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111.
We have investigated the process of evolution of target-site-based resistance to herbicides inhibiting acetyl-CoA carboxylase (ACCase) in nine French populations of black-grass (Alopecurus myosuroides Huds). To date, two different ACCase resistant alleles are known. One contains an isoleucine-to-leucine substitution at position 1781, the second contains an isoleucine-to-asparagine substitution at position 2041. Using phylogenetic analysis of ACCase sequences, we showed that 1781Leu ACCase alleles evolved from four independent origins in the nine black-grass populations studied, while 2041Asn ACCase alleles evolved from six independent origins. No geographical structure of black-grass populations was revealed. This implies that these populations, although geographically distant, are, or have until recently been, connected by gene flows. Comparison of biological data obtained from herbicide sensitivity bioassay and molecular data showed that distinct resistance mechanisms often exist in a single black-grass population. Accumulation of different resistance mechanisms in a single plant was also demonstrated. We conclude that large-scale evolution of resistance to herbicides in black-grass is a complex phenomenon, resulting from the independent selection of various resistance mechanisms in local black-grass populations undergoing contrasted herbicide and agronomical selection pressures, and connected by gene flows whose parameters remain to be determined. 相似文献
112.
Use of computed tomography to predict the outcome of a noninvasive intranasal infusion in dogs with nasal aspergillosis 下载免费PDF全文
Saunders JH Duchateau L Störk C van Bree H 《The Canadian veterinary journal. La revue veterinaire canadienne》2003,44(4):305-311
Computed tomography (CT) was performed on 36 dogs with nasal aspergillosis to assess whether this imaging technique can be used to predict the success of a noninvasive intranasal infusion of enilconazole. A CT score based on the severity of the disease was given to each dog, prior to treatment, by dividing the nasal cavities and frontal sinuses into 8 anatomical regions. After therapy, the dogs were classified into 2 response groups (success group: dogs cured after 1 treatment; failure group: dogs needing more than 1 treatment or with treatment failure). No significant relationship on the logistic scale was found between the CT score and the response to treatment. High sensitivity (treatment failures correctly predicted) and specificity (treatment successes correctly predicted) could not be obtained at the same time, whatever the cut-off value chosen. The results of this study suggest that CT cannot predict the therapeutic success of nasal aspergillosis in dogs treated with a 1-hour infusion of enilconazole. However, dogs with a low score seem to be good candidates to respond after 1 treatment. 相似文献
113.
Silvestre A Leignel V Berrag B Gasnier N Humbert JF Chartiere C Cabaret J 《Veterinary research》2002,33(5):465-480
Although the molecular bases of resistance to anthelmintic families have been intensively studied, the contributing factors for the development of anthelmintic resistance are less well known. Clear recommendations must be given to farmers in order to delay the onset of anthelmintic resistance. Until now, the main advice has concerned the reduction of treatment frequency in order to slow down the spread of resistance. Anthelmintic resistance development depends mostly on an efficient selection pressure. This means that a high treatment frequency is neither necessary nor sufficient to select for resistance. The contribution of resistant worms, which have survived an anthelmintic treatment, to the subsequent generation is the key factor that controls resistance spread. This point is illustrated by five surveys conducted on sheep and goat farms from France and Morocco. In the 52 farms studied, less than three anthelmintic treatments were given each year. Three characteristics of breeding management can be identified in the build up of anthelmintic resistance: (1) the introduction of resistant worms through the purchase of sheep/goats or the use of common pastures, grazed by several herds/flocks, (2) under-dosing of hosts and the repeated use of one class of drugs, (3) the size of the population in refugia (infective larvae on pastures) at the time of the treatment. The role played by these breeding management factors in selecting for resistance is discussed. The most efficient way to limit the increase of anthelmintic resistance remains the reduction of the selection pressure by drugs, and optimal timing to maximise their efficacy. 相似文献
114.
Casteleyn C Simoens P Van den Broeck W 《Veterinary immunology and immunopathology》2008,124(3-4):394-397
This paper describes the presence of lymphoid tissue in the mucosa of the bovine larynx. A total of 15 bovine larynges were examined both macroscopically after tissue fixation in acetic acid and microscopically using histology. It was found that no paraepiglottic tonsil was present in cattle, although a few lymphoid follicles were present in the mucosa at the base of the epiglottis. This result is in accordance with previous reports. In contrast, numerous lymphoid follicles were seen in the mucosa of the epiglottis and the corniculate processes of the arytenoid cartilages. This suggests that larynx-associated lymphoid tissue is present in cattle. Our observation could be of clinical importance, e.g. in the framework of the development of aerosolized vaccines. 相似文献
115.
The degradation and formation of major chlorinated metabolites of terbuthylazine and atrazine in three soils (loamy clay, calcareous clay and high clay) were studied in laboratory experiments using molecules labelled with 14C on the s-triazine ring. Soil microcosms were treated with the equivalent of 1 kg ha-1 of herbicide and incubated in the dark for 45 days at 20(±1)°C. The quantity of [14C]carbon dioxide evolved in the soils treated with atrazine was negligible and could not be attributed to mineralization of the parent molecule. The mineralization of terbuthylazine accounted for 0·9–1·2% of the initial radioactivity. In the soils studied, the extrapolated half-lives varied from 88 to 116 days for terbuthylazine and 66 to 105 days for atrazine, with no significant differences for the three soils and the two molecules. The deethyl metabolites of the two s-triazines and the deisopropyl-atrazine metabolite appeared during the incubation in the three soils. The completely dealkylated metabolite was not detected in any of the soils. After 45 days of incubation, the non-extractable soil residues for the high clay, loamy clay and calcareous clay soils represented for terbuthylazine, 33·5, 38·3 and 43·1% and for atrazine, 19·8, 20·8 and 22·3% of the initial radioactivity. © 1997 SCI. 相似文献
116.
117.
Agathe Dutt Didier Andrivon Stéphane Jumel Gwenola Le Roy Alain Baranger Melen Leclerc Christophe Le May 《Plant pathology》2020,69(6):1108-1124
Plant disease complexes are a playground to investigate coinfections in natural or cultivated systems. Pathogens of such complexes may affect each other through direct and/or indirect interactions and lead to changes in virulence or aggressiveness, offspring production, and transmission. As coinfections by sympatric host-pathogens can strongly influence pathogen dynamics and their evolutionary trajectories, new insights into the mechanisms of their coexistence is thus of critical importance. In order to characterize differences in ecological niches liable to explain species coexistence on the same host, the inter- and intraspecific diversity of the life history traits in natural collections of the two main pathogens (Peyronellaea (formerly Didymella) pinodes [Dp] and Phoma medicaginis var. pinodella [Pmp]) of the ascochyta blight disease complex of pea was evaluated under controlled conditions. Dp strains developed 1.3 times faster and produced longer, mainly bicellular spores and in lower amounts (3.7 times less) than Pmp strains. Pmp strains were separated into two groups, one producing more pycnidiospores, mainly bicellular, with less resources, and the other with mainly unicellular ones. These three groups can be interpreted as three distinct life history strategies: pioneer colonizer (Dp), scavenger (large-spored Pmp), and intermediate (small-spored Pmp), allowing differentiation in access to and use of resources. While this experimental work provides new insight into coexistence of two species of the ascochyta blight disease complex of pea, it also raises the question of the benefit of having two distinct life history strategies for one species (Pmp). 相似文献
118.
119.
磷改良剂对中度和高度含碳酸盐的菜园土壤中Cd和Pb环境有效性和植物有效性的影响 总被引:1,自引:0,他引:1
The behaviour of metals mainly depends on soil p H, carbonate contents and contamination level, which should be considered for the management of contaminated soils. In this study, kitchen garden topsoils(0–25 cm) were sampled from the area around three smelters in France, with different Cd and Pb contamination levels. Effect of a phosphate amendment(a mixture of diammonium phosphate and hydroxyapatite) on the environmental availability and phytoavailability of Cd and Pb was evaluated by different chemical extractions and cultivating lettuce(Lactuca sativa L.), respectively. Changes in the distribution of Cd and Pb were found in most contaminated soils after phosphate amendment. An increase of Cd and Pb in the residual phase was highlighted in almost all carbonated contaminated soils, whereas a decrease of Pb in the exchangeable, water and acid-soluble phase was observed in most contaminated soils with the lowest carbonate contents. The concentrations of extractable Cd and Pb using calcium chloride and acetic and citric acids generally decreased after the soil amendment. Lettuces grown on amended soils were acceptable for human consumption as regard to Pb concentration. In contrast, some lettuces were unacceptable for human consumption, since the concentrations of Cd in the leaves were higher than the European legislation limit. Surprisingly, in carbonated soils with very low concentration of Cd, the Cd concentrations in lettuce reached up to the European legislation limit, making the lettuce unacceptable for human consumption.Our study highlighted the fact that the total metal concentration in soils does not always allow to predict the metal accumulation in the edible parts of vegetables in order to make a judgement about their acceptability or unacceptability for human consumption. 相似文献
120.
Effect of photoperiod and tank colour on growth and survival of pelagic‐phase seahorse Hippocampus reidi 下载免费PDF全文
Maik dos Santos Cividanes da Hora Jean‐Christophe Joyeux Helder Coelho Guabiroba Mônica Yumi Tsuzuki 《Aquaculture Research》2017,48(8):4300-4307
The effect of photoperiod and tank colour on the survival and growth of juvenile seahorse Hippocampus reidi was investigated in the first 15 days after release (DAR). In the first experiment, newly released seahorses were exposed to six photoperiods – 6 h of light (L):18 h of darkness (D), 10L:14D, 12L:12D, 14L:10D, 18L:6D and 24L:0D. In the second experiment, juveniles were kept in tanks of different background colours – blue, white, black, clear and red. No significant differences were observed in the growth and survival among seahorse subjected to 10–24 h of light (P > 0.05). At the end of 15 DAR, fish exposed to 6L:18D showed lower growth in height and weight compared to other treatments (13.8 mm vs. 20.0–22.2 mm and 13.4 mg vs. 37.2–43.2 mg respectively) and lower survival (80% vs. 88–95% respectively). Tank colour did not affect growth and survival of juveniles up to 15 DAR. 相似文献