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Ce numéro comprend les articles correspondant aux présentations du Colloque Casdar 2018.; The shape is one of the essential components of the visual quality of ornamental plants. It is the resultof their architectural construction, depending on growth and branching processes under the effect of thegenetic and environmental determinism. The market currently demands compact and branched plants.To meet this demand, the plant shape can be controlled by the genetic way, with a better understandingof the heritability and the heredity of the architectural components, and by the environment (climatic andcultural). Within the framework of the project ARIAGE, in rose bush, the heritability of the mainarchitectural components was moderate, leaving open the possibility of controlling the architecture bythe environment. Two levers are thus available to control the plant shape, the variety brreding by thebreeder and the environmental monitoring of the plant by the horticulturist.; La forme est l’une des composantes essentielles de la qualité visuelle des plantes d’ornement. Ellerésulte de la construction architecturale de la plante, dépendant des processus de croissance et deramification sous l’effet des déterminismes génétiques et environnementaux. Le marché demandeactuellement des plantes compactes et ramifiées. Pour y répondre, la forme de la plante peut êtrecontrôlée par la voie génétique, avec une meilleure connaissance de l’héritabilité et de l’hérédité descomposantes architecturales, et par l’environnement (climatique et cultural). Dans le cadre du projetARIAGE, chez le rosier buisson, l’héritabilité des principales composantes architecturales étaitmodérée, laissant entrevoir la possibilité de contrôler l’architecture par l’environnement. Ainsi, deuxméthodes culturales ont montré un intérêt pour limiter la hauteur des plantes : la restriction hydrique etla stimulation mécanique. Cependant, cette réponse était dépendante du cultivar. Deux leviers sontdonc disponibles pour contrôler la forme de la plante : la création variétale par le sélectionneur et lecontrôle de l’environnement de la plante par l’horticulteur.

International audience; The shape of an ornamental plant and, therefore, its architecture are critical for its visual quality and are dependent on genetic and environmental factors, such as water supply. The aim of the study was to analyze genotypic responses at the architectural level, in eight rose cultivars ('Blush Noisette', 'Baipome' Pink Gnome (R), 'The Fairy', Hw336, 'Old Blush', Hw20, Hw154 and 'Perle d'Or'), to the alternation of water restriction (-20 kPa) and re-watering (-10 kPa) periods. Six architectural variables were measured at the plant and axis scales by 3D digitalization. Significant genotype effect was observed for all measured variables whereas significant environment effect was revealed only for the length and the insertion of long axes and the number of branching order. A strong genotype x environment interaction (GxE) was highlighted for most of the architectural measured variables. GxE interaction was mainly due to different response amplitudes between watering treatments according to genotype. Two groups of architectural responses of different intensities - weak and strong - were identified.

International audience; Floribundity defined as “the capacity of a plant to produce abundant flowers at high density on each of its branches”, is a key element of the aesthetic quality of the ornamental plants. In the case of many species, including the rosebush, this feature is strongly related to the plant architecture which is determined by the genotype, the environment and the crop management. To address these questions, the Architecture and Environment (ARCH-E) team of the Research Institute on Horticulture and Seeds (http://www6.angers-nantes.inra.fr/irhs) in collaboration with the Genetic determinism & Diversity of Ornamental plants (GDO) team of the same institute, is developing an integrative research program whereby environmental effects on the establishment of the plant architecture are examined from the molecular to the whole plant levels using plant sciences (physiology, genetics, molecular biology, biochemistry…), sensory analysis and modelling studies. The aim of the poster is to present a review of the studies (listed below) managed by the team, focusing on methods to assess and compare the floribundity of some rose cultivars, considered as example varieties by the International Union for the Protection of New Varieties of Plants (UPOV).

National audience; Plant architecture determines yield, vigour, pathogen resistance of a crop as well as shape and visual quality of plants. Controlling the establishment of plant architecture is therefore a key concern for plant breeders and horticultural growers of field and greenhouse crops. Environmental factors have a strong impact on plant architecture. Better understanding and controlling these factors should allow better mastering cultural practices and increase yield but also reduce the use of chemicals (pesticide and growth retardants). In the case of ornamental crops, this may contribute to better master plant shape and offer the way to create new products. However, the understanding of how the environment modulates plant architecture is still poor and further research is needed. To address this question, ARCH-E (Architecture and Environment) team of the Research Institute on Horticulture and Seeds (IRHS, Angers, France) is developing an integrative research program whereby environmental effects on the establishment of plant architecture are examined from the molecular to the all plant levels. Rosebush is the model plant studied in this program. Architectural analysis is used to describe and objectively discriminate plant shapes (Morel et al., 2009, Chéné et al; 2012) and the impact of environmental factors, such as quantity and quality of light, nitrogen or water restriction or mechanical stimulation on the architectural components is studied (Thélier et al., 2011, Abidi et al; 2012, Morel et al., 2012). Beside, tools to assess plant shape through sensory analysis are developed and used to train panels of assessors to characterize the rosebush visual quality (Boumaza et al; 2010). The more in-depth study of the effect of light on rose architecture is carried on and has revealed that light was essential to bud outgrowth in rose, and that blue or red lights could, each individually, trigger bud burst (Girault et al; 2008). Light was shown to be required to stimulate sugar transport (Henry et al; 2011), sugar metabolism (Girault et al, 2010) and sugar signaling (Rabot et al., 2012) as well as the synthesis of the plant hormone gibberellic acid (Choubane et al ; submitted). On the basis of these researches, functional and structural modeling is undergone to integrate these results and simulate branching in response to the light environment (Bertheloot et al., 2011)

Chapter 12; International audience; Presently, about 100–250 species are usually recognized in the genus Rosa. The low levels of DNA sequence divergence found across the genus suggest that it is a young genus with much speciation taking place after the last glaciation. Poor phylogenetic resolution and commonly occurring contradictions between chloroplast and nuclear gene phylogenies suggest that hybridization has been a strong driving force in the evolution of roses, often accompanied by polyploidization. In addition, extensive anthropogenic impact has led to the development of many new semi-wild and/or cultivated rose varieties. Some wild species have become invasive. This chapter describes the taxonomy of roses. It presents examples of interesting traits in wild species that may valuable to broaden the genetic base of cultivated roses, such as thornlessness, winter hardiness, drought resistance, and improved shelf-life. Also fragrance and compounds with possible health effects are discussed. The highest priority in rose breeding research is the development of disease resistant roses. Different resistance mechanisms have been found for black spot and powdery mildew in various wild rose species. We describe how resistance genes are being mapped using crosses between wild, diploid rose species, and how other genes for traits of interest are being identified. We proceed with a discussion of various ways to overcome the taxonomic and ploidy level barriers for introgression of traits into cultivated hybrid rose or garden rose germplasm, including dihaploidization, polyploidization, and transgenics. Even so, breeding programs with wild species are usually time-consuming. For garden roses, the genetic and morphological distance between modern cultivars and the wild species is smaller, which makes the use of wild species easier than in the case of cut roses.

The effect of cutting type (20 cm-long, three-to-four node cuttings, rooted at both ends and planted horizontally vs. vertical controls) on flowering was studied in the cut-rose cultivars 'Meidebenne', 'Meicofum' and 'Meitanet'. Rose plants were grown in rockwool cubes in a greenhouse for 9 months, with new shoots bent over to stimulate flowering. Application of indole-3-butyric acid (IBA) to cuttings significantly increased the rooting percentage. The best rooting response was obtained with distal and proximal application of IBA at 1.0 and 4.0 g l(-1). As a result of the greater number of axillary buds that sprouted, the average number of marketable flowers produced by plants propagated as horizontal cuttings was significantly higher than those from plants that originated from conventional cuttings. However, plants raised from vertical cuttings showed a better flower yield, except for 'Meitanet'.

Development of a genetic linkage map and study of candidate genes for flowering control in Rose. Plant and Animal Genome XII Confernce

International audience

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La forme est l’une des composantes essentielles de la qualité visuelle des plantes d’ornement. Elle résulte de la construction architecturale de la plante, dépendant des processus de croissance et de ramification sous l’effet des déterminismes génétiques et environnementaux. Le marché demande actuellement des plantes compactes et ramifiées. Pour y répondre, la forme de la plante peut être contrôlée par la voie génétique, avec une meilleure connaissance de l’héritabilité et de l’hérédité des composantes architecturales, et par l’environnement (climatique et cultural). Dans le cadre du projet ARIAGE, chez le rosier buisson, l’héritabilité des principales composantes architecturales était modérée, laissant entrevoir la possibilité de contrôler l’architecture par l’environnement. Ainsi, deux méthodes culturales ont montré un intérêt pour limiter la hauteur des plantes : la restriction hydrique et la stimulation mécanique. Cependant, cette réponse était dépendante du cultivar. Deux leviers sont donc disponibles pour contrôler la forme de la plante : la création variétale par le sélectionneur et le contrôle de l’environnement de la plante par l’horticulteur., The shape is one of the essential components of the visual quality of ornamental plants. It is the result of their architectural construction, depending on growth and branching processes under the effect of the genetic and environmental determinism. The market currently demands compact and branched plants. To meet this demand, the plant shape can be controlled by the genetic way, with a better understanding of the heritability and the heredity of the architectural components, and by the environment (climatic and cultural). Within the framework of the project ARIAGE, in rose bush, the heritability of the main architectural components was moderate, leaving open the possibility of controlling the architecture by the environment. Two levers are thus available to control the plant shape, the variety brreding by the breeder and the environmental monitoring of the plant by the horticulturist.