: Selection of phosphate-solubilizing bacteria to be used as soybean biofertilizers by a soil plate assay.

FERNÁNDEZ, L.; ZALBA, P.; GÓMEZ, M.; SAGARDOY, M.

Buenos Aires

Congreso; : BIOLATINA 2006. VII Feria Congreso Latinoamericano de Biotecnología. III Congres Argentino de Biotecnología.; 2006

SELECTION OF PHOSPHATE SOLUBILIZING BACTERIA TO BE USED AS SOYBEAN BIOFERTILIZERS BY SOIL PLATE ASSAY. Fernández LA. Zalba P. Gómez MA. Sagardoy MA. Laboratorio de Microbiología Agrícola y Laboratorio de Suelos  Salinos y Sódicos, Departamento de Agronomía, Universidad Nacional del Sur, Altos de Palihue s/n  (8000) Blanca, Provincia de Buenos Aires, Argentina. Fourth teen phosphate solubilizing bacteria (PSB) (4 Burkholderia sp., 5 Enterobacter sp., 4 Bradyrhizobiurn sp. and a commercial strain) were isolated from soil samples by serial dílutions of soil extracts in NBRIP`s solid medium and then quantifiying their pjosphate solubilizing capacities in liquid cultures. After these in vitro selections  the efficiency of the PSB was assessed in a soil plate assay  by evaluating soil phosphorus (P) availability. The assay was carried out in Petri dishes with 40 g of fresh  soil during 90  days at 28ºC  in a moist chamber. According to our results, Burkholderia sp PER2F, Enterobacter sp. PER3G and Bradyrhizobium sp. PER2H strains solubilized the largest quantities of P in the soil assay after 60 days as compared with a control and with the other strains. These strains were capable of release P from soil even though the high buffering capacity and the native competitive microbiota of soil. Finally, the effect of PSB as soybean biofertilizers under greenhouse conditions after one hundred days was studied. Soybean plants inoculated with Burkholderia sp.PER2F had tile highest aerial and showed an appropriate N/P ratio both indicates a promotion of soybean growth. However, none of the PSB increased P nutrition of plants. The soil plate assays developed in this work, makes it a better tool for screening strains to design efficient  bioferilizers which can to  contribute to improving farmers  profit by reducing the application of fertilizers and thus, to preserving environmental quality.