The rhizosphere microbiome and growth-promoting rhizobacteria of the Brazilian jucara palm

Jucara palm (Euterpe edulis Mart.) is a native species of great ecological and economic importance that occurs in the Brazilian Atlantic Forest. The illegal harvesting of wild jucara palm heart has brought the species onto the endangered species list. Thus, this study aims to isolate, characterize, and select native bacterial strains associated with E. edulis and estimate the correlation between soil properties and diversity. In total, out of 190 isolates obtained of E. edulis, 110 were rhizosphere isolates, and 80 were root endophytic isolates that were screened for plant growth-promoting traits. The communities associated with jucara palm mainly include the genera Pseudomonas, Stenotrophomonas, Burkholderia, Rhizobium, and Gluconobacter. The diversity indices vary from 1.60 to 1.95, and it was found that soil phosphorus was most closely related to bacterial diversity, while clay, pH, and potassium had an inverse correlation with bacterial diversity. Out of the total bacterial isolates, 42.2% were found to be efficient phosphate solubilizers among which the Burkholderia genus was the most common, and the genus Pseudomonas was the most frequent among the siderophore-producing isolates (14.6%). Moreover, the Burkholderia and Pseudomonas were the most capable of producing auxins (80.2%); they were followed by Gluconobacter. In this regard, the isolation, identification, and the diversity of plant growth-promoting bacteria, which combine the ability to fix nitrogen with the production of substances capable of promoting the plant growth, in the future, can be of substantial help to the jucara palm cultivation.