GENISTEIN ADDITION TO THE ROOTING MEDIUM OF SOYBEAN AT THE ONSET OF NITROGEN-FIXATION INCREASES NODULATION

In the legume-(Brady)Rhizobium symbiosis, signal exchange between the host-plant and the symbiotic bacterium is an essential step in nodule formation. Genistein is the most effective plant-to-bacterium signal i n the soybean [Glycine max (L.) Merr.] N-2-fixing symbiosis. Its conce ntration in soybean root system increases with seedling development, a nd decreases immediately after the onset of N-2 fixation. This study w as conducted to determine whether addition of genistein to the rooting medium at the onset of N-2 fixation would increase nodulation thereaf ter. The results indicated that watering soybean plants with a solutio n containing genistein beginning at the onset of N-2-fixation increase d nodule size, nodule number and nodule weight per plant. Shoot nitrog en (N) concentration was also increased. Soybean cultivar AC Braver wa s more sensitive to genistein addition than Maple Glen.