Ilias Travlos

Glyphosate-Resistant Hairy Fleabane (Conyza bonariensis) Is Reported in Greece

Abstract Overreliance on glyphosate can increase the risks of reduced efficacy of the herbicide on weeds and weed resistance, even in regions without glyphosate-resistant crops. That is the reality in Greece, with frequent reports of reduced efficacy of glyphosate against increasingly problematic weeds, such as Conyza spp. The objectives of this study were to determine the occurrence of glyphosate resistance in hairy fleabane populations in central and southern Greece and the effect of weed growth stage on glyphosate efficacy under controlled environmental conditions and to evaluate alternative herbicides in field trials for control of glyphosate-resistant and -susceptible hairy fleabane. Plants from 60 accessions of hairy fleabane, sampled from five prefectures in Greece, were sprayed with glyphosate at 0.36 kg ae ha−1; 15 were classified as potentially resistant. After initial screening, 15 potentially susceptible or resistant accessions were selected and dose–response experiments were conducted. Glyphosate rates required to control some accessions were four to seven times greater than that for control of the reference susceptible accession, AR4. Sensitivity of a resistant hairy fleabane accession to glyphosate was strongly dependent on growth stage, with plants at the seedling stage being most sensitive to the herbicide. A field trial indicated that diquat, glufosinate, or glufosinate + oxyfluorfen controlled glyphosate-resistant or -susceptible hairy fleabane. These herbicides, along with various integrated management strategies, have good potential to manage or slow the spread of glyphosate resistance in this species. Nomenclature: Diquat; glufosinate; glyphosate; oxyfluorfen; hairy fleabane, Conyza bonariensis (L.) Cronq. ERIBO.

Effects of Presowing Pulsed Electromagnetic Treatment of Tomato Seed on Growth, Yield, and Lycopene Content

The use of magnetic field as a presowing treatment has been adopted by researchers as a new environmental friendly technique. The aim of this study was to determine the effect of magnetic field exposure on tomato seeds covering a range of parameters such as transplanting percentage, plant height, shoot diameter, number of leaves per plant, fresh weight, dry weight, number of flowers, yield, and lycopene content. Pulsed electromagnetic field was used for 0, 5, 10, and 15 minutes as a presowing treatment of tomato seeds in a field experiment for two years. Papimi device (amplitude on the order of 12.5 mT) has been used. The use of pulsed electromagnetic field as a presowing treatment was found to enhance plant growth in tomato plants at certain duration of exposure. Magnetic field treatments and especially the exposure of 10 and 15 minutes gave the best results in all measurements, except plant height and lycopene content. Yield per plant was higher in magnetic field treatments, compared to control. MF-15 treatment yield was 80.93% higher than control treatment. Lycopene content was higher in magnetic field treatments, although values showed no statistically significant differences.

Environmental Conditions Influence Induction of Key ABC-Transporter Genes Affecting Glyphosate Resistance Mechanism in Conyza canadensis

Conyza canadensis has been reported to be the most frequent weed species that evolved resistance to glyphosate in various parts of the world. The objective of the present study was to investigate the effect of environmental conditions (temperature and light) on the expression levels of the EPSPS gene and two major ABC-transporter genes (M10 and M11) on glyphosate susceptible (GS) and glyphosate resistant (GR) horseweed populations, collected from several regions across Greece. Real-time PCR was conducted to determine the expression level of the aforementioned genes when glyphosate was applied at normal (1×; 533 g·a.e.·ha−1) and high rates (4×, 8×), measured at an early one day after treatment (DAT) and a later stage (four DAT) of expression. Plants were exposed to light or dark conditions, at three temperature regimes (8, 25, 35 °C). GR plants were made sensitive when exposed to 8 °C with light; those sensitized plants behaved biochemically (shikimate accumulation) and molecularly (expression of EPSPS and ABC-genes) like the GS plants. Results from the current study show the direct link between the environmental conditions and the induction level of the above key genes that likely affect the efficiency of the proposed mechanism of glyphosate resistance.

Non-target Site Tolerance Mechanisms Describe Tolerance to Glyphosate in Avena sterilis

Sterile wild oat (Avena sterilis L.) is an autogamous grass established in warm climate regions. This species has been used as a cover crop in Mediterranean perennial crops during the spring period prior to initiating competition with the main crop for water and nutrients. However, such cover crops need to be controlled (by glyphosate or tillage) before the beginning of summer period (due to the possibility of intense drought stress). In 2011, the olive grove farmers of southern Spain expressed dissatisfaction because of the ineffective control with glyphosate on A. sterilis. Experiments were conducted to determine whether the continued use of glyphosate over a 5 year period had selected a new resistant or tolerant species. The GR50 values obtained for A. sterilis were 297.12 and 245.23 g ae ha−1 for exposed (E) and un-exposed (UE) glyphosate accessions, respectively. The spray retention and shikimic acid accumulation exhibited a non-significant difference between the two accessions. The results of 14C- glyphosate absorption was the same in the two accessions (E and UE), while the translocation from the treated leaf to the rest of the shoots and roots was similar in A. sterilis accessions. Glyphosate metabolism to aminomethylphosphonic acid (AMPA) and glyoxylate was similar in both accessions, but increased after treatment with glyphosate, indicating that metabolism plays an important role in tolerance. Both A. sterilis accessions, present similarity in the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity enzyme with different glyphosate concentrations and without glyphosate, confirming that both accessions present the same genomic characteristics. The above-mentioned results indicate that innate tolerance to glyphosate in A. sterilis is probably and partly due to reduced herbicide absorption and translocation and metabolism compared to the susceptibility of other grasses weeds like Chloris inflata, Eleusine indica, and Lolium rigidum.

Responses of invasive silverleaf nightshade (Solanum elaeagnifolium) populations to varying soil water availability

Aspects of the invasive potential of the noxious weed silverleaf nightshade (Solanum elaeagnifolium Cav.) were studied. Greenhouse experiments were conducted in order to assess several growth, production and fecundity traits of three silverleaf nightshade populations under differing levels of water availability and to correlate them with the invasive potential of each genotype. Our results showed that water availability certainly improves growth and fecundity of this serious invasive species. In ideal conditions, S. elaeagnifoilum shows a massive seed production which clearly promotes its invasiveness. However, the three populations show different phenotypic plasticity, which could explain their different adaptation and invasiveness in habitats with different water availability. Under low water availability, plants of the Etoloakarnania (ET) population allocate more than half of their total biomass to their roots (high R/S ratio), which serve as an important reproductive organ, while they maintain a relatively high seed production. These differences in phenotypic plasticity between weed populations mean that some of them (such as ET) would be more efficient in coping with changing water availability than others and therefore should be managed on high priority.

Assessment of distribution and diversity of Avena sterilis L. and Avena fatua L. in cereal crops of Greece based on a 3-year survey and selected morphological traits

Under the view of species genetic erosion and the need of better crops, wild species could become important germplasm sources for breeding. At present, several wild Avena species are used as donors of valuable characters in oat breeding. In this study, wild oat distribution and diversity in wheat, barley and oat fields of Greece was examined by means of a 3-year survey in some typical cereal producing regions in the central part of the country. Greenhouse experiments were also conducted in order to compare seedlings grown from wild oat accessions of these regions under the same conditions. A total of 151 fields were surveyed and 158 accessions of wild oats were studied in terms of some morphological traits. The occurrence and distribution of A. sterilis was very high, while a noticeable and first-time analytically reported presence of A. fatua was evident in some of the surveyed wheat fields. The high diversity of wild oat was furthermore indicated by means of the pot experiments. The high degree of phenotypic variation in A. sterilis could be attributed to the earlier introduction of this species in the sampling area, compared to A. fatua. Wild oat distribution and diversity in a region seems crucial for the cereal production and is an important parameter which must be considered in evaluating efficacy of weed control strategies, while genes controlling these characters could be potentially used to improve cultivated forms of oats or other cereals.

Invasiveness of Cut-Leaf Ground-Cherry (Physalis angulata L.) Populations and Impact of Soil Water and Nutrient Availability

Las invasiones biologicas son una amenaza importante para los ecosistemas naturales y agroecosistemas, mientras que, globalmente, la flora de malezas parece cambiar notablemente. En este estudio se evaluo el potencial de una especie nativa de America, tomatillos de Brihuega (Physalis angulata L.), para invadir las regiones semiaridas de Grecia. Se realizaron experimentos de invernadero y laboratorio para evaluar los efectos de diferentes recursos ambientales (disponibilidad de nutrientes y agua), crecimiento de las plantulas, produccion de biomasa, fecundidad y germinacion de las semillas de cuatro poblaciones de tomatillos de Brihuega. Nuestros resultados sugieren que P. angulata no tolera una extrema sequia durante las primeras etapas de crecimiento, pero puede sobrevivir y sus semillas germinar adecuada y rapidamente (> 85%) incluso en condiciones de baja humedad del suelo. Ademas, con alta humedad y disponibilidad de nutrientes genera un alto crecimiento y produccion de biomasa y asegura una alta produccion de semillas, llegando a mas de 4000 semillas por planta. Sugerimos que la alta humedad del suelo y en segundo lugar la disponibilidad de nutrientes son los factores criticos que afectan el potencial invasor de P. angulata en ambientes semiaridos. Comprender las caracteristicas ecologicas de las plantas mediante un estudio realizado en una fase de invasion temprana en lugar de tardia, permitira adoptar medidas de control apropiadas para esta especie, las cuales deben dirigirse primeramente a campos fertilizados con frecuencia despues de eventos de precipitacion.

Study of Fitness Cost in Three Rigid Ryegrass Populations Susceptible and Resistant to Acetyl-CoA Carboxylase Inhibiting Herbicides

Evaluation of fitness differences between herbicide-resistant and susceptible weed biotypes, allows a better prediction of further dispersal of herbicide-resistance populations and the design of a management strategy in order to achieve a mitigation of the problem in the absence of herbicide. In this study an evaluation of germination and seedling emergence characteristics of three rigid ryegrass biotypes (one susceptible and two resistant populations with different mutations, namely Ile 1781 Leu and Ile 2041 Asn) and of competition between this weed and wheat using replacement series experiments was conducted. The results showed that when seeds were on the soil surface (0 cm) to depth of 2 cm and again for the depth of 6 cm, there were not any significant differences between the biotypes regarding seed germination percentage. On the contrary, when seeds were sown in 2-4 cm depth, R-1781 consistently displayed lower emergence than the S and R-2041 biotypes. Moreover, when seeds were sown at 8 cm depth, final proportions of emerged seedlings were similar for R-2041 and R-1781, while both populations had significantly higher emergence than the S population. The competitive ability of the three biotypes was similar, as determined by a replacement series experiment with wheat. Our results under competitive conditions revealed that Triticum aestivum was more competitive than Lolium rigidum. Overall, there was no apparent fitness penalty associated to ACCase-inhibitor resistance, while different mutations may impose different competitive ability and therefore require case-specific management strategies.

Impact of variety and farming practices on growth, yield, weed flora and symbiotic nitrogen fixation in faba bean cultivated for fresh seed production

ABSTRACT The main objective of this study was to investigate the performance of faba bean landraces originating from different regions of Greece under both organic and conventional farming systems focusing mainly on yield, biological nitrogen fixation (BNF), and competitiveness to weeds. Faba bean exhibited a high ability to fix nitrogen from the atmosphere, as indicated by the percentage of N2 derived from the atmosphere which exceeded 75% in all evaluated varieties, and the total amount of biologically fixed N up to full anthesis, which fluctuated from 118.5 to 193.9 kg ha−1 in the various cropping systems and cultivars. The weed density was appreciably higher in the organic plots, without significant differences among the faba bean cultivars, while wild mustard and corn poppy were the most competitive weeds. The application of inorganic starter fertiliser in the conventionally-treated plots had no negative effect on biologically-fixed nitrogen by faba bean plants, while the herbicide pendimethalin had no negative impact on the nodulation process. Protein concentrations in faba bean cultivars fluctuated from 27.3% to 31.4%. The evaluated landraces could be utilised in breeding programmes due to their earliness, and their high performance in terms of protein content, BNF ability, and productivity.

Molecular, Genetic and Agronomic Approaches to Utilizing Pulses as Cover Crops and Green Manure into Cropping Systems

Cover crops constitute one of the most promising agronomic practices towards a more sustainable agriculture. Their beneficial effects on main crops, soil and environment are many and various, while risks and disadvantages may also appear. Several legumes show a high potential but further research is required in order to suggest the optimal legume cover crops for each case in terms of their productivity and ability to suppress weeds. The additional cost associated with cover crops should also be addressed and in this context the use of grain legumes such as cowpea, faba bean and pea could be of high interest. Some of the aspects of these grain legumes as far as their use as cover crops, their genetic diversity and their breeding using conventional and molecular approaches are discussed in the present review. The specific species seem to have a high potential for use as cover crops, especially if their noticeable genetic diversity is exploited and their breeding focuses on several desirable traits.