Effects of PGPB Colonization on Ancient and Recent Rice Accessions

Purpose: Rice is accounting for more than 50% of the world’s need for food supplies, but its cultivation is currently demanding in terms of chemicals and water. Rice domestication and the selection of new high-yielding varieties led to a continuous loss of biodiversity which impacted its ability to adapt to harsh environments, also affecting the association with soil microbiota. In this work, we evaluated how different rice genotypes, developed over a century of breeding, associate with selected root endophytic bacteria, to promote plant growth and sustain yield. Methods: A microbial consortium of two endophytic PGPB strains, Kosakonia sacchari and Herbaspirillum huttiense , were tested on a collection of 40 rice accessions, evaluating the number of colony forming units per gram of treated roots. Selected accessions showing the best aptitude in establishing positive association with the PGPBs were inoculated and grown in soil pots to measure and evaluate the PGPB effects on morpho-physiological characteristics, yield parameters and metabolomic profile. Results: We demonstrated that the impact of PGPBs is highly dependent on genotype and we identified major alterations in critical developmental stages like flowering time and reproductive traits. This analysis enabled the identification of key metabolic markers in specific genotypes, providing insights into the impact of this beneficial plant–microbe association on seed composition and nutritional traits. Conclusions: Microbial consortia represent efficient tools for improving rice adaptation to the environment and have an effect also on seed metabolic composition, but their effects are strictly related to rice plant genotype interacting with them.