Gene flow of oilseed rape (Brassica napus)according to isolation distance and buffer zone

The introduction of genetically modified (GM) crops in the EU has raised questions concerning gene dispersal and co-existence with non-GM farming. Quantitative estimates of the gene dispersal from fields with GM crops to fields with conspecific non-GM crops (conventional or organic) are therefore needed in order to suggest isolation distances and other management strategies to keep GM-pollination below acceptable threshold values. A meta-analysis of available gene-flow data for oilseed rape (Brassica napus) was performed. The probability distribution that seeds of non-GM oilseed rape are fertilised by foreign pollen grains from a neighbouring field of GM oilseed rape is modelled as functions of the width of the recipient (i.e. pollen receiving) field and the distance to the pollen donor fields. Furthermore, the significance of using a buffer zone (removal of a 1-5 m border of a recipient field parallel to the pollen donor field) to reduce GM-pollination of the crop, is quantified and discussed. The predicted median and 95% credibility level of the probability of foreign pollination is calculated as a function of the width of the recipient field and the buffer zone, as well as the distance between fields. Analysis of different management strategies shows that an increasing isolation distance is more effective to reduce GM pollen dispersal than the use of a buffer zone, especially for small recipient fields. The analysis shows that increasing the width of a recipient oilseed rape field, relative to the pollen donor field, will have a large effect on reducing the average level of fertilisation by foreign pollen within the recipient field. The results indicate that a GM-pollination percentage < 0.1% will be possible if the isolation distance exceeds 100 m and the width of the non-GM field is larger than 200 m. If a threshold value of 0.3% is acceptable, an isolation distance of 50 m should be sufficient even for smaller fields. The use of a 5 m discarded buffer zone surrounding the non-GM field is expected to reduce GM pollination by about a third. The implications of the results for field management in conventional and organic farming are discussed

Effect of Elymus repens on yield of winter wheat, spring barley and faba bean in an organic crop rotation experiment

The impact of crop rotation, nutrient levels and use of catch crops on effect of E. repens on a sandy soil at Jyndevad on yield of winter wheat (2006), spring barley (2007-2008) and faba bean (2006-2008) was studied in an existing organic crop rotation experiment (Olesen et al., 2000; Rasmussen et al., 2006). Some of the objectives were to determine the yield loss at different levels of infestation of the weed, and to determine whether this relationship was influenced by the treatments. For all crops, the treatments had a high impact on the yield. The two treatments that had no manure applied for up to 12 years consistently had the lowest yields. In spring barley, the two treatments with manure and with catch crops consistently had the highest yields. In faba bean, the treatment with manure and without catch crops had the highest yields. As for the effect of E. repens shoots on yield, in spring barley, there was a larger decrease in the system without grass clover. The same tendency was seen for winter wheat. For spring barley and faba bean, within each system (with or without grass clover), the yield in treatments without manure was less influenced by E. repens than in treatments with manure

Pollen dispersal of genetically modified oilseed rape to organic fields: Analysis of available data and the possibilities for co-existence

Results from model estimations based on existing data on gene dispersal in oilseed rape indicate that the GM dispersal by pollen to organic fields primarily can be limited by the use of isolation distances. The results also indicate that because of pollen dilution, large fields are better protected from GM pollen dispersal than smaller fields. For large fields (i.e. field width > 200 m), the risk of dispersal from GM fields by pollen will be limited (approx. 0.1%) at distances above 100 m. For small fields (i.e. width = 50 m), some GM pollen dispersal (up to approx. 0.3%) may be expected even with an isolation distance of 200 m. If the fields are very close, the use of additional protective buffer zones may be required

Estimating survival rates in ecological studies with small unbalanced sample sizes: an alternative Bayesian point estimator

Increasingly, the survival rates in experimental ecology are presented using odds ratios or log response ratios, but the use of ratio metrics has a problem when all the individuals have either died or survived in only one replicate. In the empirical ecological literature, the problem often has been ignored or circumvented by different, more or less ad hoc approaches. Here, it is argued that the best summary statistic for communicating ecological results of frequency data in studies with small unbalanced samples may be the mean of the posterior distribution of the survival rate. The developed approach may be particularly useful when effect size indexes, such as odds ratios, are needed to compare frequency data between treatments, sites or studies

The Angular Power Spectrum of Heavy Ion Collisions

Particles produced in heavy ion collisions carry information about anisotropies present already in the early state of the system and play a crucial role in understanding the Quark Gluon Plasma and its evolution. We explore the angular power spectrum of particle multiplicities in such heavy ion collisions to extract fluctuations in particle multiplicities on the surface a sphere. Results are presented for Pb-Pb data at $\sqrt{s_{NN}} = 2.76\mathrm{TeV}$, extracted from the ALICE open data portal. We find that odd modes of the power spectrum display a power-law behavior with corresponding index $\beta$, which is found to be close to unity. We also demonstrate that the angular power spectrum allows us to extract accurately the flow coefficients of non-central collisions

Nutrient allocations and metabolism in two collembolans with contrasting reproduction and growth strategies

Physiological mechanisms such as allocation and release of nutrients are keys to understanding an animal\u27s adaptation to a particular habitat. This study investigated how two detrivores with contrasting life‐history traits allocated carbon (C) and nitrogen (N) to growth, reproduction and metabolism. As model organisms we used the collembolans, Proisotoma minuta (Tullberg 1871) and Protaphorura fimata (Gisin 1952). To estimate allocations of C and N in tissue, we changed the isotopic composition of the animal\u27s yeast diets when they became sexually mature and followed isotope turnover in tissue, growth and reproduction for 28 days. In addition, we measured the composition of C, N and phosphorus (P) to gain complementary information on the stoichiometry underlying life‐history traits and nutrient allocation. For P. minuta, the smallest and most fecund of the two species, the tissue turnover of C and N were 13% and 11% day−1, respectively. For P. fimata, the equivalent rates were 5% and 4% d−1, respectively. Protaphorura fimata had the lowest metabolic rate relative to total body mass but the highest metabolic rates relative to reproductive investment. Adult P. fimata retained approximately 17% of the nutrient reserves acquired while a juvenile and adult P. minuta about 11%. N and P contents of total tissue were significantly higher in P. minuta than in P. fimata, suggesting that tissue turnover was correlated with high protein‐N and RNA‐P. Our results suggest that the lower metabolism and nutritional requirements by P. fimata than P. minuta is an adaptation to the generally low availability and quality of food in its natural habitat. The methodological approach we implemented tracking mass balance, isotope turnover and elemental composition is promising for linking nutrient budgets and life‐history traits in small invertebrates such as Collembola

Contamination of oilseed rape varieties by pollen and seeds

Oilseed rape (Brassica napus) is a common crop in Denmark and mainly cultivated for its content of oil used for food and feed. The species is often genetically modified (GM), e.g. to herbicide tolerance or insect resistance. Spread of the inserted genes is likely to occur not only to the species itself, but also to its close relatives. The study showed a significant difference between phenotypes in the certified seeds and phenotypes in plants and in seeds in the field. The reason for this might be the presence of OSR volunteers from a previous crop surviving in the soil seed bank. This type of contamination is affected by e.g., harvest and post-harvest handling procedures (Fargue et al., 2003) and can consequently be reduced. More studies on homogeneity (i.e., genetic variation) between field crop plants and certified seeds may contribute to the detection of adventitious presence of GMO in organic crops and the routes of contamination

Scattering Equations and Feynman Diagrams

We show a direct matching between individual Feynman diagrams and integration measures in the scattering equation formalism of Cachazo, He and Yuan. The connection is most easily explained in terms of triangular graphs associated with planar Feynman diagrams in $\phi^3$-theory. We also discuss the generalization to general scalar field theories with $\phi^p$ interactions, corresponding to polygonal graphs involving vertices of order $p$. Finally, we describe how the same graph-theoretic language can be used to provide the precise link between individual Feynman diagrams and string theory integrands.Comment: 18 pages, 57 figure