Study of effects of Bt maize (Zea mays) events on Lepidoptera Ostrinia nubilalis, Sesamia nonagrioidesin southwestern France.

Crops of maize (Zea mays L.) were conducted in southwestern France with GMO (Genetic Modified Organism) vs isogenetic varieties in order to verify the control of European Corn Borer (ECB) Ostrinia nubilalis (Hübner) and the Corn Stalk Borer (CBS) Sesamia nonagrioides (Lefevbre) by GMO in field conditions. The bioassays were carried out in 1998 and 1999 before moratorium, then in 2005. Experiments involved respectively 18, 12 and 19 fields cultivated with Furio/Furio cb (GMO), Cecilia/ Elgina (GMO) and PR33P66/PR33P67 (GMO) varieties. These transgenic events expressed Cry1A(b) protein (Bt maize). Plants were noted for insect infestation assessment (number of larvae in stalks and ears per plant). Statistical tests used t-test on couple of plots. Results showed a significant difference in the density of both ECB and CBS between control and the two transgenic events. The two transgenic events acted differently. The control of the two Bt events on the two pests were differentiated and discussed. These experiments underlined the importance of field evaluation for testing real effects of transgenic events on crop according the environmental context.

Dehydrodimers of Ferulic Acid in Maize Grain Pericarp and Aleurone: Resistance Factors to Fusarium graminearum.

ABSTRACT The relationship between the primary cell wall phenolic acids, dehydrodimers of ferulic acid, and maize grain resistance to Fusarium graminearum, the causal agent of gibberella ear rot, was investigated. Concentrations of dehydrodimers of ferulic acid were determined in the pericarp and aleurone tissues of five inbreds and two hybrids of varying susceptibility and in a segregating population from a cross between a resistant and susceptible inbred. Significant negative correlations were found between disease severity and diferulic acid content. Even stronger correlations were observed between diferulic acid and the fungal steroid ergosterol, which is an indicator of fungal biomass in infected plant tissue. These results were consistent over two consecutive field seasons, which differed significantly for temperature and rainfall during pollination, the most susceptible stage of ear development. No correlation was found between the levels of these phenolics and deoxynivalenol levels. This is the first report of in vivo evidence that the dehydrodimers of ferulic acid content in pericarp and aleurone tissues may play a role in genotypic resistance of maize to gibberella ear rot.

[Reduction of dehydroascorbic acid by thiols in presence of biocatalytic substances: polarographic study]. / Réduction de l'acide déhydroascorbique par les thiols en présence de biocatalyseurs: étude polarographique.

The chemical reduction of dehydroascorbic acid is studied in the presence of organic and vitaminic compounds. Redox properties of the compounds: ascorbic acid, dehydroascorbic acid, thiols such as glutathion, cistein, British anti-Lewisite (BAL), thiamin, riboflavin, para amino benzoic acid, biotin, 1-4 dihydronaphtoquinone and flavonoids (flavone and derived salts, quercetin rutin, 1-epicatechin and dimer) are established by direct and pulse polarography. The redox reactions are analysed by amperometry. From the results, it appears that the catalytic effect of biocatalyst of the dehydroascorbic reduction by thiols has no direct relation with the redox properties. This catalytic effect is specifically obtained with flavan-3 ol complex with antiscorbutic activities of C2 factor type.

Biological control of plant pathogens: advantages and limitations seen through the case study of Pythium oligandrum.

The management of certain plant beneficial microorganisms [biological control agents (BCAs)] seems to be a promising and environmental friendly method to control plant pathogens. However, applications are still limited because of the lack of consistency of BCAs when they are applied in the field. In the present paper, the advantages and limitations of BCAs are seen through the example of Pythium oligandrum, an oomycete that has received much attention in the last decade. The biological control exerted by P. oligandrum is the result of a complex process, which includes direct effects through the control of pathogens and/or indirect effects mediated by P. oligandrum, i.e. induction of resistance and growth promotion. P. oligandrum antagonism is a multifaceted and target fungus-dependent process. Interestingly, it does not seem to disrupt microflora biodiversity on the roots. P. oligandrum has an atypical relationship with the plant because it rapidly penetrates into the root tissues but it cannot stay alive in planta. After root colonisation, because of the elicitation by P. oligandrum of the plant-defence system, plants are protected from a range of pathogens. The management of BCAs, here P. oligandrum, is discussed with regard to its interactions with the incredibly complex agrosystems.

Original method of showing some constitutive elements of the capillary wall.

The ascorbic acid and the 1-epi-3', 4', 5', 5, 7-pentahydroxy-flavan-3-ol have been located in the blood capillary wall by an histochemical method for electron microscopy. The method consists in an intra-arterial administration of vegetal oxydases specific of the compound to put in evidence. Those oxydases fix themselves on their effectors, and the addition of osmium and lead salts gives co-precipitates opaque to electrons.

Insecticidal effect of essential oils from mediterranean plants uponAcanthoscelides Obtectus Say (Coleoptera, Bruchidae), a pest of kidney bean (Phaseolus vulgaris L.).

The bioactivity of 22 essential oils from aromatic and medicinal plants was tested uponAcanthoscelides obtectus Say (Coleoptera, Bruchidae), a pest of kidney bean (Phaseolus vulgaris L.). The insecticidal effect was evaluated by determination of 24- and 48-hr LC50 and LC50 (from 1.50 mg/ dm(3) to more than 1000 mg/dm(3)). Isoprenoids and phenylpropanoids were identified by gas chromatography. The most efficient essential oils were extracted from plants belonging to Labiatae.Origanum marjorana andThymus serpyllum essential oils were the most toxic.

Analysis of Fusarium graminearum mycotoxins in different biological matrices by LC/MS.

The purpose of this study was to develop an LC/MS assay to accurately detect three mycotoxins produced by Fusarium graminearum in various matrices. Using different LC conditions, deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-ADON), and zearalenone (ZEN) were detected in four different matrices (fungal liquid cultures, maize grain, insect larvae and pig serum). The sensitivity of MS detection allowed us to detect concentrations as low as 8 ppb of DON and 12 ppb of ZEN. A very small quantity of matrix was therefore necessary for successful analysis of these toxins and a variety of experimental situations were successfully investigated using this technique. Production of 15-ADON and butenolide was monitored in a liquid culture of F. graminearum under controlled conditions. Using simple extraction procedures, the differential accumulation of DON and 15-ADON was followed in inoculated maize genotypes varying in susceptibility to F. graminearum. Toxicokinetic studies were carried out with maize insect pests reared continually on artificial diets containing ZEN and suggested that larvae may possess the ability to degrade ZEN. Finally, persistence of DON was assessed in pigs fed diet supplemented with DON, results indicated that DON accumulates quickly in pig blood and then levels decline progressively for 12 hours thereafter. The LC/MS study reported here is very useful and flexible for the detection of these mycotoxins in different media and at very low concentrations.