GENETIC VARIABILITY OF SUGARCANE-ASSOCIATED DIAZOTROPHIC BACTERIA CAPABLE OF INORGANIC PHOSPHATE SOLUBILIZING

The sugarcane is a culture of great importance for the Brazilian agriculture. Every year this culture consumes great amounts of nitrogen and phosphate fertilizers. However, the use of plant growth-promoting bacteria can reduce the use of the chemical fertilizers, contributing to the economy and the environment conservation. So, the goal of this study was to select sugarcane-associated diazotrophic bacteria able to solubilize inorganic phosphate and to evaluate the genetic diversity of these bacteria. A total of 68 diazotrophic bacteria, leaf and root endophytic and rizoplane, of three sugarcane varieties. The selection of inorganic phosphate solubilizing diazotrophic bacteria was assayed by the solubilization index (SI) in solid medium containing insoluble phosphate. The genetic variability was analyzed by the BOX-PCR technique. The results showed that 74% of the diazotrophic strains were able to solubilize inorganic phosphate, presenting classes of different SI. The results showed that the vegetal tissue and the genotype plant influenced in the interaction between phosphate solubilizing diazotrophic bacteria and sugarcane plants. BOX-PCR revealed high genetic variability among the strains analyzed. So, sugarcane-associated diazotrophic bacteria express the capacity to solubilize inorganic phosphate and they present high genetic diversity.