Abstract

Endophytic microorganisms are able to promote plant growth through various mechanisms, such as production of plant hormones and antimicrobial substances, as well as to provide the soil with nutrients, for instance, inorganic phosphate. This study aimed to evaluate the potential of endophytic bacteria isolated from cashew leaves to produce substances involved in the promotion of plant growth, such as indole-3-acetic acid, the phosphate solubilization capacity, and the antimicrobial activity. For this, 31 isolate samples were used, out of which 17 (54.8%) produce indole-3-acetic acid in concentrations ranging from 11.79 to 145.85 µg.mL^-1. In turn, four (12.9%) were able to solubilize phosphate and the solubilization halos range from 5 to 19 mm. Soluble phosphorus concentrations range from 62.5 to 1,605.2 mg.L^-1. It was observed that Fusarium oxysporum and Colletotrichum sp. were inhibited by 70 and 40% of the strains, respectively. It was found out that five bacteria (25%) were Gram-positive, predominantly the species Staphylococcus saprophyticus (100%), while 15 bacteria (75%) were Gram-negative. Out of these, 4 (26.6%) and 3 (20%) belong to the species Escherichia coli and Shigella flexneri, respectively. Studying the endophytic population is something important due its biotechnological applications, because it has a great potential for promoting plant growth.

Key words: Anacardium occidentale, auxin, endophytic microorganisms, secondary metabolites, phosphate solubilization.