Microbe-induced drought tolerance by ABA-mediated root architecture and epigenetic reprogramming.

The use of beneficial microbes to mitigate drought stress tolerance of plants is of great potential albeit little understood. We show here that a root endophytic desert bacterium, Pseudomonas argentinensis strain SA190, enhances drought stress tolerance in Arabidopsis. Transcriptome and genetic analysis demonstrate that SA190-induced root morphogenesis and gene expression is mediated via the plant abscisic acid (ABA) pathway. Moreover, we demonstrate that SA190 primes the promoters of target genes in an epigenetic ABA-dependent manner. Application of SA190 priming on crops is demonstrated for alfalfa, showing enhanced performance under drought conditions. In summary, a single beneficial root bacterial strain can help plants to resist drought conditions.

Synergistic Practicing of Rhizobacteria and Silicon Improve Salt Tolerance: Implications from Boosted Oxidative Metabolism, Nutrient Uptake, Growth and Grain Yield in Mung Bean.

Plant growth promoting rhizobacteria (PGPR) and silicon (Si) are known for alleviating abiotic stresses in crop plants. In this study, Bacillus drentensis and Enterobacter cloacae strains of PGPR and foliar application of Si were tested for regulating the antioxidant metabolism and nutrient uptake on grain yield of mung bean under irrigation of saline water (3.12 and 7.81 dS m-1). Bacterial inoculation and supplemental Si (1 and 2 kg ha-1) reduced salinity-induced oxidative stress in mung bean leaves. The improved salt stress tolerance was achieved by enhancing the activities of catalase (45%), peroxidase (43%) and ascorbate peroxidase (48%), while decreasing malondialdehyde levels (57%). Enhanced nutrient uptake of magnesium 1.85 mg g-1, iron 7 mg kg-1, zinc 49.66 mg kg-1 and copper 12.92 mg kg-1 in mung bean seeds was observed with foliar application of Si and PGPR inoculation. Biomass (7.75 t ha-1), number of pods per plant (16.02) and 1000 seed weight (60.95 g) of plants treated with 2 kg Si ha-1 and B. drentensis clearly outperformed treatments with Si or PGPR alone. In conclusion, application of Si and PGPR enhances mung bean productivity under saline conditions, thereby helping exploitation of agriculture in low productive areas.

Molecular evidence for the occurrence of TYLCV on Mentha longifolia in Jeddah, Saudi Arabia.

Begomoviruses are whiteflies transmitted virus causing serious disease in many important plants exhibiting variable symptoms with significant economic loss globally. Mentha is an important crop being grown here in Saudi Arabia for various purposes. The begomovirus associated disease was observed on Mentha crops during field survey which were growing near to tomato field. There is no published report available about the association of begomovirus on Mentha from this region. So, this work was conducted to identify the causative agent associated with yellow vein mosaic disease. Naturally infected samples were collected from various locations and causative agent was identified by PCR using begomovirus specific primers and further cloned and sequenced bidirectionally. The full genome had total 2785 nucleotides while betasatellite molecule had 1365 nucleotides. Based on full-genome sequence analysis, the identity matrix and phylogenetic analysis showed the highest identity (99.6%) with Tomato yellow leaf curl virus (TYLCV) reported from tomato in the Kingdom of Saudi Arabia. The identified begomovirus was observed as isolate of TYLCV.

Boosting Alfalfa (Medicago sativa L.) Production With Rhizobacteria From Various Plants in Saudi Arabia.

This study focused on rhizobacteria to promote sustainable crop production in arid regions of Saudi Arabia. The study isolated 17 tightly root-adhering rhizobacteria from various plants at Hada Al Sham in Saudi Arabia. All 17 rhizobacterial isolates were confirmed as plant growth promoting rhizobacteria by classical biochemical tests. Using 16S rDNA gene sequence analyses, the strains were identified as Bacillus, Acinetobacter and Enterobacter. Subsequently, the strains were assessed for their ability to improve the physiology, nutrient uptake, growth, and yield of alfalfa plants grown under desert agriculture conditions. The field trials were conducted in a randomized complete block design. Inoculation of alfalfa with any of these 17 strains improved the relative water content; chlorophyll a; chlorophyll b; carotenoid contents; nitrogen (N), phosphorus, and potassium contents; plant height; leaf-to-stem ratio; and fresh and dry weight. Acinetobacter pittii JD-14 was most effective to increase fresh and dry weight of alfalfa by 41 and 34%, respectively, when compared to non-inoculated control plants. Nevertheless, all strains enhanced crop traits when compared to controls plants, indicating that these desert rhizobacterial strains could be used to develop an eco-friendly biofertilizer for alfalfa and possibly other crop plants to enhance sustainable production in arid regions.

Humic Substances: Determining Potential Molecular Regulatory Processes in Plants.

Humic substances (HSs) have considerable effects on soil fertility and crop productivity owing to their unique physiochemical and biochemical properties, and play a vital role in establishing biotic and abiotic interactions within the plant rhizosphere. A comprehensive understanding of the mode of action and tissue distribution of HS is, however, required, as this knowledge could be useful for devising advanced rhizospheric management practices. These substances trigger various molecular processes in plant cells, and can strengthen the plant's tolerance to various kinds of abiotic stresses. HS manifest their effects in cells through genetic, post-transcriptional, and post-translational modifications of signaling entities that trigger different molecular, biochemical, and physiological processes. Understanding of such fundamental mechanisms will provide a better perspective for defining the cues and signaling crosstalk of HS that mediate various metabolic and hormonal networks operating in plant systems. Various regulatory activities and distribution strategies of HS have been discussed in this review.

Ethylene induced plant stress tolerance by Enterobacter sp. SA187 is mediated by 2-keto-4-methylthiobutyric acid production.

Several plant species require microbial associations for survival under different biotic and abiotic stresses. In this study, we show that Enterobacter sp. SA187, a desert plant endophytic bacterium, enhances yield of the crop plant alfalfa under field conditions as well as growth of the model plant Arabidopsis thaliana in vitro, revealing a high potential of SA187 as a biological solution for improving crop production. Studying the SA187 interaction with Arabidopsis, we uncovered a number of mechanisms related to the beneficial association of SA187 with plants. SA187 colonizes both the surface and inner tissues of Arabidopsis roots and shoots. SA187 induces salt stress tolerance by production of bacterial 2-keto-4-methylthiobutyric acid (KMBA), known to be converted into ethylene. By transcriptomic, genetic and pharmacological analyses, we show that the ethylene signaling pathway, but not plant ethylene production, is required for KMBA-induced plant salt stress tolerance. These results reveal a novel molecular communication process during the beneficial microbe-induced plant stress tolerance.

Identification of a monopartite begomovirus associated with yellow vein mosaic of Mentha longifolia in Saudi Arabia.

Mentha is a very important crop grown and used extensively for many purposes in the Kingdom of Saudi Arabia. Begomoviruses are whitefly-transmitted viruses causing serious disease in many important plants exhibiting variable symptoms with significant economic loss globally. During farmers' field survey, yellow vein mosaic disease was observed in Mentha longifolia plants growing near tomato fields in Saudi Arabia. The causative agent was identified in 11 out of 19 samples using begomovirus-specific primers and the association of begomovirus with yellow vein mosaic disease in M. longifolia was confirmed. The full-length viral genome and betasatellite were amplified, cloned, and sequenced bidirectionally. The full DNA-A genome was found to have 2785 nucleotides with 1365 bp-associated betasatellite molecule. An attempt was made to amplify DNA-B, but none of the samples produced any positive amplicon of expected size which indicated the presence of monopartite begomovirus. The sequence identity matrix and phylogenetic analysis, based on full genome showed the highest identity (99.6%) with Tomato yellow leaf curl virus (TYLCV) and in phylogenetic analysis it formed a closed cluster with Tomato leaf curl virus infecting tomato and Corchorus crop in Saudi Arabia. The sequence analysis results of betasatellites showed the highest identity (98.9%) with Tomato yellow leaf curl betasatellites infecting tomato and phylogenetic analysis using betasatellites formed a close cluster with Tomato yellow leaf curl betasatellites infecting tomato and Corchorus crops, which has already been reported to cause yellow vein mosaic and leaf curl disease in many cultivated and weed crops growing in Saudi Arabia. The identified begomovirus associated with yellow vein mosaic disease in mentha could be a mutated strain of TYLCV and tentatively designated as TYLCV-Mentha isolate. Based on published data and latest information, this is the first report of identification of Tomato yellow leaf curl virus associated with yellow vein mosaic disease of M. longifolia from Saudi Arabia.

Redox and Ionic Homeostasis Regulations against Oxidative, Salinity and Drought Stress in Wheat (A Systems Biology Approach).

Systems biology and omics has provided a comprehensive understanding about the dynamics of the genome, metabolome, transcriptome, and proteome under stress. In wheat, abiotic stresses trigger specific networks of pathways involved in redox and ionic homeostasis as well as osmotic balance. These networks are considerably more complicated than those in model plants, and therefore, counter models are proposed by unifying the approaches of omics and stress systems biology. Furthermore, crosstalk among these pathways is monitored by the regulation and streaming of transcripts and genes. In this review, we discuss systems biology and omics as a promising tool to study responses to oxidative, salinity, and drought stress in wheat.

In-Depth Genomic and Transcriptomic Analysis of Five K+ Transporter Gene Families in Soybean Confirm Their Differential Expression for Nodulation.

Plants have evolved a sophisticated network of K+ transport systems to regulate growth and development. Limited K+ resources are now forcing us to investigate how plant demand can be satisfied. To answer this complex question, we must understand the genomic and transcriptomic portfolio of K+ transporters in plants. Here, we have identified 70 putative K+ transporter genes from soybean, including 29 HAK/KT/KUP genes, 16 genes encoding voltage-gated K+ channels, 9 TPK/KCO genes, 4 HKT genes, and 12 KEA genes. To clarify the molecular evolution of each family in soybean, we analyzed their phylogeny, mode of duplication, exon structures and splice sites, and paralogs. Additionally, ortholog clustering and syntenic analysis across five other dicots further explored the evolution of these gene families and indicated that the soybean data is suitable as a model for all other legumes. Available microarray data sets from Genevestigator about nodulation was evaluated and further confirmed with the RNA sequencing data available by a web server. For each family, expression models were designed based on Transcripts Per Kilobase Million (TPM) values; the outcomes indicated differential expression linked to nodulation and confirmed the genes' putative roles. In-depth studies such as ours provides the basis for understanding K+ inventories in all other plants.

Comparative bacterial community analysis in relatively pristine and anthropogenically influenced mangrove ecosystems on the Red Sea.

Mangrove habitats are ecologically important ecosystems that are under severe pressure worldwide because of environmental changes and human activities. In this study, 16S rRNA gene amplicon deep-sequencing was used to compare bacterial communities in Red Sea mangrove ecosystems at anthropogenically influenced coastal sites with those at a relatively pristine island site. In total, 32 phyla were identified from the mangrove rhizospheres, with Proteobacteria predominating at each of the studied sites; however, the relative abundance was significantly decreased at the coastal sites (Mastorah, MG-MS; Ar-Rayis, MG-AR) compared with the pristine island site near Dhahban (MG-DBI). The phyla Actinobacteria, Firmicutes, Acidobacteria, Chloroflexi, Spirochetes, and Planctomycetes were present at a relative abundance of >1% at the MG-MS and MG-AR sites, but their concentration was <1% at the MG-DBI site. A total of 1659 operational taxonomic units (OTUs) were identified at the species level, and approximately 945 OTUs were shared across the different sampling sites. Multivariate principal coordinate data analysis separated the MG-DBI site from the MG-AR and MG-MS cluster. Specific bacterial taxa were enriched at each location, and in particular, the genera Pseudoalteromonas and Cobetia were predominantly identified in the MG-DBI site compared with the anthropogenically influenced coastal sites.

Transcriptomics and Biochemical Profiling: Current Dynamics in Elucidating the Potential Attributes of Olive.

Various transcriptome studies have remained useful in unraveling the complexity of molecular pathways regulating the oil biochemical contents and fruit characteristics of agronomic value in olive. Genes networks associated with plant architect and abiotic stress tolerance have been constructed due to robust genomic data generated by the tools of genomics. This, familiarity will accelerate the breeding programmes in making the selection of high yielding olive genotypes promptly and efficiently. Moreover, comparative transcriptome studies for endogeneous enzymes at different expression sites explicate the contribution of various pathways in phenol and lipid oxidation in olive. Recently, non-targeted metabolomics and metabolic profiling techniques have not only made the understanding of metabolic changes easy but also elucidate biomarkers in fruits related to agronomic parameters and abiotic stresses. However, the alteration in the architectural build up of phenotypes auth-enticates the conservation of their potential genetic links that will invoke interest for future olive breeding.

Genomics: A Hallmark to Monitor Molecular and Biochemical Processes Leading Toward a Better Perceptive of Seed Aging and ex-situ Conservation.

For human food security, the preservation of 7.4 million ex-situ germplasm is a global priority. However, ex-situ-conserved seeds are subject to aging, which reduces their viability and ultimately results in the loss of valuable genetic material over long periods. Recent progress in seed biology and genomics has revealed new opportunities to improve the long-term storage of ex-situ seed germplasm. This review summarizes the recent improvements in seed physiology and genomics, with the intention of developing genomic tools for evaluating seed aging. Several lines of seed biology research have shown promise in retrieving viability signal from various stages of seed germination. We conclude that seed aging is associated with mitochondrial alteration and programmed cell death, DNA and enzyme repair, anti-oxidative genes, telomere length, and epigenetic regulation. Clearly, opportunities exist for observing seed aging for developing genomic tools to increment the traditional germination test for effective conservation of ex-situ germplasm.

Plant Growth Promoting Rhizobacteria and Silicon Synergistically Enhance Salinity Tolerance of Mung Bean.

The present study explored the eco-friendly approach of utilizing plant-growth-promoting rhizobacteria (PGPR) inoculation and foliar application of silicon (Si) to improve the physiology, growth, and yield of mung bean under saline conditions. We isolated 18 promising PGPR from natural saline soil in Saudi Arabia, and screened them for plant-growth-promoting activities. Two effective strains were selected from the screening trial, and were identified as Enterobacter cloacae and Bacillus drentensis using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and 16S rRNA gene sequencing techniques, respectively. Subsequently, in a 2-year mung bean field trial, using a randomized complete block design with a split-split plot arrangement, we evaluated the two PGPR strains and two Si levels (1 and 2 kg ha(-1)), in comparison with control treatments, under three different saline irrigation conditions (3.12, 5.46, and 7.81 dS m(-1)). The results indicated that salt stress substantially reduced stomatal conductance, transpiration rate, relative water content (RWC), total chlorophyll content, chlorophyll a, chlorophyll b, carotenoid content, plant height, leaf area, dry biomass, seed yield, and salt tolerance index. The PGPR strains and Si levels independently improved all the aforementioned parameters. Furthermore, the combined application of the B. drentensis strain with 2 kg Si ha(-1) resulted in the greatest enhancement of mung bean physiology, growth, and yield. Overall, the results of this study provide important information for the benefit of the agricultural industry.

Wheat Phenological Development and Growth Studies As Affected by Drought and Late Season High Temperature Stress under Arid Environment.

This study evaluates the potential for adaptability and tolerance of wheat genotypes (G) to an arid environment. We examined the influence of drought stress (DS) (100, 75, and 50% field capacity), planting times (PT) (16-November, 01-December, 16-December and 01-January), and G (Yocoro Rojo, FKAU-10, Faisalabad-08, and Galaxy L-7096) on phenological development, growth indices, grain yield, and water use efficiency of drip-irrigated wheat. Development measured at five phenological growth stages (GS) (tillering, jointing, booting, heading, and maturity) and growth indices 30, 45, 60, and 75 days after sowing (DAS) were also correlated with final grain yield. Tillering occurred earlier in DS plots, to a maximum of 31 days. Days to complete 50% heading and physiological crop maturity were the most susceptible GS that denoted 31-72% reduction in number of days to complete these GS at severe DS. Wheat G grown with severe DS had the shortest grain filling duration. Genotype Fsd-08 presented greater adaptability to studied arid climate and recorded 31, 35, and 38% longer grain filling period as compared with rest of the G at 100-50% field capacity respectively. December sowing mitigated the drought and delayed planting effects by producing superior growth and yield (2162 kg ha(-1)) at severe DS. Genotypes Fsd-08 and L-7096 attained the minimum plant height (36 cm) and the shortest growth cycle (76 days) for January planting with 50% field capacity. At severe DS leaf area index, dry matter accumulation, crop growth rate and net assimilation rate were decreased by 67, 57, 34, and 38% as compared to non-stressed plots. Genotypes Fsd-08 and F-10 were the superior ones and secured 14-17% higher grain yield than genotype YR for severely stressed plots. The correlation between crop growth indices and grain yield depicted the highest value (0.58-0.71) at 60-75 DAS. So the major contribution of these growth indices toward grain yield was at the start of reproductive phase. It's clear that booting and grain filling are the most sensitive GS that are severely affected by both drought and delay in planting.

Study of commercial effective microorganism on composting and dynamics of plant essential metal micronutrients.

The present study addresses the problem of organic farmers' that needs local organic resources with their enhanced quality to effectively fertilize their agriculture crops. In accordance with the objective of the experiment that is about enhancing quality of compost, a blend of organic resources, comprising cow manure (CM), poultry manure (PM) and kitchen waste (KW) (2:1:1 ratio by volume) was composted with effective microorganisms (EM.1) (CompostEM.1) and without (Compostplain). During composting, temperature, pH, carbon, nitrogen, C/N ratio, total and diethylene triamine pentaacetic acid (DTPA)-extractable essential metal micronutrient (Fe3+, Cu2+, Zn2+, and Mn2+) contents of both the composts were recorded following the standard procedures. Low temperature range (24−24), low pH (6.7−7.2) and higher N-content (1.15−1.40) were recorded for CompostEM.1 as compared to Compostplain. Carbon degradation was also faster in CompostEM.1 than in Compostplain. Consequently, C/N ratio stabilization took 6 weeks in CompostEM.1 as compared to 18 weeks in Compostplain, leading to rapid completion of composting. Total concentration of micronutrients increased while their DTPA-extractable content decreased during the composting. Total micronutrient concentration was augmented more in Compostplain samples than in CompostEM.1. However, decrease in DTPA-extractable content was similar in both the composts. Increase in micronutrient content was attributed to decrease in organic matter weight, whereas decrease in metal micronutrients was attributed to the formation of organic matter-metal complexes during decomposition. Findings of the study indicated that effective micro-organisms enhanced composting process, however, further studies are required to evaluate its quality, especially effect on plant and soil.

Effect of Rht alleles on wheat grain yield and quality under high temperature and drought stress during booting and anthesis.

The present study examined the effects of gibberellin semi-sensitive reduced height (Rht) alleles on wheat grain yield and quality under high temperature and drought stress during booting and anthesis stages. Near-isogenic lines (NILs) of winter wheat (Rht (tall), Rht-B1b, Rht-D1b, Rht-B1c, Rht-8c, Rht-D1c, Rht-12) having background of Mercia and Maris Widgeon cultivars were compared under variable temperatures (day/night: 20/12, 27/19, 30/22, 33/25, 36/28, and 39/31 °C) and irrigation regimes. Pots were transferred to controlled thermal conditions (Saxcil growth chamber) during booting and anthesis stages and were maintained at field capacity (FC) or had water withheld. High temperature (>30 °C) and drought stress for seven consecutive days during booting and anthesis stages reduced the grain yield, while increased nitrogen (N) and sulphur (S) concentrations. A 50 % reduction in grain yield was fitted to have occurred at 37.4 °C for well-watered plants and at 31.4 °C for drought-stressed plants. The N and S concentrations were higher for severe dwarfs, whereas no significant differences were observed between tall and semi-dwarfs in Mercia. In the taller background (Maris Widgeon), N and S concentrations were significantly higher compared with that in Mercia. In Mercia, the severe dwarf Rht-D1c had higher Hagberg falling number (HFN) and sodium dodecyl sulphate (SDS) sedimentation volume. In both backgrounds, semi-dwarfs and severe dwarfs had higher HFN. Moreover, the SDS sedimentation volumes in Maris Widgeon were also higher than that in Mercia. Greater adaptability and improved grain quality traits suggested that severe dwarf Rht alleles are better able to enhance tolerance to high temperature and drought stress in wheat.