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Multiple resistance to acetolactate synthase (ALS, EC 2.2.1.6) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19) inhibitor herbicides was studied in two populations of Conyza canadensis (RTG and STG) harvested in southern Spain. Dose-response and enzymatic activity studies for the ALS-inhibiting herbicides showed only cross-resistance to sulfonylureas group but not to the other ALS chemical groups in the RTG population. Regarding glyphosate, the dose-response studies showed that the RTG population was 11.8 times more resistant than the STG population, while the inhibition of EPSPS enzyme (I 50) was similar for both populations. Altered/reduced absorption and translocation were the main resistance mechanisms for glyphosate but not for tribenuron-methyl. The metabolic studies to find differences in the amounts of metabolites between the two populations were carried out using thin layer chromatography (for tribenuron-methyl) and capillary electrophoresis (for glyphosate). Metabolites were significantly differed among the two populations for tribenuron-methyl but not for glyphosate. The sequencing of the target-site ALS gene from RTG plants revealed a single point mutation, Pro-197-Ala, that causes resistance to sulfonylurea herbicide in C. canadensis. Image 1 • First case in Europe of C. canadensis with multiple resistance to glyphosate and tribenuron-methyl. • TSR and NTSR mechanisms involved in sulfunylureas resistance and an NTSR mechanism in glyphosate resistance. • This species can be controlled by other chemical families of ALS-inhibiting herbicides. [ABSTRACT FROM AUTHOR]

Repeated applications of the same herbicide(s), which are characterized by the same mode of action, increase selection pressure, which in turn favours the evolution of herbicide-resistant weeds. Glufosinate is a broad-spectrum non-selective herbicide being used for weed control for many years around the world. Rigid ryegrass (Lolium rigidum Gaud.) is an economically important grass weed in Greece. Recent complaints by growers about control failure of rigid ryegrass with glufosinate require further investigation and have been the basis of this study. The objectives of this study were to confirm the existence of glufosinate-resistant L. rigidum in Greece and evaluate the effect of L. rigidum growth stage on glufosinate efficacy. Twenty populations of rigid ryegrass from Greece were sampled from five regions, and whole plant dose-response studies were conducted for five populations under controlled conditions with eight rates of glufosinate (0.0, 0.098, 0.187, 0.375, 0.75, 1.5, 3.0, and 6.0 kg a.i. ha-1). Glufosinate resistance was confirmed in three out of five populations with the level of resistance ranging from three-to seven-fold compared with the susceptible populations based on above-ground biomass reduction. Results also revealed that the level of glufosinate-resistance of rigid ryegrass was dependent on the growth stage at which it was applied. [ABSTRACT FROM AUTHOR]

Lolium spp. are troublesome weeds mainly found in winter cereal crops worldwide, including Europe. In recent years resistant mechanisms have been evolved to several important herbicides. In this study we investigated the mechanisms responsible for conferring glyphosate resistance in some Lolium spp. populations. A holistic approach was used, based on dose-response experiments, determination of shikimic acid concentration in plant leaf tissue, as well as molecular analyses. More specifically, in three Lolium spp. populations the existence of a mutation in the Pro-106 codon of the 5-enolpyruvylshikimate-3 phosphate synthase (EPSPS) gene was investigated as well as the relative transcript levels of four ABC-transporter genes were monitored at three time points after glyphosate application. The results demonstrated that glyphosate resistance is a multifactor phenomenon. Relative transcript levels of the ABC-transporter genes were abundant at very early time points after glyphosate treatments. Dose-response experiments and shikimate analyses were in accordance with the findings of the quantitative PCR (qPCR) analyses. We suggest that relative expression ratio of ABC-transporter genes can be a useful tool to rapidly identify Lolium spp. populations resistant to glyphosate. [ABSTRACT FROM AUTHOR]

The demand for organically grown products is increasing because many people are concerned about the environment and believe that organic products are healthier than conventional ones. Some studies have shown that organically produced tomato fruits contain higher levels of antioxidants, polyphenols and carotenoids than those produced conventionally. The objective of this study was to evaluate the influence of organic and inorganic fertilization on agronomic and quality characteristics of the processing tomato. The 2-year experiment was laid out in a randomized complete block design, with three replications and three fertilization treatments (untreated, compost and inorganic fertilizer). The results showed that the highest fruit number per plant (98.5), average fruit weight (63.6 g) and fruit yield (168.0 t ha-1) were obtained under inorganic fertilization. The highest total soluble solids (4.39 °Brix) and total soluble solids to titratable acidity ratio (17.4), L* (43.4) and a* (35.4) values, as well as the highest lycopene content (88.5 mg kg-1 f.w). were achieved through the application of organic fertilizer. Significantly higher total soluble solids and total soluble solids to titratable acidity ratio in organically grown tomatoes are particularly important to the processing tomato industry. Finally, the highest lycopene content produced under organic fertilization as well as the non-significant difference between the organic and conventional tomatoes in terms of lycopene yield make organic processing tomatoes suitable for lycopene production. [ABSTRACT FROM AUTHOR]

A field trial was conducted in Domokos region, in central Greece with Helianthus annuus, hybrid 'LG 5658' in order to evaluate the effects of different N fertilization and weed control methods on sunflower yield and weed flora. ANOVA showed that the interaction of fertilization and weed control had a significant effect on grain yield. Moreover, this study revealed that the density of the common weeds Amaranthus retroflexus, Abutilon theophrasti, Xanthium strumarium and Echinochloa crusgalli was increased by 60, 40, 33 and 23% in the plots of high N rate without any herbicide use. On the contrary, weeds like Datura stramonium and Convolvulus arvensis were not significantly affected by fertilization. This different responsiveness of the several weed species could be further exploited through programs of integrated crop and weed management. Moreover, our findings related to the differences in herbicide efficacy resulting from different N levels may alter weed flora and explain possible weed control failures. [ABSTRACT FROM AUTHOR]

Environmental concerns and several adverse effects of reliance on and improper use of pesticides make necessary the use of alternative methods. Allelopathy has a rather unexploited potential in integrated weed management and ought to be further studied. The allelopathic effects of velvet bean (Mucuna pruriens (L.) DC. var. utilis) on seedling emergence and first growth of the important weed rigid ryegrass (Lolium rigidum L.) were evaluated in a pot experiment conducted at Agricultural University of Athens. Leaf residues of velvet bean were used to determine their inhibitory potential on seedling emergence and growth parameters including height, leaf number, tillering and fresh and dry weight of rigid ryegrass. Moreover, the allelopathic potential of inflorescence residues of chia (Salvia hispanica L.) on rigid ryegrass was also evaluated. Our results revealed a significant weed suppressive ability of the studied plants. The plant residues incorporated into the soil significantly reduced the seedling emergence and growth parameters of rigid ryegrass as compared to the control. In particular, velvet bean's residues also reduced height, leaf number and biomass of rigid ryegrass up to 26, 51 and 62%, respectively. The indicated allelopathic activity of velvet bean and chia could be further exploited in future studies, by using either allelochemicals as models for future herbicides or the plants as useful cover crops or mulches in terms of integrated weed management. [ABSTRACT FROM AUTHOR]

Sorghum halepense (L.) Pers is a common and noxious worldwide weed of increasing distribution in many European countries. In the present review, information on the biology, ecology, agricultural, economic and environmental impact of johnsongrass is given, and the current status of this weed in Europe is discussed. Furthermore, special attention is given to the important role of field trials using glyphosate to control weeds in arable and perennial crops in many European countries. Some of the factors which affect control efficacy and should be taken into account are also discussed. Finally, several non-chemical alternative methods (cultural, mechanical, thermal, biological, etc.) for johnsongrass management are also presented. The adoption of integrated weed management (IWM) techniques such as glyphosate use, crop rotation, and deep tillage is strongly recommended to control plant species that originate from both seed and rhizomes. [ABSTRACT FROM AUTHOR]