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Bioprospection of Plant Growth-Promoting Endophytic Bacteria from the Roots of the Medicinal Plant Aloe vera

Cintia Faria da Silva, Luciana Cristina Vitorino, Maria Andreia Correa Mendonca, Edson Luiz Souchie, Welington Luiz de Araujo, Manuella Nobrega Dourado Ribeiro, Leonardo Cunha de Albuquerque, Marcos Antonio Soares

Endophytic bacterial communities are dynamic, capable of spreading throughout plant tissues, and perform metabolic functions that may benefit the host plant. Despite the current high interest in symbiotic microorganisms of medicinal plants, little is known about the functional traits of the endophilic bacteria of Aloe vera (L.) Burm. f., which has diverse chemical composition characterized by the synthesis of various bioactive substances. As this composition can be influenced by the endophytic microbiota, we tested the hypothesis that the root bacteria of Aloe vera present multifunctionality with potential in biotechnology for plant growth. A total of 129 endophytic bacteria from three environments, a field, garden, and nursery (n=3), were isolated, and phylogenetic analysis revealed the presence of four groups: Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. The functional trait for indole acetic acid (IAA) synthesis was observed in 32 of the isolates, with emphasis on the 135V Enterobacter tabaci strain, which revealed the highest production (225.2 μg mL^-1). The results found for Bayóvar phosphate solubilization were not expressive, with the highest values observed for the bacterium 149H Paraburkholderia sp. (45.7 mg L^-1). The 3V isolate Brevibacillus agri presented 45.6% antagonism against S. sclerotiorum. The greatest inhibition of the phytopathogens Fusarium sp. and Rhizoctonia sp. was observed with 149H Paraburkholderia sp. and 348V E. tabaci, respectively. This was the first study to evaluate the potential of endophytic bacteria of Aloe vera. Our results indicate that the isolates 135V and 348V E. tabaci and 149H Paraburkholderia sp. have potential for In vivo testing in promoting plant growth.