Spatial abundance and clustering of Culicoides (Diptera: Ceratopogonidae) on a local scale

BACKGROUND: Biting midges, Culicoides, of the Obsoletus group and the Pulicaris group have been involved in recent outbreaks of bluetongue virus and the former was also involved in the Schmallenberg virus outbreak in northern Europe. METHODS: For the first time, here we investigate the local abundance pattern of these two species groups in the field by intensive sampling with a grid of light traps on 16 catch nights. Neighboring trap catches can be spatially dependent on each other, hence we developed a conditional autoregressive (CAR) model framework to test a number of spatial and non-spatial covariates expected to affect Culicoides abundance. RESULTS: The distance to sheep penned in the corner of the study field significantly increased the abundance level up to 200 meters away from the sheep. Spatial clustering was found to be significant but could not be explained by any known factors, and cluster locations shifted between catch nights. No significant temporal autocorrelation was detected. CAR models for both species groups identified a significant positive impact of humidity and significant negative impacts of precipitation and wind turbulence. Temperature was also found to be significant with a peak at just below 16 degrees Celcius. Surprisingly, there was a significant positive impact of wind speed. The CAR model for the Pulicaris group also identified a significant attraction to the smaller groups of sheep placed in the field. Furthermore, a large number of spatial covariates which were incorrectly found to be significant in ordinary regression models were not significant in the CAR models. The 95% C.I. on the prediction estimates ranged from 20.4% to 304.8%, underlining the difficulties of predicting the abundance of Culicoides. CONCLUSIONS: We found that significant spatial clusters of Culicoides moved around in a dynamic pattern varying between catch nights. This conforms with the modeling but was not explained by any of the tested covariates. The mean abundance within these clusters was up to 11 times higher for the Obsoletus group and 4 times higher for the Pulicaris group compared to the rest of the field

Somatic embryogenesis in white clover (Trifolium repens L.)

I White Clover (Trifolium repens L.) is an important perennial forage legume widely cultivated in Turkey and many other countries. It also helps in improving soil structure by fixing atmospheric nitrogen, and prevents soil erosion. The application of modern tissue culture techniques to this important plant should contribute to improvement in terms of production. Hypocotyls, epicotyl and cotyledon explants of a local ecotype of white clover were treated with various concentrations of Thidiazuron (TDZ) + Naphthalene acetic acid (NAA) and kinetin + NAA in MS medium to establish an efficient in vitro somatic embryogenesis system. High frequency of embryogenesis was observed on the MS medium containing 9.29 mM kinetin + 1.07 mM NAA (14.35embryos per explant) or 0.34 mM TDZ + 0.54 mM NAA (29.62 embryos per explant). It was concluded that embryogenesis was significantly influenced by the added plant growth regulators in the concentration-dependent manner;: Plantlets from the embryos were recovered on the MS medium and were transferred to a greenhouse, where they flowered and set fertile seeds

Abiotic factors affecting in vitro pollen grain germination in sainfoin (Onobrychis viciifolia Scop.)

A reliable in vitro method for germination of sainfoin pollen grains has been developed. Highest pollen germination rate of 96% with mean pollen tube length of 223.5 mum was obtained on medium containing of 100 g/l sucrose, 200 mg/l KNO3, 150 mg/l H3BO3, 150 mg/l MgSO4, 150 mg/l Ca(NO3)(2), 175 g/l PEG 4000 and stigma extract at pH 6.5

On the existence of a second Jπ = 0+ resonance at high excitation energy in 24Mg and a possible mechanism for the occurrence of resonances in the (12C + 12C) system

Evidence for the existence of a second Jπ = 0 + resonance at high excitation energy in 24Mg (E x = 19.70 MeV) is shown from a study of the 12C( 12C, α)20Ne reaction at Ec.m. = 5.80 ± 0.05 MeV. Using this result and those obtained previously, a comparison is made with the resonances observed in the second well of the fission barrier of some actinides.L'existence d'une seconde résonance Jπ = 0+ à haute énergie d'excitation dans 24Mg (Ex = 19,70 MeV) est mise en évidence au cours d'une étude de la réaction 12C(12C, α)20Ne effectuée à E c.m. = 5,80 ± 0,05 MeV. Ce résultat ainsi que les résultats antérieurs nous amènent à établir une comparaison avec les résonances observées dans le second puits de la barrière de fission de certains actinides

Adventitious shoot regeneration and micropropagation of Plantago lanceolata L.

Shoot regeneration from hypocotyl and cotyledon explants of Plantago lanceolata treated with various concentrations of Benzylaminopurine (BAP) and Indole 3 butyric acid in MS medium was significantly influenced by the amounts of BAP and IBA in concentration and explantdependent manner: Micropropagation was accomplished using various concentrations of BAP + IBA, kinetin + IBA and TDZ + IBA. Micropropagated shoots were rooted on the MS medium containing 2.69 mu M NAA. Plants were acclimatized and transferred to greenhouse, where they flowered and set seed

Geographical location, climate and land use influences on the phenology and numbers of the aphid, Myzus persicae, in Europe

Aim The purpose of this study was to improve understanding of the relationship between the spatial patterns of an important insect pest, the aphid Myzus persicae, and aspects of its environment. The main objectives were to determine the predominant geographical, climatic and land use factors that are linked with the aphid's distribution, to quantify their role in determining that distribution, including their interacting effects and to explore the ability of artificial neural networks (ANNs) to provide predictive models. Location The study focused on four spatial scales to account for the aphid data base characteristics and available land use data sets: Europe; a broad zone over Europe covering Belgium, Denmark, France, Ireland, Italy, The Netherlands, Scotland, Sweden and Wales (Regio data base coverage); North-West Europe (i.e. Belgium, France and the United Kingdom); and England with Wales. Methods Multiple linear regression (MLR) was used to identify the variables in the Geographic location, Climate and Land use groups, that explained significant proportions of the variance in M. persicae total annual numbers and Julian date of first capture. A variance partitioning procedure was used to measure the fraction of the variation that can be explained by each environmental factor and of shared variation between the different factors. Finally, ANNs were employed as an alternative modelling approach for the two largest study areas, i.e. Europe and the Regio data base coverage, to determine whether the relationship between aphid and environmental variables was better described by more complex functions as well as their ability to generalize to new data. Results Land use variables are shown to play a significant role in explaining aphid numbers. The area of agricultural crops, in particular oilseed rape, is positively correlated with M. persicae annual numbers. Among the climatic variables, rainfall is negatively correlated with aphid numbers and temperature is positively correlated. The geographical components also explain a significant part of aphid annual numbers. However, the variance partitioning procedure indicates that while each group has an effect, none is dominant. Aphid first capture is mainly explained by climate where rainfall tends to delay migration and warmer conditions tend to advance it. Climate accounts for the greatest part of the variance when considered separately from the other factors. The geographical and land use components also have a significant effect on first capture at each scale, but their direct contribution is negligible. The ability of the ANN models to generalize to new total numbers and phenological data compared with MLR models was less for Europe (9 and 6% increase in the variance accounted for, respectively) than for the Regio data coverage where an increase of 44% in the variance accounted for was observed. Main conclusions This research supports the hypothesis that climate, land use and geographical location play a role in determining patterns of aphid annual numbers and phenology. The ability of ANN models to predict aphid distribution is improved by the inclusion of temporal land use data. However, identification of the processes involved in such relationships is difficult due to numerous interactions between the environmental factors