Glyphosate-tolerant Soybean Research Articles

Fungicide–herbicide interaction in soybean ( Glycine max)

Fungicide seed treatments are becoming increasingly popular for use with glyphosate-tolerant soybean ( Glycine max (L.) Merr.). This research was initiated in response to preliminary data indicating possible negative interaction(s) between certain agrochemicals. A 2-year field study was conducted to determine whether certain combinations of fungicide seed treatments and post-emergence herbicides affect soybean yield. The experiment involved six seed treatments (thiabendazole (TBZ), pentachloronitrobenzene (PCNB), captan, TBZ+PCNB+captan, fludioxonil and a fungicide-free control) and six weed control treatments (imazethapyr, imazamox, glyphosate, glyphosate+imazethapyr, glyphosate+cloransulam-methyl and a hand-weeded control). All 36 combinations were evaluated in four different environments in Illinois, USA. All fields had minimal disease pressure and were kept free of weeds (mechanically), allowing for the evaluation of chemical interactions independent of the confounding factors of herbicide and fungicide efficacy. The fungicide treatments did not significantly affect the crop's response to the herbicide treatments, as measured by visual injury ratings. In addition, neither fungicide, herbicide, nor fungicide–herbicide combination significantly affected crop yield. No significant chemical interactions were found to exist between any of the examined fungicidal seed treatments and post-emergence herbicides.

Effect of Cultivars, Cooking and Processing on the Trypsin Inhibitor Activity of Soybean

The trypsin inhibitor activity (TIA) of various soybean cultivars was evaluated by measuring the inhibition of trypsin activity using N-benzoyl-DL-arginine-p-nitro-anilide (BAPNA) as the substrate. The TIA values of eleven white shelled soybean cultivars including a glyphosate-tolerant soybean (16.58 to 17.90 mg/g) were not significantly different among cultivars. Black shelled soybeans had higher TIA values, ranging from 40.09 to 52.11 mg/g, compared to white shelled soybeans (p＜0.05). When the TIA of commercially processed soybean foods were determined, no TIA was detected in soysauce, tofu and soybean paste. During conventional moist heating, the IT_(50) (Time required to reach 50% inhibition of TIA) values were decreased as heating temperature and cooking pressure increased. The IT_(50) values of moist heating were estimated to be 91.68, 37.71 and 19.50 min at 60, 80 and 100℃, respectively. The IT_(50) value of microwave cooking was 4.75 min at medium heat, while that of the pressure cooking at 120℃ was only 2.62 min. Moreover, there was a negative relationship between temperature and IT_(50) values (R=0.92, p＜0.01). The TIA of soybean sprouts was completely inactivated after heating at 100℃ for 5 min, although fresh soybean sprouts showed one fifth of the TIA value of white shelled soybeans. Based on our results, pressure cooking is the most effective cooking method to reduce TIA in soybeans.

Renovating Pastures with Glyphosate Tolerant Soybeans

Pasture renovation is expensive because of lost production, costs for eliminating existing vegetation by tillage or herbicides, and direct replanting costs. Reducing costs, reducing risk of failure, and producing income from pasture land during renovation can significantly increase the profitability of improving pastures. Technology developed for soybean production can be used to renovate pasture. Roundup Ready (glyphosate-resistant) technology can be used to eliminate existing vegetation, produce income from soybeans during renovation, and prepare a good seedbed for replanting areas to forages. The goal of pasture renovation is to replace plants that do not fit your needs with forages better suited to your pasture needs. The first step is to eliminate undesirable plants with tillage or herbicides. Herbicides can significantly reduce producer’s energy input costs and soil erosion. Planting a glyphosate-tolerant soybean crop enables the use of glyphosate for weed control. This process maintains pasture residue on site, reduces soil erosion and desiccation, and produces income during renovation. Soybeans are preferable to corn because soybeans provide residual nitrogen, produce an excellent seedbed for no-till planting, and leave sufficient residue to protect the soil without interfering with seeding. We conduct grazing research and regularly use glyphosate-tolerant soybeans to replace research pastures and forage research fields. Based on our experience, we have developed some guidelines for successfully using glyphosate-tolerant soybeans for pasture renovation.

Nutritional assessment and fate of dna of soybean meal from roundup ready or conventional soybeans using rats

This study was conducted to compare the safety of soybean meal prepared from genetically modified (GM) glyphosate-tolerant (Roundup Ready; RR) soybeans and conventional soybeans. Eighty Sprague-Dawley rats (40 males and 40 females) were randomly allotted to one of four groups according to sex and body weight for a 13-week feeding experiment. The rats were fed corn-based diets containing 60% conventional soybean meal, a mixture of 30% conventional and 30% RR soybean meal, 60% or 90% RR soybean meal. All diets were adjusted to an identical nutrient level except the 90% RR diet. The two soybean meals were similar in chemical analysis and amino acid composition. During the 13-week growth trial, body weight (P < 0.05) and feed intake (P < 0.05) decreased only in rats fed with 90% RR soybean meal at the first week. No treatment-related deaths occurred during the experiment. Gross necropsy findings, haematological or urinalysis values and clinical serum parameters showed no meaningful differences between rats fed the control and RR soybean meals. A 145 bp of cp4 epsps gene specific for the GM constructs from RR soybean meal or a 407 bp of lec gene from endogenous soybean DNA could not be detected in investigated masseter muscle samples. No adverse effects of glyphosate-tolerant soybean meal on rats were seen even at levels as high as 90% of the diet.

A novel approach to determine the glyphosate tolerant trait in soybeans.

The ability of soybean breeders to accurately, economically, and rapidly determine the transfer of the CP4 gene, the gene which confers soybean tolerance to the herbicide glyphosate, to elite soybean lines is essential to development of new glyphosate tolerant soybean (GTS) cultivars. This research focused on a simple greenhouse screening procedure to replace large, costly, and laborious field screening. Non-GTS seed was determined to be susceptible to soaking in a 1% glyphosate solution for 4 h. This process is quicker, more efficient, and as reliable as field screening for determination of glyphosate susceptibility in soybean seed. Furthermore, this research clearly demonstrates that the metabolic pathway of glyphosate activity, the shikimate acid pathway, is active, and the target enzyme of glyphosate, 5-enol-pyruvyl-shikimate-3-phosphate synthase, is present during seed germination.

Widespread use of glyphosate tolerant soybean and weed community richness in Argentina

Trends in weed richness responses to widespread use of glyphosate tolerant soybean in Argentina are presented. An experiment was carried out since 1997 to analyse weed community changes associated with the continuous and exclusive use of glyphosate. Sampling results showed that weed richness in soybean decreased or remained stable early in the season before glyphosate application but increased at harvest. A survey of crop advisers indicated that 37 species were of increasing, 18 species of decreasing importance. It is suggested that successional changes are taking place in the cropping systems in response to changes in weed control practices.

A generational study of glyphosate-tolerant soybeans on mouse fetal, postnatal, pubertal and adult testicular development

The health safety of transgenic soybeans (glyphosate-tolerant or Roundup Ready) was studied using the mammalian testis (mouse model) as a sensitive biomonitor of potential toxic effects. Pregnant mice were fed a transgenic soybean or a non-transgenic (conventional) diet through gestation and lactation. After weaning, the young male mice were maintained on the respective diets. At 8, 16, 26, 32, 63 and 87 days after birth, three male mice and an adult reference mouse were killed, the testes surgically removed, and the cell populations measured by flow cytometry. Multi-generational studies were conducted in the same manner. The results showed that the transgenic foodstuffs had no effect on macromolecular synthesis or cell growth and differentiation as evidenced by no differences in the percentages of testicular cell populations (haploid, diploid, and tetraploid) between the transgenic soybean-fed mice and those fed the conventional diet. Additionally, there were no differences in litter sizes and body weights of the two groups. It was concluded that the transgenic soybean diet had no negative effect on fetal, postnatal, pubertal or adult testicular development.

Effects of Herbicides on Root Rot and Damping-off Caused by Rhizoctonia solani in Glyphosate-Tolerant Soybean.

Diseases caused by Rhizoctonia solani are one of many production constraints in soybean-growing regions. Little information is available about the diseases in soybeans tolerant to different herbicides. In 1998 and 1999, studies were conducted to evaluate the plausible interaction between glyphosate-tolerant soybean and herbicides (glyphosate, imazethapyr, lactofen, and pendimethalin) on damping-off and root rot caused by R. solani under greenhouse and field conditions. The herbicides were applied at the product recommended field rate on glyphosate-tolerant (Pioneer 93B01 and Pioneer 9344) and glyphosate-sensitive (BSR 101) soybean grown in soils infested with R. solani (isolate AG-4). Root rot and plant stand was significantly affected by soybean cultivars and herbicide treatments in the greenhouse study. A significant cultivar-treatment interaction was detected in the greenhouse study. The interaction implies that the cultivars responded differently to the various herbicides and especially to the herbicide pendimethalin. Plant stands of both cultivars were reduced by R. solani alone or in combination with different herbicides compared with the noninoculated control, and this was presumed to be due to damping-off. In a 2-year field study, cultivar and treatment main effects differed with respect to plant stand between years. In 1998, analysis of variance revealed a significant treatment effect on root rot severity but not plant stand. In 1999, analysis of variance revealed a significant effect of treatment on root rot severity and plant stand whereas cultivar showed a significant effect on plant stand only. In 1999, plant stands of both cultivars were similarly affected by most treatments. However, in BSR 101, the R. solani + pendimethalin + imazethapyr treatment significantly reduced plant stand compared with the R. solani + pendimethalin treatment. Root rot severity was generally low in both years of the field study. Some differential disease responses were detected between glyphosate-tolerant and glyphosate-sensitive cultivars following the application of certain herbicides in greenhouse and field studies. However, glyphosate-tolerant and glyphosate-sensitive cultivars reacted similarly to most herbicide treatments with respect to root rot and damping off.

IS IT FAIR TO COMPARE? ISSUES REGARDING THE TESTING OF GLYPHOSATE-TOLERANT SOYBEANS IN UNIVERSITY VARIETY PERFORMANCE TRIALS

ABSTRACT With the introduction of herbicide-tolerant crop varieties, there is concern that university variety performance trials conducted under conventional herbicide programs may be biased in terms of yield potential. Experiments on dryland and irrigated glyphosate-tolerant soybean (Glycine max) varieties conducted at two Arkansas locations in 1998 and 2000 provide evidence there are no differences in plant height or yield potential across herbicide regimes if effective weed control is established. The research compared conventional herbicide programs to various glyphosate products. While the evidence suggests that university trials are an appropriate means of determining the yield potential of glyphosate-tolerant varieties, producers are still advised to evaluate whether effective weed control will be better attained with a glyphosate or conventional herbicide program.

Field Response of Glyphosate-Tolerant Soybean to Herbicides and Sudden Death Syndrome.

Three-year field experiments were conducted to assess the development of sudden death syndrome (caused by Fusarium solani f. sp. glycines) in three soybean cultivars, tolerant (P9344 and A3071) and nontolerant (BSR101), to glyphosate following foliar application of four herbicides (acifluorfen, glyphosate, imazethapyr, and lactofen) commonly applied to soybeans in the north-central region of the United States. Cultivar A3071 is resistant to sudden death syndrome, whereas cultivars P9344 and BSR101 are susceptible to this disease. There was no statistically significant cultivar-herbicide interaction with respect to the severity of foliar symptoms of the disease and the frequency of isolation of F. solani f. sp. glycines from roots of soybean plants. Across all herbicide treatments, the level of sudden death syndrome was lower in the disease-resistant cultivar than in the susceptible ones. There was an increase in the disease levels under application of acifluorfen, glyphosate, and imazethapyr compared with nontreated or lactofen-treated plants. The results obtained indicate that the response of glyphosate-tolerant soybeans to sudden death syndrome is not different from the response of conventional soybeans to this disease following application of the selected herbicides, and the resistance of soybean to sudden death syndrome was not changed with application of glyphosate.

Plant Growth and Nitrogenase Activity of Glyphosate‐Tolerant Soybean in Response to Foliar Glyphosate Applications

Glyphosate [N‐(phosphonomethyl)glycine] inhibits 5‐enolpyruvylshikimate‐3‐phosphate synthase, EC 2.5.1.19 (EPSPS), thereby blocking aromatic amino acid synthesis. While glyphosate‐tolerant (GT) soybean [Glycine max (L.) Merr.] contains resistant EPSPS, the N2‐fixing symbiont in soybean root nodules, Bradyrhizobium japonicum, does not contain a resistant enzyme, and glyphosate spray to GT soybean may interfere with the symbiotic relationship. Glyphosate‐tolerant soybean was treated with glyphosate at several different stages of development to evaluate N2 fixation, growth, and yield in a series of greenhouse, growth chamber, and field experiments. Early applications of glyphosate generally delayed N2 fixation and decreased biomass and N accumulation in the cultivar Terral TV5866RR (TV5866RR) harvested at 19 d after emergence (DAE), but plants had recovered by 40 DAE. The biomass and N content of GT soybean were also decreased by glyphosate in plants that were grown with available soil N. There were differences in sensitivity to glyphosate among GT cultivars, with biomass decreases in response to glyphosate ranging from 0 to 30% at 40 DAE for the most tolerant and sensitive cultivars that were evaluated. In growth chamber studies, N2 fixation was more sensitive to water deficits in glyphosate‐treated plants. In field studies, there was no measured effect of glyphosate on GT soybean at Fayetteville, AR where there was adequate soil water throughout the growing season. However, glyphosate tended to decrease biomass and seed yields under conditions of limited soil water at Keiser, AR.

Competitive Potential and Economic Analysis of a Glyphosate-Tolerant/Conventional Soybean (Glycine max) Mix1

Field studies were conducted in 1997 and 1999 to determine the effect of a broadcast-seeded glyphosate-tolerant/conventional soybean seed mix on soybean seed yield, gross profit margin from weed management, and early-season weed suppression prior to a single glyphosate application. Tests were established by broadcasting and incorporating 494,000 seeds/ha glyphosate-tolerant soybean in combination with 0 to 1,976,000 seeds/ha conventional soybean. Glyphosate at 1.12 kg ai/ha was applied at the V5 to V6 soybean growth stage to kill all conventional soybean plants and emerged weeds. The broadcast planting technique was effective in establishing a soybean stand on a silt loam but was ineffective on a silty clay soil. Hemp sesbania and pitted morningglory control, resulting from interference with soybean, were correlated with percent soybean groundcover (R2 = 0.961 to 0.971) and population (R2 = 0.821 to 0.860) at the V5 to V6 soybean growth stage. Although not significant, increased yield and gross profit margin of dryland soybean occurred as the total seeding rate of the seed mix increased from 494,000 to 741,000 seeds/ha. A dryland seeding rate of 741,000 compared to 494,000 seeds/ha resulted in 438 kg/ha and $93.78/ha increase in seed yield and gross profit margin, respectively. Interference between the two soybean cultivars at 1,976,000 seeds/ha reduced yield. Irrigated soybean at 988,000 seeds/ha produced the greatest seed yield and gross profit margin at 2,987 kg/ha and $555.86/ha, respectively. Maximum yields were attributed to early-season weed suppression.Nomenclature: Glyphosate; hemp sesbania, Sesbania exaltata (Raf.) Rybd. ex A. W. Hill #3 SEBEX; pitted morningglory, Ipomoea lacunosa L. # IPOLA; soybean, Glycine max (L.) Merr. ‘Delta King 5961 RR’.Additional index words: Broadcast-seeded soybean, low-input agriculture, Roundup Ready soybean, safe site, soybean groundcover, Amaranthus hybridus, Amaranthus palmeri, AMACH, AMAPA.Abbreviations: DAP, days after planting; WAT, weeks after treatment.

The impact of glyphosate-tolerant crops on the use of other herbicides and on resistance management

Glyphosate can now be used for selective, post-emergence weed control in glyphosate-tolerant varieties of soybeans, cotton, canola and maize. It is estimated that glyphosate-tolerant soybeans in the US will account for 60–80% of the area planted by 2001. The rapid acceptance of this new technology is due to multiple factors including broad-spectrum weed control, low cost and simplicity. The use of glyphosate has resulted in a major reduction in the use of other herbicides including the ACCase inhibitors, ALS inhibitors, and Protox inhibitors. In the short term (three to five years) this change in herbicide use patterns will continue. In the long term (five to eight years), the primary reliance on glyphosate for weed control particularly in continuous cropping or in rotations of glyphosate-tolerant crops will result in a shift in the weed spectrum toward more tolerant weed species. As a result of this shift, other herbicides will be needed to fill these weed gaps. Continuous use of glyphosate may also lead to the selection of glyphosate-resistant weed populations, as has already occurred in Australia. However, shifts in the weed species' composition from highly susceptible toward more tolerant species will happen more rapidly than selection of resistance. New herbicides developed in the future will have to be extremely cost-effective to compete against glyphosate and may be geared towards controlling weeds tolerant to glyphosate. There will also be further development of new tolerant crops to other broad-spectrum, non-selective herbicides that will be able to compete directly with glyphosate. © 2000 Society of Chemical Industry

Effect of GM and Non-GM Soybeans on the Immune System of BN Rats and B10A Mice.

Subchronic animal feeding studies to examine the effect of glyphosate-tolerant soybeans, which contain the bacterial 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. strain CP4, on the immune system were conducted with BN rats and B10A mice. The studies were designed to compare the feeding value of a line of genetically modified glyphosate-tolerant soybeans (GM soybeans) to that of closely-related and one-parent same cultivar (non-GM soybeans). Heat-treated soybean meal was incorporated into the diets of the rats and mice at a concentration of 30%. The study duration was 15 weeks. Growth, food intake and weights of the liver and the spleen were compared between animals fed the non-GM and GM lines. The histopathology of the thymus, liver, spleen, mesenteric lymph node, Peyer's patches, and small intestine, and the production of soybean-specific IgE and IgG antibodies in the sera were also compared. Growth, feeding value, and the histopathology of immune-related organs showed no significant differences between animals fed GM and non-GM lines. The production of soybean-specific IgE was not detected in the sera of either group, and the increase in soybean-specific IgG was identical in the GM and non-GM groups. No immunotoxic activity was found in GM-soybean-fed rats or mice.

Genetically modified organisms in food-screening and specific detection by polymerase chain reaction.

PCR methods for the detection of genetically modified organisms (GMOs) were developed that can be used for screening purposes and for specific detection of glyphosate-tolerant soybean and insect-resistant maize in food. Primers were designed to amplify parts of the 35S promoter derived from Cauliflower Mosaic Virus, the NOS terminator derived from Agrobacterium tumefaciens and the antibiotic marker gene NPTII (neomycin-phosphotransferase II), to allow for general screening of foods. PCR/hybridization protocols were established for the detection of glyphosate-tolerant RoundUp Ready soybean and insect-resistant Bt-maize. Besides hybridization, confirmation of the results using restriction analysis was also possible. The described methods enabled a highly sensitive and specific detection of GMOs and thus provide a useful tool for routine analysis of raw and processed food products.

Compositional analysis of glyphosate-tolerant soybeans treated with glyphosate.

The compositional analyses and safety assessment of glyphosate-tolerant soybeans (GTS) were previously described. These analyses were extensive and included addressing the potential effects on seed composition from the genetic modification. Detailed compositional analyses established that GTS, which had not been treated with glyphosate, were comparable to the parental soybean line and to other conventional soybeans. In this study, two GTS lines, 40-3-2 and 61-67-1, were treated with commercial levels of glyphosate, the active ingredient in Roundup herbicide. The composition of the seed from soybeans sprayed with glyphosate was compared to that of a nonsprayed parental control cultivar, A5403. The nutrients measured in the seed included protein, oil, ash, fiber, carbohydrates, and amino acids. The concentration of isoflavones (also referred to as phytoestrogens) was also measured as these compounds are derived from the same biochemical pathway that was engineered for glyphosate tolerance. The analytical results from these studies demonstrate that the GTS soybeans treated with glyphosate were comparable to the parental soybean cultivar, A5403, and other conventional soybean varieties.

Soybean genetic resources and crop improvement

The soybean (Glycine max (L.) Merr.) is an economically important leguminous crop for feed, oil, and soyfood products. It contains about 40% protein and 20% oil in the seed and, in the international trade markets, is ranked number one in oil production (48%) among the major oil seed crops. Despite its economic importance, the genetic base of soybean cultivars is extremely narrow. The indigenous cultivars and landraces in East Asia are on the verge of extinction, because farmers are now growing high yielding soybean cultivars. The exotic germplasm, enriched with genes for abiotic and biotic stresses, has not been fully exploited by soybean breeders. Mutation breeding has improved the fatty acids of the soybeans and has produced soybeans tolerant to herbicides. By using recombinant DNA technology, Monsanto has produced stable glyphosate tolerant soybean lines known as 'Round Up Ready' soybean. DuPont is producing transgenic soybean lines with improved fatty acids content. The feasibility of developing hybrid soybeans is still an open question.Key words: soybean, Glycine spp., exotic germplasm, mutation, interspecific hybridization, biotechnology, hybrid soybeans.

The official method for the detection of genetically modified soybeans (German Food Act LMBG § 35): a semi-quantitative study of sensitivity limits with glyphosate-tolerant soybeans (Roundup Ready) and insect-resistant Bt maize (Maximizer)

The aim of the study was to settle a concent for the standardised description of the potency of a PCR setup with respect to the detection limit. The main terms used are the theoretical detection limit (Ltheor) and the practical detection limit (Lprac). These detection limits were determined for the example of two current PCR setups for the detection of genetically modified soybeans and maize. The Ltheor for the detection of Roundup Ready soybean DNA with the PCR setup applied was 0.005% genetically modified organism (GMO)/non-GMO (w/w) (corresponding to 30 copies of the GMO soya genome per single PCR reaction). In pre-mixed powder preparations (certified reference materials, CRMs) of soya it was possible to detect 0.1% GMO/non-GMO (w/w), i.e. this was the Lprac. The Ltheor for Bt maize was 0.005% GMO/non-GMO (w/w), that corresponded to 9 calculated genome copies per single reaction. Without background DNA, as few as 2 genome copies (0.01 ng GMO DNA) were clearly detectable. As for soybeans, the Lprac of the available CRMs from transgenic and conventional maize was 0.1% GMO/non-GMO (w/w). Quantitative systems for the investigation of foodstuffs are still not available as official methods, and are still being developed. Determining Ltheor and Lprac values could be important for setting limits for the GMO contents of foods, when deciding whether they should be labelled. Concerning labelling limits, it is obvious that the PCR setups investigated have more sensitive detection thresholds than the limits under discussion for the labelling of foodstuffs as "genetically modified".

Economic Comparison of Herbicides for Johnsongrass (Sorghum halepense) Control in Glyphosate-Tolerant Soybean (Glycine max)

Returns to land, management, and risk were compared where glyphosate and four graminicides (quizalofop-P, fluazifop-P, sethoxydim, and clethodim) were used for johnsongrass control in glyphosate-tolerant soybean. In 1994 and 1995, returns to land, management, and risk for glyphosate-tolerant soybean were highest using glyphosate and lowest using sethoxydim. Break-even analysis showed that yields needed for equivalent returns with any nontransgenic soybean cultivar treated with any of the graminicides could range from 67 kg/ha less to 202 kg/ha more than the yields achieved with glyphosate. Based on this methodology, farmers would increase their return to land, management, and risk by planting glyphosate-tolerant soybean if expected yield from a standard cultivar treated with a standard herbicide program were less than the break-even yield.

Biotechnology and the soybean

Glyphosate-tolerant soybeans (GTSs), the first biotechnologically improved soybeans to be marketed, became available commercially in 1996. The safety of GTSs was assessed in 2 ways: study of the introduced protein and of the soybean seed and selected processing fractions. Because soybeans are a major source of protein in most farm animals’ diets, animal feeding studies in wholesomeness were done to complement the analyses. Analysis of the expressed protein in GTSs [3-phosphoshikimate 1-carboxyvinyltransferase (EC 2.5.1.19)] showed it to be readily digestible and to possess no allergenic concerns. In addition, comparison of the composition of seeds and selected processing fractions from 2 GTS lines with the parental line showed that the lines are equivalent. Feeding studies in various animal species confirmed that the feeding value of GTS lines is comparable with that of the parental line. These studies support the conclusion that GTSs are as safe and nutritious as traditional soybeans marketed currently and can be incorporated safely into feed and food products in the near future.