Evaluation of screening procedures for breeding creeping-rooted alfalfa

Introduction of the creeping-rooted (CR) trait into nondormant alfalfa (Medicago sativa L.) populations is complicated by the time required to identify CR expression and the complex inheritance of the trait. Various procedures might be used to improve the efficiency of this breeding process. This study was conducted to examine the effects of four screening procedures on the expression of CR in transplanted and direct-seeded plants. Comparisons were made between two methods of CR parent selection (random vs. based on field CR expression), and two harvest frequencies (nine vs. five harvests in a 44-week period). Root morphology and CR expression were evaluated in 3508 F, plants grown in the field at Tucson, AZ (Aqua sandy loam; coarse, mixed, thermic Typic Torriflurent). Half of the F, population was transplanted as seedlings, the other half direct-seeded. A higher proportion of CR plants was observed among the transplanted progenies when confirmed CR parents were used in crosses than when parents were randomly selected from CR populations. If the time required to identify CR parents is considered, then use of uncharacterized parents from CR populations appears equally as efficient. No differences were observed in CR expression between F, progenies exposed to five or nine harvests. Use of uncharacterized CR parents, transplanting seedling progenies, and normal harvest management is an efficient strategy when breeding nondormant, CR alfalfa germplasm.