Harnessing synergistic PGPR consortia to boost legumes' resiliency to salt stress

Increasing drought and rising water and soil salinity pose significant challenges to both agricultural productivity and nutrition security in the Mediterranean region. Pea crop (Pisum sativum L.), which is vital for sustainable agriculture, is highly sensitive to salt stress, leading to substantial yield losses due to osmotic and oxidative damage and to the degradation of key physiological processes. Pea plants were grown in pots filled with sterile soil under greenhouse conditions. Plants were subjected to two salinity conditions: non-saline control (0 mM NaCl) and progressively increasing salt concentration (100, 150, and 200 mM NaCl). The trial included an uninoculated control and a treatment inoculated with a consortium of salt-tolerant Pseudomonas sp. and Bacillus sp. strains.

The results demonstrated that salt stress significantly reduced plant growth, biomass accumulation, and nitrogen content in uninoculated plants, while increasing electrolyte leakage and tissue sodium concentration. In contrast, consortium inoculation under salt stress resulted in significantly higher total biomass, leaf number, and leaf area than all other treatments. Furthermore, consortium inoculation increased photosynthetic activity compared with uninoculated plants, as indicated by a significantly higher SPAD index and the maintenance of a high maximum quantum yield of photosystem II, suggesting limited photo-inhibition. Additionally, under salt stress, our consortium enhanced osmotic regulation, resulting in a 3.2-fold increase in proline content, and improved membrane stability, with a 38% reduction in electrolyte leakage compared to the uninoculated treatment.

Overall, synergistic PGPR consortium effectively mitigates salt stress in peas through a multi-faceted defense mechanism, representing a promising sustainable strategy to enhance legume resilience under saline conditions.