Mycorrhizal dependence of citrus rootstock

Abstract Plant growth promoting microorganisms, such as mycorrhizal fungi, have been widely used in agriculture because they help plants in the absorption of nutrients and water, influencing their growth. The objective of this work was to verify the effect of the mycorrhizal association of Glomus clarum and Glomus etunicatum on the initial growth of the rootstocks Rangpur lime, Swingle citrumelo and Sunki mandarin. The experimental design was completely randomized with a 3 x 4 factorial arrangement, with five replications, corresponding to three rootstocks, four managements: mineral fertilization, inoculation with G. clarum (IGC), inoculation with G. etunicatum (IGE) and Control. The seedlings were produced in greenhouse, using as substrate the vermicompost earthworm, distributed in polyethylene bags, depositing three seeds of each rootstock / bag. The inoculation with mycorrhizal fungi was carried out at the time of sowing (45 spores of each species / bag). The mineral fertilization was divided into two phases: phosphorus application before sowing (40g of single superphosphate / bag); nitrogen application (1.7 g dissolved in 40 ml of water), divided in eight applications of 5 ml of the solution, via irrigation water, manually and weekly; and micronutrients (B, Cu, Fe, Mn and Zn), sprayed manually every two weeks. The following parameters were evaluated: height, stem diameter, number of leaves, shoot dry mass, colonization and mycorrhizal dependence. There was a significant interaction between the rootstocks and treatments applied in this study for most of the evaluated variables. Rangpur lime and Swingle citrumelo obtained higher height and the management that conferred higher height to the rootstocks was the mineral fertilization and IGE. The largest diameter of the stem was reached by Swingle citrumelo and the management that provided the largest diameter was the inoculation with G. etunicatum. Rangpur lime presented moderate mycorrhizal dependence for G. clarum and marginal for G. etunicatum. Mycorrhizal colonization did not show a significant interaction between rootstocks and the management with inoculation. The mycorrhizal association of G. clarum and G. etunicatum was not presented as the best management for the growth of Rangpur lime, Swingle citrumelo and Sunki mandarin, when compared to the mineral fertilization. However, the inoculation of mycorrhizal fungi provided a positive effect on the uptake of some nutrients by the rootstocks, especially K, Mg, N and P