Stress Tolerance, biocontrol and survival in wheat rhizosphere of Pseudomonas spp. SF10b

MAGRIS, S.; FISCHER S.; MORI, G.

Pinamar

Congreso; XLI Reunión anual de SAIB; 2005

SAIB

Pseudomonas spp. 10b was isolated from wheat roots and demonstrated to be PGPR, producing siderophore and indole acetic acid (IAA) and being able to solubilize phosphate. A spontaneous rifampicin resistant mutant (Pseudomonas spp. SF10bR), with similar viability than its wild type, was obtained. Wheat seedling were grown in pots with fertilized and non fertilized soil and inoculated with the spontaneous mutant, to a density of 108 cfu per plant. Fifteen, thirty and sixty days post-inoculation, bacteria were recovered from rhizosphere in both soils, but the number of viable cells was higher in non fertilized than in fertilized soil and it was maintained along the time. On the other hand, bacteria stayed in non fertilized buck soil until 30 days post-inoculation. The recount in endorhizosphere was below the resolution limits (103 cfu/ml). The same occurred in fertilized buck soil. The results indicated that the strain could survive better in soil with less nitrogen, perhaps because of low competition with native microorganisms. Pseudomonas spp. SF10b is able to tolerate up to 750 mM NaCl and it grows at 30ºC and 37ºC but not at 42ºC. Under stress conditions, the viability is similar than in normal conditions in exponential phase, but diminishes in the stationary phase. On the other hand, we studied the ability of Pseudomonas to inhibit in vitro phytopathogenic fungi: Fusarium graminearum, F. verticiloides, F. solani, F. proliferatum, Sclerotinia sclerotiorum, and S. minor.