Roots Of Wheat Plants Research Articles

Microplastic exposure inhibits nitrate uptake and assimilation in wheat plants

Microplastic (MP) contamination in soil severely impairs plant growth. However, mechanisms underlying the effects of MPs on plant nutrient uptake remain largely unknown. In this study, we revealed that NO3− content was significantly decreased in shoots and roots of wheat plants exposed to high concentrations (50–100 mg L−1) of MPs (1 μm and 0.1 μm; type: polystyrene) in the hydroponic solution. Isotope labeling experiments demonstrated that MP exposure led to a significant inhibition of NO3− uptake in wheat roots. Further analysis indicated that the presence of MPs markedly inhibited root growth and caused oxidative damage to the roots. Additionally, superoxide dismutase and peroxidase activities in wheat roots decreased under all MP treatments, whereas catalase and ascorbate peroxidase activities significantly increased under the 100 mg L−1 MP treatment. The transcription levels of most nitrate transporters (NRTs) in roots were significantly downregulated by MP exposure. Furthermore, exposure to MPs distinctly suppressed the activity of nitrate reductase (NR) and nitrite reductase (NiR), as well as the expression levels of their coding genes in wheat shoots. These findings indicate that a decline in root uptake area and root vitality, as well as in the expression of NRTs, NR, and NiR genes caused by MP exposure may have adverse effects on NO3− uptake and assimilation, consequently impairing normal growth of plants.

Responses of bread wheat to Zn-Glycine and Zn-Alanine fertilizers under saline soil condition

Zinc (Zn) deficiency and salt stress are well-known soil problems and often happen parallelly in cultivated soils. In this study, Zn-amino acid complexes (Zn-AAc) were used as a source of Zn to determine their effects on salt-induced damage in wheat plants. The bread wheat (Triticum aestivum L. cvs. Kavir) was supplied with Zn-glycine (Zn-Gly), Zn-alanine (Zn-Ala), and ZnSO4 as Zn sources at three salinity levels (EC 2, 4 and 6 dS m-). Salinity caused a significant decrease in shoot dry matter and grain yield of wheat, but this negative effect was significantly improved by the application of Zn-AAc. Salt stress decreased shoot and grain Zn concentration, but this reduction was lower in plants supplied by Zn-AAc. Calcium (Ca) and potassium (K) concentrations were increased in a shoot by salinity stress while decreased in grain. Sodium (Na) concentration decreased in shoot and grain by using Zn-AAc. At all of the salinity levels, wheat supplied with Zn-AAc had lower lipid peroxidation compared to those grown under the ZnSO4 source. Application of Zn-AAc increased the activities of catalase (CAT) and superoxide dismutase (SOD) in the roots of wheat plants in saline conditions. Based on the results, the adverse effects of salinity stress on wheat plants can moderately improve with Zn-AAc application.

Multiomics Explore the Detoxification Mechanism of Nanoselenium and Melatonin on Bensulfuron Methyl in Wheat Plants.

Combining nanoselenium (nano-Se) and melatonin (MT) was more effective than treatment alone against abiotic stress. However, their combined application mitigated the toxic effects of bensulfuron methyl, and enhanced wheat growth and metabolism has not been studied. Metabolomics and proteomics revealed that combining nano-Se and MT markedly activated phenylpropanoid biosynthesis pathways, elevating the flavonoid (quercetin by 33.5 and 39.8%) and phenolic acid (vanillic acid by 38.8 and 48.7%) levels in leaves and roots of wheat plants. Interstingly, beneficial rhizosphere bacteria in their combination increased (Oxalobacteraceae, Nocardioidaceae, and Xanthomonadaceae), which positively correlated with the enhancement of soil urease and fluorescein diacetate enzyme activity (27.0 and 26.9%) and the allelopathic substance levels. To summarize, nano-Se and MT mitigate the adverse effects of bensulfuron methyl by facilitating interactions between the phenylpropane metabolism of the plant and the beneficial microbial community. The findings provide a theoretical basis for using nano-Se and MT to remediate herbicide-contaminated soil.

Effects of the short term exposure of wheat seedlings to silver nitrate

Wheat seedlings grown in the laboratory on liquid nutrient solutions were exposed to Ag+ at concentrations of 100 mmol×L-1 and 200 mmol×L-1 by immersing theirs roots in AgNO3 solutions for 90 min. 48 hours thereafter, certain biochemical parameters of the plants were assayed using appropriate analytical methods. Following the exposure to Ag+, a marked increase of both glucose concentration and soluble peroxidases activity, along with a decrease in the concentration of soluble proteins were measured in the roots of wheat plants, compared to control plants. Leaf chlorophylls and carotenoids contents, as well as the analyzed biometric data did not vary significantly in the plants exposed to Ag+ compared to control ones. However, significant changes in root branching were observed following the exposure of wheat plants to silver. A regulatory role of Ag+ through the modulation of phytohormones’ signaling is discussed.

INFLUENCE OF RHISOSPHERIC BACTERIA ON THE PRODUCTIVITY OF WHEAT PLANTS AND THE INPUT OF ELEMENTS FROM POLLUTED SOILS

The results of a vegetation experiment on the humus horizon of soddy-podzolic sandy loamy soil (Albic Retisol), which was contaminated with heavy metals as a re sult of sewage sludge as a fertilize r, are presented. The soil was used for growing vegetables and forage grasses but has been abandoned for the last 10 years. In the experiment, the effect of rhizospheric bacteria of the genus Pseudomonas on biomass and the entry of micro- and heavy metals into the vegetative organs and root system of spring wheat plants was studied. Under the influence of inoculation with bacteria, the biomass of wheat plants increased by 10–12% and the content of the main macro- and microelements in plants changed. The content of Ca, K, Mg, Na and P decreased by 1,5–2 times in the vegetative part of wheat plants inoculated with P. fluorescens 21 and P. putida 23. The content of macroelements in wheat roots changed little, but the ratio between the content of elements increased in roots and vegetative parts of plants. The distribution of the content of trace elements and HMs was much more contrasting: the content of Cd in the roots of wheat plants exceeded that in the vegetative part of plants by 9 times without treatment with bacteria and by 18 and 11 times aft er inoculation with P. fluorescens 21 and P. putida 23, and in variants with P. fl uorescens 20 by 7 times. A decrease in the content of Cd in the vegetative part of wheat plants was noted, by 2 times upon inoculation with P. fluorescens 21 and by 1,5 times for variants with P. putida 23. The content of Zn in the aerial parts of plants also decreased upon inoculation with P. fluorescens 21 and by 1,8 times for variants with and P. putida 23 by 1,4 times. An increase in the ratio of the content of elements in the roots and vegetative mass of plants indicates an increase in the resistance of plants to the toxic effect of heavy metals and the barrier function of the roots.

Study of kabul river canal sediments for heavy metals status and its accumulation in wheat plant (triticum aestivum)

Canal cleaning is a routine activity on the canals diverted from the Kabul River. As a result, thousands of tons of sediment are removed as sludge and flushed back into the Kabul River. In Peshawar city, most people use this sediment as a soil conditioner in lawns. But the farmers are hesitant to apply it in agricultural fields. It is perceived that the sediment may be rich in heavy metal contents and, if used as a soil conditioner, may contaminate the food chain. To unveil the facts, this study was conducted with the aim of analyzing sediment samples for selected heavy metals and their uptake and accumulation in different parts of the wheat plant. For this purpose, the sediment collected from Warsak Gravity Canal (WGC) was analyzed for total essential heavy metals including iron (Fe), copper (Cu), cobalt (Co), manganese (Mn), and Zinc (Zn). Wheat crop was grown in four different pots consisting of pure soil, pure sediment, and two amendments i.e. soil mixed with 25% and 50% sediments. In comparison to sediment, the soil samples were high in copper, cobalt, and Zinc concentration. The concentration of iron and manganese was comparatively high in pure sediment but within permissible limits. The heavy metals uptake by the wheat crop was also within the permissible limits. The highest accumulation of copper, iron, and Zinc was observed in the roots of wheat plants. The highest value of cobalt was observed in the seed (0.407 mg Kg-1), which was within the safe range. Therefore, it is concluded that the sediment of the Kabul River canal cannot be considered a source of pollution in terms of heavy metals and can be used as a soil conditioner.

Influence of Nutrient Medium Composition for Culturing Bacteria and the Dose of <i>B. subtilis</i> 10-4 Biologics on Growth Indicators and Productivity of Wheat Plants

Inoculation of crop seeds with selective strains of growth-stimulating bacteria is an environmentally friendly, low-cost way to increase their yield, but may depend on some biotechnological factors affecting their physiological activity. These include the conditions for the cultivation of bacteria and the dose of the drug. The work analyzed the effectiveness of inoculation of Bashkir spring wheat with 28 different preparations of the Bacillus subtilis strain 10-4: 1 - an aqueous suspension of bacterial cells washed off potato-glucose agar (PGA), 2 - a liquid culture containing cells with exometabolites obtained by cultivating bacteria in potato- glucose broth (PGB), 3 - liquid culture of bacterial cells grown in legume-glucose broth (LGB). At the same time, the growth-stimulating effect of applying a high dose (108 cells/ml) and a low dose (104-105 cells/ml) of bacteria in the inoculum was evaluated. When comparing the preparations obtained from potato-glucose medium, it was revealed that the positive growth effect (an increase in the number of wheat plant roots) was caused only by a high dose of the drug cells in the PGA and both doses of the drug in the PGB, but a high dose of the drug in the PGB inhibited seed germination up to 74% (in the control 100%). When comparing the preparations obtained during the cultivation of bacteria in PGB and LGB, it was revealed that the best growth effect (total root length and shoot height) was greater than control in plants inoculated with a small dose of the drug in PGB and a large dose of the drug in LGB. The stimulating effect of a small dose of the drug in LGB was less and extended only to the root system. The results of laboratory experiments coincided with the effectiveness of the studied drugs in the field. The use of a drug obtained in BGO and administered at a dose of 108 cells / ml, and a drug obtained in PGB and administered at a dose of 105 cells/ml, increased grain yield by 1.6-1.7 times with a decrease in the intensity of leaf-stem diseases by 32 and 11% compared with the untreated control. The drug obtained in LGB and introduced in a small dose did not provide either an increase in yield or a protective effect compared to the control. Possible causes of the action of B. subtilis 10-4 strain preparations related to the production of phytohormones by it, depending on the composition of the medium, and with different adaptive capacity of bacteria when cultured on nitrogen-rich and less nitrogen-rich media are discussed.

Simulation Effect of Water and Nitrogen Transport under Wide Ridge and Furrow Irrigation in Winter Wheat Using HYDRUS-2D

An experiment was conducted to create a science-based program of irrigation and fertilizer application for two-year winter wheat under wide ridge and furrow irrigation in the Yellow River irrigation area. The study was performed in a test field located in Zhengzhou, Henan Province, China. A numerical model of soil water and nitrogen transport for winter wheat under wide ridge and furrow irrigation was created using HYDRUS-2D. The behavior of soil water and nitrogen was predicted for different irrigation water and nitrogen treatments and analyzed to identify pathways of nitrogen transport and transformation. The nitrogen balance was calculated for the different water and nitrogen treatments. The coefficients of determination for measured and predicted values of soil water content, nitrate nitrogen, and ammonium nitrogen in both horizontal and vertical directions were all >0.68; the mean absolute error was <0.06; and the root mean square error was <0.1. These values indicate the feasibility of using a numerical model of nitrogen transport for wide ridge and furrow irrigation. The correlation coefficient R2 between simulated values of nitrogen uptake and measured values of total crop nitrogen content was 0.88, the RMSE value was 10.58 kg/ha, and the MAE value was 5.9 kg/ha. Nitrogen loss was primarily caused by denitrification, and the quantity of gaseous nitrogen loss was 7.05–38.2% of the nitrogen form. The total quantity of ammonium nitrogen absorbed by winter wheat plant roots in each treatment was 7.6–15.1% of the total amount of nitrate nitrogen absorbed. The maximum nitrogen uptake was 155.53 kg/ha with a yield of 6888.67 kg/ha at a nitrogen application rate of 220 kg/ha and irrigating to 70% field capacity. The UE of the 220 kg/ha and irrigating to 70% field capacity treatment was relatively high, the PFP of the 120 kg/ha and irrigating to 80% field capacity treatment was relatively high, and the nitrogen use efficiency of the 320 kg/ha and irrigating to 60% field capacity treatment was the lowest overall. This study provides a basis for investigating soil water and nitrogen transport mechanisms of winter wheat under wide ridge and furrow irrigation in the Yellow River irrigation area.

Biochemical and growth effects of silver in wheat plants

Our experiments on the cultivation of wheat plants in the laboratory, on nutrient solutions supplemented with AgNO3, showed that the exposure to Ag+ at concentrations of 10 mmol×L-1 and 100 mmol×L-1 for 7 days led to growth inhibition and modification of certain biochemical indices, compared to control plants. The observed differences concerned the activity of soluble peroxidases and the degree of lipid peroxidation in the roots of wheat plants, as well as the quantity of chlorophylls in their leaves. These results may reflect both a toxic effect and a regulatory role of silver in plants.

Root morphological and anatomical responses to increasing phosphorus concentration of wheat plants grown under salinity

Understanding the role of nutrients in the alleviation of salt stress effects and the unrevealed significance of root system architecture for plant adaptation is one of the major research areas in the current context of agriculture. Root anatomy is also a valuable parameter to be considered in understanding how the root system counters soil salinity's effect on plant growth. Although Root Phosphorus Acquisition Efficiency (RPAE) under salt stress differs depending on plant species and the severity of salinity in the rhizosphere, optimising phosphorus (P) nutrition seems to bring positive results. This study was planned to investigate the combined effect of salinity and P-availability on root morphology and anatomy as well as nutrient uptake of wheat plants. A pot experiment was performed in open-field conditions using a Moroccan variety of durum wheat. Special emphasis was placed on how orthophosphate and polyphosphate fertilizer forms and phosphorus doses alter the morphology and anatomy of the roots under salt stress. Two soluble fertilizers were used: an orthophosphate (Ortho-A) and a polyphosphate (Poly-B) were applied at four P levels (0, 30, 45 and 60 ppm of P). Our findings showed that salt stress induced, at both anatomical and morphological levels, a series of modifications in the roots of wheat plants. Compared to salt-stressed and unfertilized plants, soluble P-fertilizers significantly increased soil available P, root P- content, RPAE, root length (RL), root surface area (RSA), root volume (RV), root mass density (RMD), root tissue water content (TWC), number of root tips, vascular cylinder diameter and SD/CT ratio. Furthermore, Poly-B showed a positive response in both morphological and anatomical parameters at lower doses while Ortho-A revealed significant results within the increase in P-concentration. The increased root parameters observed under P-treatments could determine the root performance and efficiency to acquire water and P and their transport to the aboveground organs of wheat plants under salinity.

Genome-based reclassification of Azospirillum brasilense Az39 as the type strain of Azospirillum argentinense sp. nov.

Strain Az39T of Azospirillum is a diazotrophic plant growth-promoting bacterium isolated in 1982 from the roots of wheat plants growing in Marcos Juárez, Córdoba, Argentina. It produces indole-3-acetic acid in the presence of l-tryptophan as a precursor, grows at 20-38 °C (optimal 38 °C), and the cells are curved or spiral-shaped, with diameters ranging from 0.5-0.9 to 1.8-2.2 µm. They contain C16 : 0, C18 : 0 and C18 : 1 ω7c/ω6c as the main fatty acids. Phylogenetic analysis of its 16S rRNA gene sequence confirmed that this strain belongs to the genus Azospirillum, showing a close relationship with Azospirillum baldaniorum Sp245T, Azospirillum brasilense Sp7T and Azospirillum formosense CC-Nfb-7T. Housekeeping gene analysis revealed that Az39T, together with five strains of the genus (Az19, REC3, BR 11975, MTCC4035 and MTCC4036), form a cluster apart from A. baldaniorum Sp245T, A. brasilense Sp7T and A. formosense CC-Nfb-7T. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) between Az39T and the aforementioned type strains revealed values below 96 %, the circumscription limit for the species delineation (ANI: 95.3, 94.1 and 94.0 %; dDDH: 62.9, 56.3 and 55.6 %). Furthermore, a phylogeny evaluation of the core proteome, including 809 common shared proteins, showed an independent grouping of Az39T, Az19, REC3, BR 11975, MTCC4035 and MTCC4036. The G+C content in the genomic DNA of these six strains varied from 68.3 to 68.5 %. Based on the combined phylogenetic, genomic and phenotypic characterization presented here, we consider that strain Az39T, along with strains Az19, REC3, BR 11975, MTCC4035 and MTCC4036, are members of a new Azospirillum species, for which the name Azospirillum argentinense sp. nov. is proposed. The type strain is Az39T (=LBPCV39T=BR 148428T=CCCT 22.01T).

Toxicity and Uptake of CuO Nanoparticles: Evaluation of an Emerging Nanofertilizer on Wheat (Triticum aestivum L.) Plant

Wet chemistry was used to produce copper oxide nanoparticles (CuO NPs). The results indicated that most nanoparticles were bacillus-shaped and relatively uniform in size (less than 30 nm). The effect of synthesized CuO NPs on wheat (Triticum aestivum L.) germination and growth parameters was studied and compared to bulk Cu. The results showed that no significant difference was obtained in germination rate among all treatments. Bulk Cu additions significantly affect the mean germination rate and mean germination time. On the contrary, germinability was significantly affected by CuO NPs additions. Seed vigor index was calculated to demonstrate the superior treatment in wheat germination parameters, and the results confirmed that 0.1 mg L−1 of CuO NPs could be successfully used to improve wheat seed germination. Moreover, the general average Cu concentrations in the plant tissue were 139 and 103 mg kg−1 dry weight for bulk and CuO NPs, respectively, indicating the dissolution behavior of CuO NPs. The addition of CuO NPs (0.1 mg L−1) promotes chlorophyll formation equal to 0.5 mg L−1 of the bulk Cu addition. This means using nanoparticles as fertilizer could reduce 80% of traditional fertilizers. Nonetheless, Cu additions in both forms (NPs and bulk) reduce root growth substantially compared to control. The effective toxic dose (EC50) for bulk Cu and CuO NPs was 0.37 mg L−1 and 0.94 mg L−1, respectively. The results indicated that approximately 2.5 times CuO NPs concentration is equal to the toxicity dose of bulk Cu due to lowered CuO NPs dissolution. Our study showed that Cu phytotoxicity is a non-nanosized effect and showed that plant-induced changes under environmentally real conditions should be considered when measuring the dissolution of CuO NPs near wheat plant roots. This study implies that using nano-CuO as a micronutrient amendment has a potential benefit rather than the soluble Cu salt for plant growth.

He-Ne laser irradiation ameliorates cadmium toxicity in wheat by modulating cadmium accumulation, nutrient uptake and antioxidant defense system

Cadmium (Cd) is one of the most hazardous heavy metals that negatively affect the growth and yield of wheat. He-Ne laser irradiation is known to ameliorate cadmium (Cd) stress in wheat. However, the underlying mechanism of He-Ne laser irradiation on protecting wheat against Cd stress is not well recognized. In present study, Cd-treated wheat showed significant reduction in growth, root morphology and total chlorophyll content, but notably increase of Cd accumulation in both roots and shoots. However, He-Ne laser irradiation dramatically reduced concentrations of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and increased total chlorophyll content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) in roots of wheat plants under Cd stress. Further, He-Ne laser irradiation significantly upregulated the transcripts of TaGR (glutathione reductase) and TaGST (glutathione-S-transferase) genes along with the increased activities of GR and GST and glutathione (GSH) concentration in roots of wheat seedlings under Cd stress. In addition, He-Ne laser irradiation enhanced the uptake of mineral elements (N, P, Mg, Fe, Zn and Cu), and significantly decreased Cd uptake and transport mainly through down-regulating the expressions of Cd transport genes (TaHMA2 and TaHMA3) in roots of wheat seedlings under Cd stress. Overall, these findings suggested that He-Ne laser irradiation alleviated the adverse effects of Cd on wheat growth by enhancing antioxidant defense system, improving mineral nutrient status, and decreasing the Cd uptake and transport. This study provides new insights into the roles of He-Ne laser irradiation in the amelioration of Cd stress in wheat and indicates the potential application of this irradiation in crop breeding and growth under Cd stress conditions.

Modulation in Biofertilization and Biofortification of Wheat Crop by Inoculation of Zinc-Solubilizing Rhizobacteria.

Zinc is an important micronutrient needed for the optimum growth and development of plants. Contrary to chemical zinc fertilizers, the use of zinc-solubilizing bacteria is an environmentally friendly option for zinc enrichment in edible parts of crops. This study was conducted with the objective of selecting potential zinc-solubilizing rhizobacteria from the rhizosphere of chickpea grown in soils of eastern Uttar Pradesh and further assessing their impact on the magnitude of zinc assimilation in wheat crops. Among 15 isolates, CRS-9, CRS-17, CRS-30, and CRS-38 produced net soluble zinc in broth to the tune of 6.1, 5.9, 5.63, and 5.6 μg ml–1, respectively, in zinc phosphate with the corresponding pH of 4.48, 5.31, 5.2, and 4.76. However, the bacterial strains CRS-17, CRS-30, CRS-38, and CRS-9 showed maximum zinc phosphate solubilization efficiency of 427.79, 317.39, 253.57, and 237.04%, respectively. The four bacterial isolates were identified as Bacillus glycinifermentans CRS-9, Microbacterium oxydans CRS-17, Paenarthrobacter nicotinovorans CRS-30, and Bacillus tequilensis CRS-38 on the basis of morphological and biochemical studies and 16S rRNA gene sequencing. Bacterial inoculants significantly colonized the roots of wheat plants and formed a biofilm in the root matrix. These strains significantly increased seed germination (%) and vigor indices in wheat grown under glasshouse conditions. After 30 days of sowing of wheat under microcosm conditions, eight zinc transporter (TaZIP) genes were expressed maximally in roots, with concomitant accumulation of higher zinc content in the bacterially treated plant compared to the absolute control. Out of the four strains tested, two bacteria, B. tequilensis CRS-38 and P. nicotinovorans CRS-30, improved seed germination (%), vigor indices (2–2.5 folds), plant biomass, grain yield (2.39 g plant–1), and biofortificated grains (54.25 μg g–1Zn) of wheat. To the best of our knowledge, this may be the first report on the presence of zinc solubilization trait in B. glycinifermentans CRS-9, M. oxydans CRS-17, and P. nicotinovorans CRS-30.

Morphological and Molecular Characterization of Fusarium chlamydosporum, F. brachygibbosum and F. flocciferum Associated with Crown and Root Rot of Wheat

Zidan, L., D. Jawdat and W. Naffaa. 2022. Morphological and Molecular Characterization of Fusarium chlamydosporum, F. brachygibbosum and F. flocciferum Associated with Crown and Root Rot of Wheat. Arab Journal of Plant Protection, 40(2): 175-181. https://doi.org/10.22268/AJPP-040.2.175181 Fusarium is one of the most important genera of fungi, causing plant, animal, and human diseases and produces mycotoxins. A total of 105 isolates of Fusarium spp. were recovered from crowns and roots of wheat plants, showing typical symptoms, collected from four Syrian provinces during 2017-2018. In previous studies, seventeen Fusarium species associated with crown and root rot (FCR) on wheat were identified in Syria. However, the identity of some isolates has not been resolved. The current study was carried out to identify and characterize through morphological approaches and sequencing a partial translation elongation factor 1-alpha (TEF1-α) gene in three Fusarium species F. chlamydosporum Wollenweber & Reinking, F. brachygibbosum Padwick and F. flocciferum Corda associated with FCR, isolated and identified for the first time in Syria. The present study will provide detailed cultural and morphological characteristics of the three species, scarcely described in literature. Keywords: First record, morphological descriptions, TEF1-α gene, Syria.

Effect of the combined use of phytohormone-producing bacteria and Chistalan herbicide on the physiological and morphological parameters of wheat plants

Results of the treatment with bacteria producing phytohormones, and herbicide-tolerant on physiological and morphological parameters of wheat plants with simultaneous exposure to Chistalan herbicide are presented. Strains of Pseudomonas sp. DA1.2 and P. koraiensis IB-4 prevented the suppression of plant growth, caused the redistribution of auxins between in favor of escape and a decrease in the content of ABA in the roots of wheat plants against the action of the herbicide Chistalan. The bacteria had a positive effect on the photosynthetic apparatus and reduced the development of oxidative stress caused by the herbicide. It is shown that herbicide stress is reduced under the influence of bacteria.

Tillage, Glyphosate and Beneficial Arbuscular Mycorrhizal Fungi: Optimising Crop Management for Plant–Fungal Symbiosis

Zero till cropping systems typically apply broad-spectrum herbicides such as glyphosate as an alternative weed control strategy to the physical inversion of the soil provided by cultivation. Glyphosate targets 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase in plants. There is growing evidence that this may have a detrimental impact on non-target organisms such as those present in the soil microbiome. Species of commercial importance, such as arbuscular mycorrhizal (AM) fungi that form a symbiotic relationship with plant roots are an important example. This study investigates the impact of soil cultivation and glyphosate application associated with conventional tillage (CT) and zero tillage (ZT) respectively on AM fungi populations under field and glasshouse conditions. Topsoil (<10 cm) was extracted from CT and ZT fields cropped with winter wheat, plus non-cropped control plots within the same field boundary, throughout the cropping year. Glyphosate was applied in glasshouse experiments at rates between 0 and 350 g L−1. Ergosterol, an indicator of fungal biomass, was measured using high performance liquid chromatography before and after glyphosate application. Fungal root arbuscules, an indicator of AM fungi–root symbiosis, were quantified from the roots of wheat plants. Under glasshouse conditions root arbuscules were consistently higher in wheat grown in ZT field extracted soils (P = 0.01) compared to CT. Glyphosate application however inhibited fungal biomass in both the ZT (P < 0.00001) and CT (P < 0.001) treatments. In the absence of glyphosate, the number of stained root arbuscules increased significantly. Ergosterol levels, used as a proxy for fungal biomass, remained lower in the soil post glyphosate application. The results suggest that CT has a greater negative impact on AM fungal growth than ZT and glyphosate, but that glyphosate is also detrimental to AM fungal growth and hinders subsequent population recovery.

Changes in root-associated fungal communities in Triticum aestivum ssp. spelta L. and Triticum aestivum ssp. vulgare L. under drought stress and in various soil processing.

Plant roots are inhabited by an enormous variety of microorganisms, including fungi, which can control the growth as well as regulate the health of the host plants. The mycobiome composition of the roots of wheat plants, especially spelt, under drought stress has been rarely investigated. Therefore, the aim of the present study was to examine the composition of fungal communities in the root endosphere and rhizosphere of three Triticum aestivum ssp. spelta L. cultivars and one Triticum aestivum ssp. vulgare L. cultivar, grown under drought and controlled conditions in different soil preparations. Culture-dependent fungal community profiling was performed to examine the impact of rhizocompartments (endosphere, rhizosphere), host genotype, watering status and different soil preparation on roots mycobiome structure. A total of 117 fungal strains, belonging to 22 genera, were found to colonize the internal and external parts of roots in T. aestivum ssp. spelta L. and T. aestivum ssp. vulgare L. cultivars. The results showed that the part of root and soil preparation type significantly determined the mycobiome composition of wheat roots.

Maximization of Siderophores Production from Biocontrol Agents, Pseudomonas aeruginosa F2 and Pseudomonas fluorescens JY3 Using Batch and Exponential Fed-Batch Fermentation

Twenty fluorescent Pseudomonas isolates were tested for their ability to produce siderophores on chrome azurol S (CAS) agar plates and their antagonistic activity against six plant pathogenic fungal isolates was assessed. Scaling-up production of siderophores from the promising isolates, P. aeruginosa F2 and P. fluorescens JY3 was performed using batch and exponential fed-batch fermentation. Finally, culture broth of the investigated bacterial isolates was used for the preparation of two economical bioformulations for controlling Fusarium oxysporum and Rhizoctonia solani. The results showed that both isolates yielded high siderophore production and they were more effective in inhibiting the mycelial growth of the tested fungi compared to the other bacterial isolates. Exponential fed-batch fermentation gave higher siderophore concentrations (estimated in 10 µL), which reached 67.05% at 46 h and 45.59% at 48 h for isolates F2 and JY3, respectively, than batch fermentation. Formulated P. aeruginosa F2 and P. fluorescens JY3 decreased the damping-off percentage caused by F. oxysporum with the same percentage (80%), while, the reduction in damping-off percentage caused by R. solani reached 87.49% and 62.5% for F2 and JY3, respectively. Furthermore, both formulations increased the fresh and dry weight of shoots and roots of wheat plants. In conclusion, bio-friendly formulations of siderophore-producing fluorescent Pseudomonas isolates can be used as biocontrol agents for controlling some plant fungal diseases.

Graphene oxide exposure suppresses nitrate uptake by roots of wheat seedlings

Despite the large number of studies reporting the phytotoxicity of graphene-based materials, the effects of these materials on nutrient uptake in plants remain unclear. The present study showed that nitrate concentrations were significantly decreased in the roots of wheat plants treated with graphene oxide (GO) at 200–800 mg L−1. Non-invasive microelectrode measurement demonstrated that GO could significantly inhibit the net NO3− influx in the meristematic, elongation, and mature zones of wheat roots. Further analysis indicated that GO could be trapped in the root vacuoles, and that the maximal root length and the number of lateral roots were significantly reduced. Additionally, root tip whitening, creases, oxidative stress, and weakened respiration were observed. These observations indicate that GO is highly unfavorable for vigorous root growth and inhibits increase in root uptake area. At the molecular level, GO exposure caused DNA damage and inhibited the expression of most nitrate transporters (NRTs) in wheat roots, with the most significantly downregulated genes being NRT1.3, NRT1.5, NRT2.1, NRT2.3, and NRT2.4. We concluded that GO exposure decreased the root uptake area and root activity, and decreased the expression of NRTs, which may have consequently suppressed the NO3− uptake rate, leading to adverse nitrate accumulation in stressed plants.