Comparison of seedlings and cuttings for evaluating winter hardiness in alfalfa

Studies of the genetic control of winter hardiness (WH) in alfalfa (Medicago sativa L.) require the replication of specific genotypes in the field. Clonal propagules would provide worthwhile information in replicated trials if seedlings and cuttings give similar genotype rankings. In this study, we compared seedlings with genetically identical cuttings for WH, fall dormancy (FD), and freezing tolerance (FT), and evaluated the relationships among these traits. Seventy-two plants each from 15 genotypes, covering a broad range of FD, were clonally propagated and transplanted to the field as seedlings and cuttings in a randomized complete block design. For all traits, genotype was a highly significant (P < 0.001) source of variation, but the genotype x establishment method (seedlings vs, cuttings) interaction was not significant (P > 0.05). Winter survival was significantly correlated with freezing sensitivity (r = -0.92, P < 0.01) and FD (r = -0.66). Our results suggest that alfalfa plants established from cuttings will faithfully represent seedling-established plants for the purpose of evaluating winter hardiness.