Pseudomonas spp. isolates with high phosphate-mobilizing potential and root colonization properties from agricultural bulk soils under no-till management in Argentina.

FERNANDEZ L; AGARAS, B; ZALBA, P; WALL LG; VALVERDE CF

BIOLOGY AND FERTILITY OF SOILS

SPRINGER

Lugar: Berlin; Año: 2012 vol. 48 p. 763 - 773

0178-2762

Seven phosphate-mobilizing pseudomonads were isolated, identified and characterized in terms of their biofertilizer potential and root-colonizing properties. Pseudomonas protegens (ex-fluorescens) CHA0 was used for comparative purposes. Four isolates (LF-MB1, LF-P1, LF-P2 and LF-P3) clustered with members of the ?P. fluorescens complex?, whereas the other three (LF-MB2, LF-V1 and LF-V2) clustered with members of the ?P. putida/P. aeruginosa complex?. Assays in buffered liquid growth medium supplemented with tricalcium phosphate enabled the separation of the isolates into two groups: group A (LF-P1; LF-P2; LF-P3; LF-V1) solubilized P from 158 up to 182 µgmL-1 and group B (LF-MB1; LF-MB2; LF-V2) solubilized less than 150 µg P mL1. In general, isolates with high tricalcium phosphate solubilization activity, also displayed the higher acid and alkaline phosphatase activities. With the exception of LF-MB2, all isolates were able to degrade phospholipids from lecithin. Additionally, all isolates exhibited extracellular protease activity and four isolates produced hydrogen cyanide, two traits that are related to biocontrol of phytopathogens. To study root colonization in non-sterile soil, isolates were doubly tagged with gfp and a tetracycline resistance cassette. After 15 days of competition with the indigenous bacterial flora, all tagged isolates colonized soybean roots at counts ranging from 6.1×104 to 1.4×106 CFU g-1. The results indicate that there are already efficient phosphate-mobilizing pseudomonads adapted to agricultural bulk soils under no-till management in Argentina and thus having excellent potential for use as biofertilizers.