Viral plant diseases represent a serious problem in agricultural production, causing large shortages in the production of food crops. Eco-friendly approaches are used in controlling viral plant infections, such as biocontrol agents. In the current study, Streptomyces cellulosae isolate Actino 48 is tested as a biocontrol agent for the management of tobacco mosaic virus (TMV) and inducing tomato plant systemic resistance under greenhouse conditions. Foliar application of a cell pellet suspension of Actino 48 (2 × 10⁷ cfu. mL⁻¹) is performed at 48 h before inoculation with TMV. Peroxidase activity, chitinase activity, protein content, and the total phenolic compounds are measured in tomato leaves at 21 dpi. On the other hand, the TMV accumulation level and the transcriptional changes of five tomato defense-related genes (PAL, PR-1, CHS, PR-3, and PR-2) are studied. Treatment with Actino 48 before TMV inoculation (48 h) induced tomato plants to increase their levels of peroxidase and chitinase enzymes. Furthermore, a significant increase in the concentration of total phenolic compounds was observed in Actino 48 and TMV-treated tomato plants compared to TMV-treated tomato plants alone. Treatment with Actino 48 reduced the TMV accumulation level (53.8%) compared to treatment with the virus alone. Actino 48 induced plant growth, where the fresh and dry weights of tomato plants increased. Additionally, significant increases of the PAL, PR-1, CHS, and PR-3 transcripts were observed. On the other hand, a higher induction of PR-2 was only observed in TMV-treated tomato plants. In conclusion, S. cellulosae isolate Actino 48 can be used as a biocontrol agent for the reduction of symptoms and severity of TMV.

Of ten actinobacterial isolates, Streptomyces cellulosae Actino 48 exhibited the strongest suppression of Sclerotium rolfsii mycelium growth and the highest chitinase enzyme production (49.2 U L⁻¹ min⁻¹). The interaction between Actino 48 and S. rolfsii was studied by scanning electron microscope (SEM), which revealed many abnormalities, malformations, and injuries of the hypha, with large loss of S. rolfsii mycelia density and mass. Three talc-based formulations with culture broth, cell-free supernatant, and cell pellet suspension of chitinase-producing Actino 48 were characterized using SEM, Fourier transform infrared spectroscopy (FTIR), and a particle size analyzer. All formulations were evaluated as biocontrol agents for reducing damping-off, root rot, and pods rot diseases of peanut caused by S. rolfsii under greenhouse and open-field conditions. The talc-based culture broth formulation was the most effective soil treatment, which decreased the percentage of peanut diseases under greenhouse and open-field conditions during two successive seasons. The culture broth formulation showed the highest increase in the dry weight of peanut shoots, root systems, and yielded pods. The transcriptional levels of three defense-related genes (PR-1, PR-3, and POD) were elevated in the culture broth formulation treatment compared with other formulations. Subsequently, the bio-friendly talc-based culture broth formulation of chitinase-producing Actino 48 could potentially be used as a biocontrol agent for controlling peanut soil-borne diseases caused by S. rolfsii.

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.

Three different concentrations of four (ethanol, acetone, methanol, and diethyl ether) extracts of licorice, doum, and banana peel were evaluated for antifungal and antimycotoxigenic efficiency against a maize aflatoxigenic fungus, Aspergillus flavus. Among them, the licorice diethyl ether 75% extract was intensely active, showing the best wet and dry weight inhibition and exhibiting the highest efficacy ratio (91%). Regarding aflatoxin B1 (AFB1) production, all the plant extracts tested were effective against AFB1 production after one month of maize storage, with average efficacy ratios ranging from 74.1% to 97.5%. At the same time, Thiram fungicide exhibited an efficacy ratio of 20.14%. The relative expression levels of three structural genes (aflD, aflP, and aflQ) and two regulatory genes (aflR and aflS) were significantly downregulated when compared to untreated maize grains or Thiram-treated maize grains. The doum diethyl ether 75% peel extract showed the highest total phenolic content (60.48 mg GAE/g dry extract wt.) and antioxidant activity (84.71 μg/mL). GC–MS analysis revealed that dimethoxycinnamic acid, aspartic acid, valproic acid, and linoleic acid might imbue the extracts with antioxidant capacities in relation to fungal growth and aflatoxin biosynthesis. Finally, the results suggest that the three plant extracts can be considered a promising source for developing potentially effective and environmentally safer alternative ways to control aflatoxin formation, thus creating a potentially protective method for grain storage.

Pests represent a huge problem in crop production causing significant losses. Currently, biocontrol is utilized as an eco-friendly approach for controlling pests and reducing the shortage in crop production. In the current study, the production of a biocontrol agent, which was identified based on sequencing of the 16S rRNA gene as Bacillusvelezensis strain GB1 with GenBank accession No. OM836750, was carried out in the stirred tank bioreactor using a batch fermentation process. For the first time, B. velezensis strain GB1 was tested as a biocontrol agent with soil drench application (10⁹ cfu mL⁻¹) for management of Bemisia tabaci and induction of squash plant systemic resistance under greenhouse conditions. β-1,3-glucanase, chitinase, polyphenol oxidase, and peroxidase activity were measured in squash leaves at 24, 48, 72, 96, and 120 h. The influence of B. velezensis strain GB1 on population density, fertility, and hatchability of B. tabaci on squash plants was studied. The batch fermentation process of B. velezensis strain GB1 maximized the production of secondary metabolites and culture biomass, which reached a maximum value of 3.8 g L⁻¹ at 10.5 h with a yield coefficient of 0.65 g cells/g glucose. Treatment with B. velezensis strain GB1 induced squash plants to boost their levels of β-1,3-glucanase, chitinase, polyphenol oxidase, and peroxidase enzymes. On the other hand, B. velezensis strain GB1 could significantly reduce the mean number of the attracted B. tabaci on squash plants. Additionally, whiteflies laid a lower mean number of 2.28 eggs/female/day on squash plants inoculated with B. velezensis strain GB1 compared to control. The percentage of B. tabaci egg hatchability declined by 5.7% in the B. velezensis-inoculated squash plants.

The present study involves the synthesis of photocatalytic composite nanofibers (NFs) comprising ilmenite nickel titanite-supported carbon nanofibers (NiTiO₃/TiO₂@CNFs) using an electrospinning process. The photocatalytic composite NFs obtained were utilized in hydrogen (H₂) production from the photohydrolysis of ammonia borane (AB). The experimental findings show that the photocatalytic composite NFs with a loading of 25 mg had a good catalytic performance for H₂ generation, producing the stoichiometric H₂ in 11 min using 1 mmol AB under visible light at 25 °C and 1000 rpm. The increase in catalyst load to 50, 75, and 100 mg leads to a corresponding reduction in the reaction time to 7, 5, and 4 min. The findings from the kinetics investigations suggest that the rate of the photohydrolysis reaction is directly proportional to the amount of catalyst in the reaction system, adhering to a first-order reaction rate. Furthermore, it was observed that the reaction rate remains unaffected by the concentration of AB, thereby suggesting a reaction of zero order. Increasing the reaction temperature results in a decrease in the duration of the photohydrolysis reaction. Furthermore, an estimated activation energy value of 35.19 kJ mol⁻¹ was obtained. The composite nanofibers demonstrated remarkable and consistent effectiveness throughout five consecutive cycles. The results suggest that composite NFs possess the capacity to function as a feasible substitute for costly catalysts in the process of H₂ generation from AB.