Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Douglas Mariani Zeffa, Luiz Júnior Perini, Mayara Barbosa Silva, Nicholas Vieira de Sousa, Carlos Alberto Scapim, André Luiz Martinez de Oliveira, Antônio Teixeira do Amaral Júnior, Leandro Simões Azeredo Gonçalves, P. Pardha-Saradhi.
The development of cultivars with an improved nitrogen use efficiency (NUE) together with the application of plant growth-promoting bacteria is considered one of the main strategies for reduction of fertilizers use. In this sense, this study: i) evaluated the effect of Azospirillum brasilense on the initial development of maize genotypes; ii) investigated the influence of A. brasilense inoculation on NUE under nitrogen deficit; and iii) sought for more NUE genotypes with higher responsiveness to A. brasilense inoculation. Twenty-seven maize genotypes were evaluated in three independent experiments. The first evaluated the initial development of maize genotypes with and without A. brasilense (strain Ab-V5) inoculation of seeds on germination paper in a growth chamber. The second and third experiments were carried out in a greenhouse using Leonard pots and pots with substrate, respectively, and the genotypes were evaluated at high nitrogen, low nitrogen and low nitrogen plus A. brasilense Ab-V5 inoculation. The inoculation of seeds with A. brasilense Ab-V5 intensified plant growth, improved biochemical traits and raised NUE under nitrogen deficit. The inoculation of seeds with A. brasilense can be considered an economically viable and environmentally sustainable strategy for maize cultivation.
The world yield and productivity of maize (Zea mays L.) doubled in the last three decades, resulting in an output of 1,034.8 million tons of grain in 2017/2018 . This significant yield increase is attributed mainly to chemical fertilizers, breeding and crop management . However, the dependence of modern agriculture on chemical fertilizers is alarming, since the indiscriminate use of these inputs has been causing serious environmental problems, e.g., water eutrophication, soil acidification and air pollution [3–5].
The results of this study indicated that maize inoculation with A. brasilense Ab-V5 improved plant growth and biochemical traits and increased NUE under N limiting conditions. Metabolic changes in maize plants in response to A. brasilense inoculation were described previously, e.g., an improved root architecture , increase in plant biomass  and N assimilation , as well as mitigation of abiotic stresses [54–56]. In this way, the results show the powerful effect of A. brasilense inoculation on maize, mainly under limiting nutritional conditions, and also reinforce the importance of the plant microbiota as an extension of the maize genome to beat developmental restrictions under limiting-growth conditions .