| dc.description.abstract | The indole acetic acid (IAA) is a phytohormone capable of providing fast
responses to plant development such as cell elongation and differentiation and
division of cells. It is known that exist in the rhizosphere there are yeasts
capable of assisting the plant development by the IAA production. In this study,
the objective was isolate yeasts of the rhizosphere and select lineages capable
of producing IAA; the selected lineage was evaluated for the influence of
temperature, pH, agitation, carbon and nitrogen on the production of IAA. For
isolation, corn rhizosphere and sugarcane were sampled from the campus area
of UFSCar, Araras/SP. The samples were plated on YEPD medium, Sabouraud
and BDA. The lineages were selected using colorimetric methodology, with
Salkowsky reagent. The best results were evaluated for the influence of factors
in the production of AIA, through experimental planning with multivariate
analysis. Six yeast strains were isolated; the strain 6S01, identified as
Torulaspora globosa, was selected. The results of the multivariate analysis
show that among the studied factors, which significantly affected the production
of IAA were pH, agitation and nitrogen. The pH showed the greatest influence
on production, because it affected significantly at all times evaluated; the
highest recorded production values were obtained in the treatment in which the
initial pH of the medium was adjusted to 9,0. The highest yields occurred
between 24 and 48 hours of incubation, and the maximum production was
217,73 μg/mL. It was observed that, in the tests in which there was no addition
of nitrogen source in the culture medium, the production was higher; probably
tryptophan provided as a precursor molecule of AIA synthesis was used by tthe
yeast as a nitrogen source and was better absorbed in the absence of other
sources of the nutrient. It is concluded that the yeast T. globosa (6S01), isolated
from maize rhizosphere presents capacity of high production of IAA, with
potential for large scale production; the best conditions for the production are in
the absence of nitrogen source and in alkaline medium. | |
