Luciana Cristina Vitorino, Fabiano GuimarÃÂ£es Silva, Marcos AntÃÂ´nio Soares, Edson Luiz Souchie, Alan Carlos Costa and William Cardoso Lima
Plant growth and development are associated with access to minerals and phytohormones. Some microorganisms solubilize phosphate, producing phytohormones with functional features of plant growth promoters. The capacity of endophytic isolates from the root of Hyptis marrubioides Epling, a Lamiaceae, to solubilize calcium phosphate in GELP medium and iron phosphate in modified Reyes basal medium was characterized. Theability of these isolates to synthesize indoleacetic acid (IAA) in DYGS medium supplemented with tryptophan was also determined. Of the 42 bacterial and six fungal strains analyzed by solubilization assays, 20% formed CaHPO4-solubilization zones, although the level of solubilization was low. None of the fungi tested solubilized CaHPO4. In contrast, 59% of the microorganisms solubilized high levels of FePO4, and all of the fungi demonstrated this capacity. Among the bacterial isolates, 52% synthesized IAA, and strainsRF18, RG9, RF13 and RG24 were notable for their significant production of this phytohormone under test conditions (95.13, 39.28, 16.21 and 11.96 µg·mL-1, respectively). From a biotechnological perspective, the RG9, RG24 and RF18 strains are significant for their solubilization of high levels of FePO4 and abundant IAA production.
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