Is selective thinning an adequate practice for adapting <Emphasis Type="Italic">Quercus ilex</Emphasis> coppices to climate change?

Introduction   

Future climatic scenarios demand an increasing involvement of management for forest preservation, but little is known on how forestry practices will benefit stands in facing variation of climatic components.     

Anomalous nitrogen isotope ratio in comets

High-resolution spectra of the CN B2 summation operator +-X2 summation operator + (0,0) band at 390 nanometers yield isotopic ratios for comets C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR) as follows: 165 +/- 40 and 115 +/- 20 for 12C/13C, 140 +/- 35 and 140 +/- 30 for 14N/15N. Our N isotopic measurements are lower than the terrestrial 14N/15N = 272 and the ratio for Hale-Bopp from measurements of HCN, the presumed parent species of CN. This isotopic anomaly suggests the existence of other parent(s) of CN, with an even lower N isotopic ratio. Organic compounds like those found in interplanetary dust particles are good candidates.     

Disease Progress Curve Parameters Help to Characterise the Types of Resistance to Late Blight Segregating in Cultivated Potato

To decrease the environmental impact of treatments against late blight caused by Phytophthora infestans on potato, plant genetic resistance is a keystone in developing new culture strategies. Nonspecific resistance to late blight is a complex trait which is difficult to evaluate, while selection is both difficult and time consuming. However, we consider it is important to select for this type of resistance as it is a promising way to achieve durable resistance. In this study, parameters derived from disease progress curves (DPCs) were used to characterise the types of resistance among individuals of three tetraploid full-sib families named G1, B2, and K2. These families were composed of 280 (G1), 280 (B2), and 150 (K2) genotypes. Our aim was to avoid visual inspection of 5,710 DPCs and to identify genotypes exhibiting stable resistance. We used three parameters: the slope of the DPC, the date of appearance of the first symptoms in the tested genotypes compared with a susceptible standard, and the relative area under the disease progress curve (rAUDPC). Using an appropriate threshold for each parameter, we demonstrated that it is possible to classify the response of each genotype in one of the following categories: susceptible, non-specific resistance, specific resistance, non-specific resistance plus specific resistance (or specific resistance not overcome). Data were obtained each year from 2005 to 2007 under conditions of natural infection. According to the parameters analysed, non-specific resistance and specific resistance segregated in the families. The year effect was more than double the family effect for rAUDPC. Empirical adjustment of threshold values in a subsample of the tested genotypes led to an increase in the effectiveness of our classification method. Calculated classification enabled detection of stable genotypes in each family. The impact of the year effect differed with the family. In the G1 family, the distribution of genotypes in each category was relatively stable over the 3 years, whereas in K2, the proportion of genotypes demonstrating specific resistance alone increased, particularly in 2007. In the B2 family, the proportion of genotypes in the non-specific resistance category decreased from 40% to 15% from 2005 to 2006, and then remained stable in 2007. The heritabilities of the parameters ranged from 61% to 96% depending on the family and on the parameter concerned.     

Diffusion of oxygen in cork

This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.     

Absence of oxysterol-like side effects in human monocytic cells treated with phytosterols and oxyphytosterols

Oxysterols, found in some commonly consumed foods, can induce a wide range of cytotoxic effects, which have been extensively studied. On the other hand, the side effects of phytosterols and oxyphytosterols are less well-known. Over the past few years, different types of foods have been enriched with phytosterols on the basis of the properties of these compounds that reduce circulating cholesterol levels in certain experimental conditions. It is therefore important to gain better knowledge of the risks and benefits of this type of diet. In this study, conducted in human monocytic U937 cells, the ability of phytosterols (sitosterol, campesterol) and oxyphytosterols (7β-hydroxysitosterol, 7-ketositosterol) to induce cell death, polar lipid accumulation, and pro-inflammatory cytokine (MCP-1; IL-8) secretion was determined and compared to that of oxysterols (7-ketocholesterol, 7β-hydroxycholesterol). Phytosterols and oxyphytosterols had no significant effects on the parameters studied; only 7β-hydroxysitosterol slightly increased cell death, whereas at the concentration used (20 μg/mL), strong cytotoxic effects were observed with the oxysterols. With sitosterol, campesterol, and 7-ketositosterol, IL-8 secretion was decreased, and with campesterol the intracellular polar lipid level was reduced. The data show that phytosterols and oxyphytosterols have no oxysterol-like side effects, and they rather argue in favor of phytosterols' beneficial effects.     

Triiodothyronine is necessary for the action of growth hormone in acclimation to seawater of brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss)

Brown (BT) and rainbow trout (RT) in freshwater (FW) were treated with ovine growth hormone (GH), GH + iopanoic acid (IOP), and GH + IOP plus triiodothyronine (T₃) for RT only. After 1 week of treatment, trout were transferred to 30 o/oo SW and treatment continued. In FW, GH treatment increased significantly plasma T₃ level (BT) and T₃/T₄ ratio (BT and RT) by stimulating T₄ to T₃ deiodination. In the GH + IOP group, the plasma T₃ levels and T₃/T₄ ratio fell significantly as T₄ to T₃ deiodination was inhibited. In GH + IOP + T₃-treated RT, plasma T₃ and T₃/T₄ ratios increased significantly relative to other groups. No mortality occurred and plasma osmolarity (PO) was not altered by any treatment in FW. After transfer to SW, all IOP + GH trout died within 2 (BT) or 3 days (RT). All GH-treated or control BT survived to the end of the experiment (6 days). RT survival rates tended to be improved in GH and GH + IOP + T₃ groups relative to controls. Correlatively on day 1 the PO increase was significantly higher in IOP + GH groups (BT and RT) than in the other groups and significantly lower in GH and GH + IOP + T₃ treated RT than in controls from days 1 to 6. These data confirm the requirement of T₃ and deiodination of T₄ to T₃ for the development of hypoosmoregulatory mechanisms in SW as previously shown (Lebel and Leloup 1992). Furthermore, the suppression of the hypoosmoregulatory effect of GH, when conversion of T₄ to T₃ was inhibited by IOP and the reversal when T₃ was added to IOP + GH treatment suggests that GH osmoregulatory action in SW acts via the simulation of T₄-5′ monodeiodination which increases T₃ production.     

Ovarian vascular hamartoma in a cow

A 5-year-old Holstein cow was examined for a unilateral enlarged ovary. A clinical diagnosis of ovarian tumor was established before a histological diagnosis of ovarian vascular hamartoma was made. Ovarian vascular hamartoma has not been reported previously in a live animal.     

Expressed sequence tags from the phytopathogenic fungus Botrytis cinerea

A large set of genes was identified in the phytopathogenic fungus Botrytis cinerea by using an expressed sequence tag approach. The fungus was grown in axenic culture and a cDNA library was produced. From this library, 6559 ESTs were obtained. The combined sequences represent 3026 unisequences that corresponds to approximately one-quarter of the estimated total number of genes in B. cinerea. Approximately 18% of the ESTs showed significant similarities with genes coding for proteins with known functions,~56% were similar to genes coding for proteins with unknown functions and ~26% were orphans. A substantial B. cinerea gene inventory including putative virulence factors was therefore obtained and is now available at the Génoplante-Info Database interface (http://urgi.infobiogen.fr///Projects/GPiDB/Interface/).     

Soil tillage and eyespot: influence of crop residue distribution on disease development and infection cycles

Two deep-working soil tillage tools, one which inverts soil (plough) and one which does not (chisel), were used before sowing wheat after various crop successions combining eyespot host and non-host crops. Soil structure was nearly the same and crop residues were located in the different soil layers. Eyespot sporulation was estimated by visually assessing pot plants which had been on the trial plots for a fixed length of time. Field plants were also assessed for disease at several wheat growth stages. A kinetic equation expressing disease level as a function of degree-days was fitted to the disease levels observed on the field plants. This equation is based on eyespot epidemiology and depends on two parameters reflecting the importance of the primary and the secondary infection cycles respectively. Pot plant and early field plant disease levels and primary infection were closely correlated to the presence of crop residues in the top layer. The amount of residues depended on both crop succession and soil tillage. Where the previous crop was a host crop preceded by a non-host crop, soil inversion buried host residues, thus decreasing the primary infection risk. Where however the previous crop was a non-host crop preceded by a host crop, soil inversion carried the host residues back to soil surface, thus increasing the primary infection risk. Secondary infection was not correlated to either crop succession or soil tillage.