Importance of Endophytic Strains Pantoea agglomerans in the Biological Control of Rhizoctonia solani

Antagonistic activity of microorganisms against phytopathogens is mainly the results of plants’ health improvement due to the inhibition of pathogens growth and the induction of plants resistance against diseases. The aim of the research was to determine antagonistic properties of Pantoea agglomerans against Rhizoctonia solani. The properties of two strains P. agglomerans BC17 and BC45 were assessed according to the following criteria: mycelial growth of R. solani in the presence of bacterial metabolites, an impact of P. agglomerans on the growth of sugar beet in the pots containing soil with and addition of R. solani and without it, the ability to produce indole-3-acetic acid (IAA). It has been recorded that antagonistic properties of tested strains are different. In the presence of metabolites of BC17 strains, the mycelial growth of R. solani was inhibited by 78 % and for the strain BC45 the value amounted 46 %. In the pot bioassay the number of infested plants growing in the soil inoculated with P. agglomerans and the pathogen was lower when compared with the pots containing R solani. A higher reduction of infested plants, amounting 23 %, was obtained for the strain BC17. Both strains had the ability to produce IAA - a plant hormone of the auxin class, in the presence of tryptophan and its absence in the medium. The highest concentration of IAA was recorded after 7 days of culturing in the supernatant obtained from the media containing 2000 μg/cm³ of tryptophan. For the strain BC17 the concentration of IAA marked in the post - culturing liquid amounted 71.57 μg/cm³, and for the BC45 strain it amounted over 80 μg/cm³. Obtained results prove that P. agglomerans may be used in the biological protection against phytopatogenic strains of R. solani.