Endophytic microorganisms, including bacterial and fungal species, establish symbiotic relationships within plant tissues, contributing to plant growth, nutrient acquisition, and stress resilience. In this review, multiple roles of endophyte-plant interactions have been discussed. Endophytes aid in nitrogen fixation for plants, enhance nutrient solubilization and uptake, control the attack of phytopathogens on plants, and help the plants to tolerate environmental stresses. The molecular mechanisms of these interactions, uncovered by the advancements in genomics, metabolomics, and microbiome engineering, reveal novel bioactive compounds and metabolic pathways that can improve crop resilience. The integration of multi-omics technologies and functional validation holds great potential for sustainable agriculture, offering new strategies for formulating effective biostimulants, bioinoculants, and biocontrol agents to improve crop health, agricultural productivity, and nutritional quality.

Ephedra alata Decne is a medicinal plant widely used in traditional medicine for the management of bronchial asthma and cancer. Phytochemical analysis and biological activities, including antioxidant and anticancer effects, were investigated in the current work as new findings for the plant E. alata, a species growing wildly in the marsh and saline environments of the central area of Saudi Arabia. The Ultra Pressure Liquid Chromatography coupled with Electron spray ionization-Quadropole-Time of flight (UPLC-ESI-Q-TOF) system was used for the phytochemical analysis of the plant constituents. In addition, Polyphenolic profiling including the total phenolic (TPC) and flavonoid (TFC) contents of the plant extracts were measured. Phenolic acids were found at the highest relative percentages among all the identified compounds and were measured at 66.07 mg GAE (Gallic acid equivalent). The UPLC analysis of the E. alata extract indicated the presence of chlorogenic acid, syringic acid, caffeic acid, vanillic acid, rosmarinic acid, umbelliferone, isorhoifolin, and apigenin at the highest relative percentages. Mineral analysis indicated that the microelement content of E. alata was relatively low, except for magnesium (Mg). In vitro antioxidant assays revealed the ability of the plant to scavenge DPPH free radicals, reduced molybdenum ions, and ferrous at levels of 14.63, 19.97, and 27.78 mg Trolox equivalents, respectively. The extract induced transition metal chelation at 31.36 mg EDTA equivalents. The extract induced cytotoxic effects against MDA-231 and A549 cell lines at IC50 levels of 25.31 and 39.81 mu g/mL, respectively. The plant extract inhibited the colonization and migration of cancer cells as part of its potential anticancer effects. In addition, major E. alata constituents like isorhoifolin, chlorogenic acid, apigenin, and rosmarinic acid exhibited the lowest binding energy to the CAIX enzyme at - 8.41, - 6.64, - 6.32, and - 6.26 kcal/mol, respectively, compared to the binding energy (- 7.72 kcal/mol) of the co-crystallized ligand (Y0R). The docking results further supported the selection of the CAIX enzyme as a standard predictive therapeutic target, since it exhibited significant binding interactions with the major constituents of the plant.

Vermicompost (VC) products have grown in popularity in plant nutrition and are widely used to improve plant growth and suppress plant diseases. In addition, the choice of chemical-free food and increased public concern for human health and the environment due to the impacts of hazardous inorganic fertilizers have motivated farmers to seek safer and more eco-friendly alternatives. The present study aimed to evaluate the plant-growth-promoting and biocontrol potential of macrophyte biomass-based VC products in tomato plants. The results indicated that tomato plants treated with VC + vermicompost tea (VCT) resulted in 30.74% higher plant height, 20.70% more leaves, 29.05% more fruits, and 61.26% higher total yield than the control plants. In addition, VC products significantly reduced disease incidence by 35-60%, whereas the untreated control had the highest wilt incidence (75%). The study concludes that VC products produced from free-floating aquatic weed biomass (Azolla, Lemna, and Salvinia) could be used as a potential alternative to inorganic fungicides to manage Fusarium wilt disease and as bioinoculants to improve the growth and yield of tomato plants for sustainable crop production.

Botryosphaeriaceae fungi cause infections that generate disease symptoms in plants in extreme environments. The present study identified the causal agent of dieback disease on lebbeck trees in Saudi Arabia. Albizia lebbeck trees showed widespread dieback, decline and cracking symptoms of samples taken during a Qassim University, Saudi Arabia survey. The survey showed that over 80% of lebbeck trees showed wilted roots, stem cankers and death of wilted trees. Fungal colonies were obtained from symptomatic tissues cultured on water agar for 3 weeks at 25 degrees C. Elongation factor alpha (EF1-728 F, AL33R), ITS (ITS4) and LSU (128) regions of the rDNA operon and the partial beta-tubulin gene (tub2; Bt2aF, Bt2bR) were sequenced for molecular identification. Based on morphological and molecular characterization, the pathogen was identified as Neoscytalidium dimidiatum. During the pathogenicity investigation, the fungus re-isolated from the infected seedlings expressed the same morphological characteristics on the culture media as the N. dimidiatum isolate. A host range study involving six tree species inoculation with N. dimidiatum caused wilting and death in three plants. To our knowledge, this study is the first to report on N. dimidiatum in Saudi Arabia.

The aim of the study was to estimate the impact of soil amendments (i.e., phosphogypsum and plant growth-promoting rhizobacteria (PGPR)) separately or their combination on exchangeable sodium percentage (ESP), soil enzymes’ activity (urease and dehydrogenase), pigment content, relative water content (RWC), antioxidant enzymatic activity, oxidative stress, productivity, and quality of quinoa under deficient irrigation conditions in two field experiments during the 2019–2020 and 2020–2021 seasons under salt-affected soil. Results revealed that ESP, soil urease activity, soil dehydrogenase activity, leaf chlorophyll a, b, and carotenoids, leaf K content, RWC, SOD (superoxide dismutase), CAT (catalase), and POD (peroxidase) activities were declined, resulting in overproduction of leaf Na content, proline content, and oxidative stress indicators (H2O2, malondialdehyde (MDA) and electrolyte leakage) under water stress and soil salinity, which negatively influence yield-related traits, productivity, and seed quality of quinoa. However, amendment of salt-affected soil with combined phosphogypsum and seed inoculation with PGPR under deficient irrigation conditions was more effective than singular application and control plots in ameliorating the harmful effects of water stress and soil salinity. Additionally, combined application limited Na uptake in leaves and increased K uptake and leaf chlorophyll a, b, and carotenoids as well as improved SOD, CAT, and POD activities to ameliorate oxidative stress indicators (H2O2, MDA, and electrolyte leakage), which eventually positively reflected on productivity and quality in quinoa. We conclude that the potential utilization of phosphogypsum and PGPR are very promising as sustainable eco-friendly strategies to improve quinoa tolerance to water stress under soil salinity.

Iron-deficiency-induced anemia is associated with poor neurological development, including decreased learning ability, altered motor functions, and numerous pathologies. Siderophores are iron chelators with low molecular weight secreted by microorganisms. The proposed catechol-type pathway was identified based on whole-genome sequences and bioinformatics tools. The intended pathway consists of five genes involved in the biosynthesis process. Therefore, the isolated catechol-type siderophore (Sid) from Streptomyces tricolor HM10 was evaluated through an anemia-induced rat model to study its potential to accelerate recovery from anemia. Rats were subjected to an iron-deficient diet (IDD) for 42 days. Anemic rats (ARs) were then divided into six groups, and normal rats (NRs) fed a standard diet (SD) were used as a positive control group. For the recovery experiment, ARs were treated as a group I; fed an IDD (AR), group II; fed an SD (AR + SD), group III, and IV, fed an SD with an intraperitoneal injection of 1 μg Sid Kg−1 (AR + SD + Sid1) and 5 μg Sid Kg−1 (AR + SD + Sid5) twice per week. Group V and VI were fed an iron-enriched diet (IED) with an intraperitoneal injection of 1 μg Sid Kg−1 (AR + IED + Sid1) and 5 μg Sid Kg−1 (AR + IED + Sid5) twice per week, respectively. Weight gain, food intake, food efficiency ratio, organ weight, liver iron concentration (LIC) and plasma (PIC), and hematological parameters were investigated. The results showed that ~50–60 mg Sid L−1 medium could be producible, providing ~25–30 mg L−1 purified Sid under optimal conditions. Remarkably, the AR group fed an SD with 5 μg Sid Kg−1 showed the highest weight gain. The highest feed efficiency was observed in the AR + SD + Sid5 group, which did not significantly differ from the SD group. Liver, kidneys, and spleen weight indicated that diet and Sid concentration were related to weight recovery in a dose-dependent manner. Liver iron concentration (LIC) in the AR + IED + Sid1 and AR + IED + Sid5 groups was considerably higher than in the AR + SD + Sid1 AR + SD + Sid5 groups or the AR + SD group compared to the AR group. All hematological parameters in the treated groups were significantly closely attenuated to SD groups after 28 days, confirming the efficiency of the anemia recovery treatments. Significant increases were obtained in the AR + SD + Sid5 and AR + IED + Sid5 groups on day 14 and day 28 compared to the values for the AR + SD + Sid1 and AR + IED + Sid1 groups. The transferrin saturation % (TSAT) and ferritin concentration (FC) were significantly increased with time progression in the treated groups associatively with PIC. In comparison, the highest significant increases were noticed in ARs fed IEDs with 5 μg Kg−1 Sid on days 14 and 28. In conclusion, this study indicated that Sid derived from S. tricolor HM10 could be a practical and feasible iron-nutritive fortifier when treating iron-deficiency-induced anemia (IDA). Further investigation focusing on its mechanism and kinetics is needed.

Siderophores are iron-chelating low-molecular-weight compounds that bind iron (Fe3+) with a high affinity for transport into the cell. The newly isolated strain Streptomyces tricolor HM10 secretes a pattern of secondary metabolites. Siderophore molecules are the representatives of such secondary metabolites. S. tricolor HM10 produces catechol, hydroxamate, and carboxylate types of siderophores. Under 20 μM FeCl3 conditions, S. tricolor HM10 produced up to 6.00 µg/mL of catechol siderophore equivalent of 2,3-DHBA (2,3-dihydroxybenzoic acid) after 4 days from incubation. In silico analysis of the S. tricolor HM10 genome revealed three proposed pathways for siderophore biosynthesis. The first pathway, consisting of five genes, predicted the production of catechol-type siderophore similar to petrobactin from Bacillus anthracis str. Ames. The second proposed pathway, consisting of eight genes, is expected to produce a hydroxamate-type siderophore similar to desferrioxamine B/E from Streptomyces sp. ID38640, S. griseus NBRC 13350, and/or S. coelicolor A3(2). The third pathway exhibited a pattern identical to the carboxylate xanthoferrin siderophore from Xanthomonas oryzae. Thus, Streptomyces strain HM10 could produce three different types of siderophore, which could be an incentive to use it as a new source for siderophore production in plant growth-promoting, environmental bioremediation, and drug delivery strategy.

Water deficit is a pivotal abiotic stress that detrimentally constrains rice growth and production. Thereupon, the development of high-yielding and drought-tolerant rice genotypes is imperative in order to sustain rice production and ensure global food security. The present study aimed to evaluate diverse exotic and local parental rice genotypes and their corresponding cross combinations under water-deficit versus well-watered conditions, determining general and specific combining ability effects, heterosis, and the gene action controlling important traits through half-diallel analysis. In addition, the research aimed to assess parental genetic distance (GD) employing simple sequence repeat (SSR) markers, and to determine its association with hybrid performance, heterosis, and specific combining ability (SCA) effects. Six diverse rice genotypes (exotic and local) and their 15 F1 hybrids were assessed for two years under water-deficit and well-watered conditions. The results revealed that water-deficit stress substantially declined days to heading, plant height, chlorophyll content, relative water content, grain yield, and yield attributes. Contrarily, leaf rolling and the sterility percentage were considerably increased compared to well-watered conditions. Genotypes differed significantly for all the studied characteristics under water-deficit and well-watered conditions. Both additive and non-additive gene actions were involved in governing the inheritance of all the studied traits; however, additive gene action was predominant for most traits. The parental genotypes P1 and P2 were identified as excellent combiners for earliness and the breeding of short stature genotypes. Moreover, P3, P4, and P6 were identified as excellent combiners to increase grain yield and its attributes under water-deficit conditions. The hybrid combinations; P1 × P4, P2 × P5, P3 × P4, and P4 × P6 were found to be good specific combiners for grain yield and its contributed traits under water-deficit conditions. The parental genetic distance (GD) ranged from 0.38 to 0.89, with an average of 0.70. It showed lower association with hybrid performance, heterosis, and combining ability effects for all the studied traits. Nevertheless, SCA revealed a significant association with hybrid performance and heterosis, which suggests that SCA is a good predictor for hybrid performance and heterosis under water-deficit conditions. Strong positive relationships were identified between grain yield and each of relative water content, chlorophyll content, number of panicles/plant, number of filled grains/panicle, and 1000-grain weight. This suggests that these traits could be exploited as important indirect selection criteria for improving rice grain yield under water-deficit conditions.

Streptomyces is a genus with known biocontrol activity, producing a broad range of biologically active substances. Our goal was to isolate local Streptomyces species, evaluate their capacity to biocontrol the selected phytopathogens, and promote the plant growth via siderophore and indole acetic acid (IAA) production and phosphate solubilization. Eleven isolates were obtained from local soil samples in Saudi Arabia via the standard serial dilution method and identified morphologically by scanning electron microscope (SEM) and 16S rRNA amplicon sequencing. The biocontrol of phytopathogens was screened against known soil-borne fungi and bacteria. Plant growth promotion capacity was evaluated based on siderophore and IAA production and phosphate solubilization capacity. From eleven isolates obtained, one showed 99.77% homology with the type strain Streptomyces tricolor AS 4.1867, and was designated S. tricolor strain HM10. It showed aerial hyphae in SEM, growth inhibition of ten known phytopathogens in in vitro experiments, and the production of plant growth promoting compounds such as siderophores, IAA, and phosphate solubilization capacity. S. tricolor strain HM10 exhibited high antagonism against the fungi tested (i.e., Colletotrichum gloeosporides with an inhibition zone exceeding 18 mm), whereas the lowest antagonistic effect was against Alternaria solani (an inhibition zone equal to 8 mm). Furthermore, the most efficient siderophore production was recorded to strain HM8, followed by strain HM10 with 64 and 22.56 h/c (halo zone area/colony area), respectively. Concerning IAA production, Streptomyces strain HM10 was the most effective producer with a value of 273.02 μg/ml. An autochthonous strain S. tricolor HM10 should be an important biological agent to control phytopathogens and promote plant growth.

From 2015 to 2017 symptoms associated with phytoplasmas were observed in vegetable crop farms located in Uyun AlJiwa and Al-Dawadmi, cities located in the Al-Qassim Region and the Riyadh Province, respectively. Affected eggplants exhibited symptoms of phyllody, little leaves and witches broom, symptomatic cabbage showed multiple heads, beetroot showed reddening, stunting and leaves proliferation symptoms, while celery plants showed stunting and yellowing symptoms. To determine if the symptomatic samples were affected by phytoplasmas, PCR was performed with phytoplasma universal primers P1/P7 followed by a nested PCR with primer pair R16mF2/R16mR2, which target the 16S rRNA-encoding gene locus. PCR revealed that 20/20 symptomatic eggplants, 15/20 symptomatic cabbage, 26/30 symptomatic beetroot, and 9/11 symptomatic celery plants were infected with phytoplasma, and sequencing of the amplified genes revealed that the phytoplasmas belonged to the peanut witches’-broom group (16SrII). Sequence analysis using in silico restriction fragment length polymorphism (RFLP) and phylogenetic analysis revealed the presence of two closely related but distinct sequences from the 16SrII-D and the recently described 16SrII-X subgroups. The two sequences differed by a single base pair and both subgroups were detected in cabbage, beetroot, and celery, while eggplant was only affected by subgroup 16SrII-X. Sequence analysis of the chaperonin-60 universal target confirmed the classification of these phytoplasma strains in the 16SrII group and their close phylogenetic relationship. This is the first report of eggplant, cabbage, beetroot, and celery affected by phytoplasma in Saudi Arabia, and the first report of these plant hosts affected by the 16SrII-X subgroup.

Knowledge of combining ability and genetic diversity are important prerequisites for the development of outstanding hybrids that are tolerant to high plant density. This work was carried out to assess general combining ability (GCA) and specific combining ability (SCA), identify promising hybrids, estimate genetic diversity among the inbred lines and correlate genetic distance to hybrid performance and SCA across different plant densities. A total of 28 F1 hybrids obtained by crossing eight adverse inbred lines (four local and four exotic) were evaluated under three plant densities 59,500 (D1), 71,400 (D2) and 83,300 (D3) plants ha−1 using spilt plot design with three replications at two locations during 2018 season. Increasing plant density from D1 to D3 significantly decreased leaf angle (LANG), chlorophyll content (CHLC), all ear characteristics and grain yield per plant (GYPP). Contrarily, days to silking (DTS), anthesis–silking interval (ASI), plant height (PLHT), ear height (EHT), and grain yield per hectare (GYPH) were significantly increased. Both additive and non-additive gene actions were involved in the inheritance of all the evaluated traits, but additive gene action was predominant for most traits. Inbred lines L1, L2, and L5 were the best general combiners for increasing grain yield and other desirable traits across research environments. Two hybrids L2 × L5 and L2 × L8 were found to be good specific combiners for ASI, LANG, GYPP and GYPH. Furthermore, these hybrids are ideal for further testing and promotion for commercialization under high plant density. Genetic distance (GD) among pairs of inbred lines ranged from 0.31 to 0.78, with an average of 0.61. Clustering based on molecular GD has effectively grouped the inbred lines according to their origin. No significant correlation was found between GD and both hybrid performance and SCA for grain yield and other traits and proved to be of no predictive value. Nevertheless, SCA could be used to predict the hybrid performance across all plant densities. Overall, this work presents useful information regarding the inheritance of maize grain yield and other important traits under high plant density.

This research was carried out under field conditions to study the effect of foliar application of zinc-oxide nanoparticles on some physiological, yield components and quality attributes of four flax cultivars under different irrigation treatments. Three irrigation treatments were applied through three separated irrigation experiments each season. Each irrigation experiment was carried out using a split-plot design with three replications. The four cultivars were plotted in the main plots. However, nano-zinc oxide treatments were arranged in the sub-plots. Irrigation treatment IT3 (Irrigate two irrigations after life irrigation) had superiority and ranked the first for all straw yield traits, no. of capsules per plant, seed and oil yields per hectare, fiber length and fiber yield per hectare. However, irrigation treatment IT2 (Irrigate one irrigation after life irrigation) recorded the highest total fiber percentage. The data showed that, Sakha 3 gave the highest values for plant height, technical stem length, fiber length, fiber fineness, total fiber percentage and fiber yield per hectare, while, Giza 11 and Giza 12 recorded the highest values of main stem diameter and straw yield per hectare. Besides, Sakha 5 scored the highest number of capsules per plant, seed and oil yields per hectare and oil percentage. One irrigation treatment (IT1) gave the lowest concentrations of chlorophyll a and b, while, the highest levels of proline, CAT and PDX were recorded. With respect to nano-zinc oxide application, foliar spray of Zinc oxide nanoparticles induced a significant increment in all straw, oil and fiber traits except fiber fineness. Application of the highest concentration of zinc-oxide NPs (100 mg/Litre) recorded the highest values of the previous mentioned traits.

The fitness of microbes and their colonization efficiency in plants is significant for promotion of plant growth, but the mechanism between plants and bacteria in rhizospheric region is not clearly explained. This study focused on identification and characterization of some plant growth promoting biocontrol bacteria. A total of 94 bacteria strains were isolated and tested for different plant growth promotion activities and their antagonistic behaviors towards different pathogenic fungi. The isolated bacteria were categorized into 23 bacterial genera, using 16S rRNA. The most predominant genera of bacterial isolates were Pseudomonas (4 species) and Bacillus (6 species). The isolates (Qassim University Saudi Arabia (QUSA) 52 and 45) and their transposon mutagenesis mutants inhibited mycelium growth of Rhizoctonia solani, Alternria sp., and Colletotrichum sp. Isolates 52 and 45 of P. fluorescens and their mutants' 52-M12, 45-M19, and 45-M20 yielded the highest dry weight and shoot, and root length in alfalfa plants. Furthermore, the efficiency of these bacterial isolates and mutants against R. solani was considerably higher than the control treatment. Therefore, application of biocontrol agents can significantly control the soil-born fungal pathogen in alfalfa plants.

In recent years, the number of plant hosts affected by peanut witches’-broom group (16SrII) phytoplasma in Saudi Arabia has increased at a concerning speed. Since 2015 symptoms resembling phytoplasma-related diseases have been reported in Al-Qassim region affecting the wild plants globe amaranth, amaranthus, black nightshade, and buckthorn. Except for globe amaranth, which showed flower deformations, the other plants showed witches’ broom and little leaves. All the symptomatic samples collected in this study were positive for phytoplasma using universal primers targeting the 16S rRNA-encoding gene. Sequence analysis identified the phytoplasma as a member of the 16SrII-X subgroup, originally described in Saudi Arabia by our group. This is the first report of globe amaranth, amaranthus, black nightshade, and buckthorn as phytoplasma hosts in Saudi Arabia, and the first report worldwide of globe amaranth as a phytoplasma host and buckthorn being affected by 16SrII phytoplasma group.

This study evaluated the efficacy of three bacterial species. Acinetobacter sp. (concentration 2.237×108 cfu/ml), Bacillus subtilis (concentration 2.470×108 cfu/ml) and Bacillus qassimus (concentration 3.320×108 cfu/ml) were tested against the two-spotted spider mite, Tetranychus urticae, infesting eggplants under laboratory and greenhouse conditions. In addition, we studied their side effects on the predatory mite, Phytoseius plumifer. The highest efficiency rate on T. urticae was observed with Acinetobacter sp. sprays. Three days after treatment, mite mortality reached 87.15 and 77.29 % under laboratory and greenhouse conditions, respectively. Moreover, the mortality rates were significantly lower (72.22 and 67.11 % and 70.74 and 65.19 %) using B. subtilis and B. qassimus under lab and greenhouse conditions, seven days after treatment. The predatory mite, P. plumifer, showed higher tolerance than T. urticae to the three bacterial preparations. The results of this study indicated that Acinetobacter sp. has a strong efficacy on T. urticae and slightly affected the predatory species herein tested. This study introduces a potentially new strategy for biological control of phytophagous mites.

Exposure to lead (Pb), zinc (Zn), cadmium (Cd), copper (Cu), and selenite (SeO3−2) consider the main heavy metals that threat human health. These heavy metals can interfere with the function of vital cellular components. Soil heavy metal contamination represents risks to humans and the ecosystem through drinking of contaminated groundwater, direct ingestion or the food chain, and reduction in food quality. Bioremediation means cleanup of polluted environment via transformation of toxic heavy metals into less toxic form by microbes or its enzymes. Otherwise, bioremediation by microbes has limitations like production of toxic metabolites. The efflux of metal ions outside the cell, biosorption to the cell walls and entrapment in extracellular capsules, precipitation, and reduction of the heavy metal ions to a less toxic state are mechanisms to metals' resistance.

Severe terminal bud rot disease symptoms of Washingtonia, Washingtonia robusta , palms were observed in the 5-year-old trees in a farm located at the north of Al Shehia governorate, Qassim region, Saudi Arabia. The fungus found associated with the diseased palm buds was isolated in the laboratory, and pathogenicity tests were conducted on healthy 1-year-old Washingtonia palms, at an experimental station, Agriculture and Veterinary Medicine. Pathogenicity tests showed that a single fungus caused typical symptoms of bud rot on the inoculated trees. Petiole bases and terminal buds were rotted after 5–6 weeks of inoculation. The pathogen was identified through microscopy and characterized molecularly, using internal transcribed spacer (ITS) regions of ribosomal DNA, as a fungal-like organism Phytophthora nicotianae (synonym = P . parasitica ). Experiments were conducted on the biological control of the pathogen in the laboratory, and a promising RN13 isolate of Lysobacter enzymogenes was selected for further study. This study seems to be the first report of bud rot disease of Washingtonian palms caused by P . nicotianae in Saudi Arabia. Great attention should be given to this disease because it is soil borne and may be transmitted to the date palm crop.

Environmental stressors negatively affect crop growth and yield. Limited information is available about the synergistic use of biochar and plant growth-promoting rhizobacteria (PGPR). A field study was conducted to evaluate the effect of biochar in combination with PGPR (Pseudomonas koreensis and Bacillus coagulans) for alleviating water deficit and saline soil in rice (Oryza sativa L.). Two growing seasons, 2017 and 2018, were examined using twelve combinations of three irrigation intervals every 6 days (I-1), 8 days (I-2), and 10 days (I-3) and four soil treatments (control, PGPR, biochar, and combination of PGPR + biochar) in salt-affected soil. The findings exhibited that synergistic use of biochar and PGPR alleviated the negative effect of these stressors. The integrative use of biochar and PGPR caused an increment in soil moisture content and physicochemical properties. Significant increasing in chlorophyll content, relative water content, stomatal conductance, K+ and K+/Na+ contents occurred with decreasing proline content and Na+ content, which confirmed the efficacy of this approach. As a result, the highest yield and its related traits were attained when biochar and PGPR were added together under irrigation interval I-1, which was on par with I-2. We concluded that increased nutrients uptake (N, P, and K) were the cause of the superior rice productivity resulting from co-PGPR biochar. Synergistic use of biochar and PGPR could be an effective strategy for improving plant growth and productivity under stressors.

Date palm and Mexican fan palm trees showing symptoms previously associated with phytoplasmas were observed in the Al-Qassim region, Saudi Arabia in 2017. DNA amplification, sequencing, and phylogenetic analysis revealed the presence of a 'Candidatus Phytoplasma australasia'- related strain in eighteen of the eighty-three symptomatic plants collected that were positive using 16S-based assays. This study confirmed the presence of phytoplasma affecting date palms in Saudi Arabia and it is the first report of several date palm cultivars associated with 'Ca. P. australasia'-related strains. This is also the first report worldwide of Mexican fan palm trees affected by 16SrII phytoplasma strains and the first report of this plant host affected by phytoplasmas in Saudi Arabia. The implications of these findings are vital to implement management strategies and avoid economic losses in Saudi Arabia and the Middle East, which are the main producers of dates in the world.

Potato (Solanum tuberosum) is a very economically important perennial tuberous crop in Saudi Arabia. Potato plants displaying symptoms associated with potato purple top disease, such as aerial tubers and purple and small leaves, were observed in Al-Bukairiyah, Fowlq and Buraydah, Al-Tarafiyah, Qassim governorate, Saudi Arabia. In this study, we examined samples taken from 12 symptomatic potato plants and confirmed the presence of phytoplasma DNA. Analysis of the 16S rRNA-encoding sequences revealed that the symptomatic plants were infected with phytoplasma belonging to the peanut witches’-broom group (16SrII). Sequencing of the 16S rRNA- encoding gene, computer-simulated RFLP analysis and phylogenetic analysis revealed the presence of a novel representative of the 16SrII-X subgroup. The present study identified potato plants as a novel host for novel phytoplasma strains belonging to the pigeon pea witches’-broom group in Saudi Arabia.