Effect of agrochemical application on cultivable phosphate solubilizing bacteria isolated from peanut cultivated soils of Córdoba

ANZUAY, S., FROLA, O., ANGELINI, J., FABRA, A., TAURIAN, T.

Quirama, Medellín

Workshop; 9th International and 1st Lationamerican PGPR Workshop; 2012

Argentina is one of the major peanut exporters in the world, and about 90% of its production takes place in the province of Córdoba. Due to intensive agronomical practices, low levels of available phosphorus to plants have been detected in this region. Phosphate solubilizing bacteria are considered to be very important associated with plant nutrition. A major well-characterized mechanism of mineral phosphate solubilization in Gram negative bacteria is gluconic acid secretion. This acid results from the extracellular oxidation of glucose via the quinoprotein GDH that requires the cofactor PQQ, whose biosynthesis involves the pqq genes. The aim of this study was to analyze the effect of agrochemicals application on the diversity of phosphate solubilizing bacteria inhabiting peanut soils and to analyze the presence of pqq genes in the genome of this bacterial group. Bacteria were isolated from agrochemical treated or untreated soils. Soil samples were obtained at 2, 30 and 120 days after agrochemicals application. Morphology of these bacteria was examined by light microscopy. Rep-PCR profiles were performed using primers ERIC and BOX and Shannon index was estimated to determine bacterial diversity. PqqE and pqqC genes were amplified by PCR. The number of Gram positive bacteria was higher in treated samples. Twenty too and 73 different Rep-PCR profiles were obtained from bacteria isolated from untreated or treated peanut soils, respectively. Shannon index revealed an increase in bacterial diversity in treated soils samples at all times analyzed. The presence of the genes pqqE and pqqC were determined in 75% of Gram-negative bacteria analyzed. It was concluded that agrochemical application increases the diversity of phosphate solubilizing bacteria and that pqq might be potential marker genes when analyzing this bacterial group in soils.   Supported by CONICET, ANPCyT, SECyT-UNRC and Fundación Mani.