engleski

Identification and characterization of an indigenous Bradyrhizobium japonicum field population

The 13 isolates of B. japonicum, obtained from different soil types in western Croatia, and two reference strains from commercial inoculant were analysed. Several methods for strain identification were used: biochemical tests, intrinsic antibiotic resistance, SDS-PAGE of total cell proteins and RAPD analysis. RAPD analysis was the most sensitive and the most reliable for B. japonicum strain identification. RAPD profiles revealed that all field isolates essentially differed from inoculant strains and so can be regarded as indigenous strains for that area. Among natural B. japonicum population two highly divergent groups were determined. Strains S4, S9 and S12 differed significantly from all other isolates and represent a very distinct and separate group of bradyrhizobia. A greenhouse pot experiment was designed to evaluate the symbiotic efficiency and the compatibility of B. japonicum strains with two soybean cultivars. All strains nodulated both soybean cultvars. Indigenous strains showed higher ineffectiveness in respect to inoculant strains. The results indicate that the inoculant strain possesing hydrogenase (S2) and indigenous strains S9, S12 and S4 can be characterized as the most efficient of all strains tested.

B. japonicum; field population; characterization; identification; RAPD analysis; symbiotic efectiveness

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