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Under natural conditions, crops typically suffer from severe challenges due to the increasing of abiotic and biotic stresses which severely affect plant growth and reduc crop yield. The present study investigated the single and combined impacts of Sclerotinia sclerotiorum and salinity stress on common bean (Phaseolus vulgaris L.) seedling which is scarcely studied. The study evaluated the in vitro and in vivo influence of two salinity tolerant Trichoderma isolates, T. koningii and T. harzianum against S. sclerotiorum under salinity stress. The results showed the ability of T. koningii and T. harzianum to grow and sporulate at high levels of salinity, 80 mM NaCl, without significantly impacting their ability to produce cell wall degrading enzymes, cellulase and chitinase. Amylase and proteinase (Prb1) genes were detected in T. harzianum. The in vitro assay revealed that both isolates could inhibit the growth of S. sclerotiorum under high salinity concentrations. In a greenhouse experiment, both Trichoderma isolates ameliorated the damaging impacts of S. sclerotiorum under salinity stress on common bean seedlings' germination and growth characteristics compared to their untreated control. Both bioagents significantly attenuated the damping-off and collar/stem rot percentages of infected common bean under salinity stress. Salinity stress intensified the effect of S. sclerotiorum on photosynthetic pigments, induced oxidative and nitrative stress, hampered ionic homeostasis, and deactivated antioxidants and defense-related molecules. On the other hand, Trichoderma isolates restrained the reduction of chlorophylls and carotenoids, ascorbate, reduced glutathione, flavonoids, phenolics, and various antioxidant enzymes, especially for single stresses and T. harzianum. All these upregulations reflected in keeping the cell membranes of common beans seedling more stable where the levels of lipid peroxidation and methylglyoxal due to the reduction of reactive oxygen species and upregulation of nitric oxide, which expressed better growth under pathogen attack or/and saline. The tested isolates, T. koningii and T. harzianum could be used as effective biological control against S. sclerotiorum on common beans in saline soils or areas irrigated with saline water.

The utilization of nanoparticles in agricultural land is widely increasing worldwide. The present study takes the advent from converting the rice husk waste to silica nanoparticles (SiNPs) to be used in two years of field experiments, as fertigation treatment, against reducing irrigation by drip system. In this respect, the experiments comprised of three drip irrigation regimes (i.e., 60, 80, and 100 % of crop evapotranspiration, ETc) and four levels of SiNPs (0, 100, 200, and 300 mg L−1). The results indicated that limited irrigation reduced the plant fresh weight, plant height, and yield of eggplants by 15, 25, and 30 %, an average of two years, at the level of 60 % ETc compared to 100 % ETc. However, these negative impacts were alleviated by SiNPs via improving the photosynthetic pigments and relative water content where the plants supplemented with 300 mg L−1 SiNPs had the highest improving effects to be 3.8 mg g−1 FW and 76 % compared to 2.2 mg g−1 FW and 63 % (average of two years), respectively at the drought level of 60 % ETc. Furthermore, SiNPs ameliorated the oxidative damage induced by different water regimes by lessening lipid peroxidation and hydrogen peroxide (10.9 and 85.4 µM g−1 FW) compared to their drought level 60 % ETc (14 and 113 µM g−1 FW). This was associated with stimulating the antioxidant enzyme system by promoting the activities of peroxidases (ascorbate- and guaiacol-dependent types), catalase, and superoxide dismutase as the concentration of silica NPs increased to be (173.84, 12.2, 49.5, and 41 unit/mg/min, respectively) at 60 % ETc and 300 mg L−1 SiNPs compared to only 60 % ETc (100.5, 7.9, 32, and 30.5 unit/mg/min, respectively). Also, efficiently increasing SiNPs levels highly significantly restrained the ionic homeostasis in the leaves of eggplant via retaining the reduction of silicon, potassium, calcium, and magnesium contents at 300 mg L−1 silica NPs especially at 60 % ETc (33, 19, 4.5, and 6 mg g−1 DW, respectively) compared to the corresponding drought level (17.33, 7, 2.1, and 3.7 mg g−1 DW, respectively) which reflected on the up-regulation of water status. Such amelioration effects of SiNPs were recommended during the two studied seasons. Altogether, the synthesized SiNPs efficiently mitigated the negative impacts of limited drip irrigation levels on ionic homeostasis, pigments, oxidative stress, and antioxidant system especially at the level of 300 mg L−1.

Microbial biostimulants (MBs) promote plant growth and stress tolerance in a sustainable manner. However, precise field trials of MBs are required in natural setting with a range of crop varieties to harness the benefits of biostimulants on crop yield improvement. This study investigated the effects of two MBs, Trichoderma album and Bacillus megaterium, on an onion cultivar's growth, nutritional qualities, antioxidant properties, and yield potentials under field conditions for two successive years. Before transplantation, onion bulbs were gelatin-coated with 2.0 and 4.0 g L−1 of each of the MB. Results revealed that MBs-pretreated onion plants exhibited better growth indices, photosynthetic pigment contents, and yield-attributing features like bulb weight than control plants. Nutraceutical analysis demonstrated that T. album-pretreated (by 2.0 g L−1) onion cultivar enhanced the level of K+ (by 105.79%), Ca2+ (by 37.77%), proline (by 34.21%), and total free amino acids (by 144.58%) in bulb tissues over the control plants. Intriguingly, the pretreatment with both T. album and B. megaterium (by 2.0 g L−1) increased the levels of total soluble carbohydrates (by 19.10 and 84.02%), as well as antioxidant properties, including increased activities of superoxide dismutase (by 58.52 and 31.34%), catalase (by 164.71 and 232%), ascorbate peroxidase (by 175.35 and 212.69%), and glutathione-S-transferase (by 31.99 and 9.34%) and improved the contents of ascorbic acid (by 19.1 and 44.05%), glutathione (by 6.22 and 33.82%), and total flavonoids (by 171.98 and 56.24%, respectively) in the bulb tissues than control plants. Although both MBs promoted the growth and nutraceutical qualities of onion bulbs, T. album pretreatment showed better effects than that of B. megaterium in the field settings. Based on the morphophysiological attributes and biochemical properties, a low dose (2.0 g L−1) was more effective than a high dose (4.0 g L−1) of T. album in promoting onion growth. Overall, the current research findings imply that T. album might be a potential MB in improving growth and quality attributes, and hence the productivity of onion cultivars under field circumstances.

The outstanding role of spermine in eliciting defense adaptation of soybean to different levels of water deficit (0, -0.1, -0.5 and -1.1 MPa) was investigated by determining the changes in growth, photosynthetic pigments, osmolytes, water relations, and antioxidants. All the studied traits clearly revealed cultivar-dependent variation in response to water deficit where cv. Giza 111 was tolerant and cv. Giza 21 was sensitive. Both cultivars came in agreement that photosynthetic limitation (chlorophylls reduction) was the troubling shot induced by water deficit. Such limitation was reflected on three directions (a) disturbances of water relations (stomatal conductance, transpiration rate, relative water content and water use efficiency), (b) down regulation of metabolites which affect osmotic adjustment and (c) elevated reactive oxygen species (increased hydrogen peroxide) and destruction of membrane stability (increment of electrolyte leakage and lipid peroxidation). The damaging impacts of water deficit on these parameters were obviously coined for sensitive cultivar compared to tolerant one. Although spermine priming did not have apparent stimulatory role on well-watered plants, unequivocal inversion from a state of down regulation to up-regulation was distinct under water stress. In this regard, spermine enhanced pigments, osmolytes accumulation, up-regulated water relations and enhanced membrane stabilization. Furthermore, spermine pre-sowing decreased oxidative stress by lowering hydrogen peroxide via activation of anthocyanins, total antioxidants and phenolic compounds.

Prospective involvement of metal oxide nanomaterials as a prominent agriculture practice for improving existing crop production directed the present investigation for synthesizing of ZnO and TiO2 nanomaterials as an attempt to enhance the transplants production of some Solanaceae crops. The morphological characterizations of the prepared nanomaterials indicated that the hydrothermal synthesized ZnO was produced in nanorod structure with an average aspect ratio of 7. However, SEM and TEM micrographs of microwave prepared TiO2 evident that it has a nanoparticle structure with an average diameter of 43 nm. The BET results confirmed the high specific areas of the two prepared metal oxide nanomaterials. The two synthesized metal oxide nanomaterials were coated in gel and mixed with the seeds of eggplant, pepper and tomato crops at four concentrations 0, 50, 100 and 150 mg/L, whilst the control seeds were germinated in distilled water without gel-coating. The results pointed to the outstanding effect of TiO2 and ZnO nanoparticles on germination characters and seedlings growth. The maximum transplants lengths, fresh and dry weight were recorded at the level 100 mg/L whatever the crop plant used. Hastening germination operation of nanomaterials-gel coated seedlings compared to control plants may be ascribed to the reduction of mean germination time and coefficient variation of the germination process besides increasing the mean germination rate and the synchrony of germination traits. Overall, better performance of growing transplants has been accredited for nanoparticles-gel coated seedlings more than the control treatments which could be efficient for the safer production of transplants in an innovative way.