New resources for studying the rose flowering process

Knowledge of the flowering process — an important trait in ornamental plants such as roses — is necessary for efficient control of flowering. This study was carried out to develop and characterize new resources to gain further insight into floral control in rose. We studied floral initiation in a nonrecurrent blooming rose (hybrid of Rosa wichurana ) and a recurrent blooming rose ( Rosa hybrida Black Baccara®). In Black Baccara®, floral initiation took place rapidly after bud burst, whereas in the greenhouse R. wichurana remained vegetative. During floral initiation, the apex enlarged and domed quickly and concomitantly. This is the first description of this transition between the vegetative and floral bud stages in rose. From these vegetative and pre-floral tissues, two cDNA libraries were constructed and 5000 ESTs sequenced. By collecting our ESTs and those available in public databases, we developed a comprehensive database representing ~5000 unique sequences after clustering. By screening this database for candidate genes involved in the flowering process, we identified 13 genes potentially involved in gibberellic acid signalling, photoperiod pathways, and floral development. Based on expression data, we put forward different hypotheses on the control of flowering in rose (photoperiod control and involvement of gibberellins) relative to what is already known in Arabidopsis .