Sugarcane.Nitrate.Amino Acids.Diazotrophic bacteria.

The use of nitrogen fertilizers for sugarcane cultivation in Brazil is relatively low when compared to other producing countries. One of the reasons for this fact could be, in part, due to the indirect improvement process of varieties grown in low fertility soils. Compared to other crops, sugarcane has a low response to the application of nitrogen fertilizers, but the causes of this low efficiency in the use of N remain unknown. In addition to biological N2 fixation by the action of diazotrophic bacteria, plants absorb N sources such as ammonium, nitrate and amino acids through membrane transporters located in plant roots. There is evidence that the association of plants with microorganisms improves the use of fertilizer N, regulates the expression of N-transporter genes and modifies the N metabolism of plants. Based on that, the objective of this work was to evaluate the effect of inoculation of five diazotrophic bacteria Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans, Azospirillum amazonense and Paraburkholderia tropica in sugarcane varieties subjected to organic N sources (inorganic N sources). amino acids). For this, the first study evaluated the performance of a mixture of five diazotrophic bacteria in the variety RB966928. Inoculation associated with nitrogen fertilizer increased sugarcane growth, improved N acquisition and assimilation. The second study evaluated the effect of inoculation on RB867515 and RB966928 supplemented with organic N in the form of amino acids and compared with inorganic N and uninoculated organic N. Organic N reveals to be an important N source for the nutrition of sugarcane inoculated under inorganic N restriction conditions, when compared to non-inoculated OR N. The third study evaluated the transcriptional profile of amino acid transporter genes in inoculated or not inoculated roots of RB867515 and RB966928 sugarcane plantlets, supplemented with five amino acids at times 4 h and 24 h. Inoculation of RB966928 and RB867515 seedlings revealed generally beneficial modifications in the transcriptional profile of amino acid transport genes SoLHT1.2, SoLHT6, SoLHT1.1, SoAAPA1.1, SoAAP3.1, SoAAP1.2, SoAAP3.2 and SoAAP2 , indicating that diazotrophic bacteria induce the expression of amino acid transport genes in sugarcane seedlings. The fourth study evaluated N metabolism enzymes and the transcriptional profile of high and low affinity nitrate transport genes (NRTs) and the expression of the glutamine synthetase (GS) gene in inoculated or not inoculated roots of sugarcane seedlings of RB867515 and RB966928, supplemented with KNO3- at times 4 h, 24 h and 72 h. The inoculated seedlings improve the activity of nitrate reductase (NR) and glutamine synthetase (GS) during 72 h. Inoculation generally modified the expression of SoNRT2.5., SoNRT2.1, SoNRT1.5, SoNRT1.4 and SoGSb between the sugarcane varieties.