Comparative Analysis of Adaptive Responses in Alfalfa (Medicago sativa L.) to Abiotic Stresses: Drought Stress and Phosphorus Deficiency.

Alfalfa (Medicago sativa L.), is a perennial legume species with significant agricultural value due to its relatively high biomass production and forage quality. As a legume, alfalfa is capable of symbiotic nitrogen fixation thus reducing the need for N fertilizers and increasing the soil N available for successive crops in a crop-rotation system. Existing challenges for alfalfa production include abiotic stresses such as drought conditions and nutrient deficiency in phosphorus-limited soils. Our strategy aims to develop new cultivars that are better able to maximize water and phosphorus acquisition and use efficiency under drought and low phosphorus conditions and can be utilized as a component of year round grazing systems. The objectives of this study are to identify natural genetic diversity for water use efficiency (WUE), phosphorus acquisition efficiency (PAE) and phosphorus use efficiency (PUE) in alfalfa accessions and breeding lines using phenotyping assays in greenhouses and field experiments under varying water and phosphorus levels. Simultaneously, transcriptome sequencing and translational approaches can increase our understanding of the genetic mechanisms and key genes in alfalfa to enhance drought tolerance and phosphorus utilization. The knowledge obtained will be used to develop and validate molecular markers associated with increased alfalfa productivity under abiotic stress conditions that can be used for marker-assisted breeding approaches. The enhanced alfalfa cultivars generated as a result of reliable phenotypic screening and genomics approaches can be used to address a practical limitation to year-round forage production systems and reduce the need for expensive on-farm inputs that directly impact biomass yield.