with cryotherapy are under investigation for CSVd eradication.
Authors
Biao Wang Jing-Wei Li Zhibo Hamborg Ren-Rui Wang Yan-Li Ma Dag-Ragnar Blystad E.R. Joachim Keller Qiao-Chun WangAbstract
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Nematodes as limiting factors in potato production in Norway Plant parasitic nematodes associated with potato feeds on roots and/or tubers. At least 68 species, representing 24 genera of have been found associated with potato. Since nematodes generally attack underground plant parts, there are no reliable foliar symptoms to show that nematodes may be the major cause of poor growth and reduced tuber yields. Potato roots damaged by nematodes may show the presence of lesions, females/cysts or galls. After a few weeks, however, roots may be attacked by other pathogens such as bacteria and fungi, and the original damage by nematodes may not be obvious. Therefore, nematode damage often may have been attributed to other factors. There are no estimations for potatoes yield losses in Scandinavia due to nematodes, however, in the United Kingdom, it is estimated that 9 % of the potato crop is lost annually because of the potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida, and it is reasonable to assume that this percentage is also applicable to Scandinavia. However, if we consider the possible additional effects of other nematode species occurring in Norway, yield reductions could be as high as 20%. Besides direct yield losses, some nematodes affect tuber quality. Yield losses depend on the pathogenicity of the species of nematode, the nematode population density at planting, the susceptibility and tolerance of the host and by a range of environmental factors. In Norway, potato cyst nematodes (G. rostochiensis and G. pallida) are by far the most important nematodes in potato. Other important nematodes include root-lesion nematodes (Pratylenchus spp.), stubby root nematodes (Trichodorus spp. and Paratrichodorus spp.) and stem and tuber nematodes (Ditylenchus spp.). Nematodes considered less important include root knot nematode (Meloidogyne hapla) and needle nematodes (Longidorus spp.). In Norway, potato cyst nematodes (Globodera rostochiensis and G. pallida) are quarantine pests subjected to regulations. PCN infestations result in costly production systems and loss in sales value of farms. Their occurrences restrict acreage available for potato production as in some cases legislative regulations forbid potato production or make the production more difficult and more expensive. Furthermore societal consequences by far exceed yield losses. It is also compulsory to sample the soil for seed potato production to document freedom from PCN. When PCN is present in the field complete eradication is not possible. Effective management requires reliable information on virulence, decline rates of population densities and infectivity in soil. It is also crucial to know what conditions or practices increase these decline rates. Today in Norway, non-virulent G. rostochiensis is managed by crop rotation, while infestations by G. pallida or virulent G. rostochiensis pathotypes capable of breaking the resistance in potato cultivars in current use results in a 40-years prohibition for growing potato in the infected field. Root-lesion nematodes (Pratylenchus spp.) cause damage to the roots and induce scabby to sunken lesions on tubers. Stubby root nematodes (Trichodorus spp. and Paratrichodorus are nematode vectors of Tobacco Rattle Virus they causes the symptom called “Spraing” in tubers. Occasionally stem and tuber nematodes (Ditylenchus spp.), have been reported as problems both in field and storage, especially when weeds are not well controlled. Management strategies aim to prevent nematode multiplication and hence protect the potato crop from damage. An efficient method of controlling nematodes as Ditylenchus spp. and root-lesion nematodes is black fallow, but this may be difficult to achieve in many cases.
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Authors
Yan-liang Wang Sissel Haugslien Marit Almvik Nicholas Clarke Anne Falk Øgaard Jihong Liu ClarkeAbstract
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Yanliang Wang Sissel Haugslien Marit Almvik Nicholas Clarke Anne Falk Øgaard Jihong Liu ClarkeAbstract
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