Verschil in reactie van wilde sla ten opzichte van besmetting met het slamozaiekvirus

Samenvatting Hoewel wij in onze opzet nl. het vinden van resistenteLactuca serriola L. niet slaagden, vonden wij zeer grote verschillen in gevoeligheid voor hetLactuca virus 1 tussen de verschillende herkomsten.De herkomsten reageerden ieder voor zich zeer uniform op het virus. Uit de vaak zeer hevige reactie en het ontbreken van symptomen op de planten onder natuurlijke cundities, concluderen wij, dat het virus in Nederland niet op planten van wilde sla voorkomt.Summary Several botanicalLactuca spp. were tested for their susceptibility toLactuca vims 1 . All appeared to be susceptible. As the exact identifications are not certain, specific names are only mentioned ofL. virosa L. andL. serriola L. Of these we tested plants of respectively six and thirty-five different places of origin.The reaction ofL. virosa to lettuce mosaic was in all cases a necrosis. The seed originating from Cologne was distinctly less susceptible (see Table 1). The reaction ofL. serriola to lettuce mosaic was not the same for the different sources of this species. The most common symptom (see Table 2) was a veinclearing followed by mosaic and sometimes necrosis at the end of the growth period. ('s-Hertogenbosch, Arnhem, Blerick, Gulpen and Braunschweig). There were also plants from certain sources which first reacted with symptoms of necrosis (see Table 2). This was a total necrosis (Velp) and there were sources from which the plants grew on with mosaic symptoms and necrotic symptoms (Maurik and Voorst, Fig. 1). The plants from Stockholm and Lent were intermediate between the latter type and the former.L. serriola from Coimbra, received under the name ofL. scariola, reacted with reddish necrotic or glassy translucent spots along the veins (Fig. 2). This symptom disappeared afterwards and changed into faint mosaic symptoms.In September, there were great differences in height of growth between the sources. Therefore, we gave all plants a rating indicating their growth. The rating 0 was given for total necrosis or total stop of growth after infection and the rating 3 for normal growth, whereas ratings 1 and 2 indicated reactions in increasing severity between 0 and 3. When the growth of all 60 plants of one source was normal after infection a total of 60 × 3 = 180 was given.In Fig. 3 the resulting data were mapped. North of the river Waal strains ofL. serriola reacting with necrosis occur. Near Venlo and south of this town strains ofL. serriola were collected which showed the mosaic symptoms accompanied by bad growth, though some strains of plants were found which hardly showed a reduction of growth after infection with the virus.

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Instituut voor Plantenziektenkundig Onderzoek te Wageningen; gedetacheerd bij het Proefstation voor de Groenteteelt in de volle grond te Alkmaar     

Early fungal community succession following crown fire in Pinus mugo stands and surface fire in Pinus sylvestris stands

The early post-fire development of mycobiota following a crown fire in mountain pine plantations and a surface fire in Scots pine plantations, and in the corresponding unburnt stands in the coastal sand dunes of the Curonian Spit in western Lithuania was investigated. Species numbers in unburnt Pinus mugo and Pinus sylvestris stands showed annual fluctuation, but in the burnt sites, the numbers of fungi increased yearly, especially in the crown fire plots. Both burnt stand types—P. mugo and P. sylvestris—showed strongly significant (two-way ANOSIM; R = 1, p < 0.05) differences in species composition; the differences between unburnt sites were clearly expressed but less significant (R = 0.86, p < 0.05). Fungal species composition of burnt P. mugo and P. sylvestris sites was qualitatively different from that of corresponding unburnt sites (two-way ANOSIM; R ≥ 0.75, p < 0.05). The chronosequence of mycobiota in surface fire burns was less clearly defined than in crown fire sites, reflecting the greater patchiness of impacts of the surface fire. Although both fire types were detrimental or at least damaging to all functional groups of fungi (saprobic on soil and forest litter, wood-inhabiting, biotrophic, and mycorrhizal and lichenized fungi), their recovery and appearance (fructification) patterns varied between the groups and among the burn types. The end of the early post-fire fungal succession (cessation of sporocarp production of pyrophilous fungi) was recorded 3 years after the fire for both crown and surface fire types, which is earlier than reported by other authors. Rare or threatened fungal species that are dependent on fire regime were not recorded during the study.     

Feeding Magnesium Supplement to Foals Reduces Osteochondrosis Prevalence

The influence of supplements containing magnesium on the etiology of osteochondrosis (OC) is unknown. We did two studies to measure the effect of additional minerals (especially magnesium) on OC. In study 1 (five studs, in total 64 mares and foals aged 0 to 5 months, equally divided into two groups), supplementation with minerals and placebo was used. Blood samples were taken from foals at age of 2, 8, and 16 weeks. At the same time, milk samples were taken from the mare. Bone biomarkers (osteocalcin and C-terminal telopeptide [CTx] of type I [CTx-1] collagen) and minerals (calcium, phosphorus, and magnesium) were measured in blood and the same minerals in milk of the mare. At the end of the study, the femoropatellar (knee), tarsocrural (hock), and metacarpophalangeal and/or metatarsophalangeal (fetlock) were radiographed and scored for the presence and grade of osteochondrotic lesions. In study 2 (six studs, 54 foals aged 5 to 12 months, equally divided into two groups), the same was repeated. At the start and end of the study, again blood samples were taken and analyzed on the same parameters as in study 1. Also, the same radiography was done. In study 1 in the mineral supplemented group, 21.9% were diagnosed with osteochondrosis compared with 41.9% in the placebo group. In study 2, there was no change in OC between 5 and 12 months in the placebo group whereas there was a drop of 14.3% in incidence in the supplement group. We concluded that magnesium supplementation reduced OC prevalence.     

Core-derived historical records of suspended sediment origin in a mesoscale mountainous catchment: the River Bléone, French Alps

Purpose

Quantifying suspended sediment fluxes and dynamics across mountains, and identifying the origin of sediment in severely eroded areas, are of primary importance for the management of water resources. This contribution aims to generalise previous results from suspended sediment fingerprinting obtained during 2007?C2009 in a mesoscale Alpine catchment (the Bléone River; 905?km²) in France, and to assess variability in sediment sources throughout the second half of the twentieth century.

Materials and methods

Sediment fingerprinting, based on elemental geochemistry and radionuclide measurements, was conducted on a sediment core collected in an alluvial floodplain at the basin outlet. This technique was combined with hydro-sedimentary time-series to reconstruct the origin of suspended sediment deposited at this location over the last 50?years.

Results and discussion

Interpretation of sedimentation based on historical hydrological databases corroborates core dating obtained with ¹³⁷Cs and ²¹⁰Pb_xs activity measurements. Black marls and (marly) limestone sources provided the main fraction of sediment throughout the sequence (40 and 22?%, respectively). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16?%, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. However, the relatively homogeneous sediment composition throughout the sequence confirms that core-derived information is representative of widespread flood events.

Conclusions

These results are consistent with those obtained in previous studies. They also outline the need to take into account the entire grain size range of fine sediment in order to provide an overall picture of sediment sources and transfers within highly erosive catchments. This study also emphasizes the importance of using archival data to validate the results of sediment fingerprinting studies conducted during short contemporary monitoring programmes, and to extend fingerprinting of sediment sources over longer time-scales which include large and widespread floods.     

Effects of Different Bedding Materials on the Behavior of Horses Housed in Single Stalls

The effects of three different bedding materials (straw, wood shavings, and straw pellets) on the behavior of six warmblood horses (four mares, two of them with foals) housed in single stalls were analyzed. Each material was used for 2 weeks in three consecutive runs. The behavior of the horses was videotaped and analyzed on the first and last 3 days for each bedding alternative in the last of the three runs. The time budgets for the behaviors including standing, eating, lying, occupation with bedding material, and other were generated. Compared with straw pellets and wood shavings, the application of straw bedding led to a significantly higher frequency and longer duration of occupation with bedding material and in turn, shorter fractions of standing and other behaviors. The total duration of lying was significantly longer on straw than on straw pellets. Straw pellets resulted in the least mean recumbency duration per occurrence of this behavior. Because occupation is one of the important functions that bedding material is supposed to fulfill, we concluded that in regard to horse behavior, straw bedding was the best among the three materials analyzed. Further investigations with a more homogeneous group of probands are necessary to verify the observed behavioral reactions.     

Investigating the use of fallout and geogenic radionuclides as potential tracing properties to quantify the sources of suspended sediment in a mining catchment in New Caledonia,South Pacific

Journal of Soils and Sediments - New Caledonia, a French island located in the south-west Pacific Ocean, has vast nickel resources. Open-cast mining has strongly increased soil erosion and the...     

Fingerprinting sediment sources in the outlet reservoir of a hilly cultivated catchment in Tunisia

Purpose

Approximately 74 % of agricultural soils in Tunisia are affected by water erosion, leading to the siltation of numerous human-made reservoirs and therefore a loss of water storage capacity. The objective of this study was to propose a methodology for estimating the relative contributions of gully/channel bank erosion and surface topsoil erosion to the sediment accumulated in small reservoirs.

Materials and methods

We tested an approach based on the sediment fingerprinting technique for sediments collected from a reservoir (which has been in operation since 1994) at the outlet of a catchment (Kamech, 2.63 km²). Sampling concentrated on the soil surface (in both cropland and grassland), gullies and channel banks. A total of 17 sediment cores were collected along a longitudinal transect of the Kamech reservoir to investigate the origin of the sediment throughout the reservoir. Radionuclides (particularly caesium-137, ¹³⁷Cs) and nutrients (total phosphorus, total nitrogen and total organic carbon (TOC)) were analysed as potential tracers.

Results and discussion

The applications of a mixing model with ¹³⁷Cs alone or ¹³⁷Cs and TOC provided very similar results: The dominant source of sediment was surface erosion, which was responsible for 80 % of the total erosion within the Kamech catchment. Additionally, we showed that the analysis of a single composite core provided information on the sediment origin that was consistent with the analysis of all sediment layers in the core. We demonstrated the importance of the core sampling location within the reservoir for obtaining reliable information regarding sediment sources and the dominant erosion processes.

Conclusions

The dominance of surface erosion processes indicates that conservation farming practices are required to mitigate erosion in the agricultural Kamech catchment. Based on the results from 17 sediment cores, guidelines regarding the number and location of sampling cores to be collected for sediment fingerprinting are proposed. We showed that the collection of two cores limited the sediment source apportionment uncertainty due to the core sampling scheme to <10 %.