Safeguarding soybeans against climate change: Identifying the role of rhizobial diversity in moderating drought and herbivore stress
Funding: USDA/NIFA
People: Brendan Randall; John Parker and Kim Komatsu at the Smithsonian Environmental Research Center
Soybeans are a leading component of global sustainable agriculture and food security because of their high protein content and relatively low fertilizer demands, due to their nitrogen-fixing rhizobial mutualists.
Although soybeans can simultaneously associate with multiple rhizobial strains, and different strains are differentially tolerant of drought and other stressors, nearly all research and agricultural applications emphasize single-strain inoculations. Here, we borrow from Biodiversity-Ecosystem Function theory to predict that rhizobial strain diversity may buffer soybeans against crashes by providing complementary benefits during drought and herbivore stress, a phenomenon termed the “ecological insurance effect”.
Results of a pilot study demonstrated that percent foliar insect damage is reduced for soybean grown with a rhizobial community with greater strain richness. This pattern tended to be stronger for soybean grown at 3°C above ambient temperatures (panel b) than soybean grown at ambient temperatures (panel a). Read the full paper here!
We test this hypothesis with greenhouse experimental assays in combination with distributed surveys and experiments in the extensive Maryland Soybean Varietal Trial Farm Network. Specifically, by altering the structure of soybean microbial (rhizobia) communities, we posit improved crop performance and stability and lower costs for farmers through reduced reliance on pesticides, irrigation, and fertilizer.
During the summer of 2019, we collected data on leaf damage, physiological traits, and insect herbivore community (see photos below). Undergrad Zoe Read also conducted an REU project on a few target soy varieties. Work will continue this winter in the greenhouse to capture rhizobia for future field inoculations!
Field Sites
Map of University of Maryland Farm Network Field Stations. Within this network, several independent farms are growing soy within each site. We will utilize this unique network to examine the effects of rhizobial diversity on soy production and quality.
