Selection of blooming seasonality in rose

Rose is one of the most successful plants in the ornamental sector for gardens, cutting flowers and flowerpots. This tremendous success can be partially explained by selection of roses that can flower continuously. Rose, genus Rosa, is a good model to study seasonality of blooming, a developmental process which is poorly understood. We have previously demonstrated that continuous flowering in rose was due to a mutation of a gene encoding a floral repressor, RoKSN, a TFL1 (TERMINAL FLOWER 1) homologue. In continuous-flowering roses, the insertion of copia retrotransposon in RoKSN gene completely blocked the transcript accumulation. Our objective was to understand the selection of the floral repressor during the process of breeding. In collaboration with historians, we studied the process of rose breeding during the 18^th and 19^th centuries, an important period for rose breeding in France. During this period, more and more recurrent roses were selected. By genotyping and sequencing RoKSN gene on a large collection of roses from this period, we showed a progressive selection of the copia allele (responsible for continuous flowering). Furthermore, we detected a new allele that can be responsible for intermediate phenotype (occasionally-reblooming). This new allele at the RoKSN locus encodes a functional RoKSN but the transcript accumulation is weaker. These results open a new way to finely control blooming in rose and more generally in perennial plants.