Resumo

Agricultural productivity worldwide is affected by several factors,such as the occurrence of acidic soils in tropical and subtropical areas of the planet.In these regions, the culture of sugarcane has contributed to the economic independence of many countries and is a major agricultural product in Brazil. The most important influence of acid soils is to increase the availability of aluminum, an extremely toxic metal. The improvement of plant productivity has been achieved with the use of biofertilizers. Several studies have shown the efficiency of diazotrophic bacteria and arbuscular mycorrhizal fungi for this purpose,but the potential of yeasts remains poorly accessed.No previous reports on the application of endophytic yeasts as biofertilizer agents in sugarcane were found. The present study describes the isolation and characterization of yeasts from sugarcane varieties grown in the State of Rio de Janeiro, Campos dos Goytacazes (PESAGRO).Thirty-eight isolates were obtained from three varieties of sugarcane CB56155, RB867515 and SP803280. The sensitivity towards aluminium and low pH was analyzed as well as the capacity to produce the indole compounds and efficiency of zinc and phosphate solubilization. All these biochemical characteristics are indicative of potential growth promoters. Indole production in the culture medium was detectedin the absence and presence of tryptophan using Salkowski reagent. Zinc and phosphate solubilization was determined on plates. Most isolates tested were resistant to low pH and aluminum,but just a few exhibited high levels of indole production. The phosphate and zinc solubilization was also a restricted characteristic among isolates. In conclusion, two of isolates, namely CBA106-19 and SPA106-12, were chosen for experimental trials for further investigation of their potential as plant-growth-promoters.