Mycorrhizal effectiveness and manganese toxicity in soybean as affected by soil type and endophyte

Abstract

Mycorrhizal plants may present Mn toxicity alleviation and this depends on the plant-endophyte-environment interaction. The effectiveness of three arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, G. etunicatum, G. intraradices) and a control without AMF in two soils: Typic Rhodudalf with high Mn availability and a Typic Quartzipsamment, with low Mn availability, was evaluated in a time-course experiment at 3, 6, 9 and 12 weeks after soybean (Glycine max L.) seedling emergence. The objective was to select the most effective AMF species to enhance plant growth and to assess its effects upon Mn uptake by plants and Mn availability in the soil. For the sandy soil, AMF inoculation resulted in increased plant biomass, especially with G. intraradices and G. etunicatum. Lower Mn concentrations were observed in shoot and root of mycorrhizal plants. For the clayey soil, there was also an increase in plant biomass, but only for plants inoculated with G. intraradices and G. etunicatum. Mycorrhizal plants presented higher Mn concentrations in shoot and root and there was an increase of available Mn in the soil, in relation to the control, especially in the treatment with G. macrocarpum. When inoculated with G. macrocarpum, plants presented Mn toxicity symptoms and reduced biomass in comparison to control plants. The effects of mycorrhizal inoculation, either positive or negative, were most intense at 9 and 12 weeks.