Co-inoculation of Anabaena cylindrica with Azospirillum brasilense increases grain yield of maize hybrids

Cyanobacteria, a group of N-2 fixing bacteria, and some species of them are free-living or associated with other bacteria, such as Azospirillum. Their association promotes the growth and productive performance of maize (Zea mays), showing variable responses according to the maize hybrid used. Thus, the aim of this study was to evaluate the effects of inoculation and co-inoculation of the Anabaena cylindrica (cyanobacteria) with Azospirillum brasilense on the development and productive performance of four maize hybrids. The field experiments were carried out in two locations (Londrina and Faxinal, Parana State, Brazil), using a randomized block experimental design, in a 4 x 4 factorial arrangement, with four replications. Four inoculation treatments were evaluated (A. cylindrica + A. brasilense, A. cylindrica, A. brasilense, and an uninoculated control) in four maize hybrids (512 PW, 2A620 PW, 2B810 PW, Status Viptera 3). The following characteristics were evaluated: plant height, ear insertion height, stem diameter, leaf area index, chlorophyll index, nitrogen, phosphorus and potassium leaf content, number of grain rows per ear, number of grains per row, number of grains per ear, number of ear per plant, mass of 1000 grains, nitrogen content in the grains and yield. The co-inoculation of A. cylindrica with A. brasilense favored the development and yield performance of maize hybrids, with an increase of 966.63 kg ha(-1) (9.37%) in Londrina and 1743.79 kg ha(-1) (23.1%) in Faxinal, in comparison to the uninoculated control. The maize hybrids showed the similar behavior, regardless of the inoculation or co-inoculation with A. brasilense and A. cylindrica. Therefore, these microorganisms can be recommended as inoculants.