[Effect of different methods of passage through a plant host on the effectiveness of clover nodule bacteria]

Four strains of clover nodule bacteria of different effectiveness and origin were studied. Each of the strains was passed through the host plant one, two, three and four times. The conventional laboratory technique was used as well as a new one developed by the author for field conditions. The effectiveness and virulence of the parent and passed strains were assayed in vegetation experiments, and were found to increase if the strains were passed through the host plant four times, particularly, in the field conditions (by 64%). However, one strain, which was passed 1-2 times under the laboratory conditions, lost its effectiveness.