Enterobacter sp. DBA51 produces ACC deaminase and promotes the growth of tomato (Solanum lycopersicum L.) and tobacco (Nicotiana tabacum L.) plants under greenhouse condition

Bacterial isolated from rhizospheric soil associated with the semi-desertic plant Coronilla juncea L. were screened for 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity, a common trait for plant-growth-promoting rhizobacteria (PGPR). Among bacterial isolates, strain DBA51 showed phosphate solubilizing index (PSI), producing indole acetic acid (IAA), and with the hemolysis-negative test. Sequencing and analysis of the 16S rDNA gene identified DBA51 as Enterobacter. DBA51 did not show antagonistic activity in vitro against bacterial (Clavibacter michiganensis, Pseudomonas syringae pv. tomato DC3000 and Pectobacterium cacticidum FHLGJ22) and fungal phytopathogens (Alternaria sp., Fusarium oxysporum fsp. lycopersici, Fusarium oxysporum fsp. cubense M5, and Rhizoctonia sp.). Root inoculations with DBA51 in tomato (Solanum lycopersicum L.) and tobacco (Nicotiana tabacum L.) plants were performed under greenhouse conditions. Plant height (20 %) and root biomass (40 %) were significantly enhanced in tomato plants inoculated with DBA51 compared to non-inoculated plants, although for tobacco plants, only root biomass (27 %) showed significant differences with DBA51. In addition, physiological parameters such as photosynthetic rate (µmol CO2 m-2 s-1), stomatal conductance (mol H2O m-2 s-1), and transpiration rate (mmol H2O m-2 s-1) were also evaluated, and no differences were detected between DBA51-inoculated and control treatment in tomato and tobacco leaves. The observed results indicate that the DBA51 strain could be used as a biofertilizer to improve yields of horticultural crops.

Covered Rutile-TiO2 Nanoparticles Enhance Tomato Yield and Growth by Modulating Gas Exchange and Nutrient Status

Nanotechnology has developed materials that can increase food production while reducing the use of conventional fertilizers. In this study, the effect of two forms of application (foliar and drench) as well as covering or non-covering of the surface of titanium dioxide nanoparticles (nTiO2) with maltodextrin (MDX) at 1500 ppm was investigated on tomato plants. The results show that treatment of tomato with nTiO2 increased yield (+21%), while covering the surface of the NPs resulted in a further yield increase (+27%). Similar trends were observed in the dry weight of vegetative plant parts. Fruit firmness (+33%) and total soluble solids (+36%) were enhanced by MDX-covered nTiO2. Application of nTiO2 resulted in enhanced SPAD index, photosynthesis rate, NO3-, K, and Ca concentration in the petiole sap, whereas in the fruits there was an increase in P and K in MDX-covered nTiO2. Considering the dilution effect due to the higher fruit yield, N, P, Mg, Cu, and B increased in plants treated with nTiO2. Covering the surface with MDX resulted in an enhanced response to nTiO2, as fruit yield and quality increased compared to plants treated with non-covered nTiO2.