|ZHANG, TIEJUN - Chinese Academy Of Agricultural Sciences|
|KESOJU, SANDYA - Columbia Basin College|
|FRASEN, STEVEN - Washington State University|
Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2017
Publication Date: 7/26/2017
Citation: Zhang, T., Kesoju, S., Greene, S.L., Frasen, S., Hu, J., Yu, L. 2017. Genetic diversity and phenotypic variation for drought resistance in alfalfa (Medicago sativa L.) germplasm collected for drought tolerance. Genetic Resources and Crop Evolution. 65(2):471-484. https://doi.org/10.1007/s10722-017-0546-9.
Interpretive Summary: Drought resistance is an important breeding target for enhancing alfalfa productivity in arid and semi-arid regions. Identification of souces of resistance is the first step toward breeding for new varieties with drought resistance in alfalfa. Using greenhouse and field experiments, we screened 200 alfalfa accessions. We characterized 20 parameters related to drought tolerance. We identified 27 alfalfa accessions with drought resistance. They can be used as genetic resources for developing superior cultivars with drought resistance and water use efficiency.
Technical Abstract: Drought is a major environmental factor hampering alfalfa productivity worldwide. Gene banks provide an array of trait diversity, frequently consisting of specific seed collection projects that focused on acquiring germplasm adapted to specific traits such as drought tolerance. These subsets provide a logical starting point to identify useful breeding resources. In the present study, we investigated the genetic diversity and evaluated 18 agronomic, physiological and quality traits associated with drought tolerance in a subset of 198 alfalfa accessions collected for their potential drought resistance. Significant differences were found among accessions for most of the traits evaluated. Water deficit significantly decreased biomass dry yield (DY) by 61.9% compared with well-watered control. A positive correlation was found between relative water content (RWC) and drought susceptible index (DSI), while negative correlations were found between RWC and leaf senescence (LS), and between RWC and canopy temperature (CT). Alfalfa accessions with high RWC showed relative lower yield reduction, cooler CT and delayed LS. Genetic variation for forage quality was also investigated and the correlation between agronomic and quality traits was analyzed. Biomass yield under drought was negatively correlated with total protein (TP), relative feed value (RFV) and relative forage quality (RFQ), suggesting that the efforts to improve yield under drought tend to negatively affect forage quality. Therefore, maintaining forage quality should be considered for breeding alfalfa with drought resistance. Alfalfa accessions with high drought resistance scores and minimum loss of quality were identified in this study and can be used as genetic resources for developing alfalfa varieties with improved drought resistance and water use efficiency while maintaining forage quality.