Transgenic Crop Varieties Research Articles

Effect of soil pH and mineralogy on the sorption and desorption of phosphite and phosphate in Ultisols of the Southeastern Coastal Plain

AbstractThe development of transgenic crop varieties capable of utilizing phosphite (Phi) as a phosphorus (P) source is a promising strategy to increase P use efficiency while decreasing reliance on phosphate (Pi)‐based fertilizers. However, little information is available on Phi sorption and desorption in soils. We conducted batch experiments to investigate the sorption of Phi and Pi by three Ultisols from the Coastal Plain of the southeastern United States. At the soils' acidic field pH (pH 4.7–6.2), Pi had a higher affinity than Phi for soil solids, where maximum sorbed concentrations of Pi were an average of 44% greater than those of Phi. The sorption of both P species decreased when experiments were repeated adjusting soil pH to 6.5. More Phi than Pi was recovered during desorption experiments, indicating that Phi was more reversibly sorbed and, therefore, may be more plant‐available than Pi. Multiple linear regression between calculated linear distribution coefficients (KD; 10 mg P L−1 input solutions) and soil properties suggested that amorphous Al‐ and Fe‐oxides controlled Pi sorption. Alternatively, amorphous Al‐oxides and gibbsite controlled Phi sorption. Our results show that a lower affinity of Phi than Pi in Ultisols could improve P availability for plant uptake of Phi‐based fertilizers but may increase the risk of soil P buildup over time.

Inhibition of Rhopalosiphum maidis (Corn Leaf Aphid) Growth on Maize by Virus-Induced Gene Silencing with Sugarcane Mosaic Virus.

The corn leaf aphid (Rhopalosiphum maidis), a damaging pest of maize (Zea mays), is not controlled by the insecticidal proteins in commercially available transgenic crop varieties. One promising approach is to reduce aphid growth and fecundity by targeting the expression of essential genes using plant-mediated RNA interference (RNAi). Here we describe a method whereby Sugarcane Mosaic Virus (SCMV), a positive-strand RNA virus in the Potyviridae family, is used for virus-induced gene silencing (VIGS) of gene expression in R. maidis. A segment of the R. maidis target gene is cloned into SCMV, maize plants are infected with the transgenic virus, aphids are placed on the virus-infected plants and, after a few days of feeding, decreases in target gene expression and aphid reproduction are assessed. This VIGS method can be used for rapid screening of suitable RNAi targets for aphid pest control, as well as to study the in vivo function of specific aphid genes.

Biofortification of Cereals and Pulses Using New Breeding Techniques: Current and Future Perspectives.

Cereals and pulses are consumed as a staple food in low-income countries for the fulfillment of daily dietary requirements and as a source of micronutrients. However, they are failing to offer balanced nutrition due to deficiencies of some essential compounds, macronutrients, and micronutrients, i.e., cereals are deficient in iron, zinc, some essential amino acids, and quality proteins. Meanwhile, the pulses are rich in anti-nutrient compounds that restrict the bioavailability of micronutrients. As a result, the population is suffering from malnutrition and resultantly different diseases, i.e., anemia, beriberi, pellagra, night blindness, rickets, and scurvy are common in the society. These facts highlight the need for the biofortification of cereals and pulses for the provision of balanced diets to masses and reduction of malnutrition. Biofortification of crops may be achieved through conventional approaches or new breeding techniques (NBTs). Conventional approaches for biofortification cover mineral fertilization through foliar or soil application, microbe-mediated enhanced uptake of nutrients, and conventional crossing of plants to obtain the desired combination of genes for balanced nutrient uptake and bioavailability. Whereas, NBTs rely on gene silencing, gene editing, overexpression, and gene transfer from other species for the acquisition of balanced nutritional profiles in mutant plants. Thus, we have highlighted the significance of conventional and NBTs for the biofortification of cereals and pulses. Current and future perspectives and opportunities are also discussed. Further, the regulatory aspects of newly developed biofortified transgenic and/or non-transgenic crop varieties via NBTs are also presented.

Ectopic expression of the apple nucleus-encoded thylakoid protein MdY3IP1 triggers early-flowering and enhanced salt-tolerance in Arabidopsis thaliana

BackgroundThe roles in photosystem I (PSI) assembly of the nucleus-encoded thylakoid protein Y3IP1 who interacts with the plastid-encoded Ycf3 protein that has been well-characterized in plants. However, its function and potential mechanisms in other aspects remain poorly understood.ResultsWe identified the apple MdY3IP1 gene, which encodes a protein highly homologous to the Arabidopsis Y3IP1 (AtY3IP1). Ectopic expression of MdY3IP1 triggered early-flowering and enhanced salt tolerance in Arabidopsis plants. MdY3IP1 controlled floral transition by accelerating sugar metabolism process in plant cells, thereby influencing the expression of flowering-associated genes. The increase in salt stress tolerance in MdY3IP1-expressing plants correlated with reduced reactive oxygen species (ROS) accumulation, and an increase in lateral root development by regulating both auxin biosynthesis and transport, as followed by enhancement of salt tolerance in Arabidopsis. Overall, these findings provide new evidences for additional functions of Y3IP1-like proteins and their underlying mechanisms of which Y3IP1 confers early-flowering and salt tolerance phenotypes in plants.ConclusionsThese observations suggest that plant growth and stress resistance can be affected by the regulation of the MdY3IP1 gene. Further molecular and genetic approaches will accelerate our knowledge of MdY3IP1 functions in PSI complex formation and plants stress resistance, and inform strategies for creating transgenic crop varieties with early maturity and high-resistant to adverse environmental conditions.

Seeds, Agricultural Systems and Socio‐natures: Towards an Actor–Network Theory Informed Political Ecology of Agriculture

AbstractAgriculture has recently been the subject of considerable research and policy attention. Events such as the 2008 ‘world food price crisis’ and concerns over the future of global food security have led to calls for a ‘New Green Revolution’, with an emphasis on boosting yields through new transgenic crop varieties. However, critics have raised concerns over the growing role of global agribusiness and transnational capital in agriculture, as well as the potential social and ecological impacts of new technologies. An analysis of emerging agricultural trends thus demands a framework that is able to negotiate the complex multi‐scalar interplay between environmental, technological, scientific, political and economic factors. In this paper, we focus on the potential contribution of a synthesis between political ecology and Actor–Network Theory to our understanding of agricultural networks. We review the literature with a view to teasing out key insights and sketching out future research priorities. We focus on questions surrounding power and agency, the political ecology of scale and the role of situated knowledges and practices.

Agrobacterium Mediated Transformation in Rice: A Novel Approach to Produce Agronomically Superior Transgenics

Rice the most important staple grain with second highest worldwide production has offered a great potential for biotechnological advances, categorized broadly in areas like transgenics, structural and functional genomics and marker-assisted breeding to provide with vital breakthroughs to achieve improvements in both quality and quantity in a sustainable manner. The ever increasing demand, increasing anthropogenic activities has posed a challenge to boost the production of rice. To cope of with this alarming situation, the advent of genetic engineering has been utilized to remove natural barriers through gene transfer/exchange. Since then, sequences from various sources like bacteria, viruses and eukaryotic systems were used to develop transgenic crop varieties. Gene transfer techniques like direct DNA transfer through particle bombardment, polyethylene glycol or electroporation and indirectly mediated by Agrobacterium are increasingly applied. Unfortunately, DNA delivered by direct methods is often integrated into the genome as rearranged or multiple copies, presumably as a result of which the expression pattern of the gene of interest is often aberrant or unstable. In contrast to this, Agrobacterium mediated transformation system offers higher transformation efficiency with discrete, unrearranged segments of DNA being inserted at fairly low copy number. Achievements, to date, through Agrobacterium mediated transfer have surpassed all previous expectations and with the development of this successful technique for genetic improvement the future is even more promising.

Hybridization between crops and wild relatives: the contribution of cultivated lettuce to the vigour of crop-wild hybrids under drought, salinity and nutrient deficiency conditions.

With the development of transgenic crop varieties, crop–wild hybridization has received considerable consideration with regard to the potential of transgenes to be transferred to wild species. Although many studies have shown that crops can hybridize with their wild relatives and that the resulting hybrids may show improved fitness over the wild parents, little is still known on the genetic contribution of the crop parent to the performance of the hybrids. In this study, we investigated the vigour of lettuce hybrids using 98 F2:3 families from a cross between cultivated lettuce and its wild relative Lactuca serriola under non-stress conditions and under drought, salinity and nutrient deficiency. Using single nucleotide polymorphism markers, we mapped quantitative trait loci associated with plant vigour in the F2:3 families and determined the allelic contribution of the two parents. Seventeen QTLs (quantitative trait loci) associated with vigour and six QTLs associated with the accumulation of ions (Na+, Cl− and K+) were mapped on the nine linkage groups of lettuce. Seven of the vigour QTLs had a positive effect from the crop allele and six had a positive effect from the wild allele across treatments, and four QTLs had a positive effect from the crop allele in one treatment and from the wild allele in another treatment. Based on the allelic effect of the QTLs and their location on the genetic map, we could suggest genomic locations where transgene integration should be avoided when aiming at the mitigation of its persistence once crop–wild hybridization takes place.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-1897-4) contains supplementary material, which is available to authorized users.

Is there a Weed Shift in Roundup Ready Maize?

AbstractThe cultivation of transgenic glyphosate-resistant crop varieties can simplify weed control in crops such as maize and others. On the other hand, the repeated use of broadly effective herbicides like glyphosate, especially in the same crop, can have a negative effect on biodiversity. Additionally there is a risk for a spread of more tolerant or even resistant weed species.It was the aim of a 6-years field study (2003-2008) to investigate weed effects of use of glyphosate in a continuous transgenic herbicide-resistant maize rotation at three sites in Germany. These sites differed significantly in terms of soil, climate and initial weed spectrum. The studies focussed on the comparison between local herbicide standards and split applications of Roundup Ready (360 g L^-1^ glyphosate) applied at dosages of 1,5 + 1,5; 2 + 2 and 3 + 3 L ha^-1^ Roundup Ready.Concerning the potential changes in weed communities over longer periods of time, the study did not indicate any negative effect on weed infestation, communities or diversity, of the glyphosate treatments compared to the local herbicide standard. Concerning species richness, there was no clear trend of the Roundup Ready treatments. Possible changes of the abundances of individual species were affected by the initial weed spectrum and consequently by the site conditions. As far as the conventional herbicides are efficiently used, they have no other effect than the glyphosate applications. Similar results were seen for the Shannon’s diversity index and Shannon’s evenness index.In sum, and looking at annual effects, it could be concluded from this 6 years study that 1) there are no statistically significant differences between local standard herbicide treatments and the glyphosate treatments assessed in this study on the mean values of seed bank, species richness, species diversity and dominance; 2) the data collected on the different parameters showed an enormous variability within sites and years; 3) a dosage of 3 + 3 L ha^-1^ Roundup Ready avoids spread of certain weed species like _Chenopodium album_ or Urtica urens; 3) as far as the standard herbicides were applied correctly in terms of a high and wide efficiency, they will have the same effect as the Roundup Ready treatments.

A spatial assessment of <i>Brassica napus</i> gene flow potential to wild and weedy relatives in the Fynbos Biome

Gene flow between related plant species, and between transgenic and non-transgenic crop varieties, may be considered a form of biological invasion. Brassica napus (oilseed rape or canola) and its relatives are well known for intra- and inter-specific gene flow, hybridisation and weediness. Gene flow associated with B. napus poses a potential ecological risk in the Fynbos Biome of South Africa, because of the existence of both naturalised (alien, weedy) and native relatives in this region. This risk is particularly pertinent given the proposed use of B. napus for biofuel and the potential future introduction of herbicide-tolerant transgenic B. napus. Here we quantify the presence and co-occurrence of B. napus and its wild and weedy relatives in the Fynbos Biome, as a first step in the ecological risk assessment for this crop. Several alien and at least one native relative of B. napus were found to be prevalent in the region, and to be spatially congruent with B. napus fields. The first requirement for potential gene flow to occur has thus been met. In addition, a number of these species have elsewhere been found to be reproductively compatible with B. napus. Further assessment of the potential ecological risks associated with B. napus in South Africa is constrained by uncertainties in the phylogeny of the Brassicaceae, difficulties with morphology-based identification, and poor knowledge of the biology of several of the species involved, particularly under South African conditions.

Characterization of promoter expression patterns of OsNrt2.1, a nitrate transporter gene of rice (Oryza sativa L.)

Nitrate is one form of available nitrogen nutrient, and its uptake and transport in plants was mediated by nitrate transporters. It is important to elucidate the transcription mechanism of nitrate genes at the molecular level. In this study, the promoter of OsNrt2.1, a rice nitrate transporter gene previously cloned in our group, has been characterized. Based on PLACE online analysis, some important cis-regulatory elements were identified. Under the control of the full length fragment of OsNrt2.1 promoter (P-2047), the expression of the reporter gene Gus was up-regulated when exposed to low nitrogen. Promoter deletion analysis indicated that the low nitrate responding elements located at position − 524 to − 1 and − 980 to − 525. Several cis-regulatory elements such as CIACADIANLELHC and − 10 promoter element, located at positions of − 524 to − 1, − 980 to − 525, − 1487 to − 981, and − 2047 to − 1488 in P-2047, were possibly involved in the circadian regulation of the OsNrt2.1 gene. Sugar signaling and sugar-responsive motif WBOXHVISO1 and TATCCAOSAMY were also identified in P-2047, suggesting that the exogenous sugar variations resulted from the photosynthesis changes were related to the up-regulated expression of Gus during the day time. It is guessed that the expression pattern of Gus with lownitrate inducible and diurnal rhythm was partly, at least, via the mediation of Ca2+ signal transduction pathway. Owing to its regulation pattern with low nitrate inducible and typical circadian pattern, the OsNrt2.1 promoter maybe has a potential role in the generation of transgenic crop varieties with high-N use efficiency in the future.

Testing assumptions underlying economic research on transgenic food crops for Third World farmers: Evidence from Cuba, Guatemala and Mexico

Transgenic crop varieties (TGVs) are being promoted as essential for improving small-scale Third World (SSTW) agriculture. Most economic research on this topic makes critical, untested assumptions, including that farmers will choose TGVs over other varieties because TGVs are economically optimal and because farmers are risk neutral profit maximizers. We tested these assumptions using data from a survey of 334 farmers in 6 communities in Cuba, Guatemala and Mexico in which farmers ranked 4 real and hypothetical maize varieties for eating and sowing. Our results did not support these assumptions. Most farmers preferred farmer varieties for sowing and especially for eating, avoiding TGVs, a preference associated with being risk averse and with non-monetary preferences. Farmers more integrated into modern agriculture were more likely to choose TGVs. These results suggest that farmers most in need of support and most important for conserving genetic diversity are least favorable toward TGVs, and that alternative ways of improving SSTW agriculture should receive more attention.

The economic impact of transgenic crops in developing countries: a note on the methods

A vast literature has accumulated since crop varieties with transgenic resistance to insects and herbicide tolerance were released to farmers in 1996 and 1997. A comparatively minor segment of this literature consists of studies conducted by agricultural economists to measure the farm-level impact of transgenic crop varieties, the size and distribution of the economic benefits from adopting them and the implications for international trade. This paper focuses only on the applied economics literature about the impact of transgenic crop varieties in non-industrialised agricultural systems, with a focus on the methods. A number of studies have surveyed the findings for both industrialised and non-industrialised agriculture at various points in time, but surveys of methods are less common and most treat one aspect of economic impact. Clearly, the methods used in research influence the findings that are presented and what they mean. Three levels of impact analysis are considered: farm, industry and trade. We conclude that because the methods used present challenges and limitations, the few transgenic crop-trait combinations released in developing economies and the relatively brief time frame of most analyses, the results are promising but the balance sheet is mixed. Thus, the findings of current case studies should not be generalised to other locations, crops and traits.

The impact of agricultural biotechnology on yields, risks, and biodiversity in low-income countries

This paper shows that the current generation of transgenic crop varieties has significant potential to improve economic welfare in low-income countries. These varieties might increase crop yields in low-income countries in cases when pesticides have not been used. They will reduce negative health effects of chemicals when they replace them. With low transaction costs, appropriate infrastructure, and access to intellectual property, multiple varieties of transgenics will be introduced. The gain from transgenics will be reduced, and crop biodiversity may be lost when only a small set of varieties is transgenetically modified. The adoption of transgenics will also be affected by risk and credit considerations.

Effects of Genetic Modification on Herbivore-Induced Volatiles from Maize

Large-scale implementation of transgenic crop varieties raises concerns about possible nontarget effects on other organisms. This study examines the effects of genetic modification on plant volatile production and its potential impact on arthropod population dynamics. We compared herbivore-induced volatile emissions from Bacillus thuringiensis Berliner (Bt) maize plants to those from a nontransformed isoline following exposure to various types of leaf damage. When equal numbers of Helicoverpa zea Boddie (Lepidoptera: Noctuidae) larvae fed on Bt and non-Bt maize, volatile emissions were significantly lower in the transgenic plants, which also exhibited less leaf damage. When damage levels were controlled by adding more larvae to Bt plants, the plants' volatile emissions increased but displayed significant differences from those of nontransgenic plants. Significantly higher amounts of linalool, beta-myrcene, and geranyl acetate were released from transgenic maize than from non-Bt plants. Manipulating the duration of feeding by individual larvae to produce similar damage patterns resulted in similar volatile profiles for Bt and non-Bt plants. Controlling damage levels more precisely by mechanically wounding leaves and applying larval regurgitant likewise resulted in similar emission patterns for Bt and non-Bt maize. Overall, changes in the herbivore-induced volatile profiles of Bt maize appeared to be a consequence of altered larval feeding behavior rather than of changes in biochemical plant defense pathways. The implications of these findings for understanding the impacts of plant-mediated cues on pest and natural enemy behavior in transgenic crop systems are discussed.

Transgenic Crops and Crop Varietal Diversity: The Case of Maize in Mexico

Transgenic crop varieties are a rapidly expanding and controversial technology. Their effects on biological and cultural diversity are a key issue in an often polarized debate. Here we provide answers to questions about one important example, that of transgenic maize in Mexico. In situ maize diversity in Mexico is present in traditional varieties in farmers' fields, and in wild and weedy relatives of maize. It is likely that transgenes are present in farmers' local maize varieties, but it is unknown whether they have introgressed. Socioeconomic changes, including migration, trade liberalization, and reduced support for Mexican farmers, may also affect maize diversity. Diversity may increase, decrease, or remain the same, but whether this is viewed as good or bad will depend on subjective values.

Detecting (trans)gene flow to landraces in centers of crop origin: lessons from the case of maize in Mexico

There is much discussion of the probability of transgene flow from transgenic crop varieties to landraces and wild relatives in centers of origin or diversity, and its genetic, ecological, and social consequences. Without costly research on the variables determining gene flow, research on transgene frequencies in landrace (or wild relative) populations can be valuable for understanding transgene flow and its effects. Minimal research requirements include (1) understanding how farmer practices and seed systems affect landrace populations, (2) sampling to optimize Ne/n (effective/census population size), (3) minimizing variance at all levels sampled, and (4) using Ne to calculate binomial probabilities for transgene frequencies. A key case is maize in Mexico. Two peer-reviewed papers, based on landrace samples from the Sierra Juárez region of Oaxaca, Mexico, reached seemingly conflicting conclusions: transgenes are present (Quist and Chapela, 2001, Nature 414: 541-543; 2002, Nature 416: 602) or "detectable transgenes" are absent (Ortiz-García et al., 2005, Proc. Natl. Acad. Sci. USA 102: 12338-12343 and 18242). We analyzed these papers using information on Oaxacan maize seed systems and estimates of Ne. We conclude that if Quist and Chapela's results showing presence are accepted, Ortiz-García et al.'s conclusions of no evidence of transgenes at detectable levels or for their introgression into maize landraces in the Sierra de Juárez of Oaxaca are not scientifically justified. This is because their samples are not representative, and their statistical analysis is inconclusive due to using n instead of Ne. Using estimates of Ne based on Ortiz-García et al.'s n, we estimate that transgenes could be present in maize landraces in the Sierra Juárez region at frequencies of approximately 1-4%, and are more likely to be present in the 90% of Oaxacan landrace area that is not mountainous. Thus, we have no scientific evidence of maize transgene presence or absence in recent years in Mexico, Oaxaca State, or the Sierra Juárez region.

Transgenic Crops to Address Third World Hunger? A Critical Analysis

Industry and mainstream research and policy institutions often suggest that transgenic crop varieties can raise the productivity of poor third world farmers, feed the hungry, and reduce poverty. These claims are critically evaluated by examining global-hunger data, the constraints that affect the productivity of small farmers in the third world, and the factors that explain their poverty. No significant role is found for crop genetics in determining hunger, productivity, or poverty, casting doubt on the ability of new transgenic crop varieties produced by genetic engineering to address these problems. An examination of the special risks these varieties pose for poor farmers in the complex, diverse, and risk-prone environments that characterize peasant agriculture on a global scale suggests that transgenic crop varieties are likely to be more of hindrance than a help to the advancement of poor farmers.

Understanding the potential impact of transgenic crops in traditional agriculture: maize farmers’ perspectives in Cuba, Guatemala and Mexico

Genetically engineered transgenic crop varieties (TGVs) have spread rapidly in the last 10 years, increasingly to traditionally-based agricultural systems (TBAS) of the Third World both as seed and food. Proponents claim they are key to reducing hunger and negative environmental impacts of agriculture. Opponents claim they will have the opposite effect. The risk management process (RMP) is the primary way in which TGVs are regulated in the US (and many other industrial countries), and proponents claim that the findings of that process in the US and its regulatory consequences should be extended to TBAS. However, TBAS differ in important ways from industrial agriculture, so TGVs could have different effects in TBAS, and farmers there may evaluate risks and benefits differently. To evaluate some potential impacts of TGVs in TBAS we used the RMP as a framework for the case of Bt maize in Mesoamerica and Cuba. We interviewed 334 farmers in Cuba, Guatemala and Mexico about farming practices, evaluations of potential harm via hypothetical scenarios, and ranking of maize types. Results suggest high potential for transgene flow via seed, grain and pollen; differences in effects of this exposure in TBAS compared with industrial agriculture; farmers see some potential consequences as harmful. Perceptions of harm differ among farmers in ways determined by their farming systems, and are different from those commonly assumed in industrial systems. An RMP including participation of farmers and characteristics of TBAS critical for their functioning is necessary to ensure that investments in agricultural technologies will improve, not compromise these agricultural systems.

English

  Diagnostic research is important in helping to create an enabling environment for promising biotechnology products in smallholder agriculture, before rather than afterrelease. The biotechnology products that now hold promise for poor people in Sub-Saharan Africa are those that tackle economically important, biotic or abiotic problems not easily addressed through conventional plant breeding or pest control, in crops that serve for food as well as cash, while posing little risk of endangering trade.  Two biotechnology products we have selected for social science research in East Africa, Btmaize in Kenya and pest and disease resistance in the East African highland banana, meet these criteria. Preliminary research suggests that the expression of the trait is much more visible to farmers in maize than in bananas; for either crop, for different reasons, bottlenecks will be encountered in planting materials systems; and despite differing crop reproduction systems, transgenic varieties of either share the same environmental hazard of heightened genetic uniformity in the inserted trait relative to conventionally bred varieties. Aside from the performance of the technology, many factors that have incidence at national, regional, and farm levels will affect the likelihood that farmers will adopt transgenic varieties. Social science research can help pinpoint necessary complementary investments.   Key words:  Bananas, maize, adoption, smallholder farmers, transgenic crop varieties.

Use of genetic engineering in plant breeding — arrival of transgenic crop varieties on the market and public acceptance

Summarising the European situation of the use of genetically modified (GM) plant varieties one may state: 1. Europe moves slowly due to over-regulation and lack of public acceptance of the technology. 2. Europe is top in high ranking science of genetic engineering. 3. In transfer and exploitation it is uneasy and anxious. 4. The globalisation of economy will change perceptions in the long term and will so, finally, lead to acceptance of the use of scientific progress in practice.