A high-density genetic map with a number of anchor markers has been created to be used as a tool to dissect genetic variation in rose. Linkage maps for the diploid 94/1 population consisting of 88 individuals were constructed using a total of 520 molecular markers including AFLP, SSR, PK, RGA, RFLP, SCAR and morphological markers. Seven linkage groups, putatively corresponding to the seven haploid rose chromosomes, were identified for each parent, spanning 487 cM and 490 cM, respectively. The average length of 70 cM may cover more than 90% of the rose genome. An integrated map was constructed by incorporating the homologous parental linkage groups, resulting in seven linkage groups with a total length of 545 cM. The present linkage map is currently the most advanced map in rose with regard to marker density, genome coverage and with robust markers, giving good perspectives for QTL mapping and marker-assisted breeding in rose. The SSR markers, together with RFLP markers, provide good anchor points for future map alignment studies in rose and related species. Codominantly scored AFLP markers were helpful in the integration of the parental maps.

The ABC model for floral development was proposed more than 10 years ago and since then many studies have been performed on model species, such as Arabidopsis thaliana, Antirrhinum majus, and many other species in order to confirm this hypothesis. This led to additional information on flower development and to more complex molecular models. AGAMOUS (AG) is the only C type gene in Arabidopsis and it is responsible for stamen and carpel development as well as floral determinacy. LLAG1, an AG homologue from lily (Lilium longiflorum Thunb.) was isolated by screening a cDNA library derived from developing floral buds. The deduced amino acid sequence revealed the MIKC structure and a high homology in the MADS-box among AG and other orthologues. Phylogenetic analysis indicated a close relationship between LLAG1 and AG orthologues from monocot species. Spatial expression data showed LLAG1 transcripts exclusively in stamens and carpels, constituting the C domain of the ABC model. Functional analysis was carried out in Arabidopsis by overexpression of LLAG1 driven by the CaMV35S promoter. Transformed plants showed homeotic changes in the two outer floral whorls with some plants presenting the second whorl completely converted into stamens. Altogether, these data strongly indicated the functional homology between LLAG1 and AG.

Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days postinoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.