Xu, LanALOMAIR, ABDULALLAH MOHAMMED2025-12-24202532402336https://hdl.handle.net/20.500.14154/77667Rangelands cover nearly half of the Earth’s surface, representing about 54% (79 million km2), and occur in different types and climates worldwide. Alfalfa (Medicago sativa L.) is a major component in rangelands and covers about (320 thousand km2), representing about 0.4% of total global rangeland area. As a critical perennial legume crop, alfalfa can improve soil health by fixing approximately 336 kg/ha/year of nitrogen and sequestering up to 614 kg/ha/year of carbon, while enhancing livestock production due to its high content level of vitamins, magnesium, minerals, fiber, and protein. However, environmental stresses such as drought, freezing, and grazing limit alfalfa stand establishment and persistence in arid and semiarid rangelands. Therefore, the development of new alfalfa cultivars to enhance stand persistence is greatly needed. The overall objective of this study was to determine how to enhance alfalfa stand persistence in the arid and semiarid rangelands. More particularly, we aimed to determine how above and below ground morphological traits of thirteen yellow-flowered alfalfa (Medicago falcata) populations and one commercial cultivar (Final Answer, Medicago sativa) served as a control contribute to improving alfalfa persistence in arid and semiarid rangelands. The study focused on: 1) the ability of root segments to regenerate adventitious shoots in a greenhouse, 2) crown morphological traits associated with vegetative reproduction, and 3) the survival, growth and biomass production of plants derived from root segments under field conditions. In addition, the study measured and evaluated stem morphological traits of root-derived plants to understand how aboveground structure related to forage production and long-term stand persistence. This study was conducted in two phases: the first phase was conducted twice in the greenhouse at South Dakota State University, Brookings, SD, in 2021 and repeated in 2022, followed by a field study conducted at the South Dakota State Field Station in Aurora in 2024 and repeated in 2025. We found that Final Answer, PI 452460, and PI 634106 did not have the capacity to resprout from root segments, unlike other populations that were able to do so. PI 634133, PI 538984, PI 631704, and PI 634114 demonstrated outstanding performance for enhancing alfalfa persistence, exhibiting high average percentage root segments sprouting (53%, 27%, 28%, and 37%, respectively) and along with biomass production (2.66, 2.84, 2.75, and 2.35 tons/ha) under field conditions. We also found an exponential increase in alfalfa biomass, accompanied by prostrate-to-bowl-shaped plants that were slightly shorter, as indicated by a positive linear regression with canopy cover. These PIs also exhibited high crown bud and stem densities, which are desirable for vegetative reproduction potential and persistence. This study contributes to developing a novel trait that can enhance alfalfa persistence. Furthermore, the study underscores the importance of field testing to identify additional populations within the NPGCC that exhibit the valuable trait of contributing to persistent forage in the working landscape by maintaining and regenerating stands with strong root sprouting capacity. This information can be valuable for ensuring benefits to farmers, ranchers, and land managers.182en-USMedicago sativaMedicago sativa subsp. falcataalfalfaadventitious shootroot sproutingpersistence alfalfacrown morphological traitsThesis