Assessing the tolerance to heavy metals of arbuscular mycorrhizal fungi isolated from sewage sludge-contaminated soils |
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| Institution: | 1. Departamento de Biologia, Universidade Estadual do Sudoeste da Bahia, Avenida José Moreira Sobrinho, s/n, Jequiezinho, CEP, 45208-409, Jequié, BA, Brasil;2. Programa de Pós-Graduação em Botânica, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros, s/n, Dois Irmãos, CEP, 52171-900, Recife, PE, Brasil;3. Programa de Pós-Graduação em Ciências Naturais, Universidade do Estado do Rio Grande do Norte, Rua Professor Antônio Campos, s/n, Mossoró/RN, CEP, 59600-000, Mossoró, RN, Brasil;5. Laboratório de Produtos Naturais Bioativos, Universidade Federal Rural de Pernambuco, Rua Dom Manuel de Medeiros, s/n, Dois Irmãos - CEP, 52171-900, Recife, PE, Brasil |
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| Abstract: | Different fungal ecotypes were isolated from soils which had received long-term applications of metal-contaminated sewage sludge with the aim of studying the degree of tolerance and adaptation to heavy metals of arbuscular mycorrhizal (AM) fungi. The development and structural aspects of AM colonization produced by the different fungal isolates were studied using two host plants, Allium porrum and Sorghum bicolor, which were grown in either contaminated or non-contaminated soils. Four different AM fungi were successfully isolated from the experimental field plots: (i) Glomus claroideum, isolated from plots receiving only inorganic fertilizer; (ii) another apparently similar ecotype of Glomus claroideum, but isolated from plots with 300 m3 ha−1 year−1 of contaminated sludge added, (iii) an unidentified Glomus sp., present only in the less contaminated plots (100 m3 ha−1 year−1 of unamended sludge) and (iv) Glomus mosseae, isolated from plots receiving 100 or 300 m3 ha−1 year−1 of amended or unamended sludge (intermediate rates of contamination). There were consistent differences in behaviour among the four AM fungi tested with regard to the colonization levels they produced in non-contaminated and contaminated soils. Both total and arbuscular colonization were affected by heavy metal contamination. The main conclusions of this study are that Glomus sp. and G. mosseae isolates are strongly inhibited by heavy metals, which acted mainly by interfering with the growth of the external mycelium, and also by limiting the production of arbuscules. Our results suggest that G. claroideum isolates, particularly the ecotype which was isolated from the plots receiving the highest dose of metal-contaminated sludge, shows a potential adaptation to increased metal concentration in soil. |
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