Co-inoculation of Azospirillum with mycorrhizal fungi in the cultivation of wheat in soils contaminated with copper

Abstract

Copper is a micronutrient essential for plant growth since it is part of the constitution of enzymes and proteins. However, it can become toxic to plants when in high concentrations in the soil. The association between microorganisms and plants is an alternative for reducing the negative effects of excess copper on plants. The objective of this work was to determine the influence of inoculation and co-inoculation of arbuscular mycorrhizal fungi and Azospirillum brasilense in a wheat crop grown on soil contaminated with copper. The experimental design used was entirely randomized in a bifactorial arrangement of 5 x 2, with five sources of inocula, (Azospirillum brasilense; Acaulospora colombiana; Gigaspora margarita; Acaulospora colombiana + Azospirillum brasilense; Gigaspora margarita + Azospirillum brasilense;), two doses of copper (0 = natural soil content and 400 mg kg-1), and eight replicates. We evaluated the height of plants, number of tillers, root length, root volume, dry root mass, specific surface area, average root diameter, copper content in the root, straw and grain, productivity, and percentage of mycorrhizal colonization. The inoculation with A. brasilense increases the number of tillers, plant height, and productivity compared to mycorrhizal fungi. The co-inoculation of these microorganisms does not contribute positively to these evaluated parameters, regardless of the dose of Cu applied to the soil. Co-inoculation of A. brasilense with mycorrhizal fungi does not reduce copper in the aerial part of wheat plants, regardless of the evaluated species, even in soil contaminated with copper.