Enhancing salinity resilience in horticultural systems through Portulaca oleracea PGPR phytoremediation with quantum dot biosensing

Soil salinity is a major constraint on productivity in greenhouse and horticultural systems, especially when saline irrigation is applied. In this study, we examined whether halotolerant plant growth-promoting rhizobacteria (PGPR) could alleviate saline–sodic stress in Portulaca oleracea . Eight PGPR strains were evaluated individually and as a multi-strain consortium in saline–sodic soil under greenhouse conditions, alongside uninoculated and 1% H₂SO₄-treated controls. Among the evaluated treatments, PGPR8 and the consortium were among the most effective in improving key plant physiological and soil biological parameters under salinity stress. Plants treated with the consortium reached about 29 cm in height, showed a shoot Na⁺/K⁺ ratio of 0.58, and had chlorophyll levels approximately ten times higher than those of acid-treated plants. Soil biological activity also improved, with microbial biomass carbon reaching about 268 µg C g −1 . In parallel, transcriptional analysis showed a 2.2–2.4-fold upregulation of SOS1 , NHX1 , SOD , and POD relative to the controls. We also applied anti-OmpA antibody-functionalized quantum dots as an exploratory approach to probe OmpA-associated bacterial surface responses. Although this assay produced a rapid, concentration-dependent fluorescence response, the results should be interpreted as preliminary surface-associated indicators rather than direct quantitative measures of PGPR activity. Overall, these findings suggest that PGPR inoculation can enhance plant resilience and improve soil function under short-term saline–sodic stress. Further field-scale validation is needed to determine the long-term agronomic relevance and sustainability of these biological treatments.