With production on almost every continent, soybean is one of the most widely cultivated crops. As the demand for this crop continues to increase, sustainable intensification of soybean systems will be of high importance. This can be achieved by breeding new soybean cultivars with desirable traits that will lead to improved growth and yield. Little work, however, has been done to examine the potential of different root and rhizosphere traits in soybean to aid in the sustainable intensification of soybean cropping systems. In the present study, we sought to determine potential benefits of having increased total root length, total root surface area, total root dry mass and total nodulation by rhizobia in soybean using Pseudomonas sp ATCC PTA-122608, a newly discovered Antarctic rhizobacterium that has been shown to alter root architecture in tomato plants, to alter soybean root and rhizosphere traits. We hypothesized Pseudomonas sp ATCC PTA-122608 would increase total root surface area, total root length length and total root dry mass accumulation in soybean and promote nodulation by rhizobia, which would all contribute to improved growth. To test this hypothesis, soybean plants were grown to maturity in the greenhouse under one of three different bacterial treatments (inoculated, non-inoculated, substrate control). Plants were harvested at maturity and root architecture, nodulation, biomass accumulation and total plant carbon/nitrogen content were quantified.
While Pseudomonas sp ATCC PTA-122608 did not increase total root surface area and total root length in soybean plants as hypothesized, it did promote root dry mass accumulation in inoculated plants. Along with these increases in root dry mass, we found significant increases in total nodulation in inoculated plants and also increases in total biomass accumulation and total carbon/nitrogen content upon inoculation. These results suggests increases in root dry mass and increased nodulation can subsequently increase biomass and nutrient acquisition in soybeans. Broadly, this work demonstrates the potential of different root and rhizosphere traits to improve soybean growth and achieve sustainable intensification of this important crop.