Selection of plant-associated Burkholderia spp. using a plant-trap scheme

LAMI, M.J.; ANTONICH, N.; BIALER, M.; WALL, L.G.; ZORREGUIETA, A.; DRAGHI W. O.

Rosario

Congreso; IX Congreso Argentino de Microbiología General; 2013

Sociedad Argentina de Microbiología General

Burkholderia species are widely dispersed in nature fulfilling different biological functions, mainly in close interaction with plants, insects and mammalians. As common inhabitant of soils, several species of Burkholderia have been found interacting with plant rhizosphere and even as endophytic microorganisms, allocating inside plants roots. The objective of this work was to select plant-associated Burkholderia species from different agronomical relevant crop species interacting during the first stages of plant growth. To select plant associated  Burkholderia  spp. we used agronomical relevant cultivars as plant-trap, such as maize, wheat, vetch, soybean and sorghum.Surface-disinfected seeds were pre-germinated in water agar plates, and at least 10 plantlets were aseptically transferred to 50 ml tubes for growing in plant mineral solution. Plantlets were inoculated with 1 ml of a suspension of 5x106c.f.u/ml composed of 100 different strains previously isolated from plant roots in PCAT, a semi-selective medium for Burkholderia species. After one week of growth, plant roots from different species were pooled, surficial disinfected, mechanically blended, and plated on PCAT medium. Identification of isolates was made through sequencing of a PCR species-specific amplicon routinely used for Burkholderia identification. This scheme of selection was repeated two more times. Around 40% of the isolates (24 out of 60) were recognized as Bukholderia species. With the exception of two strains, the remaining isolates (22 out of 24) were shown to belong to the Burkholderia cepacia complex (BCC), including B. ambifaria (7), B. cepacia (6), B. caryophylli (5), B. gladioli (4), B.terricola  (1) and  Burkholderia  sp. (1), not showing regular patterns between plant species. The main difference was observed during the 3th round, where Burkholderia isolates were only recovered from soybean and vetch. In all rounds we recovered  B. caryophylli, a  Burkholderia  species not previously found in Argentinean soil samples, remarking the ability of this species to interact with plant roots. We are currently running de-replication experiment to unravel the diversity composition at each inoculum suspension