Efficacy of Flectron-eartags (cypermethrin) for control of midges (Culicoides) as the vectors of bluetongue virus in cattle: field studies and biossays

When in 2006 infection with bluetongue for the first time occurred in Germany the registered and already against flies and tabanids in cattle proofed Flectron ear tags were used against the blood feeding vector midges (Culicoides) also. However, the efficacy against gnats was not yet proofed. The efficacy of 1 and 2 ear tags (1,067 g cypermethrin per ear tag) per animal was investigated in North Germany with 237 heifers and dairy cows. Midges were caught in suction light traps close to the cattle on pasture or became trapped by mouth operated aspirators directly at the skin of the animal bodies. Within 12,051 specimens of midges 12 species of Culicoides could be identified. On grasslands 3 species, C. obsoletus, C. pulicaris and C. dewulfi were found to be dominant. These 3 species are also known to be vectors of BTV. The toxic efficacy was found for 14 days with 1 ear tag and up to 21 days with 2 ear tags. This duration of efficacy was confirmed in the laboratory with hair clippings from the dorsal line and the ventral abdomen (bioassay). In accordance with workers in the U.S.A. it is concluded that insecticide-impregnated ear tags will reduce the number of biting midges, and by this way the risk of infection with BTV in herds of treated cattle will be reduced as well as in other cattle of a particular region. It is concluded that ear tags are of considerable value as part of an integrated control program for BT, e.g. vaccination.     

Distribution and metabolism of D/L-, L- and D-glufosinate in transgenic, glufosinate-tolerant crops of maize (Zea mays L ssp mays) and oilseed rape (Brassica napus L var napus)

The aim of the present study was to determine whether post-emergence application of glufosinate to transgenic crops could lead to an increase in residues or to the formation of new, hitherto unknown metabolites. Transgenic oilseed rape and maize plants were treated separately with L-glufosinate, D-glufosinate or the racemic mixture. Whereas about 90% of the applied D-glufosinate was washed off by rain and only 5-6% was metabolised, 13-35% of the applied L-glufosinate remained in the form of metabolites and unchanged herbicide in both transgenic maize and oilseed rape. The main metabolite was N-acetyl-L-glufosinate with total residues of 91% in oilseed rape and 67% in maize, together with small amounts, of 5% in oilseed rape and 28% in maize, of different methylphosphinyl fatty acids. These metabolites were probably formed from L-glufosinate by deamination and subsequent decarboxylation. The residues were distributed in all fractions of the plants, with the highest contents in treated leaves and the lowest in the grains (0.07-0.3% in maize and 0.4-0.6% in oilseed rape). There was no indication of an accumulation of total residues or of residue levels above the official tolerances for glufosinate.     

Differences in wound-induced changes in cell-wall peroxidase activities and isoform patterns between seedlings of Prosopis tamarugo and Prosopis chilensis

We determined changes in cell-wall peroxidase activities and isoform patterns in response to wounding in seedlings of Prosopis tamarugo Phil. (an endemic species of the Atacama Desert) and Prosopis chilensis (Mol.) Stuntz (a native species of central Chile), to assess tolerance to predation. In seedlings of both species, the maximal increase in peroxidase activity occurred 48 h after wounding, reaching three times the control value in P. tamarugo and twice the control value in P. chilensis. The activity of ionically bound cell-wall peroxidases increased only locally in wounded embryonic axes, whereas the activity of soluble peroxidases increased systemically in unwounded cotyledons. Analysis of ionic peroxidases by isoelectrofocusing revealed two groups of peroxidases in the cell walls of both species: four distinct acidic isoforms and a group of basic isoforms. In response to wounding, there was a large increase in activity of the acidic isoforms in P. tamarugo, whereas there was an increase in the activity of the basic isoforms in P. chilensis. In P. chilensis, the wound-induced increase in activity of the basic isoforms corresponded with one of the two isoforms detected in P. tamarugo prior to wounding. Experiments with protein and RNA synthesis inhibitors indicated that a preexisting basic peroxidase is activated in P. chilensis after wounding. Assays of ionically bound peroxidase activity with four different substrates corroborated the differences found in isoform patterns between species. In P. tamarugo, the largest increases in activity were found with ortho-phenylenediamine and ferulic acid as substrates, whereas in P. chilensis the largest increase in activity was found with guaiacol as substrate. Because the same basic cell-wall peroxidase that accumulated after wounding in P. chilensis was present in P. tamarugo prior to wounding, and the activity of acidic cell-wall peroxidases increased after wounding in P. tamarugo but not in P. chilensis, we conclude that P. tamarugo is more tolerant to wound stress than P. chilensis.     

<Emphasis Type="Italic">In vitro</Emphasis> Antioxidant Activity of Aged Extracts of some Italian <Emphasis Type="Italic">Allium</Emphasis> Species

Antioxidant activity of fresh Allium sativum L. (garlic) is well known and is mainly due to unstable and irritating organosulphur compounds. Fresh garlic extracted over a prolonged period (up to 20 months) produces odourless aged garlic extract (AGE) containing stable and water soluble organosulphur compounds that prevent oxidative damage by scavenging free radicals. The aim of this study was to investigate the in vitro antioxidant activity of aged (up to 20 months) 15% hydroethanolic extracts of different parts (bulbs, bulblets, flower bulblets, flowers, and leaves) of three Allium spontaneous species which are endemic for Italian flora: Allium neapolitanum Cyr., Allium subhirsutum L., Allium roseum L. and to compare it with the in vitro antioxidant activity of aged 15% hydroethanolic extracts of bulbs and leaves of garlic. The antioxidant potential of aged extracts of all species has been evaluated using two different spectrophotometric assays: 2,2-diphenylpicrylhydrazyl (DPPH) test and the ferric reducing/antioxidant power (FRAP) assay. Furthermore the polyphenol content was determined. The aged extracts obtained from the leaves showed the best antioxidant activity, followed by flowers and then by bulbs in both used tests, while flower bulblets and bulblets exhibited lower results or no activity. The polyphenol content was generally directly correlated with antioxidant/antiradical activity. This study confirms the data obtained in previous researches, the wild-type species of Allium and in particular organs other than bulbs are more active and efficacious than garlic bulb. Surely leaves of these Allium spp. deserve special attention.     

Satellite estimate of grass biomass in a mountainous range in central Italy

One of the main problems in managing ranges used for extensive pastoralism is the difficulty of obtaining reliable estimates of grass biomass over very large areas. Estimates of grass biomass are useful as an indicator of both available forage and risk of soil erosion. Nevertheless, large scale field measurements are expensive and time-consuming. The use of satellite images may provide a complementary means of estimating grass biomass over very large areas at a reasonable cost. The aim of this study was to test the use of Landsat satellite data for estimating grass biomass in a mountainous range in central Italy used primarily for sheep breeding. During each of four ground campaigns carried out over two years, grass was cut and its biomass measured in 60-90 test plots. Four Landsat images taken simultaneously to the ground campaigns were processed to obtain several vegetation indexes calculated for each ground test plot. The vegetation indexes showed significant correlations with measured grass biomass. The Normalized Difference Vegetation Index (NDVI) provided the most accurate estimate of grass biomass. When data for each of the four ground campaigns were analyzed separately, correlations for early summer campaigns were higher than correlations for late summer campaigns, indicating that when the ratio of dry/green biomass increases, satellite estimate becomes less accurate. Overall, our results show that satellite data can provide a useful source of biomass information for the management of large ranges. This revised version was published online in June 2006 with corrections to the Cover Date.     

Diversity and antagonistic potential of Pseudomonas spp. associated to the rhizosphere of maize grown in a subtropical organic farm

Pseudomonas spp. are one of the most important bacteria inhabiting the rhizosphere of diverse crop plants and have been frequently reported as biological control agents (BCAs). In this work, the diversity and antagonistic potential of Pseudomonas spp. in the rhizosphere of maize cultivars Nitroflint and Nitrodent grown at an organic farm in Brazil was studied by means of culture-dependent and -independent methods, respectively. Sampling of rhizosphere soil took place at three different stages of plant development: 20, 40 and 106 days after sowing. A PCR-DGGE strategy was used to generate specific Pseudomonas spp. fingerprints of 16S rRNA genes amplified from total community rhizosphere DNA. Shifts in the relative abundance of dominant populations (i.e. PCR-DGGE ribotypes) along plant development were detected. A few PCR-DGGE ribotypes were shown to display cultivar-dependent relative abundance. No significant differences in diversity measures of DGGE fingerprints were observed for different maize cultivars and sampling times. The characterisation and assessment of the antagonistic potential of a group of 142 fluorescent Pseudomonas isolated from the rhizosphere of both maize cultivars were carried out. Isolates were phenotypically and genotypically characterised and screened for in vitro antagonism towards three phytopathogenic fungi and the phytopathogenic bacterium Ralstonia solanacearum. Anti-fungal activity was displayed by 13 fluorescent isolates while 40 isolates were antagonistic towards R. solanacearum. High genotypic and phenotypic diversity was estimated for antagonistic fluorescent Pseudomonas spp. PCR-DGGE ribotypes displayed by antagonists matched dominant ribotypes of Pseudomonas DGGE fingerprints, suggesting that antagonists may belong to major Pseudomonas populations in the maize rhizosphere. Antagonists differing in their genotypic and phenotypic characteristics shared the same DGGE electrophoretic mobility, indicating that an enormous genotypic and functional diversity might be hidden behind one single DGGE band. Cloning and sequencing was performed for a DGGE double-band which had no corresponding PCR-DGGE ribotypes among the antagonists. Sequences derived from this band were affiliated to Pseudomonas stutzeri and P. alcaligenes 16S rRNA gene sequences. As used in this study, the combination of culture-dependent and -independent methods has proven to be a powerful tool to relate functional and structural diversity of Pseudomonas spp. in the rhizosphere.