Contaminant bacterium in the phase of in vitro establishment of guava

Abstract

The guava tree (Psidium guajava L.) is an specie which has demonstrated to be recalcitrant to micropropagation techniques by organogenesis due to microbial contamination and tissue blackening problems. The current work followed as objective: to evaluate the incidence and effect of the bacterial contamination of the guava in vitro establishment as well as to isolate and identify the main contaminants. The work was carried out with 34 nodal segments of guava tree which did not succeed the in vitro establishment. Twenty-eight out of them presented microbial contamination visible on the culture medium, around the base of the explants and sometimes colonizing the same ones. The cultural characters of the contaminants microorganisms in the culture medium for the in vitro establishment were described, isolated and purified. Traditional staining, physiological and biochemical tests were realized for the identification. The obtained results indicated that the microbial contamination and the fenolization limited the in vitro establishment of guava. It was determined that the 76.47% of the samples analyzed presented bacterial contamination, the 5.88% by yeasts and the 17.47% did not presented detectable contaminants. The most frequent contaminants belonged to the Pseudomonadaceae and Enterobacteriaceae families. The injurious effect of the contaminants on the explants of guava were observed and a total necrosis of the same ones was detected. Key words: bacterial contamination, Enterobacteriaceae in vitro propagation, Pseudomonadaceae, Psidium guajava