The green synthesis pathway for silver nanoparticles (AgNPs) used in bacterial treatment is regarded as crucial because of its cost-effectiveness, nontoxicity, and eco-friendliness. During the present work, the mangliculous marine fungi Amarenographium solium isolated from the Arabian Gulf Coast of Saudi Arabia were utilized for the synthesis of AgNP, through the bio-reduction of aqueous silver nitrate (AgNO₃) solution. The success in AgNP synthesis was visually identified by the development of dark brown color in the cell-free filtrate and was further confirmed by ultraviolet–visible spectroscopy, which showed a peak at 425 nm. The AgNPs produced were further characterized using X-ray diffraction data analysis that proved the bioreduction of silver to 20 nm, and transmission electron microscopy revealed the formation of well-dispersed spherical nanoparticles with an average mean size of 12 nm. The optimization reaction parameters of temperature, pH, and metal salt concentration were carried out and resulted in a combination of 30°C, 7 and 1.5 mM, respectively, for rapid and maximum yield production. The antibacterial activity of the produced nanoparticles was evaluated using the two-fold microdilution method and showed a minimum inhibitory concentration of 9.375 μg/mL of AgNP against multiple drug-resistant bacterial strains.

Nicotian glauca is a noxious invasive shrub in Saudi Arabia, and it is well known for its harmful impact on biodiversity, competing with native plants using various strategies. Among their strategies is their allelochemical activity, i.e., the use of chemicals to dominate and compete. The present study aims to evaluate the allelopathic potential of N. glauca aqueous extracts from leaves, flowers, and twigs on Acacia gerrardi seed germination and seedling growth. Petri dishes containing extracts from N. glauca parts with different concentrations were incubated in a growth chamber. The results indicated that extracts and concentrations negatively impact seed germination and hypocotyl. Relative to the control, the leaf extract with concentrations of 60 and 100 g/L reduced the seed germination rate by 81.11% and 93.33%, respectively. Flower extracts of similar concentrations decreased germination by 81.91 and 92.55%, while the twig extracts declined germination by 79.56 and 95.69%, respectively. The leaf, flower, and twig extracts (100 g/L) decreased hypocotyl radicle by 76.54, 78.05, and 65.75%, respectively. Overall, the concentrations of 20, 60, and 100 g/L showed the lowest growth indices. Generally, aqueous extracts, particularly 100 g/L, impacted the germination and protrusion of A. gerrardii hypocotyl. In conclusion, our study draws attention to the harmful impact of N. glauca on A. gerrardii regeneration.

Sabkha (inland and coastal—saline beds or saline lands) are widespread in Saudi Arabia and are distinguished by their hypersaline nature. These hypersaline habitats are commonly covered by halophytic vegetation. Moreover, Arbuscular mycorrhizal fungi (AMF) are an essential component of these habitats and exhibit a unique adaptation and contribute significantly to ecosystem variability, diversity, and function. Additionally, AMF from saline habitats are an essential component for the successful rehabilitation of salinity-affected areas. Despite their importance, little is known about the distribution and abundance of AMF along inland and coastal sabkhat of Saudi Arabia. Therefore, the main objective of this study was to investigate the abundance and diversity of AMF in the coastal and inland sabkhat of Saudi Arabia. Five soil samples, each from five randomly selected spots (considering the presence of dominant and co-dominant halophytic species), were collected from every location and were used to assess the AMF abundance and diversity. The study indicated that the highest number of AMF spores was recorded from Jouf, averaging ≈ 346 spores 100 g⁻¹ dry soil, and the lowest from Uqair, averaging ≈ 96 spores 100 g⁻¹ dry soil. A total of 25 AMF species were identified, belonging to eight identified genera viz., Acaulospora, Diversispora, Gigaspora, Scutellospora, Claroideoglomus, Funneliformis, Glomus, and Rhizophagus and five families. Of the total identified species, 52% belonged to the family Glomeraceae. Moreover, the highest number of species was isolated from the sabkha in Qasab. Additionally, Glomeraceae was abundant in all the studied locations with the highest relative abundance in Uqair (48.34%). AMF species Claroideoglomus etunicatum, Funneliformis mosseae, Glomus ambisporum, and Rhizophagus intraradices were the most frequently isolated species from all the Sabkha locations with isolation frequency (IF) ≥ 60%, and Claroideoglomus etunicatum (Ivi ≥ 50%) was the dominant species in all the studied locations. Furthermore, data on the Shannon–Wiener diversity index showed that the highest AMF species diversity was in Qaseem and Qasab habitats. The highest Pielou’s evenness index was recorded in Jouf. Moreover, the soil parameters that positively affected the diversity of identified species included Clay%, Silt%, HCO₃¹⁻, OM, MC, N, and P, while some soil parameters such as EC, Na⁺, SO₄²⁻, and Sand% had a significant negative correlation with the isolated AMF species. This study revealed that AMF can adapt and survive the harshest environments, such as hypersaline sabkhas, and thus can prove to be a vital component in the potential restoration of salinity-inflicted/degraded ecosystems.

The dehydrogenase activity (DHA) in the rhizospheres of tomatoes grown in different soil types – Khor Abu-Habil (KA), Bara (B), and Greenhouse (Gr) – in North Kordofan, Sudan, was determined. In addition, the abundance of soil microbes in the tomato rhizospheres during the two growth stages, after 45 and 90 days (short and long term), was analyzed. The KA site (clay soil) showed the highest DHA (81.79 CFUs/g) followed by the B site (63.76 CFUs/g) (sandy loam) after 90 days of sowing, and the Gr site showed the lowest DHA (44.50 CFUs/g) (loamy sand soil) after 45 days. Moreover, the presence of high microbial activity (total density counts, total fungi, phosphate-solubilizing bacteria, Streptomycetes sp., Azotobacter sp., Azospirillum sp., and Pseudomonas sp. density counts) after 90 days and minimum microbial abundance after 45 days were identified at all sites. The measured growth parameters of fresh and dry weight, in addition to the root-to-shoot ratio, increased significantly at the same KA site dominated by a higher microbial density after 90 days. During the long term, the growth stage was positively affected by the abundance of adapted microbials that improve and enhance plant growth.

A greenhouse experiment was conducted to determine the potential of arbuscular mycorrhizal fungi (AMF) to mitigate the allelopathic effects of invasive Nicotiana glauca on the growth of Acacia gerrardii seedlings. Aqueous extracts from N. glauca leaves and flowers (at concentrations of 20, 60, and 100 g/L) and AMF treatment (±AMF) were applied to A. gerrardii seedlings arranged in a factorial experiment with four replicates. After 6 months, vegetative (plant fresh and dry weight, height, leaf number area), physiological (photosynthesis, stomatal conductance, transpiration rate), chlorophyll a and b, proline, and root (length, surface area, diameter, volume, tip number) parameters as well as root distribution in five root diameter classes (0–5 mm, in 1 mm increments) were examined. The presence of AMF increased the seedling growth parameters. The 20 g/L treatment stimulated most of the vegetative growth, root, chlorophyll, and photosynthesis parameters at both inoculant levels for all extract types and concentrations, and the 100 g/L treatment inhibited seedling growth whether inoculated with AMF or not. This decline was alleviated in AMF-treated seedlings. For both extract sources, root length decreased as extract concentration increased, and roots <1 mm accounted for the greatest proportion of total root length, surface area, and tip number, with higher values observed in AMF-treated seedlings compared to their untreated counterparts. Further research is required at the field level to identify AMF strains and their interaction effects in alleviating the allelopathic impact of N. glauca on A. gerrardii seedling growth.

A competition experiment between Vachellia gerrardii and invasive Nicotiana glauca Graham was conducted to assess the impact of Arbuscular Mycorrhizal Fungi (AMF) symbiosis on the inter and intraspecific competition between the two species. Seedlings were established under mono and mixed plantations with different species proportions (3:1, 2:2, 1:3) and plant densities (1, 2, 3, and 4 plants/pot) for mixed and mono planting respectively, with and without AMF. The vegetative growth parameters (height, leaf area and number, total dry weight/plant, relative yield, relative yield total), roots characteristics (length, surface area, volume, tips number), competitive interaction (aggressivity), and physiological traits (chlorophyll a, chlorophyll b, photosynthesis, stomatal conductance) were measured to evaluate plant responses to AMF symbiosis and competition. The results revealed that AMF symbiosis significantly enhanced the vegetative parameters (leaf area, height, and total dry weight) in both species under mono and mixed plantations compared to plants without AMF. Under AMF treatment, in the interspecific competition, most vegetative and root parameters of N. glauca were higher than V. gerrardii. At inoculant and species proportions, the relative yield of N. glauca exceeded that for V. gerrardii; however, N. glauca was more aggressive towards V. gerrardii. N. glauca root indices were higher than V. gerrardii under inter and intraspecific competition. Simultaneously, for both species, in monoculture plantations, most parameters decreased as plant density increased, wherein the decrease was higher for plants grown without AMF. Photosynthesis increased in AMF treatment, particularly for N. glauca. In conclusion, AMF promoted the growth of invasive N. glauca more than native V. gerrardii, particularly in terms of the root system. Our results provide a critical perspective that the AMF has the potential to contribute and facilitate the invasion of N. glauca, as well as support it with a competitive advantage over V. gerrardii, thus highlighting its potential role in shaping plant–plant interaction in invaded habitats.