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.
Lower mycotoxin levels in Bt maize grain Folcher, L.; Delos, M.; Marengue, E. ...
Agronomy for sustainable development,
2010/12, Letnik:
30, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Mycotoxins produced by
Fusarium
spp. during plant cultivation induce severe diseases in animal and humans. In 2007 a European Union regulation set maximum concentrations of mycotoxins in maize and ...derivatives of 4000 ppb for fumonisins B
1
and B
2
, 1750 ppb for deoxynivalenol, and 350 ppb for zearalenone. To assess the safety of French maize food, investigations are currently being carried out by the national Biological Risk Monitoring network. Here, 84 plots were cropped with the Bt maize MON 810 and its isogenic non-Bt counterpart in 2005 and 2006 in Southwestern France. Mycotoxin levels were measured in grain at harvest. Fumonisins B
1
and B
2
, deoxynivalenol, and zearalenone were analysed by liquid chromatography-mass spectrometry. The data were analysed statistically using non-parametric tests for mycotoxins and analysis of variance for weather variables. As the climate was homogenous inside the experimental area, the transgenic event introduced into the maize was the only key parameter which differed between Bt and non-Bt maize plots. Our results show that Bt maize decreased concentrations of fumonisins by 90% and zearalenone by 50%, whereas the concentration of deoxynivalenol was slightly increased. Those findings suggest a competition among
Fusarium
species that produce fumonisins or trichothecenes. According to the European regulation, 93% of the Bt maize crops can be sold, compared with only 45% for non-Bt maize plots. Our results thus show that Bt maize improved food safety by greatly reducing mycotoxin levels in field crops in Southwestern France.
Question: Can genetic tools combined with phytogeography help to define local plants and how geographically close the source population should be to the restoration site? Location: Subalpine and ...alpine French Pyrenees. Methods: The main phytogeographic boundaries in the French Pyrenees described by different authors were studied and this geographic pattern was compared with the results of genetic analysis for the four Pyrenean plants studied (Trifolium alpinum, Festuca eskia, Festuca gautieri and Rumex scutatus), based on random amplified polymorphic DNA (RAPD) marker analysis, unweighted pair-group method with arithmetic averages (UPGMA) analysis and Mantel correlograms comparing geographic and genetic distances. Results: The genetic analysis allowed definition of two main evolutionarily significant units (ESUs) for the plants under study. Although the limit between the two zones was slightly variable according to the species considered, an eastern and a western ESU was consistently observed. This delineation was concordant with the main phytogeographic boundaries of the French Pyrenees. Conclusion: RAPD markers and associated Mantel correlograms can be useful to draw ESUs for individual species when the sampling intensity is relatively dense, and similarities were revealed between species sharing the same distribution range. This delineation allowed integration of infraspecific plant variation in the management of natural resources for revegetation in the Pyrenees. Nevertheless, caution is needed for the establishment of seed pools in order to maximize genetic diversity in each of the pools during collection and production.
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.
Abstract
Botanicals have been in use for a long time for pest control. A product of species coevolution, these compounds offer many environmental advantages. However, their uses during the 20th ...century have been rather marginal compared with other biocontrol methods of pests and pathogens. Improvement in our understanding of plant allelochemical mechanisms of activity offer new prospects for using these substances in crop protection. We examine the reasons behind their limited use and the actual crop protection developments involving plant allelochemicals, namely: (i) formulations including biopesticides of plant origin for organic or traditional agricultures, and (ii) improvement of plant resistance to pathogens through identification of genes coding for allelochemicals and stimulation of natural passive and active defenses of the plant. Commercial and regulatory aspects are discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
Concentrations of mercury and persistent organic pollutants in fish were examined in 11 lakes of the French Pyrénées spanning an elevation range of 2
km. All lakes were confined to a relatively small ...area within a 50-km diameter. Most of the lakes were within the Pyrénées National Park, which is restricted to recreational hiking, angling, and seasonal grazing of livestock, and are not subject to any known point sources of contaminants. Fish collected were mainly of 1 species (
Salmo trutta fario), which is stocked regularly in the lakes. With increasing elevation, lake temperatures declined along with electrical conductivity and planktonic chlorophyll
a. In contrast, water column nutrients (total phosphorus and total nitrogen) and epilithic periphyton biomass were not correlated with lake elevation. Of the global contaminants measured in fish, mercury, dicholorodiphenyltrichloroethane and its derivatives, and polybrominated diphenyl ethers showed the strongest positive correlation with elevation. Hg levels in some fish exceeded health consumption guidelines in these mountain lakes. Variation in fish contaminant levels was not related to differences in growth rate or to fish trophic position as determined using
δ
15N stable isotope measurements. This implies that the delivery and/or retention of many of these contaminants increase with lake elevation.
Four trichothecene-producing strains of Fusarium graminearum were grown on three maize grain fractions, whole grain, degermed grain, and the germ, to determine the effect of natural substrates on ...mycotoxin production. Monitoring the ergosterol content after 25 days of incubation indicated that fungal growth on all grain fractions was comparable. Trichothecene (TCT) production was highest on degermed grain, less on whole grain, and very low or nondetectable on the germ; similar results were found with four different strains. It was concluded that inhibitor(s) of TCT biosynthesis were present in maize germ. The presence of phenolic compounds was investigated in the different fractions. The hydroxamate 4-acetylbenzoxazolin-2-one (4-ABOA), a known inhibitor of mycotoxin production, was found in the degermed and whole grain fractions but not in the germ. Therefore, the TCT inhibition observed on the maize germ fraction used in our study is clearly not linked to 4-ABOA. Other soluble phenolic compounds were found at a much higher concentration in the germ than in the two other fractions. The inhibition property of the soluble ester-bound extracts was tested in liquid culture. A possible role for these compounds is discussed. Keywords: Fusarium; mycotoxins; trichothecenes; phenolic compounds; maize
The toxic activity of some characteristic monoterpenoids:
p-cymene, α-pinene, camphor, linalool, terpineol, cuminaldehyde, cinnamaldehyde, anethole, carvacrol, thymol, estragole and eugenol, was ...tested against
Acanthoscelides obtectus (Say), a bruchid pest of kidney bean (
Phaseolus vulgaris L.). A fumigant toxic effect was observed and LC
50 concentrations for 24h and 48h were calculated for adults.
Besides this effect, a reproductive inhibition was observed. This inhibition involved female fecundity, oviposition, and the development of neonate and intracotyledonal larvae. The effects of monoterpenes on oviposition, larval penetration inside the seeds and emergence were determined. All monoterpenes revealed a more or less pronounced vapour toxicity and significantly inhibited beetle reproduction. Oxygenated monoterpenoids: carvacrol, thymol, eugenol, linalool and terpineol were identified as the most efficient compounds in both respects and the structure-activity relationship is discussed.
In recent years, the use of essential oils (EOs) derived from aromatic plants as low-risk insecticides has increased considerably owing to their popularity with organic growers and environmentally ...conscious consumers. EOs are easily produced by steam distillation of plant material and contain many volatile, low-molecular-weight terpenes and phenolics. The major plant families from which EOs are extracted include Myrtaceae, Lauraceae, Lamiaceae, and Asteraceae. EOs have repellent, insecticidal, and growth-reducing effects on a variety of insects. They have been used effectively to control preharvest and postharvest phytophagous insects and as insect repellents for biting flies and for home and garden insects. The compounds exert their activities on insects through neurotoxic effects involving several mechanisms, notably through GABA, octopamine synapses, and the inhibition of acetylcholinesterase. With a few exceptions, their mammalian toxicity is low and environmental persistence is short. Registration has been the main bottleneck in putting new products on the market, but more EOs have been approved for use in the United States than elsewhere owing to reduced-risk processes for these materials.
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