Using signal molecule genistein to alleviate the stress of suboptimal root zone temperature on soybean-Bradyrhizobium symbiosis under different soil textures

Suboptimal root zone temperatures (RZTs) (below 25 degrees C) in Canada until July may adversely affect the secretion of interorganismal signal molecules such as genistein by soybean and hence, the soybean-Bradyrhizobium symbiosis. We also proposed for the first time that soil texture might play a role in these biochemical communications. Soybean plants, planted in undisturbed soil samples (with sandy, loamy and clay textures), collected from the field, were subjected to three different soil temperatures (14, 19 and 24 degrees C). Bradyrhizobium japonicum (strain 532C) inocula, preincubated with four levels of genistein (0, 5, 10 and 20 mu M), were used to inoculate the plants. The experiment was conducted at the research greenhouse of Macdonald Campus, McGill University, Canada. The effects of genistein 5 and 20 mM on soybean nodulation and growth were significant at 14 degrees C. As genistein was more effective in loamy and clay soils, soil texture may also be a determining factor in the biochemical communications between B. japonicum and soybean.