Hypoxic treatment decreases the physiological action of the herbicide imazamox on pisum sativum roots

The inhibition of acetolactate synthase (ALS; EC 2.2.1.6), an enzyme located in the biosynthetic pathway of branched-chain amino acids, is the target site of the herbicide imazamox. One of the physiological effects triggered after ALS inhibition is the induction of aerobic ethanol fermentation. The objective of this study was to unravel if fermentation induction is related to the toxicity of the herbicide or if it is a plant defense mechanism. Pea plants were exposed to two different times of hypoxia before herbicide application in order to induce the ethanol fermentation pathway, and the physiological response after herbicide application was evaluated at the level of carbohydrates and amino acid profile. The effects of the herbicide on total soluble sugars and starch accumulation, and changes in specific amino acids (branched-chain, amide, and acidic) were attenuated if plants were subjected to hypoxia before herbicide application. These results suggest that fermentation is a plant defense mechanism that decreases the herbicidal effect.This work was funded by the Spanish Ministry of Economy and Competitiveness (AGL2016-77531-R)

An aerated axenic hydroponic system for the application of root treatments: exogenous pyruvate as a practical case

Background: Hydroponic systems are a convenient platform for plant cultivation when treatments are applied to the roots because they provide precise control of the composition of the growth medium, ensuring the availability of different compounds. A problem arises when axenic conditions are needed but the treatment of choice (exogenous organic acids or sugars) promote the growth of unwanted microorganisms. Moreover, axenic conditions are usually applied in liquid and semi-liquid growing systems, where oxygen availability can be compromised, if no aeration is provided. Results: The driver for the development of this hydroponic system was the application of the organic acid pyruvate to the roots of plants grown under aerated axenic conditions. No contamination was detected in the nutrient solution, even after the addition of pyruvate. The system was validated in pea plants treated with either pyruvate or herbicides inhibiting amino acid biosynthesis. The effects on ethanol fermentation were compared by analysing the enzymatic activity, protein content and transcriptional levels in plants treated with either pyruvate or herbicides. Conclusions: The developed system enables the study of the exogenous application of organic acids in the nutrient solution under axenic conditions and without oxygen limitation. This system allows the study of the effect of any type of treatments applied to roots under aerated axenic hydroponic systems at physiological and molecular levels. The role of pyruvate in the induction of fermentation by herbicides cannot be simply explained by an increase in substrate availability.MGM and MFE received funding from fellowships through Universidad Pública de Navarra. This work was financially supported by a grant from the Ministerio Español de Economía y Competitividad (AGL-2016-7531R)

Enhancement of glyphosate efficacy on Amaranthus palmeri by exogenous quinate application

Glyphosate is a widely used herbicide targeting the enzyme 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) in the aromatic amino acid biosynthesis pathway (shikimate pathway) and provoking accumulation of quinate, a secondary metabolite synthesized through a side branch of this pathway. The objective of this work was to evaluate whether the efficacy of glyphosate activity in Amaranthus palmeri is enhanced by quinate application one day after herbicide treatment. To this end, one glyphosate-sensitive and one glyphosate-resistant (due to EPSPS gene amplification) population of A. palmeri were used. The 3- day time course study of the quinate treatment alone showed quinate, Tyr and Phe accumulation in both populations. When the herbicide was applied alone at 0.25× the recommended dose, no phytotoxicity or glyphosate effects were detected in the sensitive population 3 days after treatment, but the combined treatment with quinate was lethal, and markers of herbicide activity at the amino acid level could be detected. In the resistant population, an important metabolic perturbation in the flux of the shikimate pathway was detected in the combined treatment. These results raise the possibility of the joint application of quinate and glyphosate to enhance glyphosate efficacy while lowering doses in the sensitive population.This work was supported by a grant from the Ministerio de Economía y Competitividad , Spain (Project number AGL2016-77531-R ). AZ-G and MF-E received funding from fellowships trough Universidad Pública de Navarra

Nafarroako landare sorotarrak

1. edizioaEnlace a la versión en castellano: https://hdl.handle.net/2454/39450Liburu honen jatorria Flora Arvense de Navarra webgunea izan da. Weba ikasleei laguntzeko asmoz sortu eta garatu zen; hain zuzen ere, Nafarroako Unibertsitate Publikoko Nekazaritza Ingeniarien Goi Mailako Eskola Teknikoko ikasleei Nafarroako belar gaiztoen gaineko ezagutza errazteko. Aldi berean, erabilgarria da Nafarroako eta inguruko ikertzaile, teknikari eta nekazarientzat

Flora arvense de Navarra

1ª ediciónEnlace a la versión en euskera: https://hdl.handle.net/2454/39451El origen de este libro se encuentra en el sitio web de Flora Arvense de Navarra, que fue desarrollado con el objetivo de facilitar el conocimiento de las malas hierbas de Navarra al alumnado de la Escuela Técnica Superior de Ingenieros Agrónomos de la Universidad Pública de Navarra, además de el de ser útil para personal investigador, técnico y agricultores de Navarra y territorios próximos. La edición de este libro se planteó para permitir la disponibilidad del contenido del sitio web en un soporte independiente de Internet

Increased glyphosate-induced gene expression in the shikimate pathway is abolished in the presence of aromatic amino acids and mimicked by shikimate

The herbicide glyphosate inhibits the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in the aromatic amino acid (AAA) biosynthetic pathway, also known as the shikimate pathway. Amaranthus palmeri is a fast-growing weed, and several populations have evolved resistance to glyphosate through increased EPSPS gene copy number. The main objective of this study was to elucidate the regulation of the shikimate pathway and determine whether the regulatory mechanisms of glyphosate-sensitive and glyphosate-resistant plants were different. Leaf disks of sensitive and resistant (due to EPSPS gene amplification) A. palmeri plants were incubated for 24 h with glyphosate, AAA, glyphosate + AAA, or several intermediates of the pathway: shikimate, quinate, chorismate and anthranilate. In the sensitive population, glyphosate induced shikimate accumulation and induced the gene expression of the shikimate pathway. While AAA alone did not elicit any change, AAA applied with glyphosate abolished the effects of the herbicide on gene expression. It was not possible to fully mimic the effect of glyphosate by incubation with any of the intermediates, but shikimate was the intermediate that induced the highest increase (three-fold) in the expression level of the genes of the shikimate pathway of the sensitive population. These results suggest that, in this population, the lack of end products (AAA) of the shikimate pathway and shikimate accumulation would be the signals inducing gene expression in the AAA pathway after glyphosate application. In general, the effects on gene expression detected after the application of the intermediates were more severe in the sensitive population than in the resistant population. These results suggest that when EPSPS is overexpressed, as in the resistant population, the regulatory mechanisms of the AAA pathway are disrupted or buffered. The mechanisms underlying this behavior remain to be elucidated.This work was supported by two grants from the Ministerio Español de Economía y Competitividad (Project number AGL2016-77531-R). AZ-G and MB-A received funding from fellowships through Universidad Pública de Navarra

Primary metabolism in an Amaranthus palmeri population with multiple resistance to glyphosate and pyrithiobac herbicides

The objective of this work was to characterize the resistance mechanisms and the primary metabolism of a multiple resistant (MR) population of Amaranthus palmeri to glyphosate and to the acetolactate synthase (ALS) inhibitor pyrithiobac. All MR plants analysed were glyphosate-resistant due to 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene amplification. Resistance to pyrithiobac was more variable among individuals and was related to point mutations at five positions in the ALS gene sequence: A122, A205, W574, S653 and G654. All MR plants were heterozygous for W574, the most abundant mutation. In nontreated plants, the presence of mutations did not affect ALS functionality, and plants with the W574L mutation showed the highest ALS resistance level to pyrithiobac. The accumulation of the transcripts corresponding to several genes of the aromatic amino acid (AAA) and branched-chain amino acid (BCAA) pathways detected in nontreated MR plants indicated additional effects of EPSPS gene amplification and ALS mutations. The physiological performance of the MR population after treatment with glyphosate and/or pyrithiobac was compared with that of a sensitive (S) population. The increase induced in total soluble sugars, AAA or BCAA content by both herbicides was higher in the S population than in the MR population. Physiological effects were not exacerbated after the mixture of both herbicides in S or in MR populations. This study provides new insights into the physiology of a multiple resistant A. palmeri, which could be very useful for achieving effective management of this weed.This work was funded by the Spanish Ministry of Economy and Competitiveness (AGL2016-77531-R), Spain and by the Universidad Pública de Navarra, Spain (Project UPNA20-6138). M.B.-A. received funding from fellowship through Universidad Pública de Navarra. M.V.E. is the holder of a predoctoral fellowship of the Basque Government

Insights into the regulation of nitrogen fixation in pea nodules: lessons from drought, abscisic acid and increased photoassimilate availability

Nitrogen fixation in legume nodules has been shown to be very sensitive to drought and other environmental constraints. It has been widely assumed that this decline in nitrogen fixation was a consequence of an increase in the so-called oxygen diffusion barrier and a subsequent impairment to bacteroid respiration. However, it has been recently shown that nitrogen fixation is highly correlated with nodule sucrose synthase (SS) activity under drought and other environmental stresses. Whether this correlation reflects a causative relationship or not has not been proven yet. The evidence presented here suggests that SS controls nitrogen fixation under mild drought conditions. However, nitrogen fixation cannot be enhanced only by increasing glycolytic flux, as under these conditions nodules become oxygen limited. Abscisic acid also induces a decline in nitrogen fixation that is independent of SS. The overall results suggest the occurrence of a complex regulation of nodule nitrogen fixation involving, at least, both carbohydrate and oxygen fluxes within the nodule.Loli Gálvez was the holder of a grant from the Spanish Ministry of Education (Plan F.P.U.). This work was supported by DGESIC (PB98-0545)

Phytotoxic and metabolic effects of exogenous quinate on Pisum sativum L.

The final publication is available at Springer via http://dx.doi.org/10.1007/s00344-013-9345-5Quinate (1,3,4,5-tetrahydroxycyclohexanecarboxylate) is a compound synthesized in plants through a side branch of the shikimate biosynthesis pathway. Plants treated with herbicides that inhibit amino acid biosynthesis (branched-chain and aromatic) accumulate quinate in their leaves. The objective of this study was to evaluate whether quinate mimics the effects of herbicides in plants. In pea plants, exogenous application of quinate through the nutrient solution was compared with leaf spraying at a concentration of 4 and 400 mM, respectively, and evaluated in parallel to the effects of herbicides. The analysis facilitated an assessment of the phytotoxicity and potential use of quinate as a natural herbicide. The application of quinate through the nutrient solution, but not the spray, was lethal, although both treatments affected plant growth. Quinate was absorbed and translocated to other plant organs remote from the application site, and an increase in the levels of aromatic amino acids and caffeic acid (that is, compounds located after quinate in the shikimate biosynthesis pathway) was detected, which indicates that quinate was metabolized and incorporated into the shikimate pathway. Exogenous application of quinate affected the carbohydrate content in the leaves and roots in a way similar to the toxic effects of herbicides. The phytotoxic effects of quinate reported in this study suggest that this compound deregulates the shikimate pathway and mimics some physiological effects described in the mode of action of herbicides inhibiting amino acid biosynthesis.A. Zulet received a grant from the Spanish Ministry of Education and Science. This work was supported through funding from the Spanish Ministry of Science and Innovation (AGL- 2010-18621/AGR)

XVI Congreso de la Sociedad Española de Malherbología: Actas. Pamplona-Iruña, 25-27 octubre, 2017.

Comunicaciones presentadas al XVI Congreso de la Sociedad Española de Malherbología, celebrado en la Universidad Pública de Navarra, Pamplona-Iruña, entre los días 25 y 27 de octubre de 2017.Este congreso bienal, promovido por la Sociedad Española de Malherbología es la principal reunión científica dedicada al estudio de la Malherbología que se celebra de forma periódica en España. El Congreso es un foro para dar a conocer los últimos avances conceptuales y tecnológicos en el ámbito de la Malherbología, propiciando, a la vez, el intercambio y la difusión de ideas entre los participantes. Es imprescindible analizar las diversas estrategias de control de malas hierbas desde una perspectiva amplia, avanzando hacia a un manejo integrado y sostenible. El contexto actual de progresiva reducción en la disponibilidad de materias activas, y de sostenida evolución de poblaciones de malas hierbas resistentes a uno o más herbicidas, no hace sino impulsar aún más este planteamiento. La viabilidad y éxito del manejo implica un trabajo multidisciplinar que incluye el estudio de la biología y ecología de poblaciones, el manejo integrado, el control químico, las resistencias y la eco-innovación. El Congreso se estructura en diferentes sesiones que abarca los principales ámbitos de la Malherbología y ha contado con la presencia de expertos malherbólogos internacionales de reconocido prestigio en las diferentes temáticas