Diversity and selection of the continuous-flowering gene, RoKSN, in rose.

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Blooming seasonality is an important trait in ornamental plants and was selected by humans. Wild roses flower only in spring whereas most cultivated modern roses can flower continuously. This trait is explained by a mutation of a floral repressor gene, RoKSN, a TFL1 homologue. In this work, we studied the origin, the diversity and the selection of the RoKSN gene. We analyzed 270 accessions, including wild and old cultivated Asian and European roses as well as modern roses. By sequencing the RoKSN gene, we proposed that the allele responsible for continuous-flowering, RoKSNcopia, originated from Chinese wild roses (Indicae section), with a recent insertion of the copia element. Old cultivated Asian roses with the RoKSNcopia allele were introduced in Europe, and the RoKSNcopia allele was progressively selected during the 19th and 20th centuries, leading to continuous-flowering modern roses. Furthermore, we detected a new allele, RoKSNA181, leading to a weak reblooming. This allele encodes a functional floral repressor and is responsible for a moderate accumulation of RoKSN transcripts. A transient selection of this RoKSNA181 allele was observed during the 19th century. Our work highlights the selection of different alleles at the RoKSN locus for recurrent blooming in rose.