Root system architecture variation among barley (Hordeum vulgare L.) accessions at seedling stage under soil acidity condition.

MAIN CONCLUSION: Soil acidity in Ethiopian highlands impacts barley production, affecting root system architecture. Study on 300 accessions showed significant trait variability, with potential for breeding enhancement. Soil acidity poses a significant challenge to crop production in the highland regions of Ethiopia, particularly impacting barley, a crucial staple crop. This acidity serves as a key stressor affecting the root system architecture (RSA) of this crop. Hence, the objective of this study was to assess the RSA traits variability under acidic soil conditions using 300 barley accessions in a greenhouse experiment. The analysis of variance indicated substantial variations among the accessions across all traits studied. The phenotypic coefficient of variation ranged from 24.4% for shoot dry weight to 11.1% for root length, while the genotypic coefficient variation varied between 18.83 and 9.2% for shoot dry weight and root length, respectively. The broad-sense heritability ranged from 36.7% for leaf area to 69.9% for root length, highlighting considerable heritability among multiple traits. The genetic advances as a percent of the mean ranged from 13.63 to 29.9%, suggesting potential for enhancement of these traits through breeding efforts. Principal component analysis and cluster analysis grouped the genotypes into two major clusters, each containing varying numbers of genotypes with contrasting traits. This diverse group presents an opportunity to access a wide range of potential parent candidates to enhance genetic variablity in breeding programs. The Pearson correlation analysis revealed significant negative associations between root angle (RA) and other RSA traits. This helps indirect selection of accessions for further improvement in soil acidity. In conclusion, this study offers valuable insights into the RSA characteristics of barley in acidic soil conditions, aiding in the development of breeding strategies to enhance crop productivity in acidic soil environments.

Silicon regulates phosphate deficiency through involvement of auxin and nitric oxide in barley roots.

MAIN CONCLUSION: Silicon application mitigates phosphate deficiency in barley through an interplay with auxin and nitric oxide, enhancing growth, photosynthesis, and redox balance, highlighting the potential of silicon as a fertilizer for overcoming nutritional stresses. Silicon (Si) is reported to attenuate nutritional stresses in plants, but studies on the effect of Si application to plants grown under phosphate (Pi) deficiency are still very scarce, especially in barley. Therefore, the present work was undertaken to investigate the potential role of Si in mitigating the adverse impacts of Pi deficiency in barley Hordeum vulgare L. (var. BH902). Further, the involvement of two key regulatory signaling molecules--auxin and nitric oxide (NO)--in Si-induced tolerance against Pi deficiency in barley was tested. Morphological attributes, photosynthetic parameters, oxidative stress markers (O2·-, H2O2, and MDA), antioxidant system (enzymatic--APX, CAT, SOD, GR, DHAR, MDHAR as well as non-enzymatic--AsA and GSH), NO content, and proline metabolism were the key traits that were assessed under different treatments. The P deficiency distinctly declined growth of barley seedlings, which was due to enhancement in oxidative stress leading to inhibition of photosynthesis. These results were also in parallel with an enhancement in antioxidant activity, particularly SOD and CAT, and endogenous proline level and its biosynthetic enzyme (P5CS). The addition of Si exhibited beneficial effects on barley plants grown in Pi-deficient medium as reflected in increased growth, photosynthetic activity, and redox balance through the regulation of antioxidant machinery particularly ascorbate-glutathione cycle. We noticed that auxin and NO were also found to be independently participating in Si-mediated improvement of growth and other parameters in barley roots under Pi deficiency. Data of gene expression analysis for PHOSPHATE TRANSPORTER1 (HvPHT1) indicate that Si helps in increasing Pi uptake as per the need of Pi-deficient barley seedlings, and also auxin and NO both appear to help Si in accomplishing this task probably by inducing lateral root formation. These results are suggestive of possible application of Si as a fertilizer to correct the negative effects of nutritional stresses in plants. Further research at genetic level to understand Si-induced mechanisms for mitigating Pi deficiency can be helpful in the development of new varieties with improved tolerance against Pi deficiency, especially for cultivation in areas with Pi-deficient soils.

Transcriptome and metabolome analyses reveal molecular insights into waterlogging tolerance in Barley.

Waterlogging stress is one of the major abiotic stresses affecting the productivity and quality of many crops worldwide. However, the mechanisms of waterlogging tolerance are still elusive in barley. In this study, we identify key differentially expressed genes (DEGs) and differential metabolites (DM) that mediate distinct waterlogging tolerance strategies in leaf and root of two barley varieties with contrasting waterlogging tolerance under different waterlogging treatments. Transcriptome profiling revealed that the response of roots was more distinct than that of leaves in both varieties, in which the number of downregulated genes in roots was 7.41-fold higher than that in leaves of waterlogging sensitive variety after 72 h of waterlogging stress. We also found the number of waterlogging stress-induced upregulated DEGs in the waterlogging tolerant variety was higher than that of the waterlogging sensitive variety in both leaves and roots in 1 h and 72 h treatment. This suggested the waterlogging tolerant variety may respond more quickly to waterlogging stress. Meanwhile, phenylpropanoid biosynthesis pathway was identified to play critical roles in waterlogging tolerant variety by improving cell wall biogenesis and peroxidase activity through DEGs such as Peroxidase (PERs) and Cinnamoyl-CoA reductases (CCRs) to improve resistance to waterlogging. Based on metabolomic and transcriptomic analysis, we found the waterlogging tolerant variety can better alleviate the energy deficiency via higher sugar content, reduced lactate accumulation, and improved ethanol fermentation activity compared to the waterlogging sensitive variety. In summary, our results provide waterlogging tolerance strategies in barley to guide the development of elite genetic resources towards waterlogging-tolerant crop varieties.

Exogenous application of salicylic acid ameliorates salinity stress in barley (Hordeum vulgare L.).

Barley (Hordeum vulgare L.) is a significant cereal crop belonging to Poaceae that is essential for human food and animal feeding. The production of barley grains was around 142.37 million tons in 2017/2018. However, the growth of barley was influenced by salinity which was enhanced by applying a foliar spray of salicylic acid. The current study investigated to evaluated the potential effect of SA on the barley (Hordeum vulgare L.) plants under salinity stress and its possible effects on physiological, biochemical, and growth responses. The experiment was conducted at Postgraduate Research Station (PARS), University of Agriculture; Faisalabad to assess the influence of salicylic acid on barley (Hordeum vulgare L.) under highly saline conditions. The experiment was conducted in a Completely Randomized Design (CRD) with 3 replicates. In plastic pots containing 8 kg of properly cleaned sand, two different types of barley (Sultan and Jau-17) were planted. The plants were then watered with a half-strength solution of Hoagland's nutritional solution. After the establishment of seedlings, two salt treatments (0 mM and 120 mM NaCl) were applied in combining three levels of exogenously applied salicylic acid (SA) (0, 0.5, and 1 mg L-1). Data about morphological, physiological, and biochemical attributes was recorded using standard procedure after three weeks of treatment. The morpho-physiological fresh weight of the shoot and root (48%), the dry mass of the shoot and root (66%), the plant height (18%), the chlorophyll a (30%), the chlorophyll b (22%), and the carotenoids (22%), all showed significant decreases. Salinity also decreased yield parameters and the chl. ratio (both at 29% and 26% of the total chl. leaf area index). Compared to the control parameters, the following data was recorded under salt stress: spike length, number of spikes, number of spikelets, number of tillers, biological yield, and harvest index. Salicylic acid was used as a foliar spray to lessen the effects of salinity stress, and 1 mg L-1 of salicylic acid proved more effective than 0.5 mg L-1. Both varieties show better growth by applying salicylic acid (0 mg L-1) as a control, showing normal growth. By increasing its level to (0.5 mg L-1), it shows better growth but maximized growth occurred at a higher level (1 mg L-1). Barley sultan (Hordeum vulgare L.) is the best variety as compared to Jau-17 performs more growth to mitigate salt stress (0mM and 120mM NaCl) by improving morpho-physiological parameters by enhancing plan height, Root and shoot fresh and dry weights, as well as root and shoot lengths, photosynthetic pigments, area of the leaves and their index, and yield attributes and reduce sodium ions.

Global Proteome Profiling Revealed the Adaptive Reprogramming of Barley Flag Leaf to Drought and Elevated Temperature.

Plants, as sessile organisms, have developed sophisticated mechanisms to survive in changing environments. Recent advances in omics approaches have facilitated the exploration of plant genomes; however, the molecular mechanisms underlying the responses of barley and other cereals to multiple abiotic stresses remain largely unclear. Exposure to stress stimuli affects many proteins with regulatory and protective functions. In the present study, we employed liquid chromatography coupled with high-resolution mass spectrometry to identify stress-responsive proteins on the genome-wide scale of barley flag leaves exposed to drought, heat, or both. Profound alterations in the proteome of genotypes with different flag leaf sizes were found. The role of stress-inducible proteins was discussed and candidates underlying the universal stress response were proposed, including dehydrins. Moreover, the putative functions of several unknown proteins that can mediate responses to stress stimuli were explored using Pfam annotation, including calmodulin-like proteins. Finally, the confrontation of protein and mRNA abundances was performed. A correlation network between transcripts and proteins performance revealed several components of the stress-adaptive pathways in barley flag leaf. Taking the findings together, promising candidates for improving the tolerance of barley and other cereals to multivariate stresses were uncovered. The presented proteomic landscape and its relationship to transcriptomic remodeling provide novel insights for understanding the molecular responses of plants to environmental cues.

Diurnal changes in apoplast bypass flow of water and ions in salt-stressed wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.).

The aim of the present study was to quantify the contribution of apoplastic bypass flow to the uptake of water and salt across the root cylinder of wheat and barley during day and night. Plants were grown on hydroponics until they were 14-17 days old and then analysed over a single day (16 h) or night (8 h) period while being exposed to different concentrations of NaCl (50, 100, 150 and 200 mM NaCl). Exposure to salt started just before the experiment (short-term stress) or had started 6d before (longer-term stress). Bypass flow was quantified using the apoplastic tracer dye 8-hydroxy-1,3,6-pyrenesulphonic acid (PTS). The percent contribution of bypass flow to root water uptake increased in response to salt stress and during the night and amounted to up to 4.4%. Bypass flow across the root cylinder of Na+ and Cl- made up 2%-12% of the net delivery of these ions to the shoot; this percentage changed little (wheat) or decreased (barley) during the night. Changes in the contribution of bypass flow to the net uptake of water, Na+ and Cl- in response to salt stress and day/night are the combined result of changes in xylem tension, the contribution of alternative cell-to-cell flow path and the requirement to generate xylem osmotic pressure.

NaCl effect on Cd accumulation and cell compartmentalization in barley.

The effect of sodium chloride (NaCl) on cadmium (Cd) tolerance, uptake, translocation, and compartmentation was investigated in 3 barley genotypes. Seedlings were cultivated hydroponically in the absence of NaCl and Cd (control), in the presence of 50 mM NaCl alone, in the presence of 10 µM Cd alone, and in the combined addition of NaCl (50 mM) and Cd (10 µM). Plants were cultivated during one month under 16 h light period at a minimal light intensity of 250 µmol m-2 s-1, a temperature of 25 ± 3 °C, and 70-80% of relative humidity. Results showed that NaCl alone did not significantly affect plant development and biomass production; however, Cd alone reduced plant development rate leading to a decline in biomass production in Raihane and Giza 127 but did not affect that in Amalou. NaCl addition in Cd-treated plants accentuated the Cd effect on plant growth. NaCl limited Cd accumulation in the roots and in the shoots in all tested barley varieties by reducing Cd-absorption efficiency and the translocation of Cd from the root to the shoot. In all Cd-treated plants, cell Cd compartmentalization showed the following gradient: organelles < cell wall < vacuole. NaCl in the medium increased Cd accumulation in the soluble fraction and reduced that in organelle and cell wall fractions. Globally our results showed that, although NaCl reduces Cd accumulation in barley, it accentuates the Cd toxic effects, hence limiting the plant yield. We advise farmers to avoid barley cultivation near mine sites and its irrigation with moderately salty water, although this plant is considered as salt tolerant.

Cuticular transpiration is not affected by enhanced wax and cutin amounts in response to osmotic stress in barley.

The plant cuticle, which covers all aerial parts of plants in their primary developmental stage, is the major barrier against water loss from leaves. Accumulation of cutin and waxes has often been linked to drought tolerance. Here we investigated whether cutin and waxes play a role in the drought adaption of barley mimicked by osmotic stress acting on roots. We compared the cuticle properties of cultivated barley (Hordeum vulgare spp. vulgare) with wild barley (Hordeum vulgare spp. spontaneum), and tested whether wax and cutin composition or amount and cuticular transpiration could be future breeding targets for more drought-tolerant barley lines. In response to osmotic stress, accumulation of wax crystals was observed. This coincides with an increased wax and cutin gene expression and a total increase of wax and cutin amounts in leaves, which seems to be a general response triggered through root shoot signalling. Stomatal conductance decreased fast and significantly, whereas cuticular conductance remained unaffected in both wild and cultivated barley. The often-made conclusion that higher amounts of wax and cutin necessarily reduce cuticular transpiration and thus enhance drought tolerance is not always straightforward. To prevent water loss, stomatal regulation under water stress is much more important than regulation or adaptation of cuticular transpiration in response to drought.

Physiological and Epigenetic Reaction of Barley (Hordeum vulgare L.) to the Foliar Application of Silicon under Soil Salinity Conditions.

Soil salinity is an important environmental factor affecting physiological processes in plants. It is possible to limit the negative effects of salt through the exogenous application of microelements. Silicon (Si) is widely recognized as an element improving plant resistance to abiotic and biotic stresses. The aim of the research was to determine the impact of foliar application of Si on the photosynthetic apparatus, gas exchange and DNA methylation of barley (Hordeum vulgare L.) grown under salt stress. Plants grown under controlled pot experiment were exposed to sodium chloride (NaCl) in the soil at a concentration of 200 mM, and two foliar applications of Si were made at three concentrations (0.05%, 0.1% and 0.2%). Measurements were made of relative chlorophyll content in leaves (CCl), gas exchange parameters (Ci, E, gs, and PN), and selected chlorophyll fluorescence parameters (Fv/Fm, Fv/F0, PI and RC/ABS). Additionally, DNA methylation level based on cytosine methylation within the 3'CCGG 5' sequence was analyzed. Salinity had a negative effect on the values of the parameters examined. Exogenous application of Si by spraying leaves increased the values of the measured parameters in plants. Plants treated with NaCl in combination with the moderate (0.1%) and highest (0.2%) dose of Si indicated the lowest methylation level. Decrease of methylation implicated with activation of gene expression resulted in better physiological parameters observed in this group of barley plants.

Cross-species transcriptomic analyses reveals common and opposite responses in Arabidopsis, rice and barley following oxidative stress and hormone treatment.

BACKGROUND: For translational genomics, a roadmap is needed to know the molecular similarities or differences between species, such as model species and crop species. This knowledge is invaluable for the selection of target genes and pathways to alter downstream in response to the same stimuli. Here, the transcriptomic responses to six treatments including hormones (abscisic acid - ABA and salicylic acid - SA); treatments that cause oxidative stress (3-amino-1,2,4-triazole - 3AT, methyl viologen - MV); inhibit respiration (antimycin A - AA) or induce genetic damage (ultraviolet radiation -UV) were analysed and compared between Arabidopsis (Arabidopsis thaliana), barley (Hordeum vulgare) and rice (Oryza sativa). RESULTS: Common and opposite responses were identified between species, with the number of differentially expressed genes (DEGs) varying greatly between treatments and species. At least 70% of DEGs overlapped with at least one other treatment within a species, indicating overlapping response networks. Remarkably, 15 to 34% of orthologous DEGs showed opposite responses between species, indicating diversity in responses, despite orthology. Orthologous DEGs with common responses to multiple treatments across the three species were correlated with experimental data showing the functional importance of these genes in biotic/abiotic stress responses. The mitochondrial dysfunction response was revealed to be highly conserved in all three species in terms of responsive genes and regulation via the mitochondrial dysfunction element. CONCLUSIONS: The orthologous DEGs that showed a common response between species indicate conserved transcriptomic responses of these pathways between species. However, many genes, including prominent salt-stress responsive genes, were oppositely responsive in multiple-stresses, highlighting fundamental differences in the responses and regulation of these genes between species. This work provides a resource for translation of knowledge or functions between species.

Mechanistic Insights into Potassium-Conferred Drought Stress Tolerance in Cultivated and Tibetan Wild Barley: Differential Osmoregulation, Nutrient Retention, Secondary Metabolism and Antioxidative Defense Capacity.

Keeping the significance of potassium (K) nutrition in focus, this study explores the genotypic responses of two wild Tibetan barley genotypes (drought tolerant XZ5 and drought sensitive XZ54) and one drought tolerant barley cv. Tadmor, under the exposure of polyethylene glycol-induced drought stress. The results revealed that drought and K deprivation attenuated overall plant growth in all the tested genotypes; however, XZ5 was least affected due to its ability to retain K in its tissues which could be attributed to the smallest reductions of photosynthetic parameters, relative chlorophyll contents and the lowest Na+/K+ ratios in all treatments. Our results also indicate that higher H+/K+-ATPase activity (enhancement of 1.6 and 1.3-fold for shoot; 1.4 and 2.5-fold for root), higher shoot K+ (2 and 2.3-fold) and Ca2+ content (1.5 and 1.7-fold), better maintenance of turgor pressure by osmolyte accumulation and enhanced antioxidative performance to scavenge ROS, ultimately suppress lipid peroxidation (in shoots: 4% and 35%; in roots 4% and 20% less) and bestow higher tolerance to XZ5 against drought stress in comparison with Tadmor and XZ54, respectively. Conclusively, this study adds further evidence to support the concept that Tibetan wild barley genotypes that utilize K efficiently could serve as a valuable genetic resource for the provision of genes for improved K metabolism in addition to those for combating drought stress, thereby enabling the development of elite barley lines better tolerant of abiotic stresses.

Structural Equation Modeling (SEM) Analysis of Sequence Variation and Green Plant Regeneration via Anther Culture in Barley.

The process of anther culture involves numerous abiotic stresses required for cellular reprogramming, microspore developmental switch, and plant regeneration. These stresses affect DNA methylation patterns, sequence variation, and the number of green plants regenerated. Recently, in barley (Hordeum vulgare L.), mediation analysis linked DNA methylation changes, copper (Cu2+) and silver (Ag+) ion concentrations, sequence variation, ß-glucans, green plants, and duration of anther culture (Time). Although several models were used to explain particular aspects of the relationships between these factors, a generalized complex model employing all these types of data was not established. In this study, we combined the previously described partial models into a single complex model using the structural equation modeling approach. Based on the evaluated model, we demonstrated that stress conditions (such as starvation and darkness) influence ß-glucans employed by cells for glycolysis and the tricarboxylic acid cycle. Additionally, Cu2+ and Ag+ ions affect DNA methylation and induce sequence variation. Moreover, these ions link DNA methylation with green plants. The structural equation model also showed the role of time in relationships between parameters included in the model and influencing plant regeneration via anther culture. Utilization of structural equation modeling may have both scientific and practical implications, as it demonstrates links between biological phenomena (e.g., culture-induced variation, green plant regeneration and biochemical pathways), and provides opportunities for regulating these phenomena for particular biotechnological purposes.

Adjustments in photosynthesis and leaf water relations are related to changes in cell wall composition in Hordeum vulgare and Triticum aestivum subjected to water deficit stress.

In the current climate change scenario, understanding crops' physiological performance under water shortage is crucial to overcome drought periods. Although the implication of leaf water relations maintaining leaf turgor and stomatal functioning under water deprivation has been suggested, the relationships between photosynthesis and osmotic and elastic adjustments remain misunderstood. Similarly, only few studies in dicotyledonous analysed how changes in cell wall composition affected photosynthesis and leaf water relations under drought. To induce modifications in photosynthesis, leaf water relations and cell wall composition, Hordeum vulgare and Triticum aestivum were subjected to different water regimes: control (CL, full irrigation), moderate and severe water deficit stress (Mod WS and Sev WS, respectively). Water shortage decreased photosynthesis mainly due to stomatal conductance (gs) declines, being accompanied by reduced osmotic potential at full turgor (πo) and increased bulk modulus of elasticity (ε). Whereas both species enhanced pectins when intensifying water deprivation, species-dependent adjustments occurred for cellulose and hemicelluloses. From these results, we showed that πo and ε influenced photosynthesis, particularly, gs. Furthermore, the (Cellulose+Hemicelluloses)/Pectins ratio determined ε and mesophyll conductance (gm) in grasses, presenting the lowest pectins content within angiosperms. Thus, we highlight the relevance of cell wall composition regulating grasses physiology during drought acclimation.

Molecular Evaluation and Identification of Some Barley Hybrids Tolerant to Salt Stress.

<b>Background and Objective:</b> Barley is considering one of the most important cereal crops at the local and global levels. It is ranked second in terms of nutritional importance after wheat and its flour contributes significantly to bridging the large nutritional gap in the production of Egyptian bread. The aim of this study concentrated on knowing and testing the genetic behaviour responsible for salinity stress tolerance in barley as trying to improve barley crop and increase its ability for abiotic stress resistance under Egyptian conditions. <b>Materials and Methods:</b> Twenty-one crosses and ten parents of barley with different responses to salinity tolerance were evaluated in this investigation under normal and salinity conditions. Yield and its components and some physiological traits related to salt stress tolerance were the most important studied attributes evaluated in this regard under both conditions. Moreover, SSR markers were used to evaluate and identified associated markers for salinity tolerance in selected hybrids and comparing among the ten barley parents. <b>Results:</b> The final results confirmed that the three testers; Giza 123, Giza 126 and Giza 2000 besides; the crosses; Line 1XTester 1 (Giza 125XGiza 123), Line 2XTester 1 (Giza 133XGiza 123), Line 1XTester 2 (Giza 125XGiza 126), Line 2XTester 2 (Giza 133XGiza 126) and Line 1XTester 3 (Giza 125XGiza 2000) exhibited highly salinity tolerance under saline stress treatment compared with the control experiment. Among 15 analyzed barley entries, the chosen set of 11 markers amplified 20 alleles with an average of 1.81, with a range from 1-4 alleles. <b>Conclusion:</b> The results of SSR analysis and the data on valued agricultural trait loci determined the genetic distance among parents and their hybrids, which is of an unlimited rate for breeders.

HvLEAFY controls the early stages of floral organ specification and inhibits the formation of multiple ovaries in barley.

Transition to the reproductive phase, inflorescence formation and flower development are crucial elements that ensure maximum reproductive success in a plant's life cycle. To understand the regulatory mechanisms underlying correct flower development in barley (Hordeum vulgare), we characterized the multiovary 5 (mov5.o) mutant. This mutant develops abnormal flowers that exhibit mosaic floral organs typified by multiple carpels at the total or partial expense of stamens. Genetic mapping positioned mov5 on the long arm of chromosome 2H, incorporating a region that encodes HvLFY, the barley orthologue of LEAFY from Arabidopsis. Sequencing revealed that, in mov5.o plants, HvLFY contains a single amino acid substitution in a highly conserved proline residue. CRISPR-mediated knockout of HvLFY replicated the mov5.o phenotype, suggesting that HvLFYmov5 represents a loss of function allele. In heterologous assays, the HvLFYmov5 polymorphism influenced protein-protein interactions and affinity for a putative binding site in the promoter of HvMADS58, a C-class MADS-box gene. Moreover, molecular analysis indicated that HvLFY interacts with HvUFO and regulates the expression of floral homeotic genes including HvMADS2, HvMADS4 and HvMADS16. Other distinct changes in expression differ from those reported in the rice LFY mutants apo2/rfl, suggesting that LFY function in the grasses is modulated in a species-specific manner. This pathway provides a key entry point for the study of LFY function and multiple ovary formation in barley, as well as cereal species in general.

ENHANCED GRAVITROPISM 2 encodes a STERILE ALPHA MOTIF-containing protein that controls root growth angle in barley and wheat.

The root growth angle defines how roots grow toward the gravity vector and is among the most important determinants of root system architecture. It controls water uptake capacity, nutrient use efficiency, stress resilience, and, as a consequence, yield of crop plants. We demonstrated that the egt2 (enhanced gravitropism 2) mutant of barley exhibits steeper root growth of seminal and lateral roots and an auxin-independent higher responsiveness to gravity compared to wild-type plants. We cloned the EGT2 gene by a combination of bulked-segregant analysis and whole genome sequencing. Subsequent validation experiments by an independent CRISPR/Cas9 mutant allele demonstrated that egt2 encodes a STERILE ALPHA MOTIF domain-containing protein. In situ hybridization experiments illustrated that EGT2 is expressed from the root cap to the elongation zone. We demonstrated the evolutionary conserved role of EGT2 in root growth angle control between barley and wheat by knocking out the EGT2 orthologs in the A and B genomes of tetraploid durum wheat. By combining laser capture microdissection with RNA sequencing, we observed that seven expansin genes were transcriptionally down-regulated in the elongation zone. This is consistent with a role of EGT2 in this region of the root where the effect of gravity sensing is executed by differential cell elongation. Our findings suggest that EGT2 is an evolutionary conserved regulator of root growth angle in barley and wheat that could be a valuable target for root-based crop improvement strategies in cereals.

Exogenic Melatonin Reduces the Toxic Effect of Polymetallic Stress on Barley Plants.

The effect of melatonin on growth parameters, the photochemical activity of photosystem II (PS II), the content of the main photosynthetic pigments, and lipid peroxidation in barley plant leaves under polymetallic stress were studied. Melatonin reduces the toxic effect of polymetals on biomass accumulation, root growth, and maintenance of the assimilating surface. The protective action of the hormone is based on its ability to reduce the intensity of oxidative stress by maintaining the level of carotenoids and increasing the activity of superoxide dismutase, but not by regulating the photochemical activity of chloroplasts. The effectiveness of melatonin does not depend on the duration of exposure. The data obtained can be the basis for optimizing the use of melatonin as a plant priming inducer.

Major flowering time genes of barley: allelic diversity, effects, and comparison with wheat.

KEY MESSAGE: This review summarizes the allelic series, effects, interactions between genes and with the environment, for the major flowering time genes that drive phenological adaptation of barley. The optimization of phenology is a major goal of plant breeding addressing the production of high-yielding varieties adapted to changing climatic conditions. Flowering time in cereals is regulated by genetic networks that respond predominately to day length and temperature. Allelic diversity at these genes is at the basis of barley wide adaptation. Detailed knowledge of their effects, and genetic and environmental interactions will facilitate plant breeders manipulating flowering time in cereal germplasm enhancement, by exploiting appropriate gene combinations. This review describes a catalogue of alleles found in QTL studies by barley geneticists, corresponding to the genetic diversity at major flowering time genes, the main drivers of barley phenological adaptation: VRN-H1 (HvBM5A), VRN-H2 (HvZCCTa-c), VRN-H3 (HvFT1), PPD-H1 (HvPRR37), PPD-H2 (HvFT3), and eam6/eps2 (HvCEN). For each gene, allelic series, size and direction of QTL effects, interactions between genes and with the environment are presented. Pleiotropic effects on agronomically important traits such as grain yield are also discussed. The review includes brief comments on additional genes with large effects on phenology that became relevant in modern barley breeding. The parallelisms between flowering time allelic variation between the two most cultivated Triticeae species (barley and wheat) are also outlined. This work is mostly based on previously published data, although we added some new data and hypothesis supported by a number of studies. This review shows the wide variety of allelic effects that provide enormous plasticity in barley flowering behavior, which opens new avenues to breeders for fine-tuning phenology of the barley crop.

A biological agent modulates the physiology of barley infected with Drechslera teres.

Recognized as the causal agent of net blotch, Drechslera teres is responsible for major losses of barley crop yield. The consequences of this leaf disease are due to the impact of the infection on the photosynthetic performance of barley leaves. To limit the symptoms of this ascomycete, the use of beneficial bacteria known as "Plant Growth Promoting Rhizobacteria" constitutes an innovative and environmentally friendly strategy. A bacterium named as strain B25 belonging to the genus Burkholderia showed a strong antifungal activity against D. teres. The bacterium was able to limit the development of the fungus by 95% in detached leaves of bacterized plants compared to the non-bacterized control. In this study, in-depth analyses of the photosynthetic performance of young barley leaves infected with D. teres and/or in the presence of the strain B25 were carried out both in and close to the necrotic area. In addition, gas exchange measurements were performed only near the necrotic area. Our results showed that the presence of the beneficial bacterium reduced the negative impact of the fungus on the photosynthetic performance and modified only the net carbon assimilation rate close to the necrotic area. Indeed, the presence of the strain B25 decreased the quantum yield of regulated non-photochemical energy loss in PSII noted as Y(NPQ) and allowed to maintain the values stable of maximum quantum yield of PSII photochemistry known as Fv/Fm and close to those of the control in the presence of D. teres. To the best of our knowledge, these data constitute the first study focusing on the impact of net blotch fungus and a beneficial bacterium on photosynthesis and respiratory parameters in barley leaves.

Cropping systems alter hydraulic traits of barley but not pea grown in mixture.

Extreme events such as drought and heatwaves are among the biggest challenges to agricultural production and food security. However, the effects of cropping systems on drought resistance of arable crops via their hydraulic behaviour remain unclear. We investigated how hydraulic traits of a field-grown pea-barley (Pisum sativum L. and Hordeum vulgare L.) mixture were affected by different cropping systems, that is, organic and conventional farming with intensive or conservation tillage. Xylem vulnerability to cavitation of both species was estimated by measuring the pressure inducing 50% loss of hydraulic conductivity (P50 ), while the water stress plants experienced in the field were assessed using native percentage loss of hydraulic conductivity (nPLC). Pea and barley showed contrasting hydraulic behaviours: pea was less vulnerable to xylem cavitation and less stressed than barley; cropping systems affected the xylem vulnerability of barley, but not of pea. Barley grown under conventional farming with no tillage was more vulnerable and stressed than under organic farming with intensive tillage. nPLC proved to be a valuable indicator for plant water stress. Our results highlight the impact of cropping systems on crop xylem vulnerability and drought resistance, thus plant hydraulic traits, for protecting food security under future climate.