Next-Gen Bioinoculants: Bacterial, Yeast, and Mycorrhizal Consortia for Drought-Tolerance in Lettuce

Drought is a key factor that affects food production and represents one of the major challenges to global food security, especially with the increasing human population. One of the main strategies to improve drought tolerance in plants has been the use of beneficial rhizosphere microorganisms. However, within the rhizosphere, microorganisms establish diverse relationships with each other and with the host plants, positively or negatively affecting the drought tolerance. To address this complexity, the use of microorganisms that fulfill different niches producing an improved drought stress tolerance may be the basis for the design of the "Next Generation of Bioinoculants." This study aimed to develop a bioinoculant consisting of plant growth-promoting bacteria, yeast, and arbuscular mycorrhizal fungi for the cultivation of Lactuca sativa. Twenty-seven microbial consortia were inoculated on lettuce plants and submitted to drought stress for 40 days. Four consortia were selected based on their superior biomass production and tested on agricultural soil subjected to drought. Biomass production, proline and peroxidative damage, photosynthetic activity, antioxidant response, and profiles of phenolic compounds were also evaluated in lettuce leaves. Results showed that the consortium composed by Claroideoglomus lamellosum, Naganishia albida, and Burkholderia caledonica improved biomass production of shoots of lettuce plants by 43% under drought stress, primarily by enhancing proline, phosphorus, and photosynthetic pigment levels, as well as the antioxidant enzyme activities of catalase (CAT) and ascorbate peroxidase (APX), leading to reduced oxidative damage. These findings suggest that species-specific microbial consortia can serve as effective tools for improving drought tolerance in crops, contributing to sustainable agricultural practices in water-limited environments.