Search

Alfalfa production is frequently constrained by drought, indicating the importance of assessing species biodiversity in endemic close relatives to enhance forage production under future global change conditions. In the present study, plants of two ecotypes of M. tunetana, native to Tunisia, and four commercial cultivars of M. sativa were subjected to two water regimes (control vs drought [15% field capacity]). Physiological, isotopic and metabolic analyses were used to characterize leaf and nodule profiles of the plants. Biomass, gas exchange and the maximum carboxylation rate (Vc

Heatwave (HW) combined with water stress (WS) are critical environmental factors negatively affecting crop development. This study aimed to quantify the individual and combined effects of HW and WS during early reproductive stages on leaf and nodule functioning and their relation with final soybean seed yield (SY). For this purpose, during flowering (R2) and pod formation (R4) soybean (Glycine max L. Merr.) plants were exposed to different temperature (ambient[25ºC] versus HW[40ºC]) and water availability (full capacity versus WS[20% field capacity]). HW, WS and their combined impact on yield depended on the phenological stage at which stress was applied being more affected at R4. For gas exchange, WS severely impaired photosynthetic machinery, especially when combined with HS. Impaired photoassimilate supply at flowering caused flower abortion and a significant reduction in final SY due to interacting stresses and WS. On the other hand, at pod formation (R4), decreased leaf performance caused additive effect on SY by decreasing pod setting and seed size with combined stresses. At the nodule level, WS (alone or in combination with HW) caused nodule impairment, which was reflected by lower leaf N. Such response was linked with a poor malate supply to bacteroids and feed-back inhibition caused by nitrogenous compounds accumulation. In summary, our study noted that soybean sensitivity to interacting heat and water stresses was highly conditioned by the phenological stage at which it occurs with, R4 stage being the critical moment. To our knowledge this is the first soybean work integrating combined stresses at early reproductive stages., D.S. was a recipient of a PhD fellowship from the Public University of Navarra.

Main conclusion: By combining hyperspectral signatures of peanut and soybean, we predicted V and J with 70 and 50% accuracy. The PLS was the model that better predicted these photosynthetic parameters. Abstract: One proposed key strategy for increasing potential crop stability and yield centers on exploitation of genotypic variability in photosynthetic capacity through precise high-throughput phenotyping techniques. Photosynthetic parameters, such as the maximum rate of Rubisco catalyzed carboxylation (V) and maximum electron transport rate supporting RuBP regeneration (J), have been identified as key targets for improvement. The primary techniques for measuring these physiological parameters are very time-consuming. However, these parameters could be estimated using rapid and non-destructive leaf spectroscopy techniques. This study compared four different advanced regression models (PLS, BR, ARDR, and LASSO) to estimate V and J based on leaf reflectance spectra measured with an ASD FieldSpec4. Two leguminous species were tested under different controlled environmental conditions: (1) peanut under different water regimes at normal atmospheric conditions and (2) soybean under high [CO] and high night temperature. Model sensitivities were assessed for each crop and treatment separately and in combination to identify strengths and weaknesses of each modeling approach. Regardless of regression model, robust predictions were achieved for V (R = 0.70) and J (R = 0.50). Field spectroscopy shows promising results for estimating spatial and temporal variations in photosynthetic capacity based on leaf and canopy spectral properties., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

Trabajo presentado para optar al grado de Doctor por la Universidad Pública de Navarra, Departamento de Ciencias, Programa de Doctorado en Agrobiología Ambiental.--Calificación: Sobresaliente cum laude, [ES] Las leguminosas son la segunda familia, tras los cereales, en importancia agrícola, cubriendo el 14% de la superficie cultivada. En el contexto actual y en un futuro cercano, la producción de leguminosas se ve amenazada por diversos estreses abióticos asociados con el cambio climático. Estos se espera que aumenten en número y severidad durante las próximas décadas. Debido al importante desafío para la seguridad alimentaria, es clave comprender cómo se pueden mejorar los futuros cultivos de leguminosas para resistir condiciones ambientales adversas. El objetivo general de esta tesis es obtener más conocimientos sobre los mecanismos implicados en la respuesta de las leguminosas a las condiciones ambientales ([CO2], sequía y temperatura) mediante la integración de medidas de biomasa, procesos fisiológicos y bioquímicos y niveles de metabolitos y otros compuestos., [EN] The leguminosae are second to cereal crops in agricultural importance based on area and total production, covering 14% of the cultivated land. Within the current and near future context, legume production is threatened by various abiotic stresses associated with climate change, which are expected to increase in number and severity during the following decades. Due to the important challenge to food security, it is important to understand how future legume crops can be bred to withstand adverse environmental conditions. The overall aim of this thesis is to gain further insights on the mechanisms involved in legume response to environmental conditions ([CO2], drought and temperature) through the integrated investigation of biomass, physiological and biochemical processes and the levels of metabolites and other compounds of the plants., During the doctoral programme has been holder of a PhD fellowship from the Public University of Navarra / Ayuda predoctoral dentro de la convocatoria de ayudas de nueva solicitud para la Formación de Personal Investigador de la Universidad Pública de Navarra para el año 2017

Grain development in cereals depends on synthesis and remobilisation compounds such as water-soluble carbohydrates (WSCs), amino acids (AAs), minerals and environmental conditions during pre-and post-anthesis. This study analyses the impact of water stress on metabolite (WSCs, AAs and nitrogen) dynamics between the source (leaves and stems) and sink (grain) organs in triticale, bread wheat, durum wheat and barley. Plants were grown in glasshouse conditions under well-watered (WW) and water-limited (WL) regimes (from flag leaf fully expanded until maturity). The results showed that the stem WSC content and the apparent mobilisation of WSC to the grain were much higher in triticale and were associated with its larger grain size and grain number. In the four cereals, grain weight and the number of kernels per spike were positively associated with stem WSC mobilisation. After anthesis, the AA concentration in leaves was much lower than in the grain. In grain, the main AAs in terms of concentration were Asn, Pro and Gln in triticale, bread, and durum wheat, and Asn, Pro and Val in barley. The water-limited regime reduced grain weight per plant in the four cereal species, but it had no clear effects on WSC content and AAs in leaves and grain. In general, triticale was less affected by WL than the other cereals., The first author (A.M.M.-E.) was supported by FONDECYT Postdoc 3160687. The research was funded by the grants, FONDECYT N 1150353 and 1180252

Soybean (Glycine max L.) future response to elevated [CO] has been shown to differ when inoculated with B. japonicum strains isolated at ambient or elevated [CO]. Plants, inoculated with three Bradyrhizobium strains isolated at different [CO], were grown in chambers at current and elevated [CO] (400 vs. 700 ppm). Together with nodule and leaf metabolomic profile, characterization of nodule N-fixation and exchange between organs were tested through N-labeling analysis. Soybeans inoculated with SFJ14-36 strain (isolated at elevated [CO]) showed a strong metabolic imbalance, at nodule and leaf levels when grown at ambient [CO], probably due to an insufficient supply of N by nodules, as shown by N-labeling. In nodules, due to shortage of photoassimilate, C may be diverted to aspartic acid instead of malate in order to improve the efficiency of the C source sustaining N-fixation. In leaves, photorespiration and respiration were boosted at ambient [CO] in plants inoculated with this strain. Additionally, free phytol, antioxidants, and fatty acid content could be indicate induced senescence due to oxidative stress and lack of nitrogen. Therefore, plants inoculated with Bradyrhizobium strain isolated at elevated [CO] may have lost their capacity to form effective symbiosis at ambient [CO] and that was translated at whole plant level through metabolic impairment., This work was financially supported by the following grants: GRUPO Gobierno Vasco IT1022-16 and projects 32-2016-00043, 37-2017-00047, and 000049-IDA2019-38 from the Economic Development and Infrastructures Department of the Basque Country, Spain. DS was a recipient of a Ph.D. grant supported by the Public University of Navarra. AS-S was partially supported by a postdoctoral fellowship granted by the Education, and Linguistic Policy Department of the Basque Country, Spain and the Alabama Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, United States Department of Agriculture. Technical support by Azucena González, Phytotron Service, SGIker (UPV/EHU) is gratefully acknowledged.

By 2050 future global food demand is projected to require a doubling of agricultural output, and climate change will exacerbate this challenge by intensifying the exposure of field crops to abiotic stress conditions, including rising temperature, increased drought, and increased CO2 concentration ([CO2]). One of the keys to improving crop yield under different stresses is studying is photosynthesis. Photosynthetic parameters, such as the maximum rate of carboxylation of RuBP (Vc,max), and the maximum rate of electron transport driving RuBP regeneration (Jmax) vary in response to climate conditions and have been identified as a target for improvement. However, the techniques used to measure these physiological parameters are very time consuming, ranging from 30 to 70 min per measurement and require specialized personnel. Therefore, breeding or genetic mapping for these traits under these conditions is prohibitively time-consuming. Spatial and temporal variation in plant photosynthesis can be estimated using remote sensing-derived spectral vegetation indices. Spectral estimates of green vegetation biomass and vigor, including vegetation indices such as the Normalized Difference Vegetation Index (NDVI), are widely used to estimate vegetation productivity across spatial and temporal scales but are unable to provide assessments of specific photosynthetic parameters. For that reason, hyperspectral remote sensing shows promise for predicting photosynthetic capacity based on more detailed leaf optical properties. In this study, we developed and assessed estimates of Vcmax and Jmax through four different advanced regression models: PLS, BR, ARDR, and LASSO based on leaf reflectance metrics measured with an ASD FieldSpec4 Hi-RES of different crops under different environmental conditions such as (1) different varieties of soybean under high [CO2] and high temperature, (2) different varieties of peanut under drought stress and (3) 20 varieties of cotton diverse origin and grown under field conditions. Both phenotypic variability and varying levels of stress were employed with each crop to ensure adequate ranges of responses. Model sensitivities were assessed for each crop and treatment separately and in combination in order to better understand the strengths and weaknesses of each model in all the different conditions. For the combination of three species, all the models suggest a robust prediction of Vcmax around R2:0.67 and the same for the Jmax R2: 0.55.

Soybean is a crop of agronomic importance that requires adequate watering during its growth to achieve high production. In this study, we determined physiological, photochemical and metabolic differences in five soybean varieties selected from the parental lines of a nested association mapping population during mild drought. These varieties have been described as high yielding (NE3001, HY1; LD01‐5907, HY2) or drought tolerant (PI518751; HYD1; PI398881, HYD2). Nevertheless, there has been little research on the physiological traits that sustain their high productivity under water‐limited conditions. The results indicate that high‐yielding varieties under drought cope with the shortage of water by enhancing their photoprotective defences and invest in growth and productivity, linked to a higher intrinsic water use efficiency. This is the case of the variety N‐3001 (HY1), with a tolerance strategy involving a faster transition into the reproductive stage to avoid the drought period. The present study highlights the role of the physiological and biochemical adjustments of various soybean varieties to cope with water‐limited conditions. Moreover, the obtained results underscore the fact that the high phenotypic plasticity among soybean phenotypes should be exploited to compensate for the low genetic variability of this species when selecting plant productivity in constrained environments., This work was supported by grants from the Spanish Ministry of Science and Innovation and FEDER funds (AGL2014‐52396) and from the Basque Government (UPV/EHU‐GV IT‐1018‐16; IT‐932‐16). J.B. is a holder of a PhD fellowship from the Public University of Navarre. R.E. received a Juan de la Cierva‐incorporación grant (IJCI‐2014‐21452).

23 Pags.- 4 Figs. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license., Increased periods of water shortage and higher temperatures, together with a reduction in nutrient availability, have been proposed as major factors that negatively impact plant development. Photosynthetic CO2 assimilation is the basis of crop production for animal and human food, and for this reason, it has been selected as a primary target for crop phenotyping/breeding studies. Within this context, knowledge of the mechanisms involved in the response and acclimation of photosynthetic CO2 assimilation to multiple changing environmental conditions (including nutrients, water availability, and rising temperature) is a matter of great concern for the understanding of plant behavior under stress conditions, and for the development of new strategies and tools for enhancing plant growth in the future. The current review aims to analyze, from a multi-perspective approach (ranging across breeding, gas exchange, genomics, etc.) the impact of changing environmental conditions on the performance of the photosynthetic apparatus and, consequently, plant growth., This work was supported by the Spanish Innovation and Universities Ministry (AGL2016-79868-R; PCIN-2017-007).

The increase in the atmospheric CO

The increase in the atmospheric CO concentration is predicted to influence wheat production and grain quality and nutritional properties. In the present study, durum wheat (Triticum durum Desf. cv. Sula) was grown under two different CO (400 versus 700 μmol mol) concentrations to examine effects on the crop yield and grain quality at different phenological stages (from grain filling to maturity). Exposure to elevated CO significantly increased aboveground biomass and grain yield components. Growth at elevated CO diminished the elemental N content as well as protein and free amino acids, with a typical decrease in glutamine, which is the most represented amino acid in grain proteins. Such a general decrease in nitrogenous compounds was associated with altered kinetics of protein accumulation, N remobilization, and N partitioning. Our results highlight important modifications of grain metabolism that have implications for its nutritional quality., This work was supported by the Spanish Ministry of Science and Innovation (AGL2016-79868-R).

The total area under quinoa (Chenopodium quinoa Willd.) cultivation and the consumption of its grain have increased in recent years because of its nutritional properties and ability to grow under adverse conditions, such as drought. Climate change scenarios predict extended periods of drought and this has emphasized the need for new crops that are tolerant to these conditions. The main goal of this work was to evaluate crop yield and quality parameters and to characterize the physiology of two varieties of quinoa grown under water deficit in greenhouse conditions. Two varieties of quinoa from the Chilean coast (Rainbow) and altiplano (Illpa) were used, grown under full irrigation or two different levels of water deficit applied during the grain filling period. There were no marked differences in yield and quality parameters between treatments, but the root biomass was higher in plants grown under severe water deficit conditions compared to control. Photosynthesis, transpiration and stomatal conductance decreased with increased water stress in both cultivars, but the coastal variety showed higher water use efficiency and less discrimination of 13C under water deficit. This response was associated with greater root development and a better stomatal opening adjustment, especially in the case of Rainbow. The capacity of Rainbow to increase its osmoregulant content (compounds such as proline, glutamine, glutamate, K and Na) could enable a potential osmotic adjustment in this variety. Moreover, the lower stomatal opening and transpiration rates were also associated with higher leaf ABA concentration values detected in Rainbow. We found negative logarithmic relationships between stomatal conductance and leaf ABA concentration in both varieties, with significant R2 values of 0.50 and 0.22 in Rainbow and Illpa, respectively. These moderate-to-medium values suggest that, in addition to ABA signaling, other causes for stomatal closure in quinoa under drought such as hydraulic regulation may play a role. In conclusion, this work showed that two quinoa cultivars use different strategies in the face of water deficit stress, and these prevent decreases in grain yield and quality under drought conditions., This work was supported by the Government of Navarre (Rural Development, Environment and Local Administration unit)-FEADER (210160009).

The predicted increase in atmospheric CO concentration [CO] is expected to enhance photosynthesis and seed yield in crops such as soybean [Glycine max (L.) Merr.]. However, future breeding for high water use efficiency (WUE) could interfere with the amount of carbon (C) fixed by leaves and seed mineral composition under elevated [CO] due to lower stomatal conductance (g). In the present study, two genotypes with contrasting WUE were grown in open top chambers (OTC) under ambient (410 ppm; a[CO]) and elevated (610 ppm; e[CO]). In order to test performance of both cultivars to changing CO conditions, growth, photosynthetic performance (leaf and canopy level) and seed mineral composition were analyzed. The low WUE genotype had a greater response to e[CO] in terms of leaf daily photosynthetic C gain due to greater g, which was compensated in the high WUE genotype by an increase in leaf area (LA). However, in the low WUE genotype, improved daily photosynthetic C gain did not translate into greater biomass or seed yield [CO] response compared to the high WUE genotype, suggesting better assimilate partitioning by the high WUE genotype. In terms of seed composition, the high WUE genotype generally had lower mineral concentrations at e[CO] compared to a[CO], but greater total amounts of nutrient (due to higher seed yield) under e[CO] compared to the low WUE genotype. Findings presented here highlight importance of genetic variation in soybean response to future atmospheric [CO] which should be considered when breeding for future climates., David Soba is the recipient of a PhD grant supported by the Public University of Navarra, and was the recipient of a travel grant from the same institution. This project was partially funded by the Alabama Soybean Farmers Association, the Alabama agricultural experiment station and the Hatch program of the National Institute of Food and agriculture, U.S. department of Agriculture.

Alfalfa (Medicago sativa L.) is frequently constrained by environmental conditions such as drought. Within this context, it is crucial to identify the physiological and metabolic traits conferring a better performance under stressful conditions. In the current study, two alfalfa cultivars (San Isidro and Zhong Mu) with different physiological strategies were selected and subjected to water limitation conditions. Together with the physiological analyses, we proceeded to characterize the isotopic, hormone, and metabolic profiles of the different plants. According to physiological and isotopic data, Zhong Mu has a water-saver strategy, reducing water lost by closing its stomata but fixing less carbon by photosynthesis, and therefore limiting its growth under water-stressed conditions. In contrast, San Isidro has enhanced root growth to replace the water lost through transpiration due to its more open stomata, thus maintaining its biomass. Zhong Mu nodules were less able to maintain nodule N2 fixing activity (matching plant nitrogen (N) demand). Our data suggest that this cultivar-specific performance is linked to Asn accumulation and its consequent N-feedback nitrogenase inhibition. Additionally, we observed a hormonal reorchestration in both cultivars under drought. Therefore, our results showed an intra-specific response to drought at physiological and metabolic levels in the two alfalfa cultivars studied., This work was supported by the i-COOP-suelos y legumbres (2016SU0016) call funded by the National Research Council. David Soba is the recipient of a PhD grant supported by the Public University of Navarra

Although the biosynthesis and function of tocochromanols in leaves and seeds have been extensively studied, their occurrence and function in underground tissues, such as roots and nodules, is very poorly understood. Here, we performed a comparative study of the presence of tocochromanols in different plant organs (leaves, roots and nodules) of three legumes (soybean, alfalfa and pea plants). Additionally, we measured variations in tocochromanols as a function of the severity of water stress and evaluated their relationship with the extent of membrane lipid peroxidation and nodule performance (as indicated by thiobarbituric acid-reactive substances assay and 15N isotope labeling, respectively). Results showed the presence of endogenous tocopherols, mainly α-tocopherol, in the three studied organs of the three legumes. Nodules showed higher concentrations of α-tocopherol than roots, but lower than leaves. α-Tocopherol content increased under water shortage in nodules, roots and leaves of soybean as well as in roots of alfalfa, but not in the other plant systems. A strong negative correlation between α-tocopherol and thiobarbituric acid-reactive substances contents was found for roots and especially for nodules. Furthermore, nodule α-tocopherol content positively correlated with nodule N2 fixation (estimated by 15N isotope labeling). We conclude that α-tocopherol is a major antioxidant found in legume nodules.

Anthropogenic heavy metal pollution is an important health issue in urban areas, and therefore rapid and inexpensive monitoring in time and space is desirable. This study aimed (i) to assess the suitability of Tilia cordata leaves as a valuable heavy metal bioindicator, including seasonal changes in concentrations and (ii) to evaluate the use of leaf carbon and nitrogen isotope composition (δC and δN) as novel indicators of urban heavy metal pollution. Leaves were collected from three different pollution intensity locations (Bilbao, Vitoria, and Muskiz) in the Basque Country (northern Spain). Analysis of leaf heavy metals related to traffic emissions and δC and δN determinations were carried out during July-October 2018. Leaf samples from Bilbao, the most populated and traffic-intense location, showed the highest concentration of heavy metals (mainly from polluted air). Additionally, the two urban areas, Bilbao and Vitoria, showed stronger correlation between these heavy metals, indicating a traffic-related source of emissions. The source of contamination (soil or air) in relation to elements and optimal sampling time is discussed herein. On the other hand, Pearson correlation analysis revealed significant trends between leaf δC and δN and the studied heavy metals, especially Pb, Cr and Cd, supporting the hypothesis of δC and δN as tools to distinguish locations according to their heavy metal pollution levels. To our knowledge, this is the first time that δC and δN have been used as monitoring tools in heavy metal pollution and consequently more research is still needed to calibrate this tool through extensive vegetation screening., This research was supported by the Spanish Government [AGL2015-64481-C2-1-R] and the Basque Government [UPV/EHU-GV IT-1018-16]. The authors would like to thank Leire Martínez de Butron and Jon Madariaga for their support with the leaf sampling. RE received a Juan de la Cierva incorporation contract IJCI-2014-21452.