Plants constitute dynamic systems with different strategies to face biotic and abiotic stress. Water deficit is one of the most challenging abiotic factors increased by climate change, affecting seriously the quality of soils and crop yields, decreasing photosynthetic rate, increasing the accumulation of free radicals, and modifying root morphology. In this regard, the potential role of the host plant - arbuscular mycorrhizal fungi (AMF) and plant growth-promoting bacteria (PGPB) interactions within the rhizosphere in the alleviation of drought stress is being deeply studied. These symbiotic relationships not only allow a major nutrient and water uptake, but also could be integrated as a sustainable approach to improve the growth and productivity of crops under water scarcity conditions. A better comprehension of the mechanisms of these synergies between PGPB and AMF with plants is becoming an important key to develop effective applications of these natural symbiosis. In this work, the highlighted knowledge concerning these associations and their effect in the response of plants under drought stress have been reviewed, focusing on the interactions described in Solanaceae vegetables, one of the most relevant crops in the Mediterranean area.

Traditional varieties are good candidates to be grown under sustainable conditions. In this research we evaluated the effect of reducing fertilization and irrigation dose, and the use of microbial biostimulants (N-fixing + K and P solubilizing bacteria+ mycorrhizal endomycorrhizae fungi) on yield parameters of two traditional pepper varieties (BGV13004, BGV5126) and one commercial variety (Cabañeros). The treatments consisted of two fertilisation levels (100% F and 50% F) combined with two irrigation levels (100% I and 75% I). Furthermore, the effect of microbial biostimulants (B) was studied at the lowest fertilisation rate using the commercial products Bactogreen® and Agromic®. Reduced fertilisation decreased total yield in varieties BGV13004 and Cabañeros, as a consequence of reduced fruit set. On the contrary, in variety BGV5126, the decrease in the concentration of the nutrient solution (100% F vs. 50% F) led to an increase in yield, probably due to a greater sensitivity of this variety to salinity. The effect of B was highly dependent on the variety studied, with both an increase (BGV13004) and a decrease (BGV5126) or no impact (Cabañeros) on total production.