Background:Endophytic fungi, which have been reported in numerous plant species, are important components of the forest community and contribute significantly to the diversity of natural ecosystems.Objectives:The current study aimed to evaluate and characterize, at the molecular level, the diversity and antimicrobial activities of endophytic fungi from medicinal plants in Saudi Arabia.Materials and Methods:Fungi growing on plant segments were isolated and identified based on morphological and molecular characteristics. The isolates were grouped into 35 distinct operational taxonomic units, based on the sequence of the internal transcribed spacer regions in the rRNA gene. The colonization frequency and the dominant fungi percentage of these endophytic fungi were calculated. A dual culture technique was adopted to investigate the antifungal activity of these endophytes.Results:Tamarix nilotica showed the highest endophytic diversity with a relative frequency of 27.27%, followed by Cressa cretica with a relative frequency of 19.27%. The most frequently isolated species was Penicillium chrysogenum with an overall colonization rate of 98.57%. Seven out of 35 endophytic fungi exhibited strong antifungal activity to all plant fungal pathogens tested. P. chrysogenum, Fusarium oxysporum, and F. nygamai exhibited the highest inhibition against the human pathogenic bacteria Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Aspergillus sydowii, P. chrysogenum, and Eupenicillium crustaceum showed strong antimicrobial activity against Enterococcus faecalis.Conclusions:The antimicrobial activity of these endophytic microorganisms could be exploited in biotechnology, medicine, and agriculture.

Vanadium (V) can be beneficial or toxic to plant growth and the interaction between arbuscular mycorrhizal fungi (AMF) and V stress was rarely investigated at physiological and biochemical levels of plant groups (C3 and C4) and organs (roots and shoots). We tested the potential of AMF to alleviate the negative effects of V (350 mg V/Kg soil) on shoots and roots of rye and sorghum. Relative to sorghum (C4), rye (C3) showed higher levels of V and lower levels of key elements under V stress conditions. V inhibited growth, photosynthesis, and induced photorespiration (increased HDR & GO activities) and oxidative damage in both plants. AMF colonization reduced V stress by differently mitigating the oxidative stress in rye and sorghum. This mitigation was accompanied with increases in acid and alkaline phosphatase activities in plant roots and increased organic acids and polyphenols exudation into the soil, thus reduced V accumulation (29% and 58% in rye and sorghum shoot, respectively) and improved absorption of mineral nutrients including Ca, Mg and P. AMF colonization improved photosynthesis and increased the sugar accumulation and metabolism. Sugars also acted as a supplier of C skeletons for producing of antioxidants metabolite such as ascorbate. At the antioxidant level, rye was more responsive to the mitigating impact of AMF. Higher antioxidants and detoxification defence system (MTC, GST, phenolics, tocopherols and activities of CAT, SOD and POX) was recorded for rye, while sorghum (C4) improved its GR activity. The C3/C4-specificity was supported by principal component analysis. Together, this study provided both fundamental and applied insights into practical strategies to mitigate the phytotoxicity hazards of V in C3 and C4 grasses. Moreover, our results emphasize the importance of AMF as an environment-friendly factor to alleviate stress effects on plants and to improve growth and yield of unstressed plants.

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Saudi Arabia is part of a hot dry desert region and is characterized by stressful conditions. The main goal of this research was to identify endophytic fungal (EF) community composition, diversity and abundance in relation to their plant hosts and soil stress. The above-ground parts of six wild plants (Haloxylon salicornicum, Salsola kali, Heliotropium bacciferum, Erica verticillata, Salsola imbricata and Bienertia sinuspersici) were sampled, surface-sterilized and cut into small pieces, which were cultured and incubated for 4–6 weeks. Isolates were grouped and identified by using both morphological and ITS rDNA molecular data. The diversity and community structure of plant-endophyte associations were studied. A total of 455 EF isolates were grouped into 25 different taxa; 21 of which were identified at the species level, 2 at genus level and 2 were unclassified fungi. Here, 95.65% of the identified genera were Ascomycota; of which 36.36, 31.81 and 31.81% were members of the classes Dothideomycetes, Eurotiomycetes and Sordariomycetes, respectively. S. imbricata showed the highest isolation rate and colonization frequency (CF%) of EF when compared to other plant species. Additionally, S. imbricata demonstrated the highest species richness and species diversity of the EF community predominated by the genus Fusarium. Conclusively, the core culturable EF genera of six wild plants were identified (unculturable taxa were not identified in this study). The composition of the EF community was revealed to have a strong correlation to both the electrical conductivity and pH of the soil and a moderate correlation to both the host species and the host family. The abundance and diversity of EF communities of the six plants were environment-dependent.

The use of plant growth-promoting bacteria (PGPB) to enhance plant growth and protection against heavy metal toxicity has been extensively studied. However, its potentiality to reduce arsenate toxicity, a threat to plant growth and metabolism, has been hardly investigated. Moreover, the toxic effect of arsenic oxide nanoparticles (As-NPs) on plants and possible mechanisms for its alleviation has not yet been explored. In this study, the impact of the bioactive actinomycete Streptomyces spp. on the growth, physiology and stress-related metabolites, such as sugars and proline, on As-NPs-stressed wheat and maize plants was investigated. Soil amendment with arsenic oxide nanoparticles (As-NPs) induced the uptake and accumulation of As in the plants of both species, resulting in reduced growth and photosynthesis, but less marked in maize than in wheat plants. Under As-NPs-free conditions, Streptomyces spp. treatment markedly improved growth and photosynthesis in wheat only. The application of Streptomyces spp. reduced As accumulation, recovered the As-NPsinduced growth, photosynthesis inhibition, and oxidative damage in plants of both species. Wheat plants specifically accumulated soluble sugars, while both species accumulated proline. Under As-NPs stress, the ornithine pathway of proline biosynthesis was more important in maize than in wheat plants, while the glutamine pathway was dominant in wheat ones. The addition of Streptomyces spp. further induced the accumulation of proline and starch in both plant species. Overall, despite a different response to Streptomyces spp. under nontoxic conditions, the amendment of ascontaminated soil with Streptomyces spp. induced similar metabolic responses in the two tested species, which trigger stress recovery.