Indole-3-acetic acid production, solubilization of insoluble metal minerals and metal tolerance of some sclerodermatoid fungi collected from northern Thailand

Abstract

Sclerodermatoid fungi basidiomes were collected from northern Thailand and pure cultures were isolated. The morphology and molecular characteristics identified them as Astraeus odoratus, Phlebopus portentosus, Pisolithus albus and Scleroderma sinnamariense. This study investigated the in vitro ability of selected fungi to produce indole-3-acetic acid (IAA), to solubilize different toxic metal (Co, Cd, Cu, Pb, Zn)- containing minerals, and metal tolerance. The results indicated that all fungi are able to produce IAA in liquid medium. The optimum temperature for IAA production of all fungi was 30°C, and the optimum concentration of L-tryptophan of Astraeus odoratus, Pisolithus albus and Scleroderma sinnamariense was 2 mg ml-1. The highest IAA yield (65.29 ±1.17 μgml-1) was obtained from Phlebopus portentosus after 40 days of cultivation in culture medium supplemented with 4 mg ml-1 of L-tryptophan. The biological activity tests of fungal IAA showed that it can simulate coleoptile elongation, and increase seed germination and root length of tested plants. In addition, the metal tolerance and solubilizing activities varied for different minerals and fungal species. The presence of metal minerals affected fungal growth, and cobalt carbonate showed the highest toxicity. The solubilization index decreased when the concentration of metal minerals increased. Astraeus odoratus showed the lowest tolerance to metals. This is the first report of in vitro IAA production, solubilization of insoluble metal minerals and metal tolerance abilities of the tested fungi. © Springer-Verlag Berlin Heidelberg and the University of Milan 2013.