Mustafa Almaghasla

Water scarcity due to overuse and growing water pollution has led to the need for upgrading of conventional methods of wastewater treatment. The biological synthesis of zinc oxide nanoparticles (ZnO-NPs) and their photocatalytic capacity to degrade contaminants offer a promising and environment-friendly approach to municipal wastewater treatment. This technique is advantageous due to its cost-effectiveness, sustainability, and reduction in toxic residual substances. In this study, microbial-synthesized ZnO-NPs were used for the treatment of municipal wastewater. The objective of this study was to evaluate the potential of treated wastewater for wheat crop cultivation. Zinc oxide nanoparticles were synthesized from a pre-isolated bacterial strain, namely Shewanela sp., and characterized using UV–VIS, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses. The results showed that after the treatment of wastewater, the concentration of total dissolve solids (TDS), the chemical oxygen demand (COD), and sulfate and phosphate levels decreased by 76.5%, 57.1%, 81.1%, and 67.4%, respectively. However, the application of treated wastewater increased chlorophyll, carotenoids, and antioxidants by 45%, 40.8%, and 10.5 to 30.6%, respectively. Further, the application of treated wastewater also significantly decreased oxidative stress induced by hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 8.1% and 30.1%, respectively. In conclusion, biosynthesized ZnO-NPs could be an important choice to treat municipal wastewater and to improve wheat productivity.

The rise in global temperature also favors the multiplication of pests and pathogens, which calls into question global food security. Plants have developed special coping mechanisms since they are sessile and lack an immune system. These mechanisms use a variety of secondary metabolites as weapons to avoid obstacles, adapt to their changing environment, and survive in less-than-ideal circumstances. Plant secondary metabolites include phenolic compounds, alkaloids, glycosides, and terpenoids, which are stored in specialized structures such as latex, trichomes, resin ducts, etc. Secondary metabolites help the plants to be safe from biotic stressors, either by repelling them or attracting their enemies, or exerting toxic effects on them. Modern omics technologies enable the elucidation of the structural and functional properties of these metabolites along with their biosynthesis. A better understanding of the enzymatic regulations and molecular mechanisms aids in the exploitation of secondary metabolites in modern pest management approaches such as biopesticides and integrated pest management. The current review provides an overview of the major plant secondary metabolites that play significant roles in enhancing biotic stress tolerance. It examines their involvement in both indirect and direct defense mechanisms, as well as their storage within plant tissues. Additionally, this review explores the importance of metabolomics approaches in elucidating the significance of secondary metabolites in biotic stress tolerance. The application of metabolic engineering in breeding for biotic stress resistance is discussed, along with the exploitation of secondary metabolites for sustainable pest management.

The cucumber (Cucumis sativa L.) is often subjected to several fungal diseases. Rhizoctonia solani-induced cucumber damping-off and root rot are the most common diseases reported from the commercial greenhouses of the eastern area of Saudi Arabia. The objective of the current study is to explore the antagonistic activity of four Trichoderma species against R. solani in vitro and in vivo. Ten R. solani isolates (eight belonging to AG-4 and two belonging to AG-A and AG2-1) were studied. AG4 isolates were pathogenic to cucumber plants, while AG-A and AG2-1 isolates were non-pathogenic. Seven isolates of Trichoderma spp., named T. hamatum KSATR8, T. harzianum (KSATR9 and KSATR10), T. asperellum (KSATR11, KSATC, and KSAT1E), and T. longibrachiatum KSATS were isolated, and the identities of both R. solani and Trichoderma isolates were confirmed based on the phylogenetic analysis of the DNA sequence of the ITS region. The dual culture findings indicated that T. asperellum KSATC and KSAT1E exhibited the most significant inhibitory activities against R. solani, with values of 79.33 and 70.89%, respectively. Scanning electron microscope (SEM) images showed a considerable degradation in the cell wall and collapsing of R. solani hyphae by all Trichoderma species. Under greenhouse conditions, the application of T. asperellum KSATC and KSAT1E at concentrations of 2 × 108 conidia/mL revealed a reduction in root rot and damping-off incidence percentages with values that did not reveal a significant (p < 0.05) difference from those of Rizolex-T fungicide. Nevertheless, the efficacy of the fungicide attained 86.67%, being higher than that of T. asperellum KSATC, which reached 80%. Trichoderma asperellum KSATC and KSAT1E were the greatest in increasing peroxidase, catalase, and chitinase enzymes activities in cucumber plants. Conversely, a significant (p < 0.05) elevation in polyphenol oxidase enzyme (0.762 and 0.97 U/g FW) and total phenol content (0.55 and 0.62 mg/g FW) was recorded in cucumber plants treated with T. harzianum KSATR9 and KSATR10, respectively. The statistical analysis results displayed no considerable variations among cucumber plants regarding total chlorophyll content as a response to treatments with Trichoderma species and fungicides. Therefore, we endorse using T. asperellum KSATC and KSAT1E as an alternative to fungicides to manage root rot and damping-off in cucumbers.

The Alternaria species are considered to produce a plethora of several mycotoxins constituting a risk factor for both human and animal health. This work aimed mainly to explore the cytotoxicity of a combined mixture of altenuene (ALT), alternariol (AOH), tenuazonic acid (TeA), and altenuisol (AS) toxins produced by pathogenic A. alternata toward human oral epithelial cells (PCS-200-014), lung fibroblast cells (WI-38), and male albino rats. The sequencing of the multi-locus, RNA polymerase second largest subunit (rpb2), glyceraldehyde-3-phosphate dehydrogenase (gapdh), and Alternaria major allergen gene (Alt a 1) was performed to infer relationships among isolated Alternaria species. The phylogenetic analysis of gapdh, rpb2, and Alt-a 1 sequence data indicated that all isolates resided in A. alternata. The pathogenic potentiality of A. alternata was investigated on tomato plants cv. super strain B under greenhouse conditions, and all isolates were pathogenic to tomato plants, with significant (p < 0.05) variations. The ability of A. alternata isolates to produce mycotoxins was also explored using high-performance liquid chromatography (HPLC). All tested isolates were able to produce at least one of the assessed mycotoxins—ALT, AOH, TeA, and AS—and ALT was reported as the dominant mycotoxin, produced by 80% of A. alternata isolates. The cytotoxic properties of the combined mixture of ALT, AOH, TeA, and AS at concentrations of 31.25, 62.50, 125, 250, and 500 µg/mL were assessed via the MTT assay method after exposure for 24 h versus the control. The treatment of both cell lines with combined mixtures of ALT, AOH, TeA, and AS showed a dose-dependent decrease in cell viability. The highest concentrations tested at 62.50, 125, 250, and 500 µg/mL significantly decreased cell viability and caused cell damage compared to the lowest concentration of 31.25 µg/mL and the control. The cytotoxicity and genotoxicity of the combined mixtures of ALT, AOH, TeA, and AS on male albino rats were also investigated via the gene expression of (TNF-α) and using hematological (CBC), chemical (alanine aminotransferase (ALT), aspartate aminotransferase (AST) and urea and creatinine), and histopathological analyses. A marked increase was observed in the levels of ALT, AST, urea and creatinine, TNF-α gene expression, red blood cells (RBCs), white blood cells (WBCs), hemoglobin (Hb), and packed cell volume % (PCV) after 28 days of exposure relative to the untreated control. Pathological alterations were also observed in the liver and kidney tissues of rats. Conclusively, this work provides a new understanding on the cytotoxicity and genotoxicity of mycotoxins of pathogenic A. alternata from tomatoes.