Identification of two pesticide-tolerant bacteria isolated from Medicago sativa nodule useful for organic soil phytostabilization

• Ibtissem Aroua ^[1] ; Ghassen Abid ^[1] ; Fatma Souissi ^[1] ; Khdiri Mannai ^[1] ; Houcem Nebli ^[2] ; Sabrine Hattab ^[3] ; Ziad Borgi ^[2] ; Moez Jebara ^[1]
  1. [1] University of Carthage

     University of Carthage

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  2. [2] The Technical Center of Organic Agriculture in Chott Meriem
  3. [3] The Regional Center of Research in Horticulture and Organic Agriculture in Chott-Meriem Route Touristique

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• Localización: International microbiology: official journal of the Spanish Society for Microbiology, ISSN 1139-6709, Vol. 22, Nº. 1, 2019, págs. 111-120
• Idioma: inglés
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  • Plant-microbe interactions such as rhizobacteria legumes are interesting in organic farming that has undergone significant expansion in the world. The organic agriculture is as an environment-friendly technique and a sustainable alternative to intensive agricultural system. Three types of soil were chosen, organic (ORG), conventional (CON), and fallow land (NA) to isolate soil bacteria-nodulating Medicago sativa, in order to develop microbial inoculants for use in agricultural sustainable system. Soil analysis revealed significant higher amounts of total nitrogen, organic carbon, total phosphorus, and matter detected in ORG. As for heavy metals, ORG showed high Cu content due to the authorized chemical use in organic farming. A sample of 130 bacteria was isolated from Medicago sativa nodule, genetically characterized by PCR/RFLP of ribosomal 16S RNAs, and a great dominance of Sinorhizobium meliloti (88.4%, 73.8%, and 55.5%) is obtained among NA-, CON-, and ORG-managed soils, respectively. The ORG showed the high bacterial diversity with 13.3% of non-identified strains. The resistance against five pesticides (Prosper, Cuivox, Fungastop, Nimbecidine, and Maneb) revealed a maximum of inhibitory concentration about 10 mg l−1 of Prosper, 12 mg l−1 of Cuivox, 6 ml l−1 of Fungastop, 7.5 ml l−1of Nimbecidine, and 25 ml l−1 of Maneb. The analysis of the symbiotic properties and plant growth-promoting potential revealed two efficient strains significantly increased alfalfa dry weight through producing siderophores, phosphorus, and indole acetic acid (13.6 mg ml−1 and 19.9 mg ml−1 respectively). Hence, we identify two tolerant and efficient strains, Achromobacter spanium and Serratia plymuthica, isolated from Medicago sativa nodule with valuable potential able to phytostabilize pesticide-contaminated soils.