Seleção de bactérias promotoras de crescimento vegetal na cultura do morangueiro

Abstract

Strawberry (Fragaria x ananassa, Duch.) as a fruit appreciated worldwide. However, many of the results of national production and productivity have been achieved through the application of agrochemicals in the productive fields for the control of phytopathogens, as well as chemical soluble fertilizers in the soil, practices that can cause several environmental problems in the medium and long term and increase production costs. In this context, plant growth-promoting bacteria have potential applications in agricultural production, especially since these microorganisms have the capacity to stimulate plant growth through auxin synthesis, biological nitrogen fixation, phosphate solubilization and biological control of phytopathogens. The aim of this work was to evaluate in vivo and in vitro the potential of promoting growth and biological control of bacteria isolated from leaves and roots of strawberry, as well as to evaluate their main effects on strawberry plants. For this purpose, in vitro tests of phosphate solubilization, auxin synthesis, biological nitrogen fixation, antagonism to Botrytis cinerea and volatile antifungal compounds production were carried out. The effects of the antifungal compounds on the phytopathogen were still evaluated by scanning electron microscopy. The isolates were evaluated for plant growth promotion capacity in vivo, by inoculation in strawberry plants; and the capacity of biological control, by inoculation in fruits. Biometric data were collected and anatomical and physiological changes in inoculated plants were evaluated by microscopy and IRGA analyzer (infrared gas analyzer), respectively. It was also evaluated the nitrogen and phosphorus accumulation in inoculated and non-inoculated plants. In a second experiment, the effect of inoculation on yield and fruit quality, as well as volatilome and fruit phenolic composition were evaluated. Five isolates selected in vitro and the Ab-V5 isolate (Azospirillum brasilense) were able to induce plant growth and control B. cinerea. The MET12M2 isolate promoted greater effects on growth, nutrient accumulation, anatomy, physiology, fruit production and fruit quality. The volatile and phenolic profile in fruits varied according to the inoculated isolate. Among the five isolates selected in vitro, all promoted visible changes in B. cinerea hyphae and the 29 isolate presented a greater biological control potential of the phytopathogen. We conclude that the endophytic bacteria tested and selected in this study present potential for application as growth-promoters in strawberry and its effects include growth, production, fruit quality, anatomy, physiology and nutrient accumulation by plants, as well as direct effects on the growth of phytopathogens.