Degradation of Metalaxyl and Folpet by Filamentous Fungi Isolated From Portuguese (Alentejo) Vineyard Soils

Abstract

Degradation of xenobiotics by microbial populations is a potential method to enhance the effectiveness of ex situ or in situ bioremediation. The propose of this study was to evaluate the impact of repeated metalaxyl and folpet treatments on soil microbial communities and to select soil fungal strains able to degrade these fungicides. Results showed an enhanced degradation of metalaxyl and folpet in vineyards soils submitted at repeated treatments with these fungicides. Indeed, highest degradation ability was observed in vineyard soil samples submitted at higher number of treatments. Respiration activities, determined in the presence of selective antibiotics in soil suspensions amended with metalaxyl and folpet, showed that the fungal population was the microbiota community most active in the degradation process. Batch cultures performed with a progressive increase of fungicide concentrations allowed the selection of five tolerant fungal strains: Penicillium sp.1 and Penicillium sp. 2, mycelia sterila 1 and 3, and Rhizopus stolonifer. Among these strains, mycelium sterila 3 and R. stolonifer, presented only in vineyards soils treated with repeated application of these fungicides, showed tolerance higher than 1000 mg l-1 against a commercial formulations of metalaxyl (10%) plus folpet (40%). Using specific methods for inducing sporulation, mycelium sterila 3 was identified as Gongronella sp. Since this fungus is rare, it was compared by csM13-PCR with the two known species G. butleri and G. lacrispora. The high tolerance to metalaxyl and folpet demonstrated by Gongronella sp. and R. stolonifer might be correlated with their degradation ability. Our results point out that selected strains have potential for the bioremediation of metalaxyl and folpet in polluted soil sites.