Exploring the bacterial communities in date palm roots in saline versus non-saline environment

Bacterial communities associated with plant roots significantly influence plant growth and adaptation to environmental stresses, particularly in arid agroecosystems. Soil salinity is one critical abiotic stress factor that affects the microbial community structure and functionality. Understanding how soil salinity affects the composition and function of root-associated microbiota in date palms (Phoenix dactylifera L.) could offer valuable insights into enhancing plant resilience and agricultural productivity.

This study investigated the influence of soil salinity on the bacterial communities associated with date palm roots across different cultivars. Root samples were collected from date palms grown under saline (Nashella experimental station) and non-saline conditions (Al Foah experimental station). Using 16S rRNA metabarcoding coupled with culture-dependent isolation methods, significant variations in bacterial community structure and diversity were identified. Physicochemical analysis revealed that saline soils had elevated pH, electrical conductivity, and salinity levels compared with non-saline soils. The bacterial diversity significantly decreased under saline conditions, indicating reduced microbial richness and evenness. In particular, salt-tolerant date palm cultivars exhibited greater variability in bacterial diversity than cultivars grown under non-saline conditions. Non-metric multidimensional scaling (NMDS) analysis demonstrated clear clustering patterns driven by soil salinity and plant genotypes. Differential abundance analysis indicated enrichment of halotolerant and halophilic bacterial taxa in saline soils, whereas non-saline soils favoured bacterial taxa involved in beneficial plant-microbe interactions. Functional analysis using PICRUSt2 revealed that bacterial communities in saline soils had a greater abundance of stress-tolerance mechanisms, whereas those from non-saline soils emphasized metabolic versatility. Additionally, six bacterial isolates from saline and non-saline roots showed notable plant growth-promoting and stress-tolerance capabilities in Arabidopsis thaliana.

Our findings demonstrate the significant influence of soil salinity and date palm genotype on the structure, diversity, and functionality of root-associated bacterial communities. These results suggest potential applications for specific bacterial communities to improve plant tolerance to salinity stress, which is essential for sustainable agriculture in arid environments.