BACILLUS SUBTILIS ISOLATES WITH DIFFERENT ABILITIES TO PROMOTE PLANT GROWTH IN MAIZE, COTTON AND SOYBEAN CROPS ISOLATION AND CHARACTERIZATION OF BACTERIAL STRAINS

摘要

Plant growth promoting rhizobacteria is a group of bacteria living inside plant tissue or in the rhizosphere, being able to promote plant growth due to their many abilities that directly or indirectly promote plant development. The aim of this study was to isolate and identify bacteria from maize with ability to solubilize phosphorus, fix nitrogen and produce IAA. Then, all isolates were evaluated regarding their abilities to promote plant growth on soybean, maize and cotton crops. In this study, oneBacillus velezensis, eight B. subtilis and one Lactococcus lactis isolates were obtained. Indole acetic acid concentration ranged from 11.32 to 15.23 mug IAA mL-1. For maize, four of B. subtilis isolates promoted higher plant height and one isolate promoted higher root dry matter and another promoted higher shoot dry matter. For cotton, one isolate promoted higher plant height, other promoted higher root dry matter another promoted higher shoot dry matter. For soybean, one isolate promoted higher plantheight, the other promoted higher root dry matter and the other higher shoot dry matter. In addition, one B. subtilis isolate harmed root development for maize crop. These results showed that according to the selection strategy used to select maize bacteria with plant growth promotion characteristics, the largest number of isolates was from Bacillus subtilis. Furthermore, B. subtilis isolates showed different growth promotion levels in the various cultures tested. This shows the importance of knowing if the correct bacterial isolate is being used for the appropriate plant.