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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[R]). In Black Baccara[R], 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. Key words: EST, floral initiation, rose, recurrent blooming. La connaissance de la floraison, un caractere important chez les plantes ornementales comme le rosier, est necessaire pour un controle efficace de ce processus. L'objectif de cette etude etait de developper et caracteriser de nouvelles ressources pour mieux comprendre la floraison chez le rosier. Nous avons etudie 'initiation florale chez un rosier non remontant (hybride de Rosa wichurana) et remontant (Rosa hybrida Black Baccara[R]). Chez Black Baccara[R], 'initiation florale a lieu rapidement apres le debourrement du bourgeon alors qu'en serre R. wichurana demeure vegetatif. Lors de 'initiation florale, 'apex s'elargit et emerge rapidement et simultanement. Il s'agit de la premiere description des evenements precoces de la transition florale chez le rosier. A partir de ces tissus vegetatifs et pre-floraux, 2 banques d'ADNc ont ete construites et 5000 ESTs sequencees. En regroupant nos ESTs et les ESTs deja disponibles dans les bases de donnees publiques, nous avons developpe une base de donnees complete, qui apres regroupement comporte environ 5000 sequences uniques. En criblant cette base de donnees pour des genes candidats impliques dans le controle de la floraison, 13 genes ont ete caracterises et sont potentiellement impliques dans la signalisation des acides gibberelliques, la voie photoperiodique et le developpement floral. A partir de donnees d'expression, differentes hypotheses sur le controle de la floraison chez le rosier (controle par la photoperiode et implication des gibberellines) ont ete proposees a partir de ce qui etait connu chez Arabidopsis. Mots-cles : EST, initiation florale, rose, floraison remontante., Introduction Flowering is a complex plant development process that is especially important with ornamental plants because of the high market value of flowers. Flowering has been extensively studied in monocarpic [...]

The genus Rosa has a complex evolutionary history caused by several factors, often in conjunction: extensive hybridization, recent radiation, incomplete lineage sorting, and multiple events of polyploidy. We examined the applicability of AFLP markers for reconstructing (species) relationships in Rosa, using UPGMA clustering, Wagner parsimony, and Bayesian inference. All trees were well resolved, but many of the deeper branches were weakly supported. The cluster analysis showed that the rose cultivars can be separated into a European and an Oriental cluster, each being related to different wild species. The phylogenetic analyses showed that (1) two of the four subgenera (Hulthemia and Platyrhodon) do not deserve subgeneric status; (2) section Carolinae should be merged with sect. Cinnamomeae; (3) subsection Rubigineae is a monophyletic group within sect. Caninae, making sect. Caninae paraphyletic; and (4) there is little support for the distinction of the five other subsections within sect. Caninae. Comparison of the trees with morphological classifications and with previous molecular studies showed that all methods yielded reliable trees. Bayesian inference proved to be a useful alternative to parsimony analysis of AFLP data. Because of their genome-wide sampling, AFLPs are the markers of choice to reconstruct (species) relationships in evolutionary complex groups. Key words: amplified fragment length polymorphism (AFLP); Bayesian inference; parsimony; phylogeny; Rosa; Rosaceae; roses; UPGMA.

This study investigates the impact of hybridization and polyploidy in the evolution of eastern North American roses. We explore these processes in the Rosa carolina complex (section Cinnamomeae), which consists of five diploid and three tetraploid species. To clarify the status and origins of polyploids, a haplotype network (statistical parsimony) of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) nuclear gene was estimated for polyploids of the complex and for diploids of section Cinnamomeae in North America. A genealogical approach helped to decipher the evolutionary history of polyploids from noise created by hybridization, incomplete lineage sorting, and allelic segregation. At the diploid level, species west of the Rocky Mountains are distinct from eastern species. In the east, two groups of diploids were found: one consists of R. blanda and R. woodsii and the other of R. foliolosa, R. nitida, and R. palustris. Only eastern diploids are involved in the origins of the polyploids. Rosa arkansana is derived from the blanda--woodsii group, R. virginiana originated from the foliolosa--nitida--palustris group, and R. carolina is derived from a hybrid between the two diploid groups. The distinct odgins of these polyploid taxa support the hypothesis that the three polyploids are separate species. Key words: haplotype network; incomplete lineage sorting; multiple origins; polyploidy; reticulate evolution; Rosa carolina complex; statistical parsimony.

Molecular evidence through analysis of nuclear ribosomal DNA data that dogroses are complex allopolyploids resulting from multiple hybridization events is reported. Findings reveal that the origin of pentaploid Caninae genome was originated from different members of nondogroses and the now extinct Protocaninae.

Genomic in situ hybridization was performed to localize nucleolar organizer regions (NORs) bearing the 18S-26S ribosomal DNA repeat in a set of samples composed of five rose species and one tetraploid cultivar. Among the diploid species, one NOR per genome seen as a pair of strong subterminal signal was detected. The tetraploid rose cultivar, on the other hand, was shown to have four strong subterminal signals, thus, also representing one NOR per genome.