Biofertilization with plant growth-promoting bacteria (PGPB) could optimize chemical fertilization for strawberry crop cultivation. A greenhouse study was arranged to assess the impact of an isolated PGPB consortium from halophytes on strawberry development, physiological traits, and nutritional balance subjected to two phosphorus fertilization limitation treatments (with and without insoluble phosphorus form application). Biofertilization had a positive effect on strawberry development. Thus, shoot and root biomass was c. 20 and 32% higher in inoculated plants grown with insoluble phosphorus. This effect was mediated by a positive bacterial impact on plant carbon absorption capacity and water use efficiency, through a reduction in CO₂ diffusional and biochemical photosynthesis limitation. Thus, net photosynthetic rate and intrinsic water use efficiency showed increments of 21–56% and 14–37%, respectively. In addition, inoculation led to a better efficiency of the plant photochemical apparatus, as indicated by the invariable higher PSII photochemistry parameters. Furthermore, these effects correlated with improved nutritional balance of phosphorus and nitrogen, which was directly related to the beneficial impact on carbon metabolism and, consequently, on strawberries’ growth. In conclusion, we can recommend the biofertilization based on PGPB for achieving more efficient strawberry P fertilization management practices, providing high efficiency in yields.

Coexistence impact of pollutants of different nature on halophytes tolerance to metal excess has not been thoroughly examined, and plant functional responses described so far do not follow a clear pattern. Using the Cu-tolerant halophyte Sarcocornia fruticosa as a model species, we conducted a greenhouse experiment to evaluate the impact of two concentration of copper (0 and 12 mM CuSO₄) in combination with three nitrate levels (2, 14 and 50 mM KNO₃) on plant growth, photosynthetic apparatus performance and ROS-scavenging enzymes system. The results revealed that S. fruticosa was able to grow adequately even when exposed to high concentrations of copper and nitrate. This response was linked to the plant capacity to uptake and retain a large amount of copper in its roots (up to 1500 mg kg^-1 Cu), preventing its transport to aerial parts. This control of translocation was further magnified with nitrate concentration increment. Likewise, although Cu excess impaired S. fruticosa carbon assimilation capacity, the plant was able to downregulate its light-harvesting complexes function, as indicated its lowers ETR values, especially at 12 mM Cu + 50 mM NO₃. This downregulation would contribute to avoid excess energy absorption and transformation. In addition, this strategy of avoiding excess energy was accompanied by the upregulation of all ROS-scavenging enzymes, a response that was further enhanced by the increase in nitrate concentration. Therefore, we conclude that the coexistence of nitrate would favor S. fruticosa tolerance to copper excess, and this effect is mediated by the combined activation of several tolerance mechanisms.

Hydro- and xerohalophytes withstand stress thanks to the resistance traits they have, complemented with the functions of their associated microbiota. Besides, given a higher exposition of the phyllosphere to environmental conditions compared to roots, their endospheric bacteria should be more resistant to stress. In this study, we analysed the composition and functional traits of the bacterial leaf endosphere of six xero- and hydrohalophytes species in two seasons. We sequenced their endospheric metagenomes by shotgun and annotated genes related with Plant-Growth-Promoting (PGP) properties. We showed that the composition, structure and functions of the bacterial endosphere are mainly influenced by host plant species, followed by functional type. Moreover, plant species and functional type promoted a different relative abundance of, respectively, 62 and 6 PGP properties. This study shows that not only the composition but also the functionality of the bacterial leaf endosphere of halophytes is more influenced by host species than functional type. Moreover, the leaf endosphere of the different plant species and functional type could be an important source of bacteria with diverse PGP properties.