Identification of Plant Growth-promoting Bacterial Endophytes using Culture-dependent In Vitro and Laboratory In Planta Methods

This study examined a collection of 220 bacterial endophytes isolated from herbaceous plants growing in petroleum-contaminated soils for plant growth promotion abilities. 12% of endophytes tested induced statistically significant growth benefits in Arabidopsis. The strongest plant growth promoting endophyte, Plantibacter flavus strain 251, increased A. thaliana fresh biomass and total root length by 4.7 and 5.8 times respectively over control plants and contained genes for auxin and ACC deaminase production. In vitro tests showed that 26% of endophytes from 19 different genera were potentially capable of nitrogen fixation, while 42% of endophytes from 16 different genera were capable of phosphate solubilization. Of the potential nitrogen fixers, 80% demonstrated free-living nitrogen fixation capability when grown in nitrogen-free media. None of the three endophytes tested improved Arabidopsis tolerance to drought stress. Overall, this study showed that a large variety of bacterial endophytes are capable of direct plant growth promotion.M.Sc.2020-06-30 00:00:0