Effect of Rhizobium melilotti Tn5 mutant with changed lipopolysaccharides on manifestation of alfalfa mycoplasmosis

Aim. Improving of plant safety functions by strengthening their physiological state and assimilation of nutrients is of particular importance as environmentally sound way of reducing the harmfulness of plant mycoplasmosis. The aim was to establish the effect of rhizobia including of mutant with modified polysaccharide characteristics which enter into symbiosis with leguminous plants to the manifestation of experimental mycoplasmosis of plants in the laboratory conditions. Methods. Tn5-transposon mutagenesis, polyacrylamide gel electrophoresis, microbiological methods, microvegetation experiment, biometric measurements. Results. From typical highly effective strain Rhizobium meliloti 425a it was obtained mutant Tb29 which differed from the parent strain on the synthesis of lipopolysaccharide. Medicago sativa plants inoculated by mutant were green and did not differ from plants with the parent strain. Acholeplasma infection of alfalfa without rhizobia treatment led to a certain stimulation of plants, that was manifested in some increasing of plant mass and size, but simultaneously causing symptoms of yellowing and leaf shape change. Conclusions. Formation of symbiotic relationships between M. sativa and R. meliloti 425a and Tb29 led to improvement of plant state and reduces the negative effect of plant pathogenic mollicute Acholeplasma laidlawii var. granulum118. Keywords: mollicutes, plant pathogenic acholeplasma, rhizobia, mutant, lipopolysaccharides.