Alfalfa is the main forage legume in crop livestock systems worldwide. It does not only provide forage for animals, but also improves soil nitrogen, provides sources for pollinator and potential for biofuel. Alfalfa has been introduced to the semiarid Northern Great Plains region; however, its stand establishment and persistence are negatively influenced by drought condition in this region. Therefore, the development of drought-tolerant alfalfa cultivars is of great need. Seedling root development plays a critical role in seedling survival and stand establishment, particular its morphological and physiological traits associated with drought tolerance. Yellow-flowered alfalfa (Medicago sativa subspp. falcata) is characterized by fibrous root with abundant branches compared to conventional alfalfa (M. sativa) taproots. Information on the variations of root morphological traits would be useful for identifying potential alfalfa for breeding drought tolerance, persistence and productivity cultivars for the northern Great Plains. The objective of this study was to evaluate the variability of root morphological and physiological traits of eleven alfalfa populations under different drought stress treatments. Eleven entries were evaluated: one M. sativa population as control, seven M. sativa subspp. falcata populations, and three naturalized variegated populations. Fourteen uniform growth stage seedlings from each population were selected and transplanted into individual cone-container filled with potting soil in a greenhouse. The study was consisted of three drought treatment regime (100, 50 and 25% field capacity) combined with two drought durations (15 d vs. 30 d). At each drought duration sampling date, root total length, surface area, average diameter, and volume were measured using WinRhzio; stomata conductance was measured by a porometer. Meanwhile, root and shoot biomass were harvested at each sampling date. Variations of these measured parameters among eleven populations under different drought stress treatment are being analyzed and to be presented at the SRM meeting.
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