Endophytic bacteria from Ilex paraguariensis shoot cultures: localization, characterization, and response to isothiazolone biocides

Abstract

Nodal segment explants of Ilex paraguariensis, collected from greenhouse-grown plants, were found tocontain endophytic bacteria. After culturing in bioreactors, 16 rRNA gene analyses and analytical profile index biochemicaltests were used to identify these bacteria asStenotrophomonas malthophilia. The presence of bacterialcells in the intercellular spaces of stem cortical parenchymawas detected in histological sections by scanning electronmicroscopy. A range of commercial isothiazolone biocideswere tested for their ability to repress the growth of Gramnegativebacteria grown in liquid media during themicropropagation phase. The addition of 0.75 ml l−1 Delcide? TG (5-chloro-2-methyl-4-isothiazolin-3-one + 2-methyl-4-isothiazolin-3-one, 1.05% and 0.45%, respectively) to the culture media resulted in 100% visibly clean cultures, with no suppression of shoot growth.