Metabolic mechanisms involved in the resistance of field populations of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) to spinosad

Tuta absoluta (Meyrick) resistance to insecticides has become a significant problem in many tomato production areas in South America. New insecticides are now available for the management of this pest (i.e. spinosad), however there is scarce information about their efficacy on field populations.With the aim of determining the susceptibility of T. absoluta to spinosad we evaluated the response of second instar larvae, from five field populations (Azapa 1, Azapa 2, Lluta, Colín and Valdivia) and a laboratory reference strain (S), to a diagnostic concentration of the insecticide. We also determined the activity of the detoxifying enzymes mixed-function oxidases (MFO), glutathione-S-transferases (GST) and esterases (EST) in the same larval stage. Larval mortality in field populations was significantly lower in Azapa 1 (50.0%), Azapa 2 (44.9%), Lluta (39.9%) and Colín (53.5%) when compared to the laboratory strain (91.7%). MFO activities in field populations were between 1.8 and 4.6 times higher than those observed in the S strain, while for EST, the ratio varied from 1.7 to 14.7. The lowest ratios were observed for the GST (0.5-2.7), however, significant differences were detected for the three enzyme systems. We conclude that the evaluated mechanisms would be involved in spinosad resistance of populations of T. absoluta, presenting an increased MFO activity in all populations.     

Impacts of conservation buffers and grasslands on total phosphorus loads using hydrological modeling and remote sensing techniques

To better assess the impacts of conservation buffers and grasslands on water quality at large spatial scales, development and integration of novel approaches are crucial to ensure that these land management practices are functioning properly and meeting their original goals. Recent developments in remote sensing technology have greatly enriched the availability of geospatial data that can be used in hydrological modeling to assess the potential hydrological response of conservation practices over larger areas. A methodology was developed using the object-based image analysis approach with Landsat-5 TM imagery of the year 2005 and thematic layers of streams to quantify conservation buffers and grasslands (OBIA-2005). The OBIA-2005 land cover data was used in the Soil and Water Assessment Tool hydrologic model to assess the impacts of vegetative conservation practices on total phosphorus (TP) loads. The model was calibrated and validated for discharge and TP loads in the Cedar Creek Watershed (CCW) in northeast Indiana. In general model efficiency for streamflow values was within acceptable statistical ranges. While calibration of TP loads was satisfactory for the total contributing area of two nested catchments within the upper CCW. Vegetative buffers of 30.5 m and 61 m combined with conservation grasslands generated from the OBIA-2005 resulted in a large reduction of TP loads as compared to no practices. The results also showed that including conservation grassland alone reduced TP loads by less than 2%. However, the combination of these practices with the width of edge-of-field buffer strips module of the SWAT model achieved the largest TP loads reduction. These findings demonstrate that improved representation of vegetative conservation practices in geospatial land cover data sets are more effective in assessing the impacts of conservation buffers and grasslands on water quality through hydrologic modeling.     

Calorie restriction promotes mammalian cell survival by inducing the SIRT1 deacetylase

A major cause of aging is thought to result from the cumulative effects of cell loss over time. In yeast, caloric restriction (CR) delays aging by activating the Sir2 deacetylase. Here we show that expression of mammalian Sir2 (SIRT1) is induced in CR rats as well as in human cells that are treated with serum from these animals. Insulin and insulin-like growth factor 1 (IGF-1) attenuated this response. SIRT1 deacetylates the DNA repair factor Ku70, causing it to sequester the proapoptotic factor Bax away from mitochondria, thereby inhibiting stress-induced apoptotic cell death. Thus, CR could extend life-span by inducing SIRT1 expression and promoting the long-term survival of irreplaceable cells.     

Femtotesla magnetic field measurement with magnetoresistive sensors

The measurement of magnetic fields in the femtotesla (fT, 10(-15) tesla) range is important for applications such as magnetometry, quantum computing, solid-state nuclear magnetic resonance, and magnetoencephalography. The only sensors capable of detecting these very small fields have been based on low-temperature superconducting quantum interference devices operating at 4.2 kelvin. We present a magnetic field sensor that combines a superconducting flux-to-field transformer with a low-noise giant magnetoresistive sensor. The sensor can be operated up to 77 kelvin. Our small-size prototype provides the capability of measuring 32 fT.     

Protective socking material for cultivated mussels: a potential non-disruptive deterrent to reduce losses to diving ducks

Predation of cultivated mussels by diving ducks can threaten the viability of mussel farms. Conventional scaring tactics have had limited success at deterring ducks from feeding on cultivated mussels, because of rapid habituation and 24-h feeding cycles of some waterfowl species. We tested a socking material containing a biodegradable protective layer against predation by diving ducks on experimental blue mussel (Mytilus edulis) aquaculture sites in Prince Edward Island, Canada. We also assessed the effect of this new socking material on mussel growth and survival. Results showed that the protective socking has the potential to reduce losses to ducks, but did not perform well for all mussel seed sizes used by the industry. The protective layer also did not biodegrade fast enough, trapping a portion of mussels inside the sock, affecting growth and survival of these mussels. Improvements are needed to make this solution effective for all mussel sizes used by the industry and to make its production more cost effective.     

Effects of seed size and density on growth, tissue-to-shell ratio and survival of cultivated mussels (Mytilus edulis) in Prince Edward Island, Canada

In suspended aquaculture, the size of mussel seed and the density at which these mussels are placed in socks are two important factors affecting mussel production. However, the effect of these two factors has yet to be examined simultaneously. We conducted two large-scale field experiments to assess the effect of seed size and initial density on growth, tissue-to-shell ratio and survival of blue mussels (Mytilus edulis) grown on longlines. Experimental mussel sites were set up during the autumn of two consecutive years in two bays on the north shore of Prince Edward Island, Canada. At each site, socks containing combinations of three seed sizes (small, medium and large) at two initial densities (low and high) were deployed and monitored over time. Small seed grew faster than large seed and often reached commercial size in the same time period. Furthermore, initial density generally did not affect shell growth. During the pre-spawning period following the autumn deployment, seed at low initial density had a higher tissue-to-shell ratio than seed at high initial density, especially for large seed. This effect of initial density disappeared in early summer. Early in the experiments (< about 10 months), mussel survival on socks was affected by seed size only: small seed generally had lower survival rates than larger seed. Late in the experiments (> 10 months), there appeared to be an interaction between seed size and initial density on mussel survival: survival of small seed generally decreased with increasing initial density, while survival of large seed was not affected by initial density. Since large seed tended to be packed at lower initial density than small seed, lack of crowding was likely responsible for the absence of density-dependent loss. Our study thus assessed different seeding strategies, and results were generally consistent across years and sites.     

Estimation of soil classes and their relationship to grapevine vigor in a Bordeaux vineyard: advancing the practical joint use of electromagnetic induction (EMI) and NDVI datasets for precision viticulture

Precision Agriculture - Working within a vineyard in the Pessac Léognan Appellation of Bordeaux, France, this study documents the potential of using simple statistical methods with...     

Prevalence, antibiotic resistance, virulence traits and genetic lineages of Staphylococcus aureus in healthy sheep in Tunisia

Nasal swabs of 163 healthy sheep were obtained from two farms and one abattoir in Tunisia during 2010. Samples were inoculated in Baird Parker agar and ORSAB medium for Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) recovery, respectively. MRSA was detected in 5 of these 163 samples (3%) in ORSAB medium, and one isolate per sample was further studied. MRSA isolates were mecA-positive, typed as ST153-CC80-t044-agrIII, and contained blaZ, ant(6)-Ia, aph(3')-IIIa, erm(C), tet(K), and fusB genes encoding penicillin, streptomycin, kanamycin, erythromycin, tetracycline and fusidic acid resistance, respectively. These MRSA isolates showed indistinguishable or closely related PFGE-patterns and harboured the lukF/lukS gene encoding the Panton-Valentine leukocidin and the luk-ED, hla, hld, and hlg(v) genes. Methicillin-susceptible S. aureus (MSSA) were recovered in 68 of the 163 samples (41.7%) and one isolate per sample was characterized. Most of MSSA (82.4%) showed susceptibility to the tested antibiotics with exceptions: penicillin (6%, carrying blaZ gene), tetracycline (19%, carrying tet(K) gene) and fusidic acid (9%). The following toxin-genes were identified among MSSA: tst (53 isolates), luk-M (52), luk-ED, hla, hlb, hld and hlg(v) (67), hlg (1), sec (49), sel (52), and the egc-cluster-like sen-sem-sei-seo-seg (1). Ten spa-types (two of them new ones) and nine sequence types (six new ones) were detected among the 73 S. aureus isolates, and they were ascribed to agr types I and III. All MRSA and MSSA isolates were able to coagulate bovine plasma and MRSA harboured the immune-evasion-gene-cluster type E. Conclusions. Nares of healthy sheep could be a reservoir of PVL-positive community-associated-MRSA and also of TSST-positive S. aureus isolates, with potential implications in public health.     

Surface and profile soil moisture spatio-temporal analysis during an excessive rainfall period in the Southern Great Plains,USA

In this work we analyze the temporal stability of soil moisture at the field and watershed scales in the Little Washita River Experimental Watershed (LWREW), as part of the remote sensing Cloud and Land Surface Interaction Campaign (CLASIC07) during June 2007 in south-central Oklahoma. Temporal stability of surface and profile soil moisture data were investigated for 20 LWREW soil moisture measurement stations. In addition, daily surface and profile soil moisture measurements were obtained in four 800 m by 800 m fields (remote sensing footprint), including two rangeland sites and two winter wheat fields. The work aimed to analyze the temporal stability of soil moisture at the watershed and field scale and to identify stations within the watershed, as well as locations within each field, that were representative of the mean areal soil moisture content. We also determined the relationship between sites found to be temporally stable for surface soil moisture versus those determined stable for average profile soil moisture content. For the unusually wet experimental period, results at the watershed scale show that LWREW stations 133 and 134 provided stable underestimates, while stations 132 and 154 provided stable overestimates of the watershed mean at all depths. In addition, station 136 had very high non-zero temporal stability at the 25 cm and 45 cm depths indicating that it could be used as representative watershed site provided a constant offset value is used to acquire a watershed mean soil water content value. In general, the deeper depths exhibited higher soil moisture spatial variability, as indicated by the higher standard deviations. At the field scale, measured average profile soil moisture was higher in the winter wheat fields than the rangeland fields with the majority of the winter wheat depth intervals having high non-zero temporal stability. Field scale temporal stability analysis revealed that 4 of the 16 sampling sites in the rangeland fields and 3 of the 16 sampling sites in the winter wheat fields either under or overestimated the field means in the 0–5 and 0–60 cm depth intervals. Field sites considered temporally stable for the surface soil moisture were not stable for the profile soil moisture, except for the LW45 field where two sites were stable at both the surface and profile soil moisture. This finding is significant in terms of soil moisture ground-truth sampling for calibrating and validating airborne remotely sensed soil moisture products under extremely wet conditions. In addition, identification of temporally stable sites at the watershed and field scales in the LWREW provide insight in determining future measurement station locations and field scale ground sampling protocol, as well as providing data sets for hydrologic modeling.