Use of Cellular Automata Modelling Approaches to Understand Potential Impacts of GM Grasses on Grassland Communities

In order to predict the potential unintended ecological impacts of genetically modified (GM) grasses, we must understand how the engineered traits, in this case herbicide resistance, are expressed in an ecological context. It would be a daunting task to experimentally evaluate the full multiplicity of potential pair-wise interactions between GM plants and native plants under a broad variety of actual environmental conditions. We have employed the modelling methodology of cellular automata (CA), where a plant\u27s distribution within a two-dimensional environmental grid is determined by rules relating to phenomena such as seed dispersal, clonal expansion and interactions with adjacent plants. We have used CA simulation to model interactions between GM grasses and the natural environment by describing the plants and the effect of the GM trait in terms of plant functional types. This approach takes the external factors which limit the amount of plant material present in any habitat and classifies them into two categories: (1) stress, defined with regard to the availability of nutrients and (2) disturbance, which refers to the destruction of plant material. The ecological characteristics of all the plants can be described based on three functional types C (competitor), S (stress-tolerator) and R (ruderal) as determined by their quantifiable physiological relationships to stress and disturbance. By ascribing the large number of plant ecological characteristics to a smaller number of functional types the problem, of describing how the engineered trait of herbicide resistance is expressed in an ecological context, becomes tractable

Accumulation of 137Cs and 90Sr from contaminated soil by three grass species inoculated with mycorrhizal fungi

The use of plants to accumulate low level radioactive waste from soil, followed by incineration of plant material to concentrate radionuclides may prove to be a viable and economical method of remediating contaminated areas. We tested the influence of arbuscular mycorrhizae on 137Cs and 90Sr uptake by bahia grass (Paspalum notatum), johnson grass (Sorghum halpense) and switchgrass (Panicum virginatum) for the effectiveness on three different contaminated soil types. Exposure to 137Cs or 90Sr over the course of the experiment did not affect above ground biomass of the three grasses. The above ground biomass of bahia, johnson and switchgrass plants accumulated from 26.3 to 71.7% of the total amount of the 137Cs and from 23.8 to 88.7% of the total amount of the 90Sr added to the soil after three harvests. In each of the three grass species tested, plants inoculated with Glomus mosseae or Glomus intraradices had greater aboveground plant biomass, higher concentrations of 137Cs or 90Sr in plant tissue, % accumulation of 137Cs or 90Sr from soil and plant bioconcentration ratios at each harvest than those that did not receive mycorrhizal inoculation. Johnson grass had greater aboveground plant biomass, greater accumulation of 137Cs or 90Sr from soil and plant higher bioconcentration ratios with arbuscular mycorrhizal fungi than bahia grass and switchgrass. The greatest accumulation of 137Cs and 90Sr was observed in johnson grass inoculated with G. mosseae. Grasses can grow in wide geographical ranges that include a broad variety of edaphic conditions. The highly efficient removal of these radionuclides by these grass species after inoculation with arbuscular mycorrhizae supports the concept that remediation of radionuclide contaminated soils using mycorrhizal plants may present a viable strategy to remediate and reclaim sites contaminated with radionuclides

Potential remediation of 137Cs and 90Sr contaminated soil by accumulation in Alamo switchgrass

Cesium-137 ( 137Cs) and Strontium-90 ( 90Sr) are radionuclides characteristic of nuclear fallout from nuclear weapons testing and nuclear reactor accidents. Alamo switchgrass (Panicum virginatum L.) is a perennial C4 species native to central North America that produces exceptionally high biomass yields in short periods of time. In three separate experiments, Alamo switchgrass plants were tested for their ability to accumulate 137 Cs and 90 Sr from a contaminated growth medium. Plants in experiment I were grown in 33 x 20 x 7 cm plastic pans containing 2.5 kg sand. Plants in experiments 2 and 3 were grown in 30 x 3 cm diameter test tubes containing 0.3 kg growth medium. After 3 months of plant growth, either 102 Bq 137 Cs or 73 Bq 90Sr g-1 soil were added to the growth medium. Plants in all three experiments were grown within a greenhouse that was maintained at 22 ± 2 °C with a photosynthetic active radiation of 400-700 umol m-2 s-1 and a 14-16 h photoperiod. Above-ground plant biomass did not differ between plants that were not exposed to these radionuclides (controls) and those that were exposed to growth medium containing 137Cs or 90Sr over the course of the experiment. Plants accumulated 44 and 36% of the total amount of 90Sr and 137CS added to growth medium after the first 5 harvests. After the first two harvests, the concentration of 137CS and 90Sr in plant tissue and the amount of 137Cs or 90Sr removed from growth medium declined with each successive harvest. Duration of exposure correlated curvilinearly with accumulation of both 90Sr and 137CS by plants (r2 = 0.95 and 0.78, respectively). As concentration of both 137Cs and 90Sr in growth medium increased, plant accumulation of both radionuclides increased and correlated curvilinearly in seedlings (r2 = 0.83 and 0.89 respectively)

Statement on a conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific statement presenting a conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010. This framework will be used in the evaluation made by the Panel, but the expert judgement of the scientific background, on a case-by-case basis, remains essential to reach a final conclusion. The outcome of the re-evaluation of food additives taking into account all available information is presented in the document, as well as the exposure assessment scenarios to be carried out by the Panel considering the use levels set in the legislation and the availability of adequate usage or analytical data

Pollen-Mediated Gene Flow from Genetically Modified Herbicide Resistant Creeping Bentgrass

Approximately 162 ha of multiple experimental fields of creeping bentgrass (Agrostis stolonifera L.) genetically modified for resistance to Roundup ®herbicide, were planted in central Oregon in 2002. When the fields flowered for the first time in the summer of 2003, a unique opportunity was presented to evaluate methods to monitor potential pollen-mediated gene flow from the experimental GM crop fields to compatible sentinel and resident plants that were located in surrounding, primarily non-agronomic areas

Influence of adverse soil conditions on the formation and function of Arbuscular mycorrhizas

The majority of plants have mycorrhizal fungi associated with them. Mycorrhizal fungi are ecologically significant because they form relationships in and on the roots of a host plant in a symbiotic association. The host plant provides the fungus with soluble carbon sources, and the fungus provides the host plant with an increased capacity to absorb water and nutrients from the soil. Adverse conditions are a pervasive feature in both natural and agronomic soils. The soil environment is constantly changing with regard to moisture, temperature and nutrient availability. In addition, soil properties are often manipulated to improve crop yields. In many cases, soils may be contaminated through disposal of chemicals that are toxic to plants and microorganisms. The formation and function of mycorrhizal relationships are affected by edaphic conditions such as soil composition, moisture, temperature, pH, cation exchange capacity, and also by anthropogenic stressors including soil compaction, metals and pesticides. Arbuscular mycorrhizal fungi are of interest for their reported roles in alleviation of diverse soil-associated plant stressors, including those induced by metals and polychlorinated aliphatic and phenolic pollutants. Much mycorrhizal research has investigated the impact of extremes in water, temperature, pH and inorganic nutrient availability on mycorrhizal formation and nutrient acquisition. Evaluation of the efficacy of plant–mycorrhizal associations to remediate soils contaminated with toxic materials deserves increased attention. Before the full potential benefits of arbuscular mycorrhizal fungi to reclaim contaminated soils can be realized, research advances are needed to improve our understanding of the physiology of mycorrhizae subjected to adverse physical and chemical conditions. This paper will review literature and discuss the implications of soil contamination on formation and function of arbuscular mycorrhizal associations

Arbuscular mycorrhizal response to adverse soil conditions

Adverse conditions are a pervasive feature in both natural as well as agronomic soils. The soil environment is constantly changing with regard to moisture, temperature and nutrition. In addition, soil properties such as fertility, pH and aeration are often changed to improve crop yields. Soils have been unintentionally contaminated as a result of accidents that occur during agronomic operations or intentionally contaminated in mining or manufacturing operations by disposal of chemicals that are toxic to plants and micro-organisms. Mycorrhizal associations in terrestrial ecosystems influence organic and inorganic nutrient relationships, water relations and carbon cycling in plants. Relatively little is known about factors that control the vigour and extent of mycorrhization. This lack of understanding arises in large part from the difficulty of studying the intact association, which is a functionally and anatomically distinct structure comprising two biologically different organisms, e.g., plants and arbuscular mycorrhizae (AM) fungi. The formation and function of mycorrhizal relationships are affected by edaphic conditions such as soil composition, moisture, temperature, pH, cation exchange capacity. They are also affected by anthropogenic stressers such as heavy metals, pesticides and soil compaction. An organism's response to stress may involve interactions among various avoidance and tolerance mechanisms (Taylor, 1978; Tingey and Taylor, 1982; Tingey and Anderson, 1991). Stress avoidance mechanisms influence the amount and rate at which stress will reach the target site in the plant. Stress tolerance is defined as resistance via an ability "to come to thermodynamic equilibrium to the stress" without being killed (Levitt, 1980). In this chapter, we shall review the effects of a number of soil-associated stressers, including soil moisture, temperature, pH, heavy metals, agricultural practices and pesticides on AM development and function and host plant tolerance to these stresses. Several publications have reviewed the impact of various stresses on plant-mycorrhizal interactions (Anderson and Rygiewicz, 1991; Read, 1991; Van Duin et al, 1991; Sylvia and Williams, 1992), which provide additional information on this subject

Sub-lethal glyphosate exposure alters flowering phenology and causes transient male-sterility in Brassica spp

BACKGROUND: Herbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. Results from our previous studies suggest that sub-lethal levels of the herbicide glyphosate can alter the pattern of gene flow between glyphosate resistant Canola®, Brassica napus, and glyphosate sensitive varieties of B. napus and B. rapa. The objectives of this study were to examine the phenological and developmental changes that occur in Brassica crop and weed species following sub-lethal doses of the herbicides glyphosate and glufosinate. We examined several vegetative and reproductive traits of potted plants under greenhouse conditions, treated with sub-lethal herbicide sprays. RESULTS: Our results indicate that exposure of Brassica spp. to a sub-lethal dose of glyphosate results in altering flowering phenology and reproductive function. Flowering of all sensitive species was significantly delayed and reproductive function, specifically male fertility, was suppressed. Higher dosage levels typically contributed to an increase in the magnitude of phenotypic changes. CONCLUSIONS: These results demonstrate that Brassica spp. plants that are exposed to sub-lethal doses of glyphosate could be subject to very different pollination patterns and an altered pattern of gene flow that would result from changes in the overlap of flowering phenology between species. Implications include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to sub-lethal glyphosate.Keywords: Glyphosate, Herbicide drift, Brassica, Canola®, Glufosinate, Transgene escapeKeywords: Glyphosate, Herbicide drift, Brassica, Canola®, Glufosinate, Transgene escap

A metapopulation model for the introgression from genetically modified plants into their wild relatives

Most models on introgression from genetically modified (GM) plants have focused on small spatial scales, modelling gene flow from a field containing GM plants into a single adjacent population of a wild relative. Here, we present a model to study the effect of introgression from multiple plantations into the whole metapopulation of the wild relative. The most important result of the model is that even very low levels of introgression and selection can lead to a high probability that the transgene goes to fixation in the metapopulation. Furthermore, the overall frequency of the transgene in the metapopulation, after a certain number of generations of introgression, depends on the population dynamics. If there is a high rate of migration or a high rate of population turnover, the overall transgene frequency is much higher than with lower rates. However, under an island model of population structure, this increased frequency has only a very small effect on the probability of fixation of the transgene. Considering these results, studies on the potential ecological risks of introgression from GM plants should look not only at the rate of introgression and selection acting on the transgene, but also at the metapopulation dynamics of the wild relative