In semiarid regions is important to use native strains best adapted to these environments to optimize plant-PGPR interaction. We aimed to isolate and characterize PGPR from roots and rhizosphere of a tomato crop, as well as studying the effect of its inoculation on tomato seedlings growth. We selected four strains considering their effectiveness of fixing nitrogen, solubilizing phosphate, producing siderophores and indole acetic acid. They belong to the genera Enterobacter, Pseudomonas, Cellulosimicrobium, and Ochrobactrum. In addition, we also analyzed the ability to solubilize Ca3(PO4)2, FePO4 and AlPO4 and the presence of one of the genes encoding the cofactor PQQ in their genome. Enterobacter 64S1 and Pseudomonas 42P4 showed the highest phosphorus solubilizing activity and presence of pqqE gene. Furthermore, in a tomato-based bioassay in speed-bed demonstrated that a sole inoculation at seedling stage with the strains increased dry weight of roots (49–88%) and shoots (39–55%), stem height (8–13%) and diameter (5–8%) and leaf area (22–31%) and were equal or even higher than fertilization treatment. Leaf nitrogen and chlorophyll levels were also increased (50–80% and 26–33%) compared to control. These results suggest that Enterobacter 64S1 and Pseudomonas 42P4 can be used as bio-inoculant in order to realize a nutrient integrated management.

Salinity is one of the principal abiotic stresses that limit the growth and productivity of crops. The use of halotolerant plant growth‐promoting rhizobacteria (PGPR) that increase the growth of salt‐stressed crops is an environmentally friendly alternative to promote plant yield under salinity. The aim of this study was to test native PGPR, isolated according to their tolerance to NaCl, and to evaluate their influence on morphological, physiological, and biochemical traits promoted by salt stress in tomato plants. Enterobacter 64S1 and Pseudomonas 42P4 were selected as the most efficient strains in terms of salt tolerance. Both strains were classified as moderately resistant to salinity (NaCl) and maintained their plant growth‐promoting activities, such as nitrogen fixation and phosphate solubilization, even in the presence of high levels of salt. The results of a greenhouse experiment demonstrated that PGPR inoculation increased root and shoot dry weight, stem diameter, plant height, and leaf area compared to control noninoculated plants under nonsaline stress conditions, reversing the effects of salinity. Inoculated plants showed increased tolerance to salt conditions by reducing electrolyte leakage (improved membrane stability) and lipid peroxidation and increasing chlorophyll quantum efficiency (Fv/Fm) and the performance index. Also, inoculation increased the accumulation of proline and antioxidant nonenzymatic compounds, such as carotenes and total phenolic compounds. The catalase and peroxidase activities increased with salinity, but the effect was reversed by Enterobacter 64S1. In conclusion, Enterobacter 64S1 and Pseudomonas 42P4 isolated from salt‐affected regions have the potential to alleviate the deleterious effects of salt stress in tomato crops.

Crop inoculation with plant growth-promoting rhizobacteria (PGPR) is a sustainable alternative to diminish the excessive use of chemical fertilizers in agriculture. However, there is little information about PGPR inoculation effects under field conditions and even less on industrial tomato production. We aimed to study the effects of a sole inoculation at seedling stage with Pseudomonas fluorescens Rt6M10, Azospirillum brasilense Az39, and their combination on growth and yield of two industrial tomato varieties UCO 14 (UCO) and Harris Moran 3861 (HM). We compared these PGPR inoculation treatments with chemically fertilized and nonfertilized (control) seedlings under field conditions. We found that inoculation with Rt6M10, Az39, and their combination increased seedling root dry weight by 62%, 41%, and 23%, respectively and shoot dry weight by 29%, 23%, and 2%, respectively compared with non-inoculated control, improving tolerance to transplant stress. Inoculation with Rt6M10, Az39, and their combination increased stem diameter by 15%, 16%, and 13%, respectively, while Rt6M10 and the combination treatments increased leaf chlorophyll and carotenoid levels compared with non-inoculated plants. Az39 increased fruit number (35%) and fruit weight (38%) per plant in HM, whereas in UCO variety, the increase was the highest (48% and 49%, respectively). Seedling inoculation increase fruit firmness and equatorial and polar fruit diameter by 24%, 10%, and 12%, respectively in HM and by 21%, 14%, and 14%, respectively in UCO. Overall, bio-inoculation with Rt6M10 and/or Az39 was beneficial for tomato seedlings at transplanting and supported fruit yield and quality (total soluble solid content, pH, and titratable acidity) equally or better than chemically fertilized seedlings.

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The production of pepper plants for industrial use is not enough to satisfy the demand of consumers and agrochemicals are frequently used to increase production. In this study four native plant growth promoting rhizobacteria (PGPR) was tested as an alternative to select the most effective to enhance growth, development, and productivity of pepper plants. Seedlings were inoculated with Pseudomonas 42P4, Cellulosimicrobium 60I1, Ochrobactrum 53F, Enterobacter 64S1 and cultivated on pots in the greenhouse and the morphological, biochemical, and physiological parameters were determined. In addition, the phenolic compound profiles were evaluated. All four strains increased the different parameters evaluated but Pseudomonas 42P4 and Cellulosimicrobium 60I1 were the most effective strains, improving leaf and root dry weight, stem diameter, nitrogen level, stomatal conductance, chlorophyll quantum efficiency, chlorophyll SPAD index, total chlorophyll and carotenoid levels, number of flowers and fruits per plant, and the length, diameter and dry weight of the fruit. Also, these strains modified the phenolic compound profiles, and 18 compounds were quantified. Pseudomonas 42P4 inoculation modified the phenolic compound profile similarly to the Fertilized treatment and induced the synthesis of different endogenous compounds in the flavonoid family, also increasing catechin, naringin, naringenin, myricetin, procyanidin B1, epigallocatechin-gallate, cinnamic, and ferulic acids related to antioxidant activity and catechin, cinnamic, and ferulic acids related to the induced systemic response. Pseudomonas 42P4 can be used as a bioinoculant in pepper plants to enable better agronomic management, decreasing the use of chemical fertilizer to contribute to sustainable agriculture.