Adaptation of Phytophthora infestans to Partial Resistance in Potato: Evidence from French and Moroccan Populations

ABSTRACT The use of partially resistant cultivars should become an essential component of a sustainable management strategy of potato late blight, caused by Phytophthora infestans. It is therefore important to determine to what extent P. infestans populations can be selected for increased aggressiveness by potato cultivars with different levels of partial resistance. To this end, we sampled P. infestans populations from France and Morocco, chosen as locations where late blight occurs regularly but which differ in the distribution of potato cultivars. Cross-inoculation experiments were used to determine the aggressiveness of all populations to potato cvs. Bintje (prevalent in France but not grown in Morocco) and Désirée (popular in Morocco but cultivated to a very small extent in France). French populations were more aggressive on cv. Bintje than on cv. Désirée, irrespective of the site they were sampled from. Their aggressiveness increased between early and late samplings, suggesting that both cultivars selected for increased aggressiveness during epidemics. By contrast, Moroccan populations were more aggressive on Désirée, regarded as partially resistant in Europe, than on Bintje, highly susceptible under European conditions. These data indicate that P. infestans populations adapt to locally dominant cultivars, irrespective of their resistance levels, and can therefore overcome polygenic, partial resistance. This adaptive pattern may render partial resistance nondurable if not properly managed.     

Comparison of wind tunnel and field experiments to measure potential deposition of fenpropimorph following volatilisation from treated crops

The potential for short-range transport via air, i.e. volatilisation from the area of application and subsequent deposition on adjacent non-target areas, was investigated for the fungicide fenpropimorph in a wind tunnel system and under outdoor conditions in a higher-tier field study. Fenpropimorph 750 g L(-1) EC was applied post-emergence to cereal along with a reference standard lindane EC. Stainless steel containers of water were placed at different distances downwind of the application area to trap volatile residues during a study period of 24 h following application. Meteorological conditions in the wind tunnel as well as on the field were constantly monitored during the study period. The wind tunnel system was a partly standardised system on a semi-field scale, i.e. wind direction and wind speed (2 m s(-1)) were constant, but temperature and humidity varied according to the conditions outside. In the field experiment, the average wind speed over the 24 h study period was 3 m s(-1) and no rainfall occurred. Three different measuring lines were installed on the non-target area beside the treated field to cover potential variations in the wind direction. However, no significant differences were observed since the wind direction was generally constant. Fenpropimorph was detected in minor amounts of 0.01-0.05% of the applied material in the wind tunnel experiment. Even at a distance of 1 m beside the treated field, no significant deposition occurred (0.04% of applied material after 24 h). In the field, less than 0.1% of the applied fenpropimorph was detected at 0 m directly beside the treated field. At 5 m distance the deposition values were below 0.04%, and at 20 m distance about 0.01%. In general, the amounts of deposited fenpropimorph detected in the partly standardised wind tunnel system and the higher-tier field study were in good agreement.     

Endoscopically guided nasojejunal tube placement in dogs for short‐term postduodenal feeding

Objective – To evaluate a method for endoscopically guided nasojejunal tube placement allowing short‐term postduodenal feeding and chyme withdrawal in dogs. Design – Pilot study. Setting – University teaching hospital. Animals – Three healthy Beagle dogs with jejunal nipple valve fistulas. Interventions – After the dogs were anesthetized, an 8 Fr, 250‐cm polyvinyl chloride catheter was advanced through a gastroscope into the jejunum. Correct jejunal placement was established using endoscopic visualization and confirmed by fluoroscopy and radiography. The proximal end of the tube was pulled out through 1 nostril and sutured to the skin of the forehead. Thereafter, jejunal feeding was administered for 4 days. Follow‐up examinations included daily confirmation of the tube's position using radiography, physical examination, and blood analyses. Withdrawal of jejunal chyme was performed after jejunal and oral feeding. Measurements and Main Results – Fluoroscopic examination confirmed that endoscopic visualization alone allowed correct jejunal placement. During a 4‐day postduodenal feeding period, repeated radiographic examination revealed stable positioning of the tubes within the jejunum with minor cranial displacement. The tubes were functional throughout the study without causing identifiable problems. Repeated physical examinations and blood analysis showed no abnormalities. We were able to administer the daily caloric requirements as a liquid diet. Jejunal chyme was successfully withdrawn via the tube. Conclusions – Endoscopically guided nasojejunal tube placement was shown to be a minimally invasive, well‐tolerated method for short‐term jejunal feeding in healthy dogs. This technique is a viable option for dogs requiring jejunal feeding but not laparotomy. The feasibility of chyme sampling is another unique application of the procedure.     

Computation-guided backbone grafting of a discontinuous motif onto a protein scaffold

The manipulation of protein backbone structure to control interaction and function is a challenge for protein engineering. We integrated computational design with experimental selection for grafting the backbone and side chains of a two-segment HIV gp120 epitope, targeted by the cross-neutralizing antibody b12, onto an unrelated scaffold protein. The final scaffolds bound b12 with high specificity and with affinity similar to that of gp120, and crystallographic analysis of a scaffold bound to b12 revealed high structural mimicry of the gp120-b12 complex structure. The method can be generalized to design other functional proteins through backbone grafting.     

Are cadmium, lead and mercury concentrations in mosses across Europe primarily determined by atmospheric deposition of these metals?

Purpose

This study aimed at investigating correlations between heavy metal concentrations in mosses and modelled deposition values as well as other site-specific and regional characteristics to determine which factors primarily affect cadmium, lead and mercury concentrations in mosses. The resulting relationships could potentially be used to enhance the spatial resolution of heavy metal deposition maps across Europe.

Materials and methods

Modelled heavy metal deposition data and data on the concentration of heavy metals in naturally growing mosses were integrated into a geographic information system and analysed by means of bivariate rank correlation analysis and multivariate decision trees. Modelled deposition data were validated annually with deposition measurements at up to 63 EMEP measurement stations within the European Monitoring and Evaluation Programme (EMEP), and mosses were collected at up to 7,000 sites at 5-year intervals between 1990 and 2005.

Results and discussion

Moderate to high correlations were found between cadmium and lead concentrations in mosses and modelled atmospheric deposition of these metals: Spearman rank correlation coefficients were between 0.62 and 0.67, and 0.67 and 0.73 for cadmium and lead, respectively (p?<?0.001). Multivariate decision tree analyses showed that cadmium and lead concentrations in mosses were primarily determined by the atmospheric deposition of these metals, followed by emissions of the metals. Low to very low correlations were observed between mercury concentrations in mosses and modelled atmospheric deposition of mercury. According to the multivariate analyses, spatial variations of the mercury concentration in mosses was primarily associated with the sampled moss species and not with the modelled deposition, but regional differences in the atmospheric chemistry of mercury and corresponding interactions with the moss may also be involved.

Conclusions

At least for cadmium and lead, concentrations in mosses are a valuable tool in determining and mapping the spatial variation in atmospheric deposition across Europe at a high spatial resolution. For mercury, more studies are needed to elucidate interactions of different chemical species with the moss.     

Long-term fertilization and plastic film mulching modify temporal incorporation of 13C/15N-labelled particulate organic matter

Plastic film mulching (PFM) is critical for agricultural planting and maximizing production in semiarid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator for evaluating the effects of different agricultural practices on soil fertility and the soil organic carbon (SOC) pool. Soil aggregates have the function of ‘wrap’ and protect the POM stored in them. However, there is limited information regarding how PFM and fertilization jointly influence the dynamic changes of newly added stalk-derived POM in brown earth. Consequently, an in-depth study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues within the particulate organic carbon (POC) and particulate organic nitrogen (PON) fractions in soil aggregates was undertaken. Its outcome would contribute to better predictions on the active organic matter components sequestered in the soil. The dynamics and accumulation of newly added maize stalk C and N as POC and PON in different soil aggregates (using the dry sieving method divided into >2, 1–2, 0.25–1 and <0.25 mm) were analysed by an in situ ¹³C/¹⁵N-tracing technique under PFM and different fertilization treatments. Over 360 days of cultivation, the POC and PON contents were significantly (p < 0.05) larger in the nitrogen (N) and organic manure (M) treatments than in the MN (manure combined with nitrogen) and Control treatments. The PFM treatment accelerated the decomposition of maize stalk C in the N fertilizer treatment, with an increase of 64% in stalk-derived POC after the 1-day cultivation period. Stalk-derived POM tended to accumulate in <0.25 mm microaggregates in the early cultivation period and then decreased rapidly with the extension of the cultivation period affected by PFM coupled with fertilization. However, stalk-derived POM accumulation in macroaggregates (>0.25 mm) fluctuated over the 360-day cultivation period. Accordingly, PFM application and fertilization practices had important effects on the accumulation of newly added stalk-derived POM in soil aggregates. We conclude that the accumulation of maize residue POM was primarily affected by soil fertilization type, rather than by the presence or absence of PFM. These results provide new insights into agricultural management strategies for improving soil carbon sequestration capacity.     

Asymmetric competition increases leaf inclination effect on light absorption in mixed canopies

? Context

The effects of leaf inclination on plant light capture, growth, and water balance of monospecific canopies are well documented, but we still lack information on such effects in the case of multispecific canopies.

? Aims

We investigated the effects of leaf inclination on the absorption of photosynthetically active radiation (PAR) of a mixed forest.

? Methods

We ran a 3D mechanistic radiation transfer model for a Mediterranean forest where Pinus halepensis makes the upper strata while Quercus ilex occupies the lower strata. As factors, we included (1) the distributions of leaf inclinations that ranged from vertical to horizontal (including the actual inclinations), (2) the fraction of diffuse light, sun position, and leaf area index (LAI), and (3) the Pinus/Quercus LAI ratio.

? Results

Simulated PAR absorption was more than twice as sensitive to leaf inclination in oaks than in pines because oaks depended on PAR transmitted below the pine layer. The extent of the effect depended on season, fraction of diffuse light, LAI, and vegetation spatial structure. None of the observed inclinations maximized PAR absorption, suggesting a trade-off with water economy.

? Conclusion

Erroneous assumptions about leaf inclination lead to larger errors when modelling heterogeneous, mixed canopies. This also highlights potential caveats when using models that do not account for the spatial structure of canopies.     

Strong resistance to the fungicide fenhexamid entails a fitness cost in Botrytis cinerea, as shown by comparisons of isogenic strains

BACKGROUND: Fenhexamid, a sterol biosynthesis inhibitor effective against Botrytis, inhibits the 3‐ketoreductase (Erg27) involved in C‐4 demethylation. Several fenhexamid‐resistant phenotypes have been detected in Botrytis cinerea populations from French vineyards. The field isolates with the highest resistance levels display amino acid changes in Erg27 (F412S, F412I or F412V). RESULTS: Fenhexamid‐resistant mutants were generated by site‐directed mutagenesis of the erg27 gene in a sensitive recipient strain to overcome the impact of different genetic backgrounds. The wild‐type erg27 allele was replaced by the three mutated alleles (erg27^F412S/I/V) by homologous recombination. These isogenic strains were shown to be fenhexamid‐resistant and were used to quantify the impact of F412 mutations on fungal fitness. Several parameters, including radial growth, the production of sclerotia and conidia, freezing resistance and aggressiveness, were quantified in laboratory conditions. Analysis of variance demonstrated significant differences between the mutant and parental strains for some characters. In particular, the mutants grew more slowly than the wild‐type strain and displayed variations in the production of sclerotia and conidia with temperature and susceptibility to freezing. CONCLUSIONS: The results highlight a moderate but significant impact of F412 mutations on the survival capacity of B. cinerea strains displaying high levels of resistance to fenhexamid in laboratory conditions, potentially limiting their dispersal and persistence, particularly in terms of overwintering, in field conditions. Copyright © 2011 Society of Chemical Industry     

The fission yeast FANCM ortholog directs non-crossover recombination during meiosis

The formation of healthy gametes depends on programmed DNA double-strand breaks (DSBs), which are each repaired as a crossover (CO) or non-crossover (NCO) from a homologous template. Although most of these DSBs are repaired without giving COs, little is known about the genetic requirements of NCO-specific recombination. We show that Fml1, the Fanconi anemia complementation group M (FANCM)-ortholog of Schizosaccharomyces pombe, directs the formation of NCOs during meiosis in competition with the Mus81-dependent pro-CO pathway. We also define the Rad51/Dmc1-mediator Swi5-Sfr1 as a major determinant in biasing the recombination process in favor of Mus81, to ensure the appropriate amount of COs to guide meiotic chromosome segregation. The conservation of these proteins from yeast to humans suggests that this interplay may be a general feature of meiotic recombination.     

In ovo leptin administration affects hepatic lipid metabolism and microRNA expression in newly hatched broiler chickens

Background: A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation. Results: Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR. Conclusions: These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.