Available online at www.inia.es/sjar ISSN: 1695-971-X Role of Bradyrhizobium japonicum induced by genistein on soybean stressed by water deficit

The soybean (Glycine max (L.) Merr.) is a crop mainly grown under rain fed conditions although irrigation is increas-ingly being used. Water deficiency is the main factor limiting seed production. The symbiosis process is also negatively affected by water stress. The isoflavone genistein have been recognized as a powerful inducer of Nod factors production by Bradyrhizobium and its addition to inocula has been shown to increase nodule number and promote soybean nitrogen (N) fixation at low temperatures. This study looks for answers about the possible role of genistein in countering the stress on nodulation produced by water deficit in soybeans. Bradyrhizobium japonicum SEMIA 5079 was grown in culture media induced or not induced with genistein. Inocula were applied to plants growing at different moisture levels. The effect of the treatments on nodulation and N content was evaluated. An improved response to drought stress was observed when the bac-teria were grown in presence of genistein as a Nod factors inducer. Nodulation values under moisture stress differed from 8.9 nodules plant-1 with genistein at 10 µM to 1.8 nodules plant-1 when no inducer was used. Genistein reduced the nega-tive effect on nodulation caused by water deficiency. Additional key words: humidity, inoculants, nitrogen fixation, nodulation, soil. Resumen Papel de Bradyrhizobium japonicum inducido por genisteína en soja estresada por déficit hídric