Tolerance to ozone might impose restrictions to plant disease management in tomato

Tropospheric ozone (O3) is considered a major air pollutant having negative effects on plant growth and productivity. Background concentrations are expected to rise in several regions of the world in the next 50 years, affecting plant responses to diseases, thus requiring new management strategies for food production. The effects of elevated O3 on the severity of a bacterial disease, and the effectiveness of a chemical defence inducer, were examined in two cultivars of tomato, Roma and Moneymaker, which present different tolerance to this pollutant. The two cultivars differ in their ability to produce and accumulate reactive oxygen species (ROS) in leaf tissues. Tomato plants were challenged with a strain of Xanthomonas vesicatoria, Xv9, which is pathogenic on tomato. Ozone consistently increased severity of the disease by over 40% in both cultivars. In the more tolerant cultivar, O3 pollution increased disease intensity, even after applying a commercially available product to enhance resistance (acibenzolar-S-methyl, BTH). In the more susceptible cultivar, level of disease attained depended on the oxidative balance that resulted from other stress factors. The antioxidant capacity of the plant at the time of infection was relevant for controlling development of the disease. Our results suggest that development of O3 tolerance in commercial crops might impose a penalty cost in terms of disease management under projected higher O3 concentrations.Fil: Romero, Ana M.. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Menéndez, A. I.. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Folcia, Ana María. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; 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; Argentin

Aphid and episodic O3 injury in arugula plants (Eruca sativa Mill) grown in open-top field chambers

Aphid attacks and tropospheric ozone (O3) cause stress and considerable damage in both wild and cultivated plants. Induced defense responses to aphid attacks and O3 exposure share signaling pathways with common points. We investigated the plant-aphid interaction under O3 exposure using open-top O3 chambers. Ozone leaf injury was lower in aphid-infested plants than in aphid-free plants, although herbivore damage was not evident. Aphid population growth was strongly affected by previous exposure to O3 but no direct effect of O3 was observed. The possibility that during O3 episodes, herbivores may reduce O3 damage on host plants and that the offspring of the exposed aphids have lower population growth rates opens new and intriguing questions about potential effects of future increased tropospheric O3 levels on plant-insect interactions. © 2009 Elsevier B.V. All rights reserved.Fil: Menéndez, Analía. 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: Romero, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; ArgentinaFil: Folcia, A. M.. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal; 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; Argentin

Impact of plant and aphid stress history on infestation in arugula plants

Plants can activate inducible defence mechanisms against pests, pathogens, or chemical elicitors, such as ozone, mediated by reactive oxygen species (ROS), particularly hydrogen peroxide (H2O2). An unfavourable balance between ROS production and the plant antioxidant capacity seems to be responsible for the resulting susceptibility of the plant to insect attack. Arugula plants [Eruca sativa Mill. (Brassicaceae)] and green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), were used in this study to test the hypothesis that the growth of an aphid population depends on both plant and insect stress history. We investigated the impact of density and duration of a previous aphid infestation, and the time lag before re-infestation, on aphid population growth. In a second experiment, we assessed the effect on aphid population growth of previous ozone exposure of arugula plants in open top chambers receiving a continuous O3 fumigation of 100–120 p.p.b., 90 min per day during 3 days. A third experiment was conducted to study the effect of aphid density during a previous infestation on the population growth on an uninfested host. Both previous herbivory and ozone changed the oxidative status of plant tissues and facilitated aphid population growth, which increased with the duration and density of a previous infestation by aphids. Colonization success also depended on the aphids' own history. Aphids coming from high-density populations and/or longer infestation periods produced larger populations on an (initially) uninfested plant. Pest outbreaks in a polluted environment might be expected to be modulated by the hosts' spatial-temporal heterogeneity related to the ozone exposure and previous herbivory.Fil: Menéndez, A. I.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Folcia, A. M.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Produccion Vegetal; ArgentinaFil: Vizgarra, L.. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Produccion Vegetal; ArgentinaFil: Romero, Ana María. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Vegetal. Cátedra de Produccion Vegetal; 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; Argentina. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Recursos Naturales y Ambiente; Argentin

Legacy of historic ozone exposure on plant community and food web structure.

Information on whole community responses is needed to predict direction and magnitude of changes in plant and animal abundance under global changes. This study quantifies the effect of past ozone exposure on a weed community structure and arthropod colonization. We used the soil seed bank resulting from a long-term ozone exposure to reestablish the plant community under a new low-pollution environment. Two separate experiments using the same original soil seed bank were conducted. Plant and arthropod richness and species abundance was assessed during two years. We predicted that exposure to episodic high concentrations of ozone during a series of growing cycles would result in plant assemblies with lower diversity (lower species richness and higher dominance), due to an increase in dominance of the stress tolerant species and the elimination of the ozone-sensitive species. As a consequence, arthropod-plant interactions would also be changed. Species richness of the recruited plant communities from different exposure histories was similar (≈ 15). However, the relative abundance of the dominant species varied according to history of exposure, with two annual species dominating ozone enriched plots (90 ppb: Spergula arvensis, and 120 ppb: Calandrinia ciliata). Being consistent both years, the proportion of carnivore species was significantly higher in plots with history of higher ozone concentration (≈3.4 and ≈7.7 fold higher in 90 ppb and 120 ppb plots, respectively). Our study provides evidence that, past history of pollution might be as relevant as management practices in structuring agroecosystems, since we show that an increase in tropospheric ozone may influence biotic communities even years after the exposure

Community structure of the experimental plots during ozone exposure at 0, 90 and 120 ppb and after transplanting under common ecological conditions.

<p>Community structure of the experimental plots during ozone exposure at 0, 90 and 120 ppb and after transplanting under common ecological conditions.</p

Relative abundance of <i>Spergula arvensis</i>, <i>Calandrinia ciliata</i> and other species in plant communities selected under different episodic concentrations of tropospheric ozone.

<p>Ozone concentrations in the open top chambers during long-term exposure were 0 ppb (white bars), 90 ppb (grey bars) and 120 ppb (dark bars). Data represents species abundances during the first (a) and second (b) year of experiment after original soil seed bank was transplanted to a common natural field environment. Relative abundance for each plant species was calculated as the summed abundances of each plant species for a particular year/total number of seedlings recorded in the plot (n = 3). Error bars represent standard error. Year a ANOVA <i>P</i> _species < 0.01, <i>P</i>_ozone 0.016, <i>P</i>_{species x ozone} 0.034; year b ANOVA <i>P</i> _species < 0.01, <i>P</i>_ozone 0.024, <i>P</i>_{species x ozone} 0.042</p

Mean seedling density in 1 m² plots established from plant communities. selected under different episodic concentrations of tropospheric ozone (0, 90 and 120 ppb).

<p>Mean seedling density in 1 m² plots established from plant communities. selected under different episodic concentrations of tropospheric ozone (0, 90 and 120 ppb).</p

Means and statistics from analysis of variance of species richness (<i>S</i>), species diversity (Shannon-Weaver index, H´) and species evenness (<i>H</i>´/log_e (<i>S</i>)) for arthropod communities established from different historic exposure regimens.

<p>Means and statistics from analysis of variance of species richness (<i>S</i>), species diversity (Shannon-Weaver index, H´) and species evenness (<i>H</i>´/log_e (<i>S</i>)) for arthropod communities established from different historic exposure regimens.</p