Fungi-assisted phytoextraction of lead: tolerance, plant growth-promoting activities and phytoavailability

Lead (Pb) is known for its low mobility and persistence in soils. The main aim of the present study was to explore potential of different fungal strains to promote phytoextraction of Pb-contaminated soils. Five non-pathogenic fungal strains (Trichoderma harzianum, Penicillium simplicissimum, Aspergillus flavus, Aspergillus niger, and Mucor spp.) were tested for their ability to modify soil properties (pH and organic matter) and to increase Pb phytoavailability at varying concentrations. Lead tolerance of fungal strains followed the decreasing order as A. niger > T. harzianum > A. flavus > Mucor sp. > P. simplicissimum. Lead solubility induced by A. flavus and Mucor spp. was increased by 1.6- and 1.8-fold, respectively, as compared to the control soil (Pb added, without fungi). A. flavus and Mucor spp. lowered the soil pH by - 0.14 and - 0.13 units, in soils spiked with 2000 mg Pb kg(-1). The maximum increase in the percentage of organic matter (OM) recorded was 1.7-fold for A. flavus at 500 mg Pb kg(-1) soil. Plant growth-promoting assays confirmed the beneficial role of these fungal strains. Significantly high production of IAA (249 mu g mL(-1)) and siderophores (61%) was observed with A. niger, and phosphate solubilization with P. simplicissimum (58 mu g mL(-1)). Based on the results in Pb-contaminated soils, Pelargonium hortorum L. inoculated with Mucor spp. showed the potential to enhance phytoextraction of Pb by promoting Pb phytoavailability in soil and improving plant biomass production through plant growth-promoting activities.