CONICET | Buscador de Institutos y Recursos Humanos

Peanut is a widespread leguminous plant of great agricultural and economic significance. Argentina is one of the main peanut producer countries in the world and 94% of its production is concentrated in Córdoba province. Due to intensity of agricultural practices, peanut soils of Cordoba have decreased their availability of phosphorus to plants. The aim of this work was to analyze the effect of phosphate rhizobacteria in peanut growth in microcosm experiments. For this study, a peanut cultivated soil from cropping area of Cordoba with low content of phosphorus was employed. Three native isolates obtained from peanut soils of Cordoba were selected considering their phosphate solubilization ability and other PGPR properties: J49, J157 and S57. The formers produced the highest phosphate solubilizing halo in Frioni`s medium and all of them showed siderophore production. Isolate J157 showed antibiosis against Sclerotinia minor and S.sclerotiorum, two phytopatogen fungus of high incidence in peanut crop of Córdoba. On the other hand, isolate S57 demonstrated indolacetic acid phytohormone production.Peanut seedlings were inoculated with a bacterial suspension (10 9 ufc/ml) and sown in sterilized plastic cups filled with sterilized soil with low phosphorus content. Five replicates were performed for each treatment. The treatements were as follows: 1.Non-inoculated plants (negative control) 2.fertilized treatment: non inoculated seedlings watered regularly with PO4KH2 (0,002M),3.(NH4PO4 fertilized treatment: pots containing non inoculated seedlings and (NH4)2PO4 (70 kg/ha), 4.Plants inoculated with Pseudomonas fluorescens (?Rizofos?), 5. Peanut seedlings inoculated with isolate J49. 6. Peanut seedlings inoculated with isolate S57, 7. Peanut seedlings inoculated with isolate J157. Plants were grown under controlled environmental conditions, watered regularly with sterilized tap water and, twice a month, with Hoagland´s phosphorus free medium. The plants were harvested at 60 days post-inoculation and plant and root dry weight, aerial plant length were determined.Results showed that plant dry weight was statistically higher in peanut plants inoculated with isolates J49 and S57 (Table 1, Figure 1) while aerial plant length was higher in pseudomonads and ammonium phosphate plant treatments (Table 1, Figure 2). No differences were observed between the treatments and negative control in root dry weight Table 1, Figure 3)and, on the other hand, phosphorus content was highest in potassium phosphate fertilized treatment (Table 1). Although field experiments are necessary, results show that peanut soil in the province of Cordoba harbor rhizobacteria with major PGPR properties which represent a potential source of new strains that could be used as biological inoculants in agriculture.

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