Béatrice Denoyes-Rothan

The genome of woodland strawberry ( Fragaria vesca )

The woodland strawberry, Fragaria vesca (2n = 2x = 14), is a versatile experimental plant system. This diminutive herbaceous perennial has a small genome (240 Mb), is amenable to genetic transformation and shares substantial sequence identity with the cultivated strawberry (Fragaria × ananassa) and other economically important rosaceous plants. Here we report the draft F. vesca genome, which was sequenced to ×39 coverage using second-generation technology, assembled de novo and then anchored to the genetic linkage map into seven pseudochromosomes. This diploid strawberry sequence lacks the large genome duplications seen in other rosids. Gene prediction modeling identified 34,809 genes, with most being supported by transcriptome mapping. Genes critical to valuable horticultural traits including flavor, nutritional value and flowering time were identified. Macrosyntenic relationships between Fragaria and Prunus predict a hypothetical ancestral Rosaceae genome that had nine chromosomes. New phylogenetic analysis of 154 protein-coding genes suggests that assignment of Populus to Malvidae, rather than Fabidae, is warranted.

Bioactive compounds in berries relevant to human health

Berries contain powerful antioxidants, potential allergens, and other bioactive compounds. Genetic and environmental factors affect production and storage of such compounds. For this reason breeding and biotechnological approaches are currently used to control or to increase the content of specific health-related compounds in fruits. This work reviews the main bioactive compounds determining the nutritional quality of berries, the major factors affecting their content and activity, and the genetic options currently available to achieve new genotypes able to provide, under controlled cultivation conditions, berries with the proper balance of bioactive compounds for improving consumer health.

Comparative Genetic Mapping Between Octoploid and Diploid Fragaria Species Reveals a High Level of Colinearity Between Their Genomes and the Essentially Disomic Behavior of the Cultivated Octoploid Strawberry

Macrosynteny and colinearity between Fragaria (strawberry) species showing extreme levels of ploidy have been studied through comparative genetic mapping between the octoploid cultivated strawberry (F. ×ananassa) and its diploid relatives. A comprehensive map of the octoploid strawberry, in which almost all linkage groups are ranged into the seven expected homoeologous groups was obtained, thus providing the first reference map for the octoploid Fragaria. High levels of conserved macrosynteny and colinearity were observed between homo(eo)logous linkage groups and between the octoploid homoeologous groups and their corresponding diploid linkage groups. These results reveal that the polyploidization events that took place along the evolution of the Fragaria genus and the more recent juxtaposition of two octoploid strawberry genomes in the cultivated strawberry did not trigger any major chromosomal rearrangements in genomes involved in F. ×ananassa. They further suggest the existence of a close relationship between the diploid Fragaria genomes. In addition, despite the possible existence of residual levels of polysomic segregation suggested by the observation of large linkage groups in coupling phase only, the prevalence of linkage groups in coupling/repulsion phase clearly demonstrates that the meiotic behavior is mainly disomic in the cultivated strawberry.

Genetic diversity and pathogenic variability among isolates of colletotrichum species from strawberry.

ABSTRACT Ninety-five isolates of Colletotrichum including 81 isolates of C. acutatum (62 from strawberry) and 14 isolates of C. gloeosporioides (13 from strawberry) were characterized by various molecular methods and pathogenicity tests. Results based on random amplified polymorphic DNA (RAPD) polymorphism and internal transcribed spacer (ITS) 2 sequence data provided clear genetic evidence of two subgroups in C. acutatum. The first subgroup, characterized as CA-clonal, included only isolates from strawberry and exhibited identical RAPD patterns and nearly identical ITS2 sequence analysis. A larger genetic group, CA-variable, included isolates from various hosts and exhibited variable RAPD patterns and divergent ITS2 sequence analysis. Within the C. acutatum population isolated from strawberry, the CA-clonal group is prevalent in Europe (54 isolates of 62). A subset of European C. acutatum isolates isolated from strawberry and representing the CA-clonal and CA-variable groups was assigned to two pathogenicity groups. No correlation could be drawn between genetic and pathogenicity groups. On the basis of molecular data, it is proposed that the CA-clonal subgroup contains closely related, highly virulent C. acutatum isolates that may have developed host specialization to strawberry. C. gloeosporioides isolates from Europe, which were rarely observed were either slightly or nonpathogenic on strawberry. The absence of correlation between genetic polymorphism and geographical origin in Colletotrichum spp. suggests a worldwide dissemination of isolates, probably through international plant exchanges.

Inheritance of Resistance to Colletotrichum acutatum in Fragaria x ananassa.

ABSTRACT Anthracnose, caused by Colletotrichum acutatum, is a major disease of the octoploid cultivated strawberry, Fragaria x ananassa The inheritance of high and intermediate level plant resistances to C. acutatum, pathogenicity group 2, was investigated in an 8 x 8 factorial design. A single dominant gene (Rca2) controlled the high-level resistance, although minor genes may also contribute to resistance in cultivars such as Belrubi. The intermediate level of resistance was quantitative and controlled by minor genes. Analysis of 26 genotypes and cultivars from Fragaria spp. showed that the dominant gene was not rare in the germ plasm of F. x ananassa and that anthracnose resistance was also present in other species of Fragaria. These findings have important implications for anthracnose resistance breeding.

Inheritance of Resistance to Colletotrichum acutatum in Fragaria × ananassa

ABSTRACT Anthracnose, caused by Colletotrichum acutatum, is a major disease of the octoploid cultivated strawberry, Fragaria x ananassa The inheritance of high and intermediate level plant resistances to C. acutatum, pathogenicity group 2, was investigated in an 8 x 8 factorial design. A single dominant gene (Rca2) controlled the high-level resistance, although minor genes may also contribute to resistance in cultivars such as Belrubi. The intermediate level of resistance was quantitative and controlled by minor genes. Analysis of 26 genotypes and cultivars from Fragaria spp. showed that the dominant gene was not rare in the germ plasm of F. x ananassa and that anthracnose resistance was also present in other species of Fragaria. These findings have important implications for anthracnose resistance breeding.

Comparison of six inoculation techniques withColletotrichum acutatum on cold stored strawberry plants and screening for resistance to this fungus in French strawberry collections

Six inoculation techniques were compared for their ability to evaluate resistance toColletotrichum acutatum of five strawberry cultivars. Inoculation by dipping the whole cold stored plants in a suspension of conidia adjusted to 2.106 conidia ml−1 made it possible to screen cultivars resistant to crown rot at 28 days after inoculation. Using the dipping technique, 44 strawberry cultivars were evaluated for their resistance to one strain ofC. acutatum, 1267b. Twelve of them did not show wilt symptoms and could be classified as resistant. When another strain ofC. acutatum, 494a, was inoculated to seven cultivars, all of them including Dover, resistant to 1267b, showed wilt symptoms. This result showed the importance of investigations on genotype × isolate interactions to conduct an efficient breeding programme for screening resistance toC. acutatum.