Abstract

The enrichment of plant rhizosphere with beneficial bacteria is a strategy that favors the production of more vigorous seedlings, which is essential for the success of vegetable cultivation. The aim of this study was to screen fluorescent pseudomonads that are able to act as plant growth-promoting rhizobacteria. Production of indole acetic acid (IAA) and phosphate solubilization were used as traits for initial screening of 78 strains. In addition, we evaluated kale growth promoting ability under greenhouse conditions in unsterilized soil.  Strains that significantly increased the dry mass of plants were characterized based on biochemical traits and by 16S rRNA sequencing. All isolates produced IAA. From these, 59 solubilized CaHPO₄. Seven strains which promoted kale growth, presented low or intermediate solubilization efficiency and IAA production ability and were characterized as Pseudomonas putida. Seven growth promoting strains with potential for the development of inoculants were selected for future tests under field conditions. This study also shows that growth promoting capability was not consistently related in vitro to IAA production and phosphate solubilization.

Key words: Rhizospheric soil, auxin, phosphorus, kale, root colonization.