Genistein addition to the rooting medium of soybean at the onset of nitrogen fixation increases nodulation

Abstract

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 in the soybean [Glycine max (L.) Merr.] N₂‐fixing symbiosis. Its concentration in soybean root system increases with seedling development, and decreases immediately after the onset of N₂ fixation. This study was conducted to determine whether addition of genistein to the rooting medium at the onset of N₂ fixation would increase nodulation thereafter. The results indicated that watering soybean plants with a solution containing genistein beginning at the onset of N₂‐fixation increased nodule size, nodule number and nodule weight per plant. Shoot nitrogen (N) concentration was also increased. Soybean cultivar AC Bravor was more sensitive to genistein addition than Maple Glen.