ISOLATION AND CHARACTERIZATION OF ZN SOLUBILIZING BACTERIA FROM RICE RIZHOSPHERE IN ENTRE RIOS, ARGENTINA

SALAZAR A; MAIALE SJ; RODRIGUEZ AA; ROMERO FM

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General; 2023

Rice in Argentina is mainly produced in Entre Ríos and Corrientes provinces, which account for more than 80% of national production. In Entre Ríos, the crop has limitations due to several stresses, among them stands out the Zn deficit. We proposed the study of zinc solubilizing bacteria isolated from the rice rhizosphere, as an alternative to increase the rice production in the area and to reduce chemical fertilization. Solubilizing bacteria were isolated on medium with an insoluble Zn source (Zn3(PO4)2) after enrichment in liquid medium. To confirm the solubilizing capacity, pH and soluble Zn were determined by the Zincon® method in culture medium. Phosphorus solubilization was also evaluated in NBRIP medium. Through this process, we obtained a collection of 99 isolates on medium with the insoluble Zn source. 15 isolates were selected from these 99 bacterial isolates based on their ability to decrease the pH of the medium (pH2-6) and to show higher Zn solubilization (100-500ppm). To determine their potential as solubilizers of other Zn sources, the solubilizing capacity was also evaluated in both solid (qualitative) and liquid (quantitative) medium using ZnO as an insoluble source. In all cases, the ability to solubilize both Zn sources was observed. The isolate 64 showed the highest values in ZnO solubilization (400-600 ug/ml); the isolate 65 was the less effective with values between 100 and 300 ug/ml. Likewise, the ability of the isolates to solubilize an insoluble source of phosphorus (Ca₃(PO₄)₂) was also detected and determined. In this case, 12 out of 15 isolates were able to solubilize phosphorus, the highest rates were obtained for isolates 64 (1.5-2) and 76 (2-3). These isolates are currently being molecularly characterized and identified. Other plant-growth promotion traits such as indole and siderophore production are also being carried out. In conclusion, this work shows different bacterial isolates with the capacity to solubilize Zn and P, that could be used as bioinoculants for rice cultivation to reduce the use of chemical fertilizers.