This study aimed to investigate the production of biofilm and exopolysaccharides by plant growth promoting rhizobacteria (PGPR) under different salt concentrations. In this study, the activity of biofilm formation and exopolysaccharides production by 20 strains of PGPR which previously isolated and identified from root samples of different crops were determined under different salt concentrations. Out of 20 strains, only 12 PGPR strains have the ability to form biofilm at 0.0, 50, 100 and 150 mM NaCl concentration. PGPR strains with the highest activity of biofilm formation and exopolysaccharides production were selected to check them on the faba bean plants under different concentration of salt stress. Inoculation with PGPR strains increased plant growth at higher level of salt concentrations compared with their corresponding uninoculated ones. The strain Pseudomonas anguilliseptica SAW 24 showed the highest activity of biofilm formation and exopolysaccharides production at different NaCl concentrations furthermore, gave the highest records of plant height (cm), fresh and dry weight (g/plant) of faba bean plants. The activities of biofilm formation and exopolysaccharides production of plant growth promoting bacteria enhance faba bean plants against different salt concentrations. Key words: Biofilm, faba bean, exopolysaccharides, salinity, plant growth promoting rhizobacteria (PGPR).

The study was conducted at green house and laboratories of Agriculture Botany Department, Faculty of Agriculture, Suez Canal University, Ismailia governorate, Egypt during 2018/2019 to test rhizosphere growth promoting bacteria as known strategy to increase salinity tolerance of six genotypes of wheat namely; Line 404, Line 356, Line 420, Line432, Sakha 93 and Line 380 were grown under 3000 ppm and 5000 ppm of salinity. Four bacterial strains were used namely; Pseudomonas fluorescens NBRC 14160, Serratia liquefaciens ATCC 27592, Bacillus subtilis SBMP4 and Bacillus megaterium NBRC 15308. All the strains could be able to tolerate salinity levels up to 3% NaCl and produced indole acetic acid (IAA). The both strains Pseudomonas fluorescens NBRC 14160 and Bacillus megaterium NBRC 15308 were grow on NA media supplemented with 6% NaCl, and showed 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and Pseudomonas fluorescens NBRC 14160 strain also fixed nitrogen. PCR results confirmed the previous results for both strains. Pseudomonas fluorescens NBRC 14160 and Bacillus megaterium NBRC 15308 were selected to study their reflection in vivo on wheat plants growth at different levels of salinity. The selected strains were able to improve plants growth under salinity stress conditions when compared with non-inoculated plants for all wheat genotypes especially sakha93 showed the highest mean values over rest genotypes under saline and non-saline conditions. Results of genetic parameters for studied traits showed that values of PCV were higher than GCV values for most studied traits. Germination percentage, shoot length and potassium content had high values of heritability and genetic advance, so these traits might use in selection of plant breeding programs for salinity tolerance.

The current study aimed to optimize the production of cellulase and chitinase enzymes by plant growth promoting rhizobacteria (PGPR). Bacteria were pre-isolated from soil and identified as; Pseudomonas fluorescens NBRC (KW1), Serratia liquefaciens ATCC 27592 (EW1), Bacillus subtilis SBMP4 (EF1) and Bacillus megaterium NBRC 15308 (TF2). The effect of different growth parameters including; pH, temperature, carbon and nitrogen sources, and incubation periods were optimized for production of cellulase and chitinase enzymes by the selected bacterial strains. Three strains mainly, B. subtilis SBMP4, S. liquefaciens ATCC 27592 and P. fluorescens NBRC) recorded positive results for cellulase production. B. subtilis SBMP4 (EF1) and S. liquefaciens ATCC 27592 (EW1) strains demonstrated significant ability to produce cellulase at 40°C, while P. fluorescens NBRC (KW1) strain showed the maximum enzyme production at 30°C. Carboxymethyl cellulose gave the highest cellulase production compared to the other carbon sources. Chitinase enzyme was optimally produced by B. subtilis SBMP4 and S. liquefaciens ATCC 27592 strains under primary screening. B. subtilis SBMP4 had the strongest ability to produce chitinase at 40oC, while S. liquefaciens ATCC 27592 at 30oC. The optimum pH observed was at pH 6.0 to get the maximum chitinase production by S. liquefaciens ATCC 27592. Potassium nitrate (KNO3) as an inorganic nitrogen source presented the highest chitinase production by B. subtilis SBMP4, whereas yeast extract demonstrated significant chitinase production by S. liquefaciens ATCC 27592.

Plant growth promoting rhizobacteria (PGPR) have evolved to thrive in challenging environments and provide the plants with defense against the harmful impacts of the environmental stressors. The present study aimed to isolate, screen, and identify PGPB obtained from the rhizosphere soil of some field crops at different sites in Ismailia, Egypt. Isolation process was carried out from drought-suffered locations to obtain efficient promising strains adapted to carry out vital processes under an irrigation water shortage. Eight bacterial isolates were selected and identified by phenotypic properties, and were subjected to screening procedures to assess their growth capabilities and evaluate their potential as PGPB. The screening process involved investigating various PGPB features, such as phosphate solubilization, formation of indole-3-acetic acid (IAA), ammonia, and hydrogen cyanide (HCN) production. Among the eight isolates, two isolates only (MW3 and AB3) gave positive results for all the tested plant growth promoting traits. The promising isolates were identified by sequencing of their16S rRNA as Arthrobacter globiformis (MW3) and Micrococcus luteus (AB3). A field trial was conducted to evaluate the activity of the two PGPB and their mixture to act as biofertilizers for maize under deficit irrigation 0.75 from crop evapotranspiration (ETc). All tested inoculants significantly increased yield components of maize, NPK uptake by plants, availability of N and P in soil, activity of some soil enzymes, and total bacterial counts compared to the un-inoculated control. Utilization of stress adapting PGPR showed great potential in overcoming the challenges of sustainable agriculture under environmental stress conditions.

The current study aimed to compare between inoculation of wheat plant with a single and combinations of several species of Arbuscular mycorrhizal fungi (AMF), and promoting its growth under water stress conditions. In a greenhouse experiment, the effect of three AMF species on wheat plant growth was studied using single-inoculations with Glomus monosporum, G. mosseae and Gigaspora gigantean, and mixtures of various AMF species. Moreover, inoculation of wheat plant with pair of AM fungi composed mainly of; SN (G. monosporum and Gigaspora gigantean) and AA (G, monosporum and Glomus mosseae) were investigated. Current findings indicate that inoculation with AMF belonging to different families was more effective in improving plant growth than AMF from the same genus and with mono-inoculation. Results showed that plant height inoculated with SN and AA increased by 27.30% and 24.95; respectively, while inoculation with Gigaspora gigantean (GG), G. mosseae (GS) and G. monosporum (GM) increased by 16.01%, 14.6% and 6.83%, respectively. Number of spikes/plant, spike length, number of spikelet/spike, 1000-grain weight and grain yield/plant of wheat plants inoculated with AMF increased significantly, compared with the non-inoculated control plants under water stress. In addition, current results demonstrated that inoculation with SN had relatively higher impact on promoting the growth of wheat plants followed by AA and GG, suggesting that inoculation with AMF consisting of different species may have a better effect than single inoculations. Furthermore, it is observed also that SN; which are combination from different genera have better effect on wheat plant growth, compared to that of AA from the same genus but of different species.

Researchers have reported that Bacillus megaterium BM18-2 reduces Cd toxicity in Hybrid Pennisetum, but understanding the interaction between plants and associated endophytes is crucial for understanding phytoremediation strategies under heavy metal stress. The current study aims to monitor the colonization patterns of GFP-labeled endophytic bacteria BM18-2 on Hybrid Pennisetum grass. Additionally, it will monitor Cd’s effect on plant bacterial colonization. Confocal laser scanning microscopy of plant roots infected with gfp tagged BM18-2 revealed that the bacterium colonised root hairs and epidermal cells at the early stage of colonization, and over time, the bacteria penetrated to the internal tissues following their colonization of the stem and leaf. The roots, stems, and leaves of H. Pennisetum grown in Cd-contaminated soil contained a higher number of bacteria than those grown in normal soil. The result of Cd translocation indicated the condensation of heavy metals in the root cells and stem, while no Cd was found in the leaf. The study will also look for the enzymatic activity of bacteria BM18-2 and use Leadmium Green AM dye to track how Cd is taken up and moved through the plant. The enzymatic activity results showed that BM18-2 can produce catalase and amylase, but did not record any cellulase or lipase activity. As a result, the pattern of useful endophytic BM18-2 colonization through H. Pennisetum grass will aid in the application and maintenance of these bacteria in farming, and it presents new opportunities for the development of innovative strategies in the fields of agriculture and biotechnology.