Effects of Fine Soils from Dismissed Bauxite Mines in Puglia (Southern Italy) on Some Selected Soil-Borne Fungi

Soil samples taken in the Puglia region, Southern Italy, around the entrance of dismissed bauxite mines at San Giovanni Rotondo, Otranto and Spinazzola, were assayed at 1% in Potato Dextrose Agar (PDA) and as liquid cultures in half-strength Potato Dextrose Broth against strains of Fusarium oxysporum f. sp. lycopersici (FOL), Sclerotinia minor (SM), Verticillium dahliae (VD) and Trichoderma harzianum (TH). In PDA experiments, all soil samples limited VD (21.9-32.2%), and SM (4.3-65.2%) or enhanced FOL (73.9-86.6%) radial growth, while the TH growth was differently altered. In solid media, soil samples lowered the FOL sporulation rate (23.53-62.75%), improved TH (5.4-109.3%) and VD (27.5-41.37%) conidia production, and had no effect on SM microsclerotia differentiation. In liquid cultures, almost all soil samples affected the mycelia biomass production, reduced VD (85-90.2%) and TH (20-70%) conidia production, and increased FOL (35-188%) sporulation. The SM strain did not produce microsclerotia in any liquid media tested. Soil samples in the liquid media also affected T. harzianum antagonistic activity mediated by secondary metabolites. Pearson correlation coefficient correlates these biological effects with pollutant total concentration, modifies contamination degree index and Nemerow integrated risk index. Data recommends soil surveys considering the impact on the biota, especially in sites of naturalistic, geological, and tourist interest.