An optimized duplex real-time PCR tool for sensitive detection of the quarantine oomycete Plasmopara halstedii in sunflower seeds

Plasmopara halstedii, the causal agent of downy mildew of sunflower, is an oomycete listed as a quarantine pathogen. This obligate parasite resides in a quiescent state in seeds of sunflower and can be spread from seed production areas to areas of crop production by international seed trade. To prevent the spread or the introduction of potentially new genotypes or fungicide-tolerant strains, an efficient method to detect P. halstedii in sunflower seed is required. This work reports the optimization of a real-time detection tool that targets the pathogen within sunflower seeds, and provides statistically validated data for that tool. The tool proved to be specific and inclusive, based on computer simulation and in vitro assessments, and could detect as few as 45 copies of target DNA. A fully optimized DNA extraction protocol was also developed starting from a sample of 1,000 sunflower seeds, and enabled the detection of <1 infected seed/1,000 seeds. To ensure reliability of the results, a set of controls was used systematically during the assays, including a plant-specific probe used in a duplex quantitative polymerase chain reaction that enabled the assessment of the quality of each DNA extract.     

Response of ectomycorrhizal communities to past Roman occupation in an oak forest

The impact of past Roman occupation on the composition of ectomycorrhizal (ECM) communities was analysed in 12 Roman settlements in an oak forest in Central France. At each Roman settlement, soils and ECM roots were sampled from two plots (600 m² each), one plot close to the remains of the buildings (<100 m), supposed to be impacted by ancient Roman agriculture, and the second plot 250-500 m away from the remains of the buildings, supposed to be less intensively influenced by previous cultivation. Soils were analysed and ECM fungal taxa were identified by morphotyping and sequencing the rDNA ITS region. The soil properties were significantly affected by the past Roman occupation, in terms of nutrient availability, especially for P, N and Mg. The enhancement of soil nutrient levels by past Roman land-use had significantly modified alpha diversity and species composition of ECM communities. Among the 67 determined ECM morphotypes, 40 were shared by the occupied and non-occupied plots, 17 were found only in the occupied plots and 10 only in the non-occupied plots. Six morphotypes were significantly more frequent near the antique remnants. Our study showed, for the first time, that ectomycorrhizal communities are impacted by previous Roman land-use, even after nearly two thousand years of forest state.     

Quality assessment of strawberries (Fragaria species)

Several cultivars of strawberries (Fragaria sp.), grown under different conditions, were analyzed by both sensory and instrumental methods. The overall appreciation, as expressed by consumers, was mainly reflected by attributes such as sweetness and aroma. No strong correlation was obtained with odor, acidity, juiciness, or firmness. The sensory quality of strawberries can be assessed with a good level of confidence by measuring the total sugar level ( degrees Brix) and the total amount of volatile compounds. Sorting out samples using the score obtained with a hedonic test (called the "hedonic classification method") allowed the correlation between consumers' appreciation and instrumental data to be considerably strengthened. On the basis of the results obtained, a quality model was proposed. Quantitative GC-FID analyses were performed to determine the major aroma components of strawberries. Methyl butanoate, ethyl butanoate, methyl hexanoate, cis-3-hexenyl acetate, and linalool were identified as the most important compounds for the taste and aroma of strawberries.     

Radiolysis of quercetin in methanol solution: observation of depside formation

Radiolysis of the flavonol quercetin, a natural antioxidant, was performed in methanol. The degradation process was followed by HPLC analyses. The major product was identified as a depside (Q1) by NMR and LC-MS. The G(Q1) radiolytic factor was plotted versus the initial concentration of quercetin. This radiolytic process was attributed to the CH3O* radicals presented in the irradiated medium. The proposed mechanism invoked a stereospecific oxidation of the 3-hydroxyl group of quercetin which led to C-ring opening and to the formation of the depside Q1. In presence of water, Q1 was transformed into another depside, Q2, by an inverse esterification reaction. A chemical equilibrium was observed between Q1 and Q2. The comprehension of the radiolytic process of quercetin in methanol solution is of importance. Indeed, the same type of oxidative reactions could occur on flavonoids during preservation of food by ionizing radiation.     

Colza (Brassica napus, v. Jaguar) Responses to Low Level of Metal Inputs Through Sewage Sludge Application: Induction of phytochelatin synthesis (10 pp)

Background, Aim and Scope   Most studies of sewage sludge disposal effects on plants have focused on high metal loadings. Less attention has been paid to plant responses to trace metal loadings below the recommended limit values. Materials and Methods: Here, a lysimetric experiment was conducted to assess the uptake, distribution and binding of trace metals by metal-induced, sulfhydryl-rich peptides (phytochelatins) in colza (Brassica napus, v. Jaguar) grown on a clayey, silty soil amended with a sewage sludge compost containing trace metal contents far below the recommended limit values established by French legislation. Chemical fractionation of unamended and sludge-amended soils was performed using a sequential extraction technique. Results: Copper concentrations in plant tissues were not affected by compost disposal. Its application at a single rate equivalent to 30 t/ha stimulated the growth of plants. Lead was not detectable in the plant material (< 1 mg g-1 dry wt.). Plants grown on the amended soil accumulated significantly more zinc than control plants. These phytochelatin complexes detected in leaves had a lower molecular weight than those extracted from roots. Those extracted from roots were composed of one type of phytochelatins (PCs) such as in leaves or a mixture of glutathione, PC2 and PC4. In comparison with control plants, sewage sludge compost application caused the synthesis of longer chain PCs in roots and in leaves. Furthermore, in comparison with control roots, glutathione and phytochelatin mixtures of higher molecular weight were detected in roots produced on the amended soil, whereas no significant increase in \total\ Cu and Zn content was observed in these organs after sludge application. Discussion: Compost application induces a significant increase in the proportion of the most labile forms of zinc and especially its pH 4.7 acid-soluble forms and, as a consequence, a higher accumulation of zinc in plants. Effects of copper are limited due to its strong affinity for humic substances and lead does not seem to be transported in any organ of plants. The presence of phytochelatins, even in plants grown on the unamended soil, proved the ability of colza to synthesize them in the presence of zinc and copper. Conclusions: These primary results seem to prove, on one hand, ability of colza (Brassica napus, v. Jaguar) to synthesize phytochelatins as well as in roots, in leaves and, on the other hand, the sensitivity of the PC induction as suggested by their identification in plants grown on the control soil. Synthesis of longer chain PCs in roots and in leaves, and formation of glutathione and phytochelatin mixtures in roots, are plant responses to sewage sludge compost application. Recommendations and Perspectives: Phytochelatin analysis is thus supposedly able to be one of the bioindicators that may be used as an ecotoxicological risk assessment of wastes. Due to its ability to synthesize phytochelatins, colza could be chosen as a plant test. Phytochelatin analysis could also be limited to roots (more sensitive than leaves). However, further experiments are needed. Quantitative analysis of phytochelatins had not been carried out due to insufficient amounts of pure phytochelatin standards, that had allow us to better study relationships between trace metal amounts to vegetal response.     

Estimating leaf area distribution in savanna trees from terrestrial LiDAR measurements

Vegetation structure parameters are key elements in the study of ecosystem functioning and global scale ecosystemic interactions. The detailed retrieval of many of these parameters by direct measurements is impractical due to the quantity of plant material in trees. Terrestrial LiDAR Scanners (TLSs) have been shown to hold great potential as an indirect means of estimating plant structure parameters with a high level of detail, while some studies identified a number of challenges inherent to this approach. In this study we investigate the use of a voxel-based approach to retrieve leaf area distribution of individual trees. The approach is based on the contact frequency method applied to co-registered TLS returns from two or more scanning positions. The contact frequency was computed for voxels being 10, 30, and 50 cm in size and subsequently corrected for the influence of occlusion effects, leaf inclination, the presence of non-photosynthetic material, and the laser beam size. The leaf area of voxels for which occlusion effects were too pronounced was estimated using modeled values based on the availability of light. We compared the TLS derived leaf area estimates against direct measurements, obtained by the harvesting of leaves, in a broad-leaved savanna of central Mali. The measured leaf area values of the sampled trees ranged from 30 to 530 m², and crown LAI values between 0.8 and 7.2. The leaf area estimates lay on average 14% from the reference measurements (general bias). Our method provides vertical as well as radial distributions of leaf area in individual trees, and lends itself to the estimation of savanna vegetation structural parameters with a high level of detail.     

Effect of heat challenge on peripheral blood mononuclear cell viability: comparison of a tropical and temperate pig breed

We evaluated the effect of heat challenge on cell viability, concanavalin A-induced proliferation and heat shock protein (HSPs) mRNA expression in peripheral mononuclear blood cells (PBMC) isolated from Creole (CR) and Large White (LW) pigs. The PBMCs were cultured for 9 h at 37°C before being subjected to heat challenge: (1) at 42°C or 45°C for 2, 4, 6 and 9 h to monitor cell viability;(2) at 45°C for 2 and 9 h followed by stimulation for 24 h at 37°C with concanavalin A to evaluate mitogen-induced proliferation; and (3) at 45°C for 3, 6 and 9 h to measure induction of HSP70.2 and HSP90 mRNA. Cell viability was affected by breed and temperature (P < 0.01), and the viability decrease caused by heat challenge was greater for LW than CR pigs. For mitogen-stimulated PBMCs, incubation at 45°C reduced lymphoblastogenesis equally in both breeds (P < 0.01). Although heat challenge for 3 and 6 h at 45°C induced expression of HSP70.2 and HSP90 mRNA, no breed difference was observed. In conclusion, differences in heat resistance between these two breeds at the whole organism level are reflected at the cellular level. Neither HSP70.2 nor HSP90 mRNA expression levels explain this effect.     

Small intestine adenocarcinoma in conjunction with multiple adenomas causing acute colic in a horse.

An 11-year-old Andalusian stallion developed marked signs of colic associated with an acute small intestine obstruction. Exploratory laparotomy revealed a distal jejunum full-thickness wall induration and multiple small adherent intraluminal masses. Fifteen centimeters of jejunum, including the induration, and several intraluminal masses were resected. Histologic examination revealed an adenocarcinoma and multiple polypoid adenomas. The horse was discharged, and no complications were reported 12 months postoperatively. Colic was considered secondary to partial jejunal lumen obstruction by the adenocarcinoma. Adenocarcinoma recurrence or transformation from remaining adenomas into an adenocarcinoma is still a major risk.     

Water loss regulation in mature Hevea brasiliensis: effects of intermittent drought in the rainy season and hydraulic regulation

Effects of soil and atmospheric drought on whole-tree transpiration (E(T)), leaf water potential (Ψ(L)) and whole-tree hydraulic conductance (K(T)) were investigated in mature rubber trees (Hevea brasiliensis, clone RRIM 600) during the full canopy stage in the rainy season in a drought-prone area of northeast Thailand. Under well-watered soil conditions, transpiration was tightly regulated in response to high evaporative demand, i.e., above reference evapotranspiration (ET(0)) ~2.2 mm day(-1) or maximum vapor pressure deficit ~1.8 kPa. When the trees experienced intermittent soil drought E(T) decreased sharply when relative extractable water in the top soil was?相似文献