Scientific and technological advances in the development of sustainable disease management tools: a case study on kiwifruit bacterial canker.

Plant disease outbreaks are increasing in a world facing climate change and globalized markets, representing a serious threat to food security. Kiwifruit Bacterial Canker (KBC), caused by the bacterium Pseudomonas syringae pv. actinidiae (Psa), was selected as a case study for being an example of a pandemic disease that severely impacted crop production, leading to huge economic losses, and for the effort that has been made to control this disease. This review provides an in-depth and critical analysis on the scientific progress made for developing alternative tools for sustainable KBC management. Their status in terms of technological maturity is discussed and a set of opportunities and threats are also presented. The gradual replacement of susceptible kiwifruit cultivars, with more tolerant ones, significantly reduced KBC incidence and was a major milestone for Psa containment - which highlights the importance of plant breeding. Nonetheless, this is a very laborious process. Moreover, the potential threat of Psa evolving to more virulent biovars, or resistant lineages to existing control methods, strengthens the need of keep on exploring effective and more environmentally friendly tools for KBC management. Currently, plant elicitors and beneficial fungi and bacteria are already being used in the field with some degree of success. Precision agriculture technologies, for improving early disease detection and preventing pathogen dispersal, are also being developed and optimized. These include hyperspectral technologies and forecast models for Psa risk assessment, with the latter being slightly more advanced in terms of technological maturity. Additionally, plant protection products based on innovative formulations with molecules with antibacterial activity against Psa (e.g., essential oils, phages and antimicrobial peptides) have been validated primarily in laboratory trials and with few compounds already reaching field application. The lessons learned with this pandemic disease, and the acquired scientific and technological knowledge, can be of importance for sustainably managing other plant diseases and handling future pandemic outbreaks.

Effect of the Interaction between Elevated Carbon Dioxide and Iron Limitation on Proteomic Profiling of Soybean.

Elevated atmospheric CO2 (eCO2) and iron (Fe) availability are important factors affecting plant growth that may impact the proteomic profile of crop plants. In this study, soybean plants treated under Fe-limited (0.5 mM) and Fe-sufficient (20 mM) conditions were grown at ambient (400 µmol mol-1) and eCO2 (800 µmol mol-1) in hydroponic solutions. Elevated CO2 increased biomass from 2.14 to 3.14 g plant-1 and from 1.18 to 2.91 g plant-1 under Fe-sufficient and Fe-limited conditions, respectively, but did not affect leaf photosynthesis. Sugar concentration increased from 10.92 to 26.17 µmol g FW-1 in roots of Fe-sufficient plants and from 8.75 to 19.89 µmol g FW-1 of Fe-limited plants after exposure to eCO2. In leaves, sugar concentration increased from 33.62 to 52.22 µmol g FW-1 and from 34.80 to 46.70 µmol g FW-1 in Fe-sufficient and Fe-limited conditions, respectively, under eCO2. However, Fe-limitation decreases photosynthesis and biomass. Pathway enrichment analysis showed that cell wall organization, glutathione metabolism, photosynthesis, stress-related proteins, and biosynthesis of secondary compounds changed in root tissues to cope with Fe-stress. Moreover, under eCO2, at sufficient or limited Fe supply, it was shown an increase in the abundance of proteins involved in glycolysis, starch and sucrose metabolism, biosynthesis of plant hormones gibberellins, and decreased levels of protein biosynthesis. Our results revealed that proteins and metabolic pathways related to Fe-limitation changed the effects of eCO2 and negatively impacted soybean production.

Effect of alkaline and deep eutectic solvents pretreatments on the recovery of lignin with antioxidant activity from grape stalks.

Grape stalks are lignocellulosic residues that can be valorized through the extraction of lignin - an underutilized biopolymer with high potential. Two lignin extraction methods, alkaline and deep eutectic solvents (DES), were studied, and experimental designs were carried out to obtain the best extraction conditions. The defined parameters for alkaline extraction allowed the recovery of ~48 % of lignin with low purity that was further improved with an autohydrolysis pretreatment (~79 % purity; ~32 % yield). Optimum parameters of DES method rendered high purity lignin (~90 %) without the need of a pretreatment and with a better yield (50.2 % (±2.3)) than the alkaline method. Both lignin fractions presented high antioxidant activities, being close to the antioxidant capacity of BHT for DPPH scavenging. Structural analysis proved the presence of lignin in both alkaline and DES samples with similar morphology. Overall, DES method was more efficient in the extraction of lignin from grape stalks besides its greener and sustainable nature. This work uses DES to extract lignin from this biomass while comparing it with a commonly classical method, proving that grape stalks can be used to extract lignin with a sustainable and efficient method rendering a final ingredient with value-added properties.

Evaluation of plant elicitation with methyl-jasmonate, salicylic acid and benzo (1,2,3)-thiadiazole-7-carbothioic acid-S-methyl ester for the sustainable management of the pine wilt disease.

Treatment with plant elicitors can be a promising method to induce Pinus pinaster tolerance against the pinewood nematode (PWN), Bursaphelenchus xylophilus, by promoting plant antioxidant system, micronutrient accumulation and by modulating plant-associated bacterial populations. To test this hypothesis, plants were sprayed with methyl jasmonate (MeJA), salicylic acid (SA) or benzo (1,2,3)-thiadiazole-7-carbothioic acid-S-methyl ester (BTH), and evaluated until 35 days after-inoculation (dai) for: i) extent of foliar symptoms; ii) nematode density inside stem tissues; iii) proxies for oxidative damage and antioxidant activity, iv) micronutrient concentration and v) bacterial diversity. Compared with non-elicited plants, plant elicitation, particularly with BTH, significantly decreased nematodes density inside stem tissues (by 0.63-fold). Concordantly, without elicitation plant mortality reached 12.5% while no mortality was observed in elicited plants. BTH-elicited plants had significantly higher concentrations of anthocyanins and carotenoids at the end of the assay than SA-elicited and MeJA-elicited plants, which possibly contributed to the lower PWN colonization and degree of foliar symptoms observed. Accordingly, MeJA and SA led to increased lipid peroxidation at 28 dai (by 2.64- and 2.52-fold, respectively) in comparison with BTH (by 1.10-fold), corroborating its higher potential in increasing plant antioxidative response during infection. Moreover, carotenoids showed a negative correlation with nematode migration, whereas polyphenols showed a positive correlation. Elicitors also induced changes in the bacterial community of infected P. pinaster plants, increasing the diversity of specific populations. Finally, elicitors induced significant changes in micronutrients accumulation in plant tissues, namely a decrease in the concentration of B, Mn and Ni in plants treated with BTH compared to those treated with the other elicitors. Altogether, results suggest that elicitation with MeJA, SA and, particularly, BTH, increases tolerance against B. xylophilus by promoting plant antioxidant system, changing the accumulation of essential micronutrients and modulating plant-associated bacterial diversity.

Widening the Perspectives for Legume Consumption: The Case of Bioactive Non-nutrients.

Legume grains have provided essential nutrients in human diets for centuries, being excellent sources of proteins, carbohydrates, fatty acids, and fibers. They also contain several non-nutrients that historically have been connotated as toxic but that in recent years have been shown to have interesting bioactive properties. The discussion on the role of bioactive non-nutrients is becoming more important due to increasing science-based evidence on their potential antioxidant, hypoglycemic, hypolipidemic, and anticarcinogenic properties. At a time when legume-based products consumption is being strongly promoted by national governments and health authorities, there is a need to clearly define the recommended levels of such non-nutrients in human diets. However, there is insufficient data determining the ideal amount of non-nutrients in legume grains, which will exert the most positive health benefits. This is aligned with insufficient studies that clearly demonstrate if the positive health effects are due to the presence of specific non-nutrients or a result of a dietary balance. In fact, rather than looking directly at the individual food components, most nutritional epidemiology studies relate disease risk with the food and dietary patterns. The purpose of this perspective paper is to explore different types of non-nutrients present in legume grains, discuss the current evidence on their health benefits, and provide awareness for the need for more studies to define a recommended amount of each compound to identify the best approaches, either to enhance or reduce their levels.

Defence-related pathways, phytohormones and primary metabolism are key players in kiwifruit plant tolerance to Pseudomonas syringae pv. actinidiae.

The reasons underlying the differential tolerance of Actinidia spp. to the pandemic pathogen Pseudomonas syringae pv. actinidiae (Psa) have not yet been elucidated. We hypothesized that differential plant-defence strategies linked to transcriptome regulation, phytohormones and primary metabolism might be key and that Actinidia chinensis susceptibility results from an inefficient activation of defensive mechanisms and metabolic impairments shortly following infection. Here, 48 h postinoculation bacterial density was 10-fold higher in A. chinensis var. deliciosa than in Actinidia arguta, accompanied by significant increases in glutamine, ornithine, jasmonic acid (JA) and salicylic acid (SA) (up to 3.2-fold). Actinidia arguta showed decreased abscisic acid (ABA) (0.7-fold), no changes in primary metabolites, and 20 defence-related genes that were only differentially expressed in this species. These include GLOX1, FOX1, SN2 and RBOHA, which may contribute to its higher tolerance. Results suggest that A. chinensis' higher susceptibility to Psa is due to an inefficient activation of plant defences, with the involvement of ABA, JA and SA, leading to impairments in primary metabolism, particularly the ammonia assimilation cycle. A schematic overview on the interaction between Psa and genotypes with distinct tolerance is provided, highlighting the key transcriptomic and metabolomic aspects contributing to the different plant phenotypes after infection.

Foliar application of 3-hydroxy-4-pyridinone Fe-chelate [Fe(mpp)3 ] induces responses at the root level amending iron deficiency chlorosis in soybean.

Iron (Fe) deficiency chlorosis (IDC) affects the growth of several crops, especially when growing in alkaline soils. The application of synthetic Fe-chelates is one of the most commonly used strategies in IDC amendment, despite their associated negative environmental impacts. In a previous work, the Fe-chelate tris(3-hydroxy-1-(H)-2-methyl-4-pyridinonate) iron(III) [Fe(mpp)3 ] has shown great potential for alleviating IDC in soybean (Glycine max) in the early stages of plant development under hydroponic conditions. Herein, its efficacy was verified under soil conditions in soybean grown from seed to full maturity. Chlorophyll levels, plant growth, root and shoot mineral accumulation (K, Mg, Ca, Na, P, Mn, Zn, Ni, and Co) and FERRITIN expression were accessed at V5 phenological stage. Compared to a commonly used Fe chelate, FeEDDHA, supplementation with [Fe(mpp)3 ] led to a 29% higher relative chlorophyll content, 32% higher root biomass, 36% higher trifoliate Fe concentration, and a twofold increase in leaf FERRITIN gene expression. [Fe(mpp)3 ] supplementation also resulted in increased accumulation of P, K, Zn, and Co. At full maturity, the remaining plants were harvested and [Fe(mpp)3 ] application led to a 32% seed yield increase when compared to FeEDDHA. This is the first report on the use of [Fe(mpp)3 ] under alkaline soil conditions for IDC correction, and we show that its foliar application has a longer-lasting effect than FeEDDHA, induces efficient root responses, and promotes the uptake of other nutrients.

Understanding the Role of the Antioxidant System and the Tetrapyrrole Cycle in Iron Deficiency Chlorosis.

Iron deficiency chlorosis (IDC) is an abiotic stress often experienced by soybean, owing to the low solubility of iron in alkaline soils. Here, soybean lines with contrasting Fe efficiencies were analyzed to test the hypothesis that the Fe efficiency trait is linked to antioxidative stress signaling via proper management of tissue Fe accumulation and transport, which in turn influences the regulation of heme and non heme containing enzymes involved in Fe uptake and ROS scavenging. Inefficient plants displayed higher oxidative stress and lower ferric reductase activity, whereas root and leaf catalase activity were nine-fold and three-fold higher, respectively. Efficient plants do not activate their antioxidant system because there is no formation of ROS under iron deficiency; while inefficient plants are not able to deal with ROS produced under iron deficiency because ascorbate peroxidase and superoxide dismutase are not activated because of the lack of iron as a cofactor, and of heme as a constituent of those enzymes. Superoxide dismutase and peroxidase isoenzymatic regulation may play a determinant role: 10 superoxide dismutase isoenzymes were observed in both cultivars, but iron superoxide dismutase activity was only detected in efficient plants; 15 peroxidase isoenzymes were observed in the roots and trifoliate leaves of efficient and inefficient cultivars and peroxidase activity levels were only increased in roots of efficient plants.

Biochemical markers to predict internal browning disorders in 'Rocha' pear during storage under high CO2.

BACKGROUND: The aim of this study was to identify biochemical markers to predict internal browning disorders (IBD) in 'Rocha' pear. Fruits from five orchards were stored for 45 days under cold air followed by 100 days in browning-inducing controlled atmosphere (CA) conditions (1 kPa O2 + 10 kPa CO2 ). RESULTS: Relationships between concentrations of ethanol (EtOH), acetaldehyde (AcDH) and ascorbic acid (AA), activities of peroxidase (POX) and polyphenoloxidase (PPO) and IBD incidence were established. The partial least square (PLS) model using the most promising markers, EtOH and AcDH, explained 89% of the variance in IBD incidence, whereas the univariate models based on the same markers explained between 89 and 94%. In contrast, the models based on AA levels and AA depletion rate only explained 57 and 82% of the variance in IBD incidence respectively. Model validation confirmed the robustness of EtOH for the prediction (R2 = 0.91, RMSE = 11.1) and allowed proposing a threshold level of 30 µL EtOH L-1 above which IBD may occur. Using this threshold value, the storage time limit associated with the occurrence of the first IBD symptoms was predicted with an acceptable RMSE of 9 days. CONCLUSION: This work clearly identifies biochemical IBD markers for 'Rocha' pear and shows that dynamic changes in ethanol concentration during the beginning of storage may be used to predict IBD development. Therefore the results presented herein represent a major step forward in the prediction of IBD in 'Rocha' pear. © 2017 Society of Chemical Industry.

Iron biofortification in the 21st century: setting realistic targets, overcoming obstacles, and new strategies for healthy nutrition.

Plant-based foods offer a wide range of nutrients that are essential for human and animal health. Among these nutrients, iron stands out as one of the most important micronutrients. Increasing the iron content in many staple and non-staple plant foods continues to be a goal of many scientists around the world. However, the success of such initiatives has sometimes fallen short of their expected targets. In this review we highlight the most recent and promising results that have contributed to increasing the iron content in different crops. We also discuss methods that to date have been used to reach iron biofortification goals and new strategies that we believe are most promising for crop biofortification in the future. Plant anatomical, physiological and metabolic hurdles still need to be tackled for making progress on further increasing currently reached levels of micronutrient improvements. New strategies need to take into account growing environmental challenges that may constrain biofortification efforts.

Effect of tris(3-hydroxy-4-pyridinonate) iron(III) complexes on iron uptake and storage in soybean (Glycine max L.).

Iron deficiency chlorosis (IDC) is a serious environmental problem affecting the growth of several crops in the world. The application of synthetic Fe(III) chelates is still one of the most common measures to correct IDC and the search for more effective Fe chelates remains an important issue. Herein, we propose a tris(3-hydroxy-4-pyridinonate) iron(III) complex, Fe(mpp)3, as an IDC corrector. Different morphological, biochemical and molecular parameters were assessed as a first step towards understanding its mode of action, compared with that of the commercial fertilizer FeEDDHA. Plants treated with the pyridinone iron(III) complexes were significantly greener and had increased biomass. The total Fe content was measured using ICP-OES and plants treated with pyridinone complexes accumulated about 50% more Fe than those treated with the commercial chelate. In particular, plants supplied with compound Fe(mpp)3 were able to translocate iron from the roots to the shoots and did not elicit the expression of the Fe-stress related genes FRO2 and IRT1. These results suggest that 3,4-HPO iron(III) chelates could be a potential new class of plant fertilizing agents.

Biochemical Basis of CO2-Related Internal Browning Disorders in Pears (Pyrus communis L. cv. Rocha) during Long-Term Storage.

This study aimed at understanding the biochemical basis of internal browning disorders (IBDs) in 'Rocha' pear. For this purpose, the effects of storage under normal controlled atmosphere (CA) (3 kPa of O2 + 0.5 kPa of CO2) and IBD-inducing CA (1 kPa of O2 + 10 kPa of CO2) on the antioxidant and fermentative metabolisms and polyphenol oxidase (PPO) activity and phenolics concentration were studied. The higher IBD incidence in high CO2-stored fruits was positively correlated with fermentative metabolites and negatively with ascorbate and H2O2 concentrations, and it was linked to PPO activation. These results indicate that both the antioxidant and fermentative metabolisms are involved in the occurrence of IBD in 'Rocha' pear. From the integration of the biochemical and enzymatic data, a schematic model illustrating the effects of high CO2 and low O2 in 'Rocha' pears during long-term storage was constructed.

Susceptibility to the pinewood nematode (PWN) of four pine species involved in potential range expansion across Europe.

The pine wilt disease (PWD), caused by the pinewood nematode (PWN) Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, is one of the most serious threats to pine forests worldwide. Here we studied several components of susceptibility to PWN infection in a model group of pine species widely distributed in Europe (Pinus pinaster Ait., P. pinea L., P. sylvestris L. and P. radiata D. Don), specifically concerning anatomical and chemical traits putatively related to nematode resistance, whole-plant nematode population after experimental inoculation, and several biochemical and physiological traits indicative of plant performance, damage and defensive responses 60 days post inoculation (dpi) in 3-year-old plants. Pinus pinaster was the most susceptible species to PWN colonization, with a 13-fold increase in nematode population size following inoculation, showing up to 35-fold more nematodes than the other species. Pinus pinea was the most resistant species, with an extremely reduced nematode population 60 dpi. Axial resin canals were significantly wider in P. pinaster than in the other species, which may have facilitated nematode dispersal through the stem and contributed to its high susceptibility; nevertheless, this trait does not seem to fully determinate the susceptible character of a species, as P. sylvestris showed similar nematode migration rates to P. pinaster but narrower axial resin canals. Nematode inoculation significantly affected stem water content and polyphenolic concentration, and leaf chlorophyll and lipid peroxidation in all species. In general, P. pinaster and P. sylvestris showed similar chemical responses after infection, whereas P. radiata, which co-exists with the PWN in its native range, showed some degree of tolerance to the nematode. This work provides evidence that the complex interactions between B. xylophilus and its hosts are species-specific, with P. pinaster showing a strong susceptibility to the pathogen, P. pinea being the most tolerant species, and P. sylvestris and P. radiata having a moderate susceptibility, apparently through distinct coping mechanisms.

Iron partitioning at an early growth stage impacts iron deficiency responses in soybean plants (Glycine max L.).

Iron (Fe) deficiency chlorosis (IDC) leads to leaf yellowing, stunted growth and drastic yield losses. Plants have been differentiated into 'Fe-efficient' (EF) if they resist to IDC and 'Fe-inefficient' (IN) if they do not, but the reasons for this contrasting efficiency remain elusive. We grew EF and IN soybean plants under Fe deficient and Fe sufficient conditions and evaluated if gene expression and the ability to partition Fe could be related to IDC efficiency. At an early growth stage, Fe-efficiency was associated with higher chlorophyll content, but Fe reductase activity was low under Fe-deficiency for EF and IN plants. The removal of the unifoliate leaves alleviated IDC symptoms, increased shoot:root ratio, and trifoliate leaf area. EF plants were able to translocate Fe to the aboveground plant organs, whereas the IN plants accumulated more Fe in the roots. FRO2-like gene expression was low in the roots; IRT1-like expression was higher in the shoots; and ferritin was highly expressed in the roots of the IN plants. The efficiency trait is linked to Fe partitioning and the up-regulation of Fe-storage related genes could interfere with this key process. This work provides new insights into the importance of mineral partitioning among different plant organs at an early growth stage.

Cultivar variability of iron uptake mechanisms in rice (Oryza sativa L.).

Rice (Oryza sativa L.) is the most important staple food in the world. It is rich in genetic diversity and can grow in a wide range of environments. Iron (Fe) deficiency is a major abiotic stress in crop production and in aerobic soils, where Fe forms insoluble complexes, and is not readily available for uptake. To cope with Fe deficiency, plants developed mechanisms for Fe uptake, and although rice was described as a Strategy II plant, recent evidence suggests that it is capable of utilizing mechanisms from both Strategies. The main objective of this work was to compare two cultivars, Bico Branco (japonica) and Nipponbare (tropical japonica), to understand if the regulation of Fe uptake mechanisms could be cultivar (cv.)dependent. Plants of both cultivars were grown under Fe-deficient and -sufficient conditions and physiological and molecular responses to Fe deficiency were evaluated. Bico Branco cv. developed more leaf chlorosis and was more susceptible to Fe deficiency, retaining more nutrients in roots, than Nipponbare cv., which translocated more nutrients to shoots. Nipponbare cv. presented higher levels of Fe reductase activity, which was significantly up-regulated by Fe deficiency, and had higher expression levels of the Strategy I-OsFRO2 gene in roots, while Bico Branco cv. induced more genes involved in Strategy II.These new findings show that rice cultivars have different responses to Fe deficiency and that the induction of Strategy I or II may be rice cultivar-dependent, although the utilization of the reduction mechanisms seems to be an ubiquitous advantage.

Evaluation of constitutive iron reductase (AtFRO2) expression on mineral accumulation and distribution in soybean (Glycine max. L).

Iron is an important micronutrient in human and plant nutrition. Adequate iron nutrition during crop production is central for assuring appropriate iron concentrations in the harvestable organs, for human food or animal feed. The whole-plant movement of iron involves several processes, including the reduction of ferric to ferrous iron at several locations throughout the plant, prior to transmembrane trafficking of ferrous iron. In this study, soybean plants that constitutively expressed the AtFRO2 iron reductase gene were analyzed for leaf iron reductase activity, as well as the effect of this transgene's expression on root, leaf, pod wall, and seed mineral concentrations. High Fe supply, in combination with the constitutive expression of AtFRO2, resulted in significantly higher concentrations of different minerals in roots (K, P, Zn, Ca, Ni, Mg, and Mo), pod walls (Fe, K, P, Cu, and Ni), leaves (Fe, P, Cu, Ca, Ni, and Mg) and seeds (Fe, Zn, Cu, and Ni). Leaf and pod wall iron concentrations increased as much as 500% in transgenic plants, while seed iron concentrations only increased by 10%, suggesting that factors other than leaf and pod wall reductase activity were limiting the translocation of iron to seeds. Protoplasts isolated from transgenic leaves had three-fold higher reductase activity than controls. Expression levels of the iron storage protein, ferritin, were higher in the transgenic leaves than in wild-type, suggesting that the excess iron may be stored as ferritin in the leaves and therefore unavailable for phloem loading and delivery to the seeds. Also, citrate and malate levels in the roots and leaves of transgenic plants were significantly higher than in wild-type, suggesting that organic acid production could be related to the increased accumulation of minerals in roots, leaves, and pod walls, but not in the seeds. All together, these results suggest a more ubiquitous role for the iron reductase in whole-plant mineral accumulation and distribution.

Nuclear magnetic resonance metabolomics of iron deficiency in soybean leaves.

Iron (Fe) deficiency is an important agricultural concern that leads to lower yields and crop quality. A better understanding of the condition at the metabolome level could contribute to the design of strategies to ameliorate Fe-deficiency problems. Fe-sufficient and Fe-deficient soybean leaf extracts and whole leaves were analyzed by liquid (1)H nuclear magnetic resonance (NMR) and high-resolution magic-angle spinning NMR spectroscopy, respectively. Overall, 30 compounds were measurable and identifiable (comprising amino and organic acids, fatty acids, carbohydrates, alcohols, polyphenols, and others), along with 22 additional spin systems (still unassigned). Thus, metabolite differences between treatment conditions could be evaluated for different compound families simultaneously. Statistically relevant metabolite changes upon Fe deficiency included higher levels of alanine, asparagine/aspartate, threonine, valine, GABA, acetate, choline, ethanolamine, hypoxanthine, trigonelline, and polyphenols and lower levels of citrate, malate, ethanol, methanol, chlorogenate, and 3-methyl-2-oxovalerate. The data indicate that the main metabolic impacts of Fe deficiency in soybean include enhanced tricarboxylic acid cycle activity, enhanced activation of oxidative stress protection mechanisms and enhanced amino acid accumulation. Metabolites showing accumulation differences in Fe-starved but visually asymptomatic leaves could serve as biomarkers for early detection of Fe-deficiency stress.

High relative air humidity influences mineral accumulation and growth in iron deficient soybean plants.

Iron (Fe) deficiency chlorosis (IDC) in soybean results in severe yield losses. Cultivar selection is the most commonly used strategy to avoid IDC but there is a clear interaction between genotype and the environment; therefore, the search for quick and reliable tools to control this nutrient deficiency is essential. Several studies showed that relative humidity (RH) may influence the long distance transport of mineral elements and the nutrient status of plants. Thus, we decided to analyze the response of an "Fe-efficient" (EF) and an "Fe-inefficient" (INF) soybean accession grown under Fe-sufficient and deficient conditions under low (60%) and high (90%) RH, evaluating morphological, and physiological parameters. Furthermore, the mineral content of different plant organs was analyzed. Our results showed beneficial effects of high RH in alleviating IDC symptoms as seen by increased SPAD values, higher plant dry weight (DW), increased plant height, root length, and leaf area. This positive effect of RH in reducing IDC symptoms was more pronounced in the EF accession. Also, Fe content in the different plant organs of the EF accession grown under deficient conditions increased with RH. The lower partitioning of Fe to roots and stems of the EF accessions relative to dry matter also supported our hypothesis, suggesting a greater capacity of this accession in Fe translocation to the aerial parts under Fe deficient conditions, when grown under high RH.