COLONIZATION OF SORGHUM BY SEED INOCULATION WITH Burkholderia tropica

BERNABEU, PAMELA; GARCIA-FERREYRA, GIMENA; GUIDI, VERÓNICA; ORMAZABAL, CELESTE; LUNA, MARÍA FLAVIA

Rosario

Congreso; IX Congreso Argentino de Microbiología General SAMIGE; 2013

Sociedad Argentina de Microbiología General (SAMIGE),

The use of Plant Growth Promoting Bacteria (PGPB) as biofertilizer and biocontrol organisms is being considered as an alternative or a supplemental way of reducing the use of chemicals in agriculture. PGPB must grow on or around the roots for further plant colonization, which is of primary importance for an effective plant microbe association. After this initial colonization step, some bacteria are able to enter roots by different mechanisms and establish endophytic populations. A N2-fixing endophytic bacterium, Burkholderia tropica MTo293, was described as potencial PGPB associated with maize and other host plants. Its colonization behavior has not been characterized in sorghum plants and it is not known what inoculum concentration is required to entering the plant. This is important to extend inoculation with this microorganism to seed propagated crops. In the present study, it was made an attempt to study the colonization behaviour of B. tropica in sorghum bicolor. Seeds were inoculated at different inoculum levels and plants grown under gnotobiotic conditions. Colony counting of homogenized tissues and microscopic observation (epifluorescence and confocal) of organ sections were performed in order to determine its colonization capability. It is shown that seed inoculation with B. tropica led to extensive root colonization of plant followed by bacterial spreading to aerial tissues, without any symptom of plant growth inhibition. Endophytic colonization was found since 15 days postinoculation irrespective of the inoculum level and the intercellular spaces were found as the sites of this effective colonization.