Rizobactérias promovem crescimento, aliviam os efeitos do déficit hídrico e reduzem antracnose em mudas de açaizeiro.

Abstract

Açaí palm (Euterpe oleracea Mart.) is native to the Amazon and presents great economic interest in Brazil and in the world. Brazil is the world's largest producer of açaí fruit, the state of Pará being the largest national producer. This production was destined for local consumption, but the conquest of new markets and the increase in exports stimulated the expansion of commercial plantations on land. However, the high demand for seedlings has limited the implantation of commercial plantations, due to the slow growth, high sensitivity to the water deficit and the occurrence of anthracnose caused by Colletotrichum. The study objective was to evaluate the growth promotion, water deficit mitigation and reduction of anthracnose by rhizobacteria in açaí palm seedlings. The experiment was carried out in a completely randomized design in the nursery conditions with açaí seedlings inoculated with rhizobacteria R-35, R-38, BRM32113, BRM32111, R-58, R-61 and R-92. All rhizobacteria promoted growth, accumulation of biomass, higher content of nutrients and chlorophylls, as well as improvements in photosynthetic performance. The rhizobacteria BRM32113, BRM32111, R-58 and R-92 were inoculated in açaí seedlings submitted to the water deficit. Depletion of soil water up to 50% of field capacity reduced water potential and photosynthetic performance. However, the higher activity of antioxidant enzymes alleviated the effects of water deficit on açaizeiro seedlings inoculated with rhizobacteria. The infection of Colletotrichum sp. in leaves of açaí seedlings altered the capture of light and the assimilation of CO2 in the mesophyll, resulting in lower photosynthetic performance. However, when the açaí seedlings were inoculated with the R-92 rhizobacteria the severity of the anthracnose was reduced and the damages in the photosynthetic apparatus were attenuated. The results show that the rhizobacteria accelerate the growth of the açaí palm seedlings, which can contribute to decrease the time of quality seedlings, greater tolerance to water deficit and greater resistance to anthracnose. The application of rhizobacteria can be used as a clean technology to aid in the sustainable management of the production of açaí palm seedlings in nurseries.