Selenium and its derivatives have been found capable of excellent biological responses. However, the element in its bulk form has low bioavailability and increased toxicity, meaning the production of effective forms with sustainable methods has become urgent. Several microorganisms, including fungi, bacteria and yeast, as well as higher plants, are capable of biosynthesizing nanoparticles such as nano-selenium (nano-Se), which has wide applications in medicine, agriculture and industry. Thus, the biosynthesis of nano-Se using some bacterial species was the main target of this study. The production of nano-Se and the monitoring of its impact on the wheat germination of seeds under salt stress (i.e., 50, 100, and 150 mM NaCl) was also evaluated in the current study. The ameliorative role of nano-Se doses (i.e., 50, 75, and 100 mg L⁻¹) in the germination of wheat seeds under salt stress was also investigated. Based on sodium selenite tolerance and reducing selenite to elemental Se-NPs, the most effective isolate (TAH) was selected for identification using the 16S rRNA gene sequence, which belonged to Bacillus cereus TAH. The final germination percent, mean germination time, vigor index and germination rate index were improved by 25, 25, 39.4 and 11%, respectively, under 15 mM sodium chloride concentration when 100 mg L⁻¹ nano-selenium was used. On the other hand, the results obtained from a gnotobiotic sand system reveal that with treatment with 100 mg L⁻¹ nano-selenium under high Ec values of 14 ds m⁻¹, the vegetative growth parameters of shoot length, root length, fresh weight and dry weight were improved by 22.8, 24.9, 19.2 and 20%, respectively, over untreated controls. The data obtained from this study reveal that the use of nano-selenium produced by Bacillus cereus offers improved wheat seed germination under a salt-affected environment.

In a trial to control charcoal rot disease in geranium using ecofriendly strategies, essential oils and antagonistic microbes were used. Five essential oils including (Syzygium aromaticum (cloves), Ocimum basilicum L. (basil), Mentha spicata (Spearmint), Majorana hortensis Moench (Marjoram) and Mentha piperita L. (Peppermint) were used with three concentrations 1, 3 and 5 microliter / plate in addition three bacterial isolates Bacillus polymixa, B. circulance, B. Subtilis and one fungus Tricoderma harzianum. were also used. The in vitro antagonistic effect of essential oils and microbial isolates against a charcoal rot of Macrophomina phaseolina isolated from infected geranium was estimated in Petri plats, the most promising treatments were applied in an artificially infested geranium in a greenhouse experiment along two growing seasons of 2017, 2018. Results indicated that among the treatments, Peppermint oil recorded the highest reduction in growth followed by Basil oil while Marjoram oil had no effect on the growth of pathogen. On the other hand, Bacillus subtilis and Trichoderma harzianum were the most promising microbes against the fungal pathogen under study using the dual culture technique. The green house experiment showed that most treatments were efficient in pathogenicity reduction but the microbial treatment exhibited an advantage over essential oil where growth and yield parameters were sharply improved.

Seed coating is the most frequently used method in application of bio-fertilizers in different crops. The treatment of seeds with fungicides for storage purposes or protection during germination represents a challenge for application of bio-fertilizers by seed coating. In the current work, the antibacterial properties of five commercial fungicides known to be used in seed protection were screened against ten bacterial strains used as bio-fertilizers (Azotobacter salinestris, Azospirillum brasilense, Azospirillum lipoferum, Enterobacter cloacae, Rhizobium leguminosarum , Rhizobium phaseoli, Bacillus subtilis, Bacillus amyloliquefaciens, Paenibacillus polymyxa, Bacillus aryabhattai ) in addition, commercial sugar beet seeds dressed with unknown fungicids were also tested and the fungicide with antibacterial activity was selected and identified using gas chromatography (GC) to be used in further work. Sugar beet Seeds treated with selected fungicide were coated with different materials (Talc powder, Biochar, Charcoal, Polyvinylpyrrolidone (PVP), Beet moss) with expected adsorption properties and the effect of this materials in protection of bio-fertilizes was studied in agar plates. The most promising treatments were applied in a pot experiment using sugar beet (Beta vulgaris) seeds. The growth of most bacterial strains was not inhibited by already known fungicides except Rhizobium phaseoli which was inhibited by Tebuconasole 2.5% while one unknown fungicide showed a remarkable antibacterial activity against most bacterial strains under study. The GC-MS identification revealed that this fungicide is thiram. The most effective material in protection of microbial strain was charcoal.