SciCombinator

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Concept: Transgenic maize

387

Despite the extensive cultivation of genetically engineered (GE) maize and considerable number of scientific reports on its agro-environmental impact, the risks and benefits of GE maize are still being debated and concerns about safety remain. This meta-analysis aimed at increasing knowledge on agronomic, environmental and toxicological traits of GE maize by analyzing the peer-reviewed literature (from 1996 to 2016) on yield, grain quality, non-target organisms (NTOs), target organisms (TOs) and soil biomass decomposition. Results provided strong evidence that GE maize performed better than its near isogenic line: grain yield was 5.6 to 24.5% higher with lower concentrations of mycotoxins (-28.8%), fumonisin (-30.6%) and thricotecens (-36.5%). The NTOs analyzed were not affected by GE maize, except for Braconidae, represented by a parasitoid of European corn borer, the target of Lepidoptera active Bt maize. Biogeochemical cycle parameters such as lignin content in stalks and leaves did not vary, whereas biomass decomposition was higher in GE maize. The results support the cultivation of GE maize, mainly due to enhanced grain quality and reduction of human exposure to mycotoxins. Furthermore, the reduction of the parasitoid of the target and the lack of consistent effects on other NTOs are confirmed.

Concepts: DNA, Scientific method, Ecology, Poaceae, Maize, James D. Watson, Genetically modified food, Transgenic maize

149

Transgenic crop “pyramids” producing two or more Bacillus thuringiensis (Bt) toxins active against the same pest are used to delay evolution of resistance in insect pest populations. Laboratory and greenhouse experiments were performed with fall armyworm, Spodoptera frugiperda, to characterize resistance to Bt maize producing Cry1A.105 and Cry2Ab and test some assumptions of the “pyramid” resistance management strategy. Selection of a field-derived strain of S. frugiperda already resistant to Cry1F maize with Cry1A.105 + Cry2Ab maize for ten generations produced resistance that allowed the larvae to colonize and complete the life cycle on these Bt maize plants. Greenhouse experiments revealed that the resistance was completely recessive (Dx = 0), incomplete, autosomal, and without maternal effects or cross-resistance to the Vip3Aa20 toxin produced in other Bt maize events. This profile of resistance supports some of the assumptions of the pyramid strategy for resistance management. However, laboratory experiments with purified Bt toxin and plant leaf tissue showed that resistance to Cry1A.105 + Cry2Ab2 maize further increased resistance to Cry1Fa, which indicates that populations of fall armyworm have high potential for developing resistance to some currently available pyramided maize used against this pest, especially where resistance to Cry1Fa was reported in the field.

Concepts: Bacillus, Leaf, Bacillus thuringiensis, Endotoxin, Genetically modified food, Army worm, Spodoptera, Transgenic maize

46

Despite widespread adoption of genetically modified crops in many countries, heated controversies about their advantages and disadvantages continue. Especially for developing countries, there are concerns that genetically modified crops fail to benefit smallholder farmers and contribute to social and economic hardship. Many economic studies contradict this view, but most of them look at short-term impacts only, so that uncertainty about longer-term effects prevails. We address this shortcoming by analyzing economic impacts and impact dynamics of Bt cotton in India. Building on unique panel data collected between 2002 and 2008, and controlling for nonrandom selection bias in technology adoption, we show that Bt has caused a 24% increase in cotton yield per acre through reduced pest damage and a 50% gain in cotton profit among smallholders. These benefits are stable; there are even indications that they have increased over time. We further show that Bt cotton adoption has raised consumption expenditures, a common measure of household living standard, by 18% during the 2006-2008 period. We conclude that Bt cotton has created large and sustainable benefits, which contribute to positive economic and social development in India.

Concepts: Economics, Bacillus, Developing country, Bacillus thuringiensis, Genetically modified food, Transgenic maize, Monsanto, Pink bollworm

38

Transgenic crops containing the bacteriumBacillus thuringiensis(Bt) genes reduce pests and insecticide usage, promote biocontrol services, and economically benefit growers. Area-wide Bt adoption suppresses pests regionally, with declines expanding beyond the planted Bt crops into other non-Bt crop fields. However, the offsite benefits to growers of other crops from such regional suppression remain uncertain. With data spanning 1976-2016, we demonstrate that vegetable growers benefit via decreased crop damage and insecticide applications in relation to pest suppression in the Mid-Atlantic United States. We provide evidence for the regional suppression ofOstrinia nubilalis(Hübner), European corn borer, andHelicoverpa zea(Boddie), corn earworm, populations in association with widespread Bt maize adoption (1996-2016) and decreased economic levels for injury in vegetable crops [peppers (Capsicum annuumL.), green beans (Phaseolus vulgarisL.), and sweet corn (Zea maysL., convar.saccharata)] compared with the pre-Bt period (1976-1995). Moth populations of both species significantly declined in association with widespread Bt maize (field corn) adoption, even as increased temperatures buffered the population reduction. We show marked decreases in the number of recommended insecticidal applications, insecticides applied, andO. nubilalisdamage in vegetable crops in association with widespread Bt maize adoption. These offsite benefits to vegetable growers in the agricultural landscape have not been previously documented, and the positive impacts identified here expand on the reported ecological effects of Bt adoption. Our results also underscore the need to account for offsite economic benefits of pest suppression, in addition to the direct economic benefits of Bt crops.

Concepts: United States, Vegetable, Maize, Bean, Transgenic maize, Sweet corn, Native American cuisine, Corn on the cob

35

Transgenic corn engineered with genes expressing insecticidal toxins from the bacterium Bacillus thuringiensis (Berliner) (Bt) are now a major tool in insect pest management. With its widespread use, insect resistance is a major threat to the sustainability of the Bt transgenic technology. For all Bt corn expressing Cry toxins, the high dose requirement for resistance management is not achieved for corn earworm, Helicoverpa zea (Boddie), which is more tolerant to the Bt toxins.

Concepts: Gene expression, Bacteria, Bacillus, Maize, Bacillus thuringiensis, Biological pest control, Genetically modified food, Transgenic maize

35

We present the first evidence that transgenic Bacillus thuringiensis (Bt) corn pollen naturally deposited on Asclepias syriaca; common milkweed, in a corn field causes significant mortality of Danaus plexippus L. (Lepidoptera: Danaidae) larvae. Larvae feeding for 48 h on A. syriaca plants naturally dusted with pollen from Bt corn plants suffered significantly higher rates of mortality at 48 h (20±3%) compared to larvae feeding on leaves with no pollen (3±3%), or feeding on leaves with non-Bt pollen (0%). Mortality at 120 h of D. plexippus larvae exposed to 135 pollen grains/cm(2) of transgenic pollen for 48 h ranged from 37 to 70%. We found no sub-lethal effects on D. plexippus adults reared from larvae that survived a 48-h exposure to three concentrations of Bt pollen. Based on our quantification of the wind dispersal of this pollen beyond the edges of agricultural fields, we predict that the effects of transgenic pollen on D. plexippus may be observed at least 10 m from transgenic field borders. However, the highest larval mortality will likely occur on A. syriaca plants in corn fields or within 3 m of the edge of a transgenic corn field. We conclude that the ecological effects of transgenic insecticidal crops need to be evaluated more fully before they are planted over extensive areas.

Concepts: Insect, Asclepias, Lepidoptera, Bacillus thuringiensis, Genetically modified food, Transgenic maize, Monarch, Asclepias syriaca

28

Qualitative and quantitative DNA-based methods were applied to detect genetically modified foods in samples from markets in the Kingdom of Saudi Arabia. Two hundred samples were collected from Al-Qassim, Riyadh, and Mahdina in 2009 and 2010. GMOScreen 35S and NOS test kits for the detection of genetically modified organism varieties in samples were used. The positive results obtained from GMOScreen 35S and NOS were identified using specific primer pairs. The results indicated that all rice samples gave negative results for the presence of 35S and NOS terminator. About 26 % of samples containing soybean were positive for 35S and NOS terminator and 44 % of samples containing maize were positive for the presence of 35S and/or NOS terminator. The results showed that 20.4 % of samples was positive for maize line Bt176, 8.8 % was positive for maize line Bt11, 8.8 % was positive for maize line T25, 5.9 % was positive for maize line MON 810, and 5.9 % was positive for StarLink maize. Twelve samples were shown to contain <3 % of genetically modified (GM) soy and 6 samples >10 % of GM soy. Four samples containing GM maize were shown to contain >5 % of GM maize MON 810. Four samples containing GM maize were shown to contain >1 % of StarLink maize. Establishing strong regulations and certified laboratories to monitor GM foods or crops in Saudi market is recommended.

Concepts: Saudi Arabia, Arabian Peninsula, Riyadh, Qualitative research, Maize, Genetically modified organism, Genetically modified food, Transgenic maize

27

Abstract 1. The objective of this study was to evaluate the effects of dietary supplementation with phytase transgenic corn (maize) (PTC) which has a phytase activity of 21 000 units (U) phytase per kg of maize on productive performance, egg quality, tibia bone quality and phosphorus (P) excretion in laying hens. 2. In the experiment, 1800 44-week-old Hy-line brown laying hens were divided into 5 groups with 6 replicates per group and 60 hens per replicate. The experiment lasted for 12 weeks. The layers in the control group (control) were given a basal diet with 0.36% non-phytate P (NPP), while the treatment groups received diets containing 360 U of exogenous phytase/kg with 0.26% NPP (EP) or 360 phytase U of PTC/kg diet with 0.26% (PTC1), 0.21% (PTC2) or 0.16% (PTC3) NPP. 3. The results showed that there was no significant difference in egg production, average daily feed intake, feed efficiency, rate of broken or soft-shell egg production or egg mass among the treatments. There was no significant difference in eggshell thickness or eggshell strength. On the other hand, no differences in any of the bone variables were found between treatments. The faecal P percentage content in EP, PTC1, PTC2 and PTC3 groups was significantly lower than the control group. 4. In summary, the PTC could be used in the feed of laying hens instead of EP to reduce P excretion without effecting production and bone mineralisation.

Concepts: Effect, Food, Femur, Chicken, Maize, Genetically modified food, Glyphosate, Transgenic maize

21

A farmer’s decision on whether to control a pest is usually based on the perceived threat of the pest locally and the guidance of commercial advisors. Therefore, farmers in a region are often influenced by similar circumstances, and this can create a coordinated response for pest control that is effective at a landscape scale. This coordinated response is not intentional, but is an emergent property of the system. We propose a framework for understanding the intrinsic feedback mechanisms between the actions of humans and the dynamics of pest populations and demonstrate this framework using the European corn borer, a serious pest in maize crops. We link a model of the European corn borer and a parasite in a landscape with a model that simulates the decisions of individual farmers on what type of maize to grow. Farmers chose whether to grow Bt-maize, which is toxic to the corn borer, or conventional maize for which the seed is cheaper. The problem is akin to the snow-drift problem in game theory; that is to say, if enough farmers choose to grow Bt maize then because the pest is suppressed an individual may benefit from growing conventional maize. We show that the communication network between farmers' and their perceptions of profit and loss affects landscape scale patterns in pest dynamics. We found that although adoption of Bt maize often brings increased financial returns, these rewards oscillate in response to the prevalence of pests.

Concepts: Agriculture, Effect, Model organism, Perception, Feedback, Maize, American films, Transgenic maize

18

The widespread planting of crops genetically engineered to produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) places intense selective pressure on pest populations to evolve resistance. Western corn rootworm is a key pest of maize, and in continuous maize fields it is often managed through planting of Bt maize. During 2009 and 2010, fields were identified in Iowa in which western corn rootworm imposed severe injury to maize producing Bt toxin Cry3Bb1. Subsequent bioassays revealed Cry3Bb1 resistance in these populations. Here, we report that, during 2011, injury to Bt maize in the field expanded to include mCry3A maize in addition to Cry3Bb1 maize and that laboratory analysis of western corn rootworm from these fields found resistance to Cry3Bb1 and mCry3A and cross-resistance between these toxins. Resistance to Bt maize has persisted in Iowa, with both the number of Bt fields identified with severe root injury and the ability western corn rootworm populations to survive on Cry3Bb1 maize increasing between 2009 and 2011. Additionally, Bt maize targeting western corn rootworm does not produce a high dose of Bt toxin, and the magnitude of resistance associated with feeding injury was less than that seen in a high-dose Bt crop. These first cases of resistance by western corn rootworm highlight the vulnerability of Bt maize to further evolution of resistance from this pest and, more broadly, point to the potential of insects to develop resistance rapidly when Bt crops do not achieve a high dose of Bt toxin.

Concepts: Bacteria, Bacillus, Maize, Western corn rootworm, Bacillus thuringiensis, Endotoxin, Genetically modified food, Transgenic maize