Twenty nine strains of Mesorhizobium ciceri were screened for indigenous plasmids and cured derivatives were obtained in fourteen parent strains. Based on plasmid profile, 1 to 3 plasmids were observed in all the M. ciceri strains and these were clubbed into 3 groups (Group 1-3). The molecular size of plasmids in all the strains ranged from 228-259 kbp. Curing of plasmid (s) was achieved with triple treatment of ethidium bromide (2 µg/ml), acridine orange (1 µg/ml) and high temperature (38 °C). Antibiotic resistance pattern of the parent strains and their cured derivatives was similar, indicating that these were true derivatives. The production of exopolysaccharide (EPS) in cured strains was less than fifty per cent of parent strains. The symbiotic effectivity of all the parent strains was higher than that of their cured derivatives.
Plasmids, Mesorhizobium ciceri, curing, exopolysaccharide, symbiotic effectivity, acridine orange, ethidium bromide, acetylene reducing activity
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