Sublethal Doses Of Glyphosate Research Articles

Glyphosate contact alters the expression of genes in the head of africanized Apis mellifera bees

The increase in the world population results in a greater demand for food, intensifying the dependence on pesticides use. Glyphosate, a pesticide widely used in crops, can contaminate resources collected by bees. In this context, this study aimed to analyze the transcriptome of the head of Africanized Apis mellifera bees during the foraging phase to determine whether contact with the herbicide glyphosate, in lethal and sublethal doses, causes changes in the gene expression profile. For this, 180 marked bees were collected from their hives, aged 21 days, and distributed into three treatment groups: 1) bees in contact with the lethal dose of glyphosate (255.73 µg/bee); 2) bees in contact with the sublethal dose of glyphosate (2.5573 µg/bee); 3) control group with distilled water. Transcriptome analysis was performed on 12 bees from each treatment after one and four hours of exposure. The results show that one hour of contact with glyphosate resulted in 57 genes presenting differential expression in relation to the control (11 lethal and 53 sublethal), interfering in the signaling, communication and metabolism processes, while four hours of exposure, 38 genes (32 lethal and 11 sublethal) related, mainly, to the stimulation of the immune response. In summary, glyphosate affects the gene expression of honey bees during the foraging phase, at both doses, resulting in negative effects on behavior, metabolism and immune system, which compromises the health, activity and development of the colonies, also compromising the process of pollination.

Transgenerational memory of drought stress and low rates of glyphosate reduce the sensitivity of Eragrostis plana to the herbicide

Background Eragrostis plana is the main invasive plant in the Pampa Biome of southern Brazil. This plant is highly competitive, tolerant to abiotic stresses, and very difficult to manage. Plants exposed to abiotic stresses and herbicides develop mechanisms that help alleviate or reduce damage caused by stressors and transmit this ability to the progenies. Objective The study’s objectives were to ascertain whether acclimatization to stress due to drought and sub-lethal doses of glyphosate may decrease plant sensitivity to glyphosate [...]

Effects of glyphosate plus foliar manganese application on the production and quality of marandu grass

In this study, the stimulatory effects of application of glyphosate herbicide coupled with manganese sulfate (8%) foliar fertilizer on the production and bromatological characteristics of Brachiaria brizantha ‘Marandu’ were evaluated. The experiments were performed using randomized complete block design with a 5×4 factorial scheme in plots subdivided over time (across four evaluations) with four repetitions, totaling 100 observations. The effects of sublethal doses of acid equivalent (a.e.) of glyphosate (5.40, 21.60, 64.80, and 108.00 g·a.e.·ha-1) and control plus manganese sulfate foliar fertilizer (1,000 g ha-1) were assessed in four successive evaluations at a defoliation frequency of 21 days. Foliage at 20 cm height (to evaluate forage production); leaf/stem ratio (LSR); and contents of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin (LIG) were measured in experimental plots with a usable area of 7.5 m2. Application of sublethal doses of glyphosate plus manganese sulfate did not increase forage production, increased LSR, reduced LIG content, and did not affect CP content in all four evaluations. NFD and ADF indicated satisfactory qualitative indices for animal feed following the application of sublethal doses of glyphosate plus manganese sulfate in all four evaluations.

Glyphosate in the production and forage quality of marandu grass

The drift of the herbicide glyphosate, used for desiccating crops or controlling weeds, can result in growth-promoting or non-target plant development effects. Thus, it is possible to use the compound to increase the biomass of forage through the hormone effect. The objective of this study was to evaluate the effects of sublethal doses of glyphosate on the production of Urochloa brizantha cv. Marandu (Marandu grass) and its nutritional quality in ruminants. The design used was completely randomized, with five replications in a factorial scheme. The treatments used were as follows: control (without glyphosate application) and four sublethal doses of glyphosate (4, 10, 14, and 20 g ha-1 of the acid equivalent). The monthly collections consisted of collecting the plant material (0.20 m) from the surface, comprising of leaves and pseudocolmos (stem and leaf sheath) to determine the dry matter production and forage chemical-bromatological parameters. The results showed that leaf/stem ratio, neutral detergent fiber, and acid detergent fiber were affected exclusively by the harvest factor. The hormone effect of the herbicide occurs in the production of dry matter and lignin in the evaluated subdoses. For crude protein, there was an interaction between the factor doses and harvest, due to the effect of glyphosate and the management applied to the harvests, showing that the sublethal doses of glyphosate promoted the production of dry matter and the food quality of Marandu grass.

Aromatic Amino Acids Partially Alleviated Glyphosate Induced Effects on Metabolites and Growth in Faba Bean with a More Phytotoxicity in Orobanche crenata Parasite

Abstract The holoparasite Orobanche crenata is considered the most damaging pathogens on the faba bean grown in the Mediterranean region. Sub-lethal dose of glyphosate was used for controlling O. crenata, but it caused injury effects on faba bean growth. Glyphosate inhibits the shikimic pathway of the synthesis aromatic amino acids (AAAs), phenylalanine, tyrosine and tryptophan. Greenhouse experiment was conducted using infested pots with O. crenata to explore the possibility of co-exposure AAAs with glyphosate to alleviate glyphosate effects on faba bean and determine their effects on the parasite. Moreover, changes in the metabolites related to shikimic pathway were examined in faba bean leaves, 3 and 7 days after treatments. Application of twice sprays with glyphosate at 170 or 340 g ai ha-1 on faba bean was effective in controlling O. crenata infestation. Co-exposure AAAs (0.5 and 1 mM) with glyphosate allowed to partially mitigating the detrimental effects of the herbicide on faba bean growth. Combined treatments produced more sever effects on O. crenata parasite and completely inhibited O. crenata parasite by 120 days from sowing. Glyphosate induced differential effects on amino acids composition, endogenous free AAAs and protein content in faba bean leaves. Moreover, it increased shikimic acid content accompanied by decreases in phenolic contents and antioxidant activity. Level of these compounds was partially mitigate by co-applied glyphosate with AAAs, proposing a potential role of AAAs in increasing tolerance of the host plant by ameliorating the glyphosate induced effects on metabolites related to shikimic acid pathway.

Doses subletais de glifosato em combinação com manganês foliar na produção de capim marandu

A deriva do herbicida glifosato pode estimular crescimento e/ou rendimento produtivo em plantas não-alvo, caracterizando efeito hormese. Ainda, manifesta-se amarelecimento momentâneo em folhas novas, característico de deficiência nutricional. Deste modo, o trabalho teve por objetivo avaliar o efeito hormese por aplicação de glifosato em Urochloa brizantha cv. Marandu. Foi avaliada a resposta produtiva aérea (PMS) e radicular (MSR) da forrageira por aplicação foliar de sete doses subletais do equivalente ácido (e.a.) de glifosato (5,40, 10,80, 21,60, 43,20, 64,80, 86,40 e 108,00, g e.a. ha-1) e controle, sob ausência e presença de manganês (1000 g ha-1) à calda de pulverização, em quatro colheitas sequenciais, caracterizando esquema fatorial 8 x 2 x 4, com quatro repetições. As doses subletais de glifosato com adição de manganês à calda de pulverização reduziram o efeito herbicida, com persistência de PMS durante período experimental (4 cortes). Para doses sem adição de manganês à calda de pulverização, houve falência produtiva nos cortes 2, 3 e 4, para doses 86,40 e 108,00 g e.a. ha-1. A presença de manganês à calda de pulverização assegurou massa seca de raiz superior àquelas sem adição de manganês, sendo constatado efeito do herbicida nas doses igual e superiores a 43,60 g e.a. ha-1.

Chronic exposure to glyphosate induces transcriptional changes in honey bee larva: A toxicogenomic study

The honey bee Apis mellifera is the most abundant managed pollinator in diverse crops worldwide. Consequently, it is exposed to a plethora of environmental stressors, among which are the agrochemicals. In agroecosystems, the herbicide glyphosate (GLY) is one of the most applied. In laboratory assessments, GLY affects the honey bee larval development by delaying its moulting, among other negative effects. However, it is still unknown how GLY affects larval physiology when there are no observable signs of toxicity. We carried out a longitudinal experimental design using the in vitro rearing procedure. Larvae were fed with food containing or not a sub-lethal dose of GLY in chronic exposure (120 h). Individuals without observable signs of toxicity were sampled and their gene expression profile was analyzed with a transcriptomic approach to compare between treatments. Even though 29% of larvae were asymptomatic in the exposed group, they showed transcriptional changes in several genes after the GLY chronic intake. A total of 19 transcripts were found to be differentially expressed in the RNA-Seq experiment, mainly linked with defensive response and intermediary metabolism processes. Furthermore, the enriched functional categories in the transcriptome of the exposed asymptomatic larvae were linked with enzymes with catalytic and redox activity. Our results suggest an enhanced catabolism and oxidative metabolism in honey bee larvae as a consequence of the sub-lethal exposure to GLY, even in the absence of observable symptoms.

Phelipanche aegyptiaca Management with Glyphosate in Potato

Two years field and greenhouse studies were carried out to evaluate the efficacy of sub-lethal doses of glyphosate (Round upR), ammonia gas, phosphoric acid and sulfuric acid against Phelipanche aegyptiaca in potato. Results showed that sequential application of sub-lethal doses of glyphosate at all tested rates significantly reduced P. aegyptiaca shoot number and shoot dry weight. While, the use of ammonia gas, phosphoric acid and sulfuric acid had no significant effect on the total level of P. aegyptiaca infection as compared to the control. The best results considering both P. aegyptiaca control and selectivity in potato were obtained by sequential application of sub-lethal doses of glyphosate at 60 and 80 g·ai·ha-1. Sequential application of glyphosate at 60 g·ai·ha-1 reduced P. aegyptiaca infection by 100% after 100 days after potato emergence (DAPE). Except for sequential application of glyphosate at 60 and 80 g·ai·ha-1, all tested rates enhanced the maturity rate of potato plants and decreased the number of marketable potato tubers.

The effect of glyphosate on the growth and competitive effect of perennial grass species in semi-natural grasslands

Biodiversity within European semi-natural biotopes in agro-ecosystem is declining, and herbicide drift from neighbouring fields is considered as an important factor for the decline. The aim of the present study was to investigate whether the growth and competitive interactions in a model system of two perennial grass species, Festuca ovina and Agrostis capillaris, are affected by sub-lethal doses of glyphosate in field margins. In a glasshouse experiment with ample nitrogen, the interspecific competitive interactions were found to be significantly affected by glyphosate; the competitive effect of F. ovina on A. capillaris increased and the competitive effect of A. capillaris on F. ovina decreased with increasing doses of glyphosate. Furthermore, the importance of interspecific competition increased with the glyphosate dose. The results of the study of competitive interactions are in agreement with the observed plant community dynamics at the field site where F. ovina was found to be more dominant in plots treated with a relatively high dose of glyphosate. Importantly, the effects of glyphosate on the plant community dynamics critically depended on the effect of glyphosate on the plant competitive interactions. The study concludes that the current practice in the environmental risk assessment of non-target effects of herbicides, where single species are tested in the greenhouse, may be inadequate for assessing the effect of herbicides in semi-natural plant communities. The presented methods can be used for assessing the importance of competitive interactions for the sensitivity of non-target plants to herbicides in risk assessment.

Impacts of a sub-lethal dose of glyphosate on water hyacinth nutrients and its indirect effects on Neochetina weevils

A sub-lethal dose of a herbicide under field conditions was applied to determine if it stimulates an increase in water hyacinth nutrients, thereby increasing feeding intensity by Neochetina spp. weevils used as biocontrol agents of the weed. Nitrogen (N) and carbon (C) were measured and compared between sprayed plants and control plants. At one site (Delta Park), N levels were lower in the sprayed plants compared to the control plants both in the leaves and the crown. At the second site (Farm Dam), leaf N was also lower in the sprayed plants than in the control plants, while no difference was found in crown N. Mean number of feeding scars per cm2 at Delta Park was significantly higher on the sprayed plants compared to the control plants, while no significant difference was found at Farm Dam. At Delta Park, there was no correlation, however, between the number of weevil feeding scars and leaf N or C:N ratio in sprayed plants. In conclusion, the sub-lethal dose of glyphosate did not directly result in an increase in weevil feeding intensity but it can be recommended in an integrated control system to retard water hyacinth growth while conserving the weevil population.

Simulation of heavy metal contamination of fresh water bodies: Toxic effects in the catfish and its amelioration with co-contamination with glyphosate

The toxic implications of fresh water contamination with zinc in the catfish, Clarias albopunctatus (Lamonte and Nicole, 1927), and the effect of a co-contamination with a sub-lethal dose of glyphosate (Roundup) was studied using the static bioassay model. Thirty six fish were divided into 3 equalgroups. Fish in Group 1 were placed in normal tap water, and served as the control group, while fish in Groups 2 and 3 were placed in water contaminated with ZnSO4 and ZnSO4 + glyphosate, respectively. The study lasted for96 hours (though sampling was done at the 48th hour). Biochemical markers of toxicity were measured and the fish liver and gill histology were studied using standard protocols. The results show that ZnSO4 was significantly toxicto the fish only after 96 hours. Co-contamination of the water with both toxicants was found to ameliorate the toxic effects of ZnSO4 significantly. The metal chelating property of glyphosate may be responsible for the observedattenuation of toxicity in the fish in Group

Competitive and allelopathic interference between soybean crop and annual wormwood ( Artemisia annua L.) under field conditions

Annual wormwood interference on soybean crop growth and yield may result from competition and allelopathy, which are modulated by crop management. Allelochemicals released by annual wormwood (e.g. artemisinin) may affect the crop directly or indirectly through the effect on the nitrogen fixing symbiont, Bradyrhizobium japonicum. The objectives were (i) to quantify the crop response (i.e. biomass production, nodulation and yield) to weed interference and (ii) to determinate the relative change of competition and allelopathy interferences, when a sublethal dose of herbicide is applied. Two split plot field experiments with three replications were used. The experiment involved a factorial combination of five weed–crop density (soybean/annual wormwood, plants m −2) levels: D1, pure soybean, 40/0 plants m −2; D2, 40/2 plants m −2; D3, 40/4 plants m −2 and D4, 40/8 plants m −2, and D5, pure annual wormwood, 0/8 plants m −2, two activated carbon (allelopathy) levels: C−, with activated carbon (reduced allelopathy) and C+, non activated carbon applied (with allelopathy) and two herbicide levels: H−, untreated and H+, treated with a sub-lethal dose of glyphosate. Activated carbon to adsorb allelochemicals (with and without activated carbon) and glyphosate application (with and no herbicide) were assigned to sub-plots. Increasing weed density did not affect crop biomass at flowering, but changed nodule number and soybean yield with a different pattern depending on carbon and herbicide treatment. Relative crop yield decreased with increasing relative weed biomass. This decrease was particularly drastic when allelopathy was reduced by activated carbon and without herbicide application. The maximum yield losses of 33% in 2006 and 17% in 2007 were observed with the highest weed density (8 plants m −2). In contrast, without carbon (high allelopathy level), soybean yield remained stable within the explored range of annual wormwood biomass, despite the fact that weed biomass at high densities (D4) was high enough to generate competition. The lack of response to increasing weed density could be related to the indirect effect of allelochemicals interacting with soil microorganisms (i.e. B. japonicum) that positively affected the nodulation (e.g. larger nodules in 2006 and increased nodules biomass due to higher number of roots in 2007 at high densities). With herbicide application, soybean yield of both carbon treatments remained stable when biomass of annual wormwood increased. This research provided strong evidence in support of the existence of positive effect of allelopathic and competitive interactions between annual wormwood and soybean crop under field conditions that may be overridden under herbicide application.

Selective control of Orobanche ramosa in potato with rimsulfuron and sub-lethal doses of glyphosate

Previous studies indicated that foliar applications of rimsulfuron were effective in controlling Orobanche ramosa but phytotoxic to potato plants, while sub-lethal doses of glyphosate slightly reduced Orobanche infestation but were selective in potato. In this study, a single foliar application of rimsulfuron at 12.5 g ai/ha followed by single and sequential foliar applications [20, 35, 50 days after potato emergence (DAPE)] of sub-lethal doses of glyphosate (100, 200 and 300 g ai/ha) were used. All doses except the single application of rimsulfuron followed by sequential applications of glyphosate at 200 and 300 g ai/ha had no negative effect on potato growth and marketable yield, but had variable effects on Orobanche infestation. All doses significantly reduced O robanche shoot number 75 and 90 DAPE, while triple application of glyphosate following rimsulfuron was the most effective in reducing Orobanche shoot number after 110 DAPE and dry weight compared to the control. The best results considering both Orobanche control and selectivity in potato was obtained by application of rimsulfuron at 12.5 g ai/ha followed by sequential foliar application (three times) of glyphosate at 100 g ai/ha.

Effect of Glyphosate on Auxin Transport in Corn and Cotton Tissues

Basipetal auxin transport in 6-day-old dark-grown corn coleoptiles was severely inhibited by increasing levels of glyphosate applied during the transport period.The velocity of basipetal transport of [(14)C]indoleacetic acid in hypocotyls from 7-day-old cotton seedlings was significantly reduced when sublethal doses of glyphosate [N-(phosphonomethyl)glycine] were applied to the cotyledonary leaves 24 hours before transport measurement. Simultaneous application of glyphosate and indoleacetic acid during transport measurement had no effect on basipetal transport in cotton hypocotyl sections.Slowing of transport was inversely proportional to the dosage applied to both species.

Reduction of Glyphosate-Induced Tillering in Sorghum (Sorghum bicolor) by Several Chemicals

Sublethal doses of glyphosate [N-(phosphonomethyl)glycine] applied in a 50-μl drop in the partially furled third true leaf of 30-day-old sorghum [Sorghum bicolor(L.) Moench ‘Tophand’] seedlings induced basal stem swelling and bud release. Combining glyphosate with cycloheximide {3-[2-(3,5-dimethyl-2-oxycyclohexyl)-2-hydroxyethyl]glutarimide}, a cytokinin [N6(2-isopentenyl)adenine], or L-phenylalanine significantly reduced the incidence of basal stem swelling. No such reductions was observed when indole-3-acetic acid or L-tyrosine was combined with glyphosate. The fresh weights of the seedlings given the combination treatments reflected the effects of glyphosate, except one combination that included tyrosine significantly reduced fresh weight and three combinations that included phenylalanine significantly increased fresh weight.