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.
2020
Authors
Hella Ellen Ahrends Stefan Siebert Ehsan Eyshi Rezaei Sabine Julia Seidel Hubert Hüging Ewert Frank Thomas Döring Victor Rueda-Ayala Werner Eugster Thomas GaiserAbstract
Yield stability is important for food security and a sustainable crop production, especially under changing climatic conditions. It is well known that the variability of yields is linked to changes in meteorological conditions. However, little is known about the long-term effects of agronomic management strategies, such as the supply of important nutrients. We analysed the stability of four major European crops grown between 1955 and 2008 at a long-term fertilization experiment located in Germany. Six fertilizer treatments ranged from no fertilization over the omission of individual macronutrients to complete mineral fertilization with all major macronutrients (nitrogen, phosphorus, potassium and calcium). Yield stability was estimated for each crop x treatment combination using the relative yield deviation in each year from the corresponding (nonlinear) trend value (relative yield anomalies). Stability was lowest for potato, followed by sugar beet and winter wheat and highest for winter rye. Stability was highest when soils had received all nutrients with the standard deviation of relative yield anomalies being two to three times lower than for unfertilized plots. The omission of nitrogen and potassium was associated with a decrease in yield stability and a decrease in the number of simultaneous positive and negative yield anomalies among treatments. Especially in root crops nutrient supply strongly influenced both annual yield anomalies and changes in anomalies over time. During the second half of the observation period yield stability decreased for sugar beet and increased for winter wheat. Potato yields were more stable during the second period, but only under complete nutrient supply. The critical role of potassium supply for yield stability suggests potential links to changes in the water balance during the last decades. Results demonstrate the need to explicitly consider the response of crops to long-term nutrient supply for understanding and predicting changes in yield stability.
Abstract
Pythium species are ubiquitous organisms known to be pathogens to terrestrial plants and marine algae. While several Pythium species (hereafter, Pythium) are described as pathogens to marine red algae, little is known about the pathogenicity of Pythium on marine green algae. A strain of a Pythium was isolated from a taxonomically unresolved filamentous Ulva collected in an intertidal area of Oslo fjord. Its pathogenicity to a euryhaline Ulva intestinalis collected in the same area was subsequently tested under salinities of 0, 15, and 30 parts per thousand (ppt). The Pythium isolate readily infected U. intestinalis and decimated the filaments at 0 ppt. Mycelium survived on U. intestinalis filaments for at least 2 weeks at 15 and 30 ppt, but the infection did not progress. Sporulation was not observed in the infected algal filaments at any salinity. Conversely, Pythium sporulated on infected grass pieces at 0, 15, and 30 ppt. High salinity retarded sporulation, but did not prevent it. Our Pythium isolate produced filamentous non-inflated sporangia. The sexual stage was never observed and phylogenetic analysis using internal transcribed spacer suggest this isolate belongs to the clade B2. We conclude that the Pythium found in the Oslo fjord was a pathogen of U. intestinalis under low salinity.
Authors
Selamawit Araya Kidane Beira H. Meressa Solveig Haukeland Trine Hvoslef-Eide Christer Magnusson Marjolein Couvreur Wim Bert Danny L. CoyneAbstract
Enset (Ensete ventricosum) is an important starch staple crop, cultivated primarily in south and southwestern Ethiopia. Enset is the main crop of a sustainable indigenous African system that ensures food security in a country that is food deficient. Related to the banana family, enset is similarly affected by plant-parasitic nematodes. Plant-parasitic nematodes impose a huge constraint on agriculture. The distribution, population density and incidence of plant-parasitic nematodes of enset was determined during August 2018. A total of 308 fields were sampled from major enset-growing zones of Ethiopia. Eleven plant-parasitic nematode taxa were identified, with Pratylenchus (lesion nematode) being the most prominent genus present with a prominence value of 1460. It was present in each sample, with a highest mean population density per growing zone of 16 050 (10 g root)−1, although densities as high as 25 000 were observed in fields at higher altitudes in Guraghe (2200-3000 m a.s.l.). This lesion nematode is found in abundance in the cooler mountainous regions. Visible damage on the roots and corms was manifested as dark purple lesions. Using a combination of morphometric and molecular data, all populations were identified as P. goodeyi and similar to populations from Kenya, Uganda and Spain (Tenerife). Differences in population densities amongst cultivars indicate possible resistance of enset to P. goodeyi.
Authors
Svenja B. Kroeger Daniel T. Blumstein Kenneth B. Armitage Jane Margaret Reid Julien G.A. MartinAbstract
No abstract has been registered
Abstract
Key message This literature review identified the main factors for the success of different silvicultural approaches to regenerate sessile oak naturally and unveiled at the same time important knowledge gaps. Most previous studies were only short-term and restricted to a few factors and single locations. Hence, the findings of these studies are of limited explanatory power and do not allow to develop general, widely applicable management recommendations. Context Successful natural regeneration of sessile oak (Quercus petraea (Matt.) Liebl.) through silvicultural actions depends on a number of biotic, abiotic and management factors and their interactions. However, owing to a limited understanding about the influence of these critical factors, there is great uncertainty about suitable silvicultural approaches for natural oak regeneration, in particular regarding the size of canopy openings and speed of canopy removal. Aims This study aimed at critically evaluating documented information on natural regeneration of sessile oak. Specifically, we identified (i) the factors that determine the success of approaches for natural regeneration and (ii) evaluated the evidence base associated with different silvicultural approaches. Methods A comprehensive literature search was done considering relevant peer-reviewed publications of ISI-listed journals as well as non-ISI listed published papers and reports by practitioners. Out of more than 260 collected references, a set of 53 silvicultural ‘core publications’ was identified and analyzed using a catalogue of numeric and categorical evaluation criteria. Results The most important factors determining regeneration success extracted from the literature were light availability, presence of competing vegetation, initial oak seedling density, browsing of seedlings and intensity of stand tending measures. However, the review revealed also great uncertainty regarding the interactions between these factors and the magnitude of their influence. Most studies were of short duration and restricted to single locations. In only 20% of the experimental studies, the observation period exceeded five years. Total costs of regeneration efforts were quantified and reported in only two studies. This lack of data on the expenses of different approaches to natural oak regeneration appears to be one of the most crucial knowledge deficits revealed in this literature review. Conclusion Natural regeneration of sessile oak may be achieved under a wide range of canopy openings, if competing vegetation and browsing is negligible, seedling density is high and tending to remove competing vegetation is carried out consistently. However, since the silvicultural regeneration success depends on the interactions among these factors, which have often not been adequately considered, we caution against general recommendations for silvicultural systems developed from case studies and call for new long-term studies with comprehensive experimental designs.
Authors
Anita SønstebyAbstract
No abstract has been registered
Abstract
One of the most important factors affecting photosynthesis and metabolism is light absorbance by leaves and penetration through the canopy. The aim of this study was to evaluate the influence of planting density and tree development stages on photosynthetic activity, photosynthetic pigments, and carbohydrates in apple (Malus domestica Borkh.) trees in a combined way. The apple tree, Auksis, was grafted on dwarfing rootstock P 22. Space between rows was 3 m, trees were planted in 2001 in four distances: 0.25 m, 0.50 m, 0.75 m, and 1.00 m. Measurements and leaf samples were taken in the end of May (leaves fully expanded BBCH 20–25), in the middle of July (beginning of apple maturity BBCH 73–75) and at the end of August (harvest time BBCH 87–88) according BBCH—growth stages. Photosynthetic rate was significantly the lowest in the spring and tended to rise until fruit ripening, when it increased up to 19.4% compared to spring. Significantly the highest chlorophyll b and carotene α and β contents were found at the BBCH 73–75. The lowest levels of fructose and sorbitol in leaves were found at BBCH 73–75. The amount of starch accumulated in the leaves increased three times in summer compared to spring. Reduced distance between trees to four times (from 1 m to 0.25 m) showed clear competitive stress, as the decrease of photosynthetic rate (up to 36.4–38.6%) and total starch (up to 37–53%) was observed. The photosynthetic behaviour of apple trees was significantly affected by the development stage during the particular season which is related with physiological changes of metabolites transport and their distribution during fruit ripening and leaf senescence.
Abstract
No abstract has been registered
Authors
Jakob GeipelAbstract
No abstract has been registered
Authors
Jamie N. Orr Roy Neilson Thomas E. Freitag David M. Roberts Keith Davies Vivian C. Blok Peter J. A. CockAbstract
Pasteuria spp. are endospore forming bacteria which act as natural antagonists to many of the most economically significant plant parasitic nematodes (PPNs). Highly species-specific nematode suppression may be observed in soils containing a sufficiently high density of Pasteuria spp. spores. This suppression is enacted by the bacteria via inhibition of root invasion and sterilization of the nematode host. Molecular methods for the detection of Pasteuria spp. from environmental DNA (eDNA) have been described; however, these methods are limited in both scale and in depth. We report the use of small subunit rRNA gene metabarcoding to profile Pasteuria spp. and nematode communities in parallel. We have investigated Pasteuria spp. population structure in Scottish soils using eDNA from two sources: soil extracted DNA from the second National Soil Inventory of Scotland (NSIS2); and nematode extracted DNA collected from farms in the East Scotland Farm Network (ESFN). We compared the Pasteuria spp. community culture to both nematode community structure and the physiochemical properties of soils. Our results indicate that Pasteuria spp. populations in Scottish soils are broadly dominated by two sequence variants. The first of these aligns with high identity to Pasteuria hartismeri, a species first described parasitizing Meloidogyne ardenensis, a nematode parasite of woody and perennial plants in northern Europe. The second aligns with a Pasteuria-like sequence which was first recovered from a farm near Edinburgh which was found to contain bacterial feeding nematodes and Pratylenchus spp. encumbered by Pasteuria spp. endospores. Further, soil carbon, moisture, bulk density, and pH showed a strong correlation with the Pasteuria spp. community composition. These results indicate that metabarcoding is appropriate for the sensitive, specific, and semi-quantitative profiling of Pasteuria species from eDNA.