Genetic resources management with networks: the example of the network "Carrot and other Daucus"

International audienceAs for many other species, the request of the producers, distributors and consumers for more homogeneous and more uniform products in carrot resulted in a considerable reduction of the number of cultivated varietal types. In order to face this possible genetic erosion, actions of conservation were committed in the world. In a majority of countries, these actions are concentrated within organizations such as multi-species gene banks. On the contrary, the French organization is based on networks specialized in a species or group of species. The Office of Genetic Resources (BRG) ensures the coordination of these networks. The network "Carrot and other Daucus" was created in 1996, and involves research institutes, seed companies, experimental and technical agencies as well as botanical gardens or amateurs, all experts of the carrot species. Each year, about 40 accessions are characterized and 5 to 10 accessions to be introduced in the national collection are regenerated. In accordance, the objectives of the network are to gather, evaluate, preserve the old carrot varieties and related species, and thus to contribute to the safeguard, verification and diffusion of the French genetic inheritanc

Carotenoid Content and Root Color of Cultivated Carrot: A Candidate-Gene Association Study Using an Original Broad Unstructured Population

Article de revue (Article scientifique dans une revue à comité de lecture)International audienceAccumulated in large amounts in carrot, carotenoids are an important product qualityattribute and therefore a major breeding trait. However, the knowledge of carotenoid accumulationgenetic control in this root vegetable is still limited. In order to identify the geneticvariants linked to this character, we performed an association mapping study with a candidategene approach.We developed an original unstructured population with a broad geneticbasis to avoid the pitfall of false positive detection due to population stratification. Wegenotyped 109 SNPs located in 17 candidate genes – mostly carotenoid biosynthesisgenes – on 380 individuals, and tested the association with carotenoid contents and colorcomponents. Total carotenoids and β-carotene contents were significantly associated withgenes zeaxanthin epoxydase (ZEP), phytoene desaturase (PDS) and carotenoid isomerase(CRTISO) while α-carotene was associated with CRTISO and plastid terminal oxidase(PTOX) genes. Color components were associated most significantly with ZEP. Our resultssuggest the involvement of the couple PDS/PTOX and ZEP in carotenoid accumulation, asthe result of the metabolic and catabolic activities respectively. This study brings new insightsin the understanding of the carotenoid pathway in non-photosynthetic organs.</p

Carrot resistance to Alternaria leaf blight: from genetics to metabolomics

International audienc

Link between carrot leaf secondary metabolites and resistance to Alternaria dauci

Alternaria Leaf Blight (ALB), caused by the fungus Alternaria dauci, is the most damaging foliar disease affecting carrots (Daucus carota). In order to identify compounds potentially linked to the resistance to A. dauci, we have used a combination of targeted and non-targeted metabolomics to compare the leaf metabolome of four carrot genotypes with different resistance levels. Targeted analyses were focused on terpene volatiles, while total leaf methanolic extracts were subjected to non-targeted analyses using liquid chromatography couple to high-resolution mass spectrometry. Differences in the accumulation of major metabolites were highlighted among genotypes and some of these metabolites were identified as potentially involved in resistance or susceptibility. A bulk segregant analysis on F3 progenies obtained from a cross between one of the resistant genotypes and a susceptible one, confirmed or refuted the hypothesis that the metabolites differentially accumulated by these two parents could be linked to resistance

Combined Alternaria dauci infection and water stresses impact carotenoid content of carrot leaves and roots

Carotenoids are important secondary metabolites involved in plant photosynthesis, vegetable nutritional quality but also in metabolic prevention in human health. Carrot represents one of the most important carotenoid intakes and is a very interesting model to study carotenoid metabolism. Till now, the knowledge about the impact of stress on carotenoid accumulation is limited. The purpose of this work was to investigate the impact of abiotic and biotic stresses applied separately or in combination on carotenoid accumulation in carrot leaves and roots. Results showed that combined stress decreased dramatically carotenoid content in both organs. In roots, the decrease in carotenoid content could be mostly associated in carrot response to A. dauci infection. Moreover, carotenoid and sugar contents were highly correlated, which suggests that stored metabolites are directly or indirectly involved in plant response to pathogen infection. In leaves, in contrast to results observed in roots, stresses impact carotenoid content depending on the genotype and the year. Moreover, carotenoid content variations were correlated to chlorophyll contents suggesting that a common mechanism of regulation for photosynthetic biosynthesis pigment exists

Etude de la résistance partielle de la carotte à Alternaria dauci par une approche de phénotypage multi critères

The development of carrot varieties with a high and durable level of resistance inevitably requires implementation of highly discriminating phenotyping methods, reproducible and which can beimplemented on large numbers of plants. Current methods of phenotyping are still very often based on visual scoring of symptoms. We report various methods of alternative phenotyping to characterize either the asymptomatic phase by use of new technologies such as qPCR, thermography or chlorophyllfluorescence measurement or the symptomatic phase in using tests under controlled conditions. Advantages and limitations of these methods are discussed.La création de variétés présentant un niveau de résistance fort et durable passe immanquablement par la mise en œuvre de méthodes de phénotypage toujours plus discriminantes, reproductibles et pouvant être mises en œuvre sur de grands effectifs. Les méthodes actuelles de phénotypage font encore très souvent appel à une notation visuelle des symptômes. Nous rapportons ici la mise en œuvre de différentes méthodes de phénotypage alternatives permettant de caractériser, soit la phase asymptomatique par l’utilisation de nouvelles technologies telles que la qPCR, la thermographie ou la mesure de fluorescence de chlorophylle, soit la phase symptomatique à l’aide de tests en conditions contrôlées. Les avantages et les limites de ces méthodes sont abordés

Manhattan plots of the K-SNP model for carotenoid content.

<p>Grey horizontal line indicates the significance threshold. Genes are displayed in the pathway order.</p

Boxplots of the ZEP-117 alleles for total carotenoids, β-carotene, phytoene and phytofluene content.

<p>Mean and group according to Kruskal-Wallis test are given for each boxplot.</p

Principal component analysis of population based on SNP markers.

<p>Numbers in parentheses refer to the proportion of explained variance.</p

Population stratification according to STRUCTURE based on 15 SSR markers.

<p>Plots of (A) Delta K and (B) the log likelihood. Each individual is represented by a single vertical box broken in colored segments according to the number of assumed populations: 2 (C), 3 (D), 5 (E). Vertical box length is proportional to each cluster assignment probability (y-axis).</p