Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 16, 1997
Publication Date: N/A
Interpretive Summary: Persistence, nutrient uptake, and overall plant productivity are associated with root growth pattern in alfalfa. Seven root traits including taproot diameter, lateral root number and size, and fibrous root mass were evaluated in historical and contemporary cultivars and in alfalfa collections from different geographic regions. Root data from these evaluations were used to study associations among root traits and their relationships to geographic origin and fall dormancy response. Alfalfa collections from similar geographic regions were similar in root characteristics. Root traits differed for different dormancy response classes in the alfalfa collections and cultivars released before 1970. However, these relationships between root characteristics and dormancy diminished or disappeared in the contemporary cultivars. Greater differences for root traits were evident in the alfalfa collections compared to the contemporary cultivars. Wide differences in root traits exist across all alfalfa germplasm sources. Therefore, selection for unique combinations of root traits in alfalfa would be feasible to create new cultivars with unique root growth patterns which may increase alfalfa productivity and persistence.
Technical Abstract: Alfalfa (Medicago sativa L.) root morphology is important because it is associated with plant persistence and productivity traits. The objectives of this research were to evaluate root morphological traits for 1067 plant introductions (P.I.s) from diverse geographic origins and from 110 historical and contemporary U.S. cultivars. All entries were grown in 2 m rows at the University of Minnesota Agricultural Experiment Station at Rosemount, MN. Plants from both studies were evaluated during autumn of the establishment year for taproot diameter, lateral root number, lateral root diameter, lateral root position, fibrous root mass, percentage of determinate taproots, and determinate taproot position. Significant variability was observed among P.I.s for all seven root traits. Discriminate analysis of root traits effectively separated P.I.s from the most geographically diverse germplasm origins. Plant introductions from more closely related geographic origins were similar in root characteristics. Significant variability for root traits was observed among the cultivars. Correlations between the seven root traits and fall dormancy were significant for P.I.s and for cultivars released prior to 1970, but the relationships essentially disappeared in the more recently released cultivars. The cultivars tended to have a reduced range for the seven root traits compared to the P.I.s. Determinate taproot percentage and determinate taproot position were affected by the environment more than other root traits. Extensive variability in root morphology existing among alfalfa germplasm sources indicates that it should be possible to select for many combinations of root traits.