The aim of the performed experiments was to analyse relationships occurring between endophytic
bacteria from the Herbaspirillum genus and Sinorhizobium meliloti Bp nodule bacteria and to examine the
condition of plants subjected to coinoculation with the above-mentioned strains in in vitro conditions. In experiments examining the impact of Herbaspirillum frisingense on Sinorhizobium meliloti BP, the stimulation of
growth of inoculated bacteria from the Sinorhizobium genus was recorded in all three combinations (48-hour
culturing, sediment and supernatant). On the other hand, the examination of interactions between the Sinorhizobium meliloti strain and Herbaspirillum frisingense strain revealed that in the case of culture and supernatant, an
antagonistic action was recorded. Besides, it was found that such coinoculation exerted a beneficial influence on
the process of seed lucerne symbiosis and yielding as confirmed by increased numbers of root nodules, higher
nitrogenase activity and greater plant mass.