1,721,021 research outputs found
Algunos aspectos acerca de la aparición de resistencia a herbicidas en poblaciones de malezas
Get PDFActualmente la mayor parte de las cosechas de grano en la Argentina están provistas por sistemas de producción agrícola permanente. Esto ha inducido el reemplazo de especies y la selección de fenotipos nuevos en las poblaciones de las malezas que acompañan los cultivos. Estos cambios se manifiestan a través de un incremento en las fallas en el control químico, debido a que las especies escapan, aumentan la tolerancia o resisten a los controles. En respuesta a estos problemas los agricultores han incrementado las dosis, la frecuencia de aplicación de herbicidas y el abanico de productos utilizados. Estas medidas, que apuntan a resolver las ineficiencias en el control de malezas, han acentuado en términos generales el problema de la reestructuración de las comunidades de malezas y el de la selección de poblaciones resistentes a los herbicidas. Ejemplos paradigmáticos de este proceso son la resistencia a glifosato y atrazina, dos de los herbicidas que se usan con mayor frecuencia.Fil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferraro, Diego Omar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Fuzzy assessment of herbicide resistance risk: Glyphosate-resistant johnsongrass, Sorghum halepense (L.) Pers., in Argentina's croplands
Get PDFA fuzzy-logic based model was built in order to assess the relative influence of different ecological and management drivers on glyphosate resistance risk (GRR) in Sorghum halepense (L.) Pers. The model was hierarchically structured in a bottom-up manner by combining 16 input variables throughout a logical network. Input data were related to 1) herbicide usage, 2) crop rotation, 3) landscape characterization, 4) weed dispersal, and 5) mean maximum and minimum seasonal temperature. Mean maximum and minimum seasonal temperatures and the dominance of glyphosate use were the variables that showed the highest sensitivity to input changes. Application of the model at a regional scale resulted in a wide range of GRR values. The lowest range values (lower than 0 and between 0 and 0.25) were represented in 5.5% and 21.5% of the cropping area, respectively. Intermediate GRR range (between 0.25 and 0.5) were assessed in 57.3% of the cropping area whilst the highest GRR range values (0.5e0.7) were represented in only 15.6% of the studied area. The assessment of trade-offs between different ecosystem functions through expert opinion can complement traditional analyses for predicting herbicide resistance risk based on solely the genetic aspect of the evolutionary processFil: Ferraro, Diego Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente. Catedra de Ecologia; Argentin
Incorporating the process of vertical transmission into understanding of host-symbiont dynamics
Get PDFVariation exists in the frequency of obligate, vertically transmitted symbiotic organisms within and among host populations; however, these patterns have not been adequately explained by variable fitness effects of symbionts on their hosts. In this forum, we call attention to another equally important, but overlooked mechanism to maintain variation in the frequency of symbioses in nature: the rate of vertical transmission. On ecological time scales, vertical transmission can affect the equilibrium frequencies of symbionts in host populations, with potential consequences for population and community dynamics. In addition, vertical transmission has the potential to influence the evolution of symbiosis, by affecting the probability of fixation of symbiosis (and therefore the evolution of complexity) and by allowing hosts to sanction against costly symbionts. Here we use grass-epichloae symbioses as a model system to explore the causes and consequences of variation in vertical transmission rates. We identify critical points for symbiont transmission that emerge from considering the host growth cycle devoted to reproduction (asexual vs sexual) and the host capability to maintain homeostasis. We also use information on the process of transmission to predict the environmental factors that would most likely affect transmission rates. Altogether, we aim to highlight the vertical transmission rate as an important process for understanding the ecology and evolution of symbiosis, using grass-epichloae interactions as a case study.Fil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Rudgers J. A.. Rice University; Estados UnidosFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin
Plant oxidative status under ozone pollution as predictor for aphid population growth: The case of Metopolophium dirhodum (Hemiptera: Aphididae) in Triticum aestivum (Poales: Poaceae)
Get PDFOzone is a secondary air pollutant that affects plants and animals through several physiological mechanisms that involve changes in redox status. However, the consequences of ozone pollution on aphids are not well understood. Therefore, we have experimentally tested: if oxidative stress on the host plant affects lipid peroxidation in aphids or aphid population growth. Wheat plants (Triticum aestivum) were exposed to 140 p.p.b. of ozone or filtered air in open top chambers for three consecutive days and Metopolophium dirhodum (Walker, 1849, Hemiptera: Aphididae) aphids were transferred to the plants immediately after ozone exposure or 72 h later. Ozone exposure reduced antioxidant potential within plant tissues and had no effect on plants’ lipid peroxidation. Lipid peroxidation in aphids fed upon these plants was similar among treatments. Although aphids successfully colonised the plants in all the treatments, the populations established on plants immediately after ozone exposure grew at higher rates than those established 72 h after ozone exposure had ended, independently of ozone level. In conclusion, aphids were tolerant to plant mediated effects of ozone. Therefore, a greater attention should be put in the direct effects of ozone on M. dirhodum - T. aestivum interaction.Fil: Telesnicki, Marta Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Martinez-Ghersa, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin
Threshold modelling Lolium multiflorum seed germination: Effects of Neotyphodium endophyte infection and storage environment
Get PDFSeveral forage species establish mutualistic associations with vertically-transmitted endophytic fungi that improve their fitness. However, the endophyte may be related to livestock toxicosis and hence ageing seeds has been used to remove the fungus since it loses viability before the seeds. The effect of endophyte on seed quality has rarely been studied. We conducted an experiment to study the relationship between the endophyte Neotyphodium occultons and seed germination characteristics in Lolium multiflorum. Infected and non-infected seeds were stored under six different conditions and seed germination rate and viability were monitored over two years. Seed water content was evaluated and the ageing-time model was used to describe the dynamics of seed germination in relation to storage period. The model provided a good description of the seed germination, and parameters appear to work better when seed viability is affected. The endophyte not only affected negatively the seed viability but also the germination rate. Although the endophyte modified the water content, this effect was not associated with the negative effect on viability. Since non-toxic endophytes are being selected to improve forage grasses, further research should incorporate the endophyte viability dynamics in the population-based model to better predict both seed quality decay and endophyte losses.Fil: Gundel, Pedro Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentina. MTT Agrifood Research Finland; FinlandiaFil: Martinez-Ghersa, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentin
Structural complexity of arthropod guilds is affected by the agricultural landscape heterogeneity generated by fencerows
Get PDFIntensive farming imposes harsh conditions impeding the persistence of most arthropod species within crop fields. Hence, arthropods surviving the unfavourable conditions prevailing within crop fields may disperse towards nearby uncropped margins, such as fencerows. Here, we evaluate the influence of landscape heterogeneity on the abundance of different guilds, particularly herbivores and their natural enemies. Said heterogeneity mostly derives from fencerow network density. Hence, we developed an approach based on fitting linear-mixed models to elucidate the effects of landscape heterogeneity and field position (fencerows and crop interiors) on arthropod diversity. Mixed models were fitted to arthropod data obtained by pitfall trap samplings in 36 crop fields. Arthropod communities were structurally and functionally more complex along fencerows than within nearby crop interiors. Arthropods abundance was modulated by landscape heterogeneity, increasing the abundance of natural enemies as the landscape heterogeneity increased. On the contrary, herbivores abundance decreased as landscape heterogeneity increased. Consequently, the ratio between herbivores and natural enemies also decreased as landscapes became more heterogeneous. Natural enemies with larger body sizes, mostly carabid beetles, were more sensitive to landscape homogenisation. Our study reveals that, despite the coarse-grained landscapes in the Rolling Pampa, fencerow density appears as a key factor for structuring complex arthropod guilds in intensively farmed agricultural mosaics. In landscapes with higher density of fencerows, arthropods tend to concentrate along them, thus increasing the community structural complexity as well as the predation pressure over herbivores. This structural complexity of upper trophic levels enhances the 'top-down' regulation of herbivore populations, consequently decreasing the probability of pest outbreaks within crop fields.Fil: Molina, Gonzalo Alberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. ; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; ArgentinaFil: Poggio, Santiago Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. ; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. ; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente; Argentin
Arthropod assemblage related to volatile cues in flowering wheat: interaction between aphid herbivory and soil conditions as induction factors
No full textVolatile cues released by plants play an important role in plant-insect interactions and are influenced by pests or soil conditions affecting plant metabolism. Field microcosm experiments were used to characterize arthropod spontaneous assemblies in homogenous unstressed wheat patches exposed to volatile cues coming from wheat plants with different levels of stress. The design was a factorial completely randomized block design with three replications. Source wheat pots combined two stress factors: 1) soil degradation level: high and low, and 2) aphid herbivory: with (A) and without (B). Eighteen experimental units consisted of source stressed wheat pots, connected by tubes conducting the volatile cues to sink wheat patches. These patches were located at the end of the tubes placed in a flowering wheat field. Arthropod assemblies on wheat sinks were different between years and they were associated to the source cues. Soil condition was the main discriminating factor among arthropods when a clear contrast between high and low soil degradation was observed, whereas aphid herbivory was the main discriminating factor when soil condition effects were absent. Main soil properties related with arthropods assembly were Mg and K in the first year and cation exchange capacity, total nitrogen, and pH in the second year of experiment. According to this study, spontaneous arthropod distributions in the homogeneous, unstressed wheat patch responded to the volatile cues coming from wheat sources growing in particular soil conditions. It is possible to suggest that soil-plant-herbivore interactions change wheat cues and this phenomenon produces significant differences in neighboring arthropod community structure.Fil: Lenardis, Adriana Ester. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Produccion Vegetal; ArgentinaFil: Szpeiner, Alfonsina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; Argentin
The arable plant diversity of intensively managed farmland: effects of field position and crop type at local and landscape scales
No full textAgro-ecosystem biodiversity is threatened by increasing spatial homogenisation of intensively managed farmland. Yet current understanding of patterns of arable plant diversity at various scales remains limited. We evaluated the extent to which species richness of arable plants in the Rolling Pampas of Argentina is determined by field position (fencerow, edge and centre) and crop type, at both field (local) and landscape scales. Plant richness was assessed in maize, soybean and wheat–soybean fields across four landscape types differing in spatial complexity, as defined by percentage area devoted to cropland. Species richness was hierarchically nested within landscape types, field positions and crop types. Landscape richness (γ-diversity, the cumulative number of species in a set of fields) was additively partitioned into two components, one for local richness (α-diversity, the mean number of species per field) and one denoting differences in species composition among fields (β-diversity, where β = γ − α). Field position was the main determinant of landscape-scale plant richness. Overall, γ-diversity declined from fencerows, through field edges to field centres, but was unaffected by crop type. Spatial variation in species composition (β-diversity), rather than species packing within fields (α-diversity), accounted for most of the variation in arable γ-diversity. Higher β-diversity in field edges than in field centres suggested that propagule dispersal from fencerow vegetation may create a ‘mass effect’ onto certain crop types. Shifts in γ-diversity of major perennial life-forms (chamaeophytes and phanerophytes) between field positions and crop types reflected the contrasting disturbance regimes affecting plant communities of fencerows and cultivated fields. Our results indicate that preserving coherent and extensive fencerow networks is essential to conserve farmland biodiversity. Moreover, maintaining landscape heterogeneity to support elevated β-diversities of arable plants requires cropping systems that promote crop diversity in both space and time.Fil: Poggio, Santiago Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Chaneton, Enrique Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; Argentin
Weed vegetation of sugarcane cropping systems of northern argentina: Data-mining methods for assessing the environmental and management effects on species composition
Get PDFWeed composition may vary because of natural environment, management practices, and their interactions. In this study we presented a systematic approach for analyzing the relative importance of environmental and management factors on weed composition of the most conspicuous species in sugarcane. A data-mining approach represented by k-means cluster and classification and regression trees (CART) were used for analyzing the 11 most frequent weeds recorded in sugarcane cropping systems of northern Argentina. Data of weed abundance and explanatory factors contained records from 1976 sugarcane fields over 2 consecutive years. The k-means method selected five different weed clusters. One cluster contained 44% of the data and exhibited the lowest overall weed abundance. The other four clusters were dominated by three perennial species, bermudagrass, johnsongrass, and purple nutsedge, and the annual itchgrass. The CART model was able to explain 44% of the sugarcane's weed composition variability. Four of the five clusters were represented in the terminal nodes of the final CART model. Sugarcane burning before harvesting was the first factor selected in the CART, and all nodes resulting from this split were characterized by low abundance of weeds. Regarding the predictive power of the variables, rainfall and the genotype identity were the most important predictors. These results have management implications as they indicate that the genotype identity would be a more important factor than crop age when designing sugarcane weed management. Moreover, the abiotic control of cropweed interaction would be more related to rainfall than the environmental heterogeneity related to soil type, for example soil fertility. Although all these exploratory patterns resulting from the CART data-mining procedure should be refined, it became clear that this information may be used to develop an experimental framework to study the factors driving weed assembly. Nomenclature: Bermudagrass, Cynodon dactylon Pers. (CYNDA); johnsongrass, Sorghum halepense (L.) Pers. (SORHA); purple nutsedge, Cyperus rotundus L. (CYPRO); itchgrass, Rottboellia exaltata (L.) L.f.(ROOEX). © Weed Science Society of America.Fil: Ferraro, Diego Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Rivero, Diego Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía; Argentin
Uncropped field margins to mitigate soil carbon losses in agricultural landscapes
Get PDFAgricultural intensification is a major cause of habitat transformation. Continuous cropping alters ecosystem services, such as biodiversity and carbon sequestration. Empirical evidence from agricultural lands in Argentina has shown that permanently vegetated areas imbedded in the agricultural matrix (uncropped margins) play a critical role in plant and animal communities compared to the usual situation of crops surrounded by other crops (cultivated margins). However, the potential impact of uncropped margins on their own carbon stocks and fluxes and on those of their neighbouring cropped fields remains unknown. We investigated the impact of uncropped (herbaceous and woody) and cropped margins (cultivated fields) on their own topsoil carbon stocks and fluxes and on those of their neighbouring croplands (soybean fields). We identified soybean fields adjacent to one of three possible margin types: herbaceous or woody permanent vegetation, and field crop, which acted as control because it is the most frequent situation in the region. In each of these margin?soybean pairs, we sampled transects from the margin towards the centre of the soybean field (50 m). Woody margins showed the greatest soil carbon content, the least decomposable plant litter and the greatest influence on the neighbouring crop. Conversely, herbaceous margins had the lowest litter accumulation and the most decomposable litter. Only woody margins influenced soil properties in the first metres of the cropped neighbourhood. Centres of soybean fields were similar, irrespective of margin type. The decomposition of common substrates was not affected by margin type. These findings suggest that woody margins are the unique element of the current landscape with a potential to mitigate soil carbon loss from agroecosystems, albeit spatially limited. In contrast, the low biomass and highly decomposable litter of herbaceous margins reveal the urgent need to re-think their current management strategies.Fil: D'acunto, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Semmartin, María Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ghersa, Claudio Marco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin
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