Identification of Arbuscular Mycorrhizal Fungal Species That Help Soybeans Tolerate Water Stress.

Drought is a major cause of yield loss in soybean, because under drought conditions plants cannot compensate for water lost through transpiration. Several studies indicate that arbuscular mycorrhizal fungi (AMF) have potential to reduce the adverse effects of drought conditions on plant productivity. These microorganisms are thought to reduce drought stress by maintaining the hydration of plant tissues, facilitating more efficient absorption of water, and reducing mobilization of abscisic acid in the xylem. However, over 200 species of AMF have been identified to date, and the benefits they confer under drought stress could depend on AMF species present. Using extraction and morphological identified of spores, we previously determined that AMF communities were more diverse in soil managed using organic than conventional farming practices. Furthermore, only four species were present in both systems. When soybeans were grown in inoculum from these systems and subject to drought stress, plants grown in pots amended with organic system inoculum had greater stomatal conductance, total plant biomass, and dry weight of seed pods. Plants grown with inoculum from both organic and conventional systems had greater tolerance to drought stress than plants grown with a commercial AMF inoculum or control treatment with no AMF.  In this study, we used culture independent techniques to identify the AMF species colonizing plant roots from the previous study. Roots were ground in liquid nitrogen and DNA extracted using PowerPlant® Pro DNA Isolation Kit (MO BIO Laboratories). DNA was amplified using a nested PCR approach and PCR products were sequenced using Illumina MiSeq. Results of these studies indicate that management practices such as planting cover crops and amending soil with compost can increase AMF diversity and help plants withstand drought stress.