Microscopic studies of the phytoplasma infection effect on the symbiotic system Medicago sativa – Rhizobium meliloti in simulated conditions

Aim. Aim of the study was to microscopically investigate the interaction of Acholeplasma laidlawii var. granulum 118 with the target plant Medicago sativa, as well as to determine the role of Rhizobium meliloti strains with natural and defective polysaccharides in the plant’s resistance occurrence. Methods. Cultivation of plants and their inoculation with bacteria was performed under conditions of microvegetation experiment. The study of the ultrastructure of alfalfa roots and nodules was carried out with both light and electron microscopy. Results. The rhizobial mutant strain, defective in the synthesis of lipopolysaccharides, more often formed atypical nodules on M. sativa, which aged faster. In the variant with double inoculation of alfalfa with rhizobia together with acholeplasma changes in the morphology of the lateral roots of plants, as well as deformation of the nodules were observed. Conclusions. Results of this study indicate not only the ability of phytoplasmas to penetrate the root system and migrate to plant aboveground organs, but also demonstrate the possibility of their presence in the nodules formed by rhizobia. Keywords: Mollicutes, acholeplasma, rhizobia, mutant, lipopolysaccharides.