Clonal propagation is a valuable tool for plant breeders to maintain heterozygous genotypes in crop species that are not amenable to self-pollination or apomixis. An example is the drought-tolerant forage and N-fixing cover crop hairy vetch (Vicia villosa Roth), which primarily outcrosses and is developed into composite cultivars by plant breeders. The ability to obtain clones of desirable genotypes in breeding nurseries would enable the maintenance of heterozygous genotypes for genetic study or the ability to reconstitute a true synthetic cultivar. We developed an efficient method of clonal propagation from stem cuttings to maintain genotypes in a vegetative state for a minimum of 2 yr, even when obtained from flowering parental plants. The long-term viability of such clones is unknown, however. We determined that hairy vetch, which flowers under long days, exhibits a form of partial flowering where vegetative meristems are maintained during conditions that induce flowering. Clones obtained from flowering parents would resume reproductive growth and eventually senesce if kept in inductive conditions. However, if clones were grown under a continuous 6-h photoperiod, reproductive development would cease and vegetative growth would resume indefinitely.
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The authors wish to acknowledge Noble Research Institute researchers Maria Monteros and Tim Hernandez for sharing their observations of propagation efficiency, and University of Minnesota's Donn Vellekson for advice on stem cutting techniques.