Zn SOLUBILIZING FUNGI FROM PATAGONIAN SOILS IN ARGENTINA

SALAZAR TAMAYO ANDY; SAEZ JULIETA; RODRÍGUEZ ANDRÉS ALBERTO; ROMERO MATIAS; MAIALE SANTIAGO JAVIER

Congreso; XVIII congreso SAMIGE; 2023

Pecan is grown in Argentina from Rio Negro to Misiones. In Rio Negro Valley, pecan plants have nutritional limitations, mainly due to soil alkalinity. One of the main limitations is Zn availability, since this micronutrient is required in higher proportion by pecan plants (50-200 ppm) than by other plants. Plants can interact with different symbiotic fungi, which help with nutrient uptake. The aim of this work was to isolate and characterize Zn solubilizing fungi from pecan rhizosphere in Río Negro Valley in order to find an alternative to chemical fertilization. The isolation was carried out from rhizosphere soil of pecan plants, that were grown in greenhouses, in medium with an insoluble source of Zn (ZnO). Presence of solubilization halo was used as selection criterion. Zn solubilization index was calculated as the ratio between area of solubilization halo and colony area. Quantification of Zn solubilization was evaluated by Zincon® method in liquid medium. Morphological identification of isolates was carried out after safranin stain. Sixteen fungal isolates showed solubilization halo on Petri plates with ZnO, to which a quantification of the solubilization halo in relation to the area occupied by mycelium was performed. Then, four isolates (2,14,15,21) that showed the highest solubilization indexes (ratios ranging 5-6) in solid medium, were selected. To continue the characterization of these isolates, their ability to solubilize Zn in liquid medium was determined, and solubilization levels of 75-190 ppm were observed. In this way, isolate 21 showed the highest solubilization level. At the same time, the hydrogenionic concentration in culture medium was determined. It showed values between 1x10-7 and 4x10-7. In order to identify the isolates, samples of each one of them were prepared, asexual reproductive structures were observed by optical microscopy. Thus, it was possible to identify that these isolates belong to Aspergillus genus. Molecular identification is currently in progress. In conclusion, fungal isolates of Aspergillus genus were obtained from rhizosphere of pecan plants with Zn solubilizing capacity. This capacity correlates with an increased presence of hydronium ions in the culture medium. These isolates can be used for biofertilizers formulation in order to reduce agrochemicals use.