In situ effects of Lathyrus sativus- PGPR to remediate and restore quality and fertility of Pb and Cd polluted soils

Rehabilitation of heavy metals contaminated soils using association between legumes and beneficial rhizospheric microorganisms such as plant growth-promoting bacteria (PGPR) is a major challenge in agronomy. The present study focuses on assessing the impact of field inoculation with 11 (Rhizobium leguminosarum (M5) + Bacillus simplex + Luteibacter sp. + Variovorax sp.) and 15 (R. leguminosarum (M5) + Pseudomonas fluorescens (K23) + Luteibacter sp. + Variovorax sp.) on growth and phytoremediation potential of Lathyrus sativus plants as well as soil quality and fertility. The experimentation was carried out in mine tailings of northern Tunisia. Obtained Results indicated that the in situ inoculation with 11 and 15 significantly increased the shoots (47% and 22%) and roots dry weights (22% and 29%), as well as nodules number (48% and 31%), respectively, compared to uninoculated plants. The maximum Pb accumulation in the above-ground tissue was recorded in plants inoculated with 15 (1180.85 mg kg(-1) DW). At the same time, we noticed a reduction in total Pb and Cd in the rhizosphere of inoculated plots mainly in those inoculated with 15 reaching 46% and 61%, respectively, compared to uninoculated plots. Likewise, 15 inoculum significantly enhanced soil total nitrogen (35%) and available phosphorus (100%), as well as beta-glucosidase (16%), urease (32%) and alkaline phosphatase (12%) activities. Here we demonstrate the usefulness of L. sativus inoculated with 15 inoculum formed by mixing efficient and heavy metals resistant PGPR to boost an efficient reclamation of Cd and Pb contaminated soils and, ultimately, to improve their quality and fertility.