Le compartiment sauvage de la carotte en France : des ressources génétiques importantes et pourtant méconnues

La France est considérée comme centre secondaire de diversification de la carotte, du fait de l’activité importante de sélection (par des maraîchers ou semenciers), ce qui justifie les actions de conservation et connaissance des variétés anciennes menées par le réseau de ressources génétiques « Carotte et autres Daucus ». Par contre, le compartiment sauvage est méconnu et sous-exploité, alors qu’il s’agit d’une espèce pour laquelle de nombreuses populations existent sur le territoire français, avec une situation très contrastée. Si la carotte sauvage D. carota spp carota n’est pas en danger, d’autres sous espèces sont protégées (ssp gadecaei) ou menacées du fait de la dégradation de leur milieux naturels notamment en zone littorale ou de possibles introgressions avec la sous-espèce carota. Le travail présenté porte donc sur : i/ la sauvegarde et la mise à disposition des ressources génétiques sauvages, à travers l’inventaire de populations in situ et la constitution de collections ex-situ ; ii/ l’approfondissement de la connaissance et de l’identification taxonomique des sous-espèces sauvages ; iii/ la connaissance de la diversité au sein du compartiment sauvage (marqueurs SSR et données écologiques) ; et iv/ l’évaluation des ressources génétiques sauvages de carotte pour permettre leur exploitation (fertilité, croisements avec le compartiment cultivé, tolérance à différents bioagresseurs). Ce programme fait l’objet du soutien d’un contrat de branche du ministère de l’agriculture et implique les membres du réseau « Carotte et autres Daucus ».

QTL mapping for brown rot (Monilinia fructigena) resistance in an intraspecific peach (Prunus persica L. Batsch) F1 progeny

Brown rot (BR) caused by Monilinia spp. leads to significant post-harvest losses in stone fruit production, especially peach. Previous genetic analyses in peach progenies suggested that BR resistance segregates as a quantitative trait. In order to uncover genomic regions associated with this trait and identify molecular markers for assisted selection (MAS) in peach, an F1 progeny from the cross "Contender" (C, resistant) 7 "Elegant Lady" (EL, susceptible) was chosen for quantitative trait loci (QTL) analysis. Over two phenotyping seasons, skin (SK) and flesh (FL) artificial infections were performed on fruits using a Monilinia fructigena isolate. For each treatment, infection frequency (if) and average rot diameter (rd) were scored. Significant seasonal and intertrait correlations were found. Maturity date (MD) was significantly correlated with disease impact. Sixty-three simple sequence repeats (SSRs) plus 26 single-nucleotide polymorphism (SNP) markers were used to genotype the C 7 EL population and to construct a linkage map. C 7 EL map included the eight Prunus linkage groups (LG), spanning 572.92 cM, with an average interval distance of 6.9 cM, covering 78.73 % of the peach genome (V1.0). Multiple QTL mapping analysis including MD trait as covariate uncovered three genomic regions associated with BR resistance in the two phenotyping seasons: one containing QTLs for SK resistance traits near M1a (LG C 7 EL-2, R2 = 13.1-31.5 %) and EPPISF032 (LG C 7 EL-4, R2 = 11-14 %) and the others containing QTLs for FL resistance, near markers SNP_IGA_320761 and SNP_IGA_321601 (LG3, R2 = 3.0-11.0 %). These results suggest that in the C 7 EL F1 progeny, skin resistance to fungal penetration and flesh resistance to rot spread are distinguishable mechanisms constituting BR resistance trait, associated with different genomic regions. Discovered QTLs and their associated markers could assist selection of new cultivars with enhanced resistance to Monilinia spp. in fruit

Quantitative trait analysis of resistance to plum pox virus in the apricot F1 progeny "Harlayne" x "Vestar"

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audiencePlum pox virus (PPV) is a devastating stone fruit disease of major importance, and better understanding of the genetic control of resistance to this trait would be useful for more efficient development of resistant cultivars. Previous studies have reported a locus of major effect from PPV resistance on linkage group 1. The current study confirms these results by mapping plum pox virus resistance in a F1 progeny issued from a cross between "Harlayne", as a PPV-resistant parent, and "Vestar" as a susceptible parent. The hybrids were grafted simultaneously and subsequently inoculated with the PPV-M and D strains. The symptom scoring on leaves was performed nine times over two vegetative cycles. Marker-trait associations were analyzed using the Kruskal-Wallis (KW) non-parametric test, and the PPV resistance loci were mapped using composite interval mapping (CIM). We show that both analyses (KW and CIM) highlighted the upper part of linkage group 1 of the apricot "Harlayne" genitor

Flanking the major Plum pox virus resistance locus in apricot with co-dominant markers (SSRs) derived from candidate resistance genes

Plum pox virus (PPV) is a potyvirus that causes sharka disease in infested stone fruit trees (Prunus species, peach, apricot, plum). In apricots, the resistance is controlled by a major quantitative trait locus that explains up to 70% of the phenotypic variance; it is localised in the upper part of linkage group 1. In this report, we transformed candidate genes that mapped in the region of the apricot resistance locus into polymerase chain reaction markers (SSCP and SSR) and tested for their co-localisation with the major PPV resistance locus in related and unrelated populations. Three populations of F1 and F2 individuals issued from crosses between the PPV-resistant cultivar ‘Stark Early Orange’ or ‘Goldrich’ and three susceptible parents were used in this study. Molecular-marker data were collected to determine the linkage relationship between the PPV resistance locus in apricots and markers that target candidate disease-resistance genes. In addition, SSR markers linked to resistance-gene candidates were mapped to positions flanking the PPV resistance locus in different apricot populations. Therefore, we demonstrate that this strategy helps to saturate the major genomic region controlling resistance to PPV in apricot with valuable co-dominant marker

Genetic analysis of iron chlorosis tolerance in Prunus rootstocks

39 Pags., 4 Tabls., 4 Figs. The definitive version is available at: http://link.springer.com/journal/11295The high economic losses caused by the occurrence of iron chlorosis in Prunus orchards in the Mediterranean area justifies the implementation of breeding programs to generate high-performance rootstocks for different edaphoclimatic area conditions. For that reason, the genetic control of iron chlorosis tolerance was studied in an F1 population derived from a three-way interspecific cross between a Myrobalan plum (P 2175) and an almond × peach hybrid (Felinem). Several phenotypic measurements were assessed to guarantee an accurate data set for genetic analysis. SPAD (Soil and Plant Analyzer Development) values, chlorophyll concentration, and visual diagnostic symptoms were highly correlated with leaf chlorosis in trees. SPAD value was the most reliable measure, since it was an objective, unbiased, and non-destructive method. Two significant quantitative trait loci (QTLs) involved in SPAD and chlorophyll concentration were identified for Felinem in linkage groups 4 and 6. Both QTLs were detected in four of the six consecutive years of the experiment. For P 2175, two of the three putative QTLs identified, pspad4.1 and chl4.1, were placed in linkage group 4. These QTLs were related to the SPAD values and chlorophyll concentration, respectively, and co-localized with QTLs detected in the Felinem map affecting the same traits. Candidate gene PFIT, related to iron metabolism, was localized within the confidence interval of the QTL in linkage group 4. This research suggests an association of this chromosome region with tolerance to iron chlorosis in Prunus, and it provides a first approach to localize candidate genes involved in tolerance to this abiotic stress.This research was funded by MICINN (Spanish Ministry of Science and Innovation, AGL 2008-00283) and co-funded with a FEDER project and Gobierno de Aragón (A44). M.J. Gonzalo was the beneficiary of an I3P-PC2006 contract from the CSIC-FSE.Peer reviewe