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National audience; Plusieurs espèces de Brassica sont conservées au sein du Centre de Ressources Biologique BrACySol à Ploudaniel (https://www6.rennes.inrae.fr/igepp/L-IGEPP/Plateformes/BrACySol). Pour le chou (Brassica oleracea, CC,2n=18) et le navet (Brassica rapa, AA, 2n=20), les ressources comprennent essentiellement des populations fermières collectées dans les années 1980. Ces deux espèces existent cependant sous forme de populations sauvages ou férales sur l’ensemble du territoire français, et leurs collectes s’avèrent indispensables pour élargir les ressources disponibles. Dans le cadre du projet H2020 Prima BrasExplor comprenant 11 partenaires de six pays, nous proposons de collecter environ 100 populations sauvages et fermières de chacune de ces deux espèces, sur un gradient nord de la France jusqu’à la zone subsaharienne d’Afrique du Nord. Ce matériel offre une opportunité très originale (i) d’identifier les déterminants génétiques responsables de l’adaptation aux contraintes climatiques, et (ii) de valoriser des populations fermières. Nous présentons ici la méthodologie suivie, les collectes en cours sur le territoire français et les travaux qui seront engagés dans le cadre du projet BrasExplor.Ces travaux ouvrent des perspectives d’amélioration vis-à-vis des contraintes abiotiques et biotiques chez le chou, le navet, ou encore le colza (Brassica napus, AACC, 2n=38) issu de l’hybridation naturelle entre ces deux espèces diploïdes.

Author Keywords:Pinus nigra Arn.; Tree-ring; Climate change; Dendroecology; Growth-climate response; Intraspecific variation; Provenances; International audience; In the Mediterranean region, the effects of climate change on tree growth have been more and more noticeable in recent decades. Pinus nigra is one of the most common mid-elevation pine in this region and one of the species most affected by increasing dryness. In Tunisia, in order to guide species selection for future reforestation of the Khroumirie Mountains, research studies are under way to improve knowledge of black pine ecology. The effects of interannual climate variations on radial growth were compared for 19 provenances of black pine in a 51-year-old common garden experiment in Souiniet (NW Tunisia, 492m) in a humid Mediterranean bioclimate. A significant positive correlation with April precipitation and a significant negative correlation with spring temperature were noted. A cool wet spring is beneficial to growth as it affects tree water balance at the onset of the growing season; in contrast, spring drought is responsible for low annual growth. Mild January–February temperatures have a positive influence on ring width as mild winters may foster photosynthesis and promote early resumption of cambial activity. Analysis of the pointer years showed that winter snow and hail are major factors limiting growth of black pine in the studied area. Despite overall similarities in ring width to climate relationships among provenances, differences observed attest to the interaction of the environment and genetic control of black pine diameter growth.

International audience; Plants tend to decrease transpiration under water deficit and/or high evaporative demand by closing stomata. Stomatal conductance is central for the trades‐off between hydraulics and photosynthesis. We aimed at deciphering its genetic control and that of its responses to evaporative demand and water deficit, a nearly impossible task with gas exchanges measurements. Whole‐plant stomatal conductance was estimated via inversion of the Penman–Monteith equation from data of transpiration and plant architecture collected in a phenotyping platform. We have analyzed jointly 4 experiments with contrasting environmental conditions imposed to a panel of 254 maize hybrids. Estimated whole‐plant stomatal conductance closely correlated with gas‐exchange measurements and biomass accumulation rate. Sixteen robust quantitative trait loci (QTLs) were identified by genome wide association studies and co‐located with QTLs of transpiration and biomass. They accounted for 58% of the additive genetic variance and 40% of the genotype × environment interaction. Light, vapour pressure deficit (VPD), or soil water potential largely accounted for the differences in allelic effects between experiments, thereby providing strong hypotheses for mechanisms of stomatal control and explaining part of the observed genotype × environment interaction. Light positively affected the allelic effects of three QTLs (e.g. R2 = 0.74), whereas VPD and water deficit negatively affected the allelic effects of other four QTLs. The combination of SNP effects, as affected by environmental conditions, accounted for the variability of stomatal conductance across a range of hybrids and environmental conditions (R2 = 0.86). This approach may therefore contribute prediction of stomatal control in diverse environments and to breeding for water efficient maize.

ispartof: FRONTIERS IN PLANT SCIENCE vol:9 ispartof: location:Switzerland status: published

National audience

Understanding the genetic basis of phenotypic plasticity is crucial for predicting and managing climate change effects on wild plants and crops. Here, we combined crop modeling and quantitative genetics to study the genetic control of oil yield plasticity for multiple abiotic stresses in sunflower. First we developed stress indicators to characterize 14 environments for three abiotic stresses (cold, drought and nitrogen) using the SUNFLO crop model and phenotypic variations of three commercial varieties. The computed plant stress indicators better explain yield variation than descriptors at the climatic or crop levels. In those environments, we observed oil yield of 317 sunflower hybrids and regressed it with three selected stress indicators. The slopes of cold stress norm reaction were used as plasticity phenotypes in the following genome-wide association study. Among the 65,534 tested SNP, we identified nine QTL controlling oil yield plasticity to cold stress. Associated SNP are localized in genes previously shown to be involved in cold stress responses: oligopeptide transporters, LTP, cystatin, alternative oxidase, or root development. This novel approach opens new perspectives to identify genomic regions involved in genotype-by-environment interaction of a complex traits to multiple stresses in realistic natural or agronomical conditions.

Porcine reproductive and respiratory syndrome virus (PRRSV) replicates primarily in pulmonary alveolar macrophages (PAMs) and the resulting lung damage is influenced by strain virulence. To better understand the pathogenesis of PRRSV infection, we performed a longitudinal study of the PAM population and lung cytokines in specific pathogen-free pigs infected either with the highly pathogenic Lena strain or with the low pathogenic Finistere strain in comparison to uninfected pigs. Bronchoalveolar lavage fluid (BALF) and blood were collected to follow viral, cellular and cytokine changes in lung with respect to clinical signs and systemic events. Compared to Finistere-infected pigs, Lena-infected pigs exhibited more severe clinical signs and 10- to 100-fold higher viral loads in BALF and blood. Similarly, they showed an earlier drop in BALF cell viability and phagocytic activity along with a decrease in the macrophage count. From 8 to 15 days post-infection (dpi), monocytes increased both in BALF and blood from Lena-infected pigs. BALF and blood showed contrasting cytokine patterns, with low increase of IFN-α and TNF-α levels and high increase for IL-1α and IL-8 in BALF after Lena-infection. In contrast, in the blood, the increase was marked for IFN-α and TNF-α but limited for IL-1β and IL-8. Down-regulation of PAM functions combined with inflammatory cytokine and monocyte recruitment may promote lung pathogenesis and virus replication in PRRSV infections with the highly pathogenic Lena strain. In contrast, the low pathogenic Finistere strain showed prolonged viral replication in lung, possibly related to the weak IFN-γ response. Electronic supplementary material The online version of this article (doi:10.1186/s13567-017-0420-y) contains supplementary material, which is available to authorized users.

High-throughput techniques for the compositional analysis of lignocellulosic biomass are essential to allow the genetic analysis and genetic improvement of bioenergy feedstocks. In this study, we investigated the feasibility of using near-infrared (NIR) spectroscopy for rapid assessment of wood chemical traits in a large sample of Populus nigra L. individuals evaluated in clonal trials at two contrasting sites. Spectra were acquired from 5799 wood samples collected in 3 harvests corresponding to two coppice rotations at one site and one coppice rotation at the second. Calibrations were developed and validated using 120 reference samples, representing spectral and chemical variations in the samples. The resulting global and site specific calibrations for most of the traits were at least good enough for ranking of genotypes, demonstrating the usefulness of NIR analysis for phenotyping the studied population. Clonal repeatability (View the MathML sourceHc2) estimates of the studied traits based on all samples were moderate to high (View the MathML sourceHc2 ranging from 0.57 to 0.89 in the 3 harvests). When data were pooled over coppice rotations or sites, the genotype × environment interaction was more evident across sites than across rotations. However, the interaction was smaller than the genotype main effect for all traits, except for glucose and extractives contents. Importantly, the interaction resulted mainly from re-ranking of a few genotypes leaving a substantial amount of stable and performant genetic material, which may encourage breeding for improved main wood components. Optimization of the NIR analysis for assessing clonal trials would facilitate the exploitation of standing genetic variation of energy or chemical related traits in tree breeding program.

Understanding the genetic basis of phenotypic plasticity is crucial for predicting and managing climate change effects on wild plants and crops. Here, we combined crop modeling and quantitative genetics to study the genetic control of oil yield plasticity for multiple abiotic stresses in sunflower. First we developed stress indicators to characterize 14 environments for three abiotic stresses (cold, drought and nitrogen) using the SUNFLO crop model and phenotypic variations of three commercial varieties. The computed plant stress indicators better explain yield variation than descriptors at the climatic or crop levels. In those environments, we observed oil yield of 317 sunflower hybrids and regressed it with three selected stress indicators. The slopes of cold stress norm reaction were used as plasticity phenotypes in the following genome-wide association study. Among the 65,534 tested SNP, we identified nine QTL controlling oil yield plasticity to cold stress. Associated SNP are localized in genes previously shown to be involved in cold stress responses: oligopeptide transporters, LTP, cystatin, alternative oxidase, or root development. This novel approach opens new perspectives to identify genomic regions involved in genotype-by-environment interaction of a complex traits to multiple stresses in realistic natural or agronomical conditions., 12 pages, 5 figures, Plant, Cell and Environment

Despite the interest foresters have for inter-specific hybrid trees, still little is known about their quantitative genetics. This is especially true for the hybrid (HL) between Larix decidua (EL) and L. kaempferi (JL). Long-term, well-designed, multi-site experiments are necessary to estimate the parameters required for HL breeding programs. This paper presents the results from a diallel mating trial between nine EL and nine JL, set up in three contrasted sites. Growth traits (height, circumference), quality traits (wood density, stem form, heartwood proportion), and bud flush were measured from plantation to up to 18 years after plantation. Wood density and heartwood proportion were assessed using increment cores. We did a spatial analysis to take into account environmental heterogeneity at the tree level, and we fitted a multi-trait, Bayesian MCMC (Markov chain Monte Carlo) genetic model. Our study confirmed, in most situations, that HL expressed heterosis over its best parent for growth traits taking advantage of an early faster growth, with no loss in wood density. However, growth traits showed low levels of heritability. On the other hand, bud flush and stem flexuosity had high heritabilities, and wood density was clearly under JL control. Site-dependent heritabilities were expressed by EL. Additive genetic correlations were presented. The traits with high heritabilities showed high correlation between their performances in pure species and in hybridization, as well as high across-site correlations. The discussion focused on the interest of these genetic parameters for the hybrid larch breeding programs.

A panel of 300 tomato accessions including breeding materials was built and characterized with >11,000 SNP. A population structure in six subgroups was identified. Strong heterogeneity in linkage disequilibrium and recombination landscape among groups and chromosomes was shown. GWAS identified several associations for fruit weight, earliness and plant growth. Genome-wide association studies (GWAS) have become a method of choice in quantitative trait dissection. First limited to highly polymorphic and outcrossing species, it is now applied in horticultural crops, notably in tomato. Until now GWAS in tomato has been performed on panels of heirloom and wild accessions. Using modern breeding materials would be of direct interest for breeding purpose. To implement GWAS on a large panel of 300 tomato accessions including 168 breeding lines, this study assessed the genetic diversity and linkage disequilibrium decay and revealed the population structure and performed GWA experiment. Genetic diversity and population structure analyses were based on molecular markers (>11,000 SNP) covering the whole genome. Six genetic subgroups were revealed and associated to traits of agronomical interest, such as fruit weight and disease resistance. Estimates of linkage disequilibrium highlighted the heterogeneity of its decay among genetic subgroups. Haplotype definition allowed a fine characterization of the groups and their recombination landscape revealing the patterns of admixture along the genome. Selection footprints showed results in congruence with introgressions. Taken together, all these elements refined our knowledge of the genetic material included in this panel and allowed the identification of several associations for fruit weight, plant growth and earliness, deciphering the genetic architecture of these complex traits and identifying several new loci useful for tomato breeding.

This chapter presents models of the processes involved in floral initiation and development. It begins by briefy presenting models of hormonal transport. The focus is on two key aspects of floral development, namely floral initiation, due to the periodic local accumulation of auxin (a plant hormone) near the plant apex, and the genetic regulation of floral development. The main assumptions about auxin transport that have been proposed and tested in the literature are described, and it is shown how the use of models makes it possible to test assumptions expressed in terms of local cell-cell interaction rules and to check if they lead to patterning in the growing tissue that is consistent with observation. The gene regulatory networks (GRNs) that control the initial steps of floral development and differentiation are investigated. In a simplified form, this network contains dozens of components that interact with each other in space and time. The understanding of such a complex system also requires a modeling approach in order to quantify these interactions and analyze their properties. There are two main formalisms that are used to model GRN: the Boolean and the ODE formalisms. Both these are illustrated on a submodule of the floral GRN and their main advantages and drawbacks are discussed. It is shown how manipulations of the network models can be used to make predictions corresponding to possible biological manipulations of the GRN (e.g., loss-of-function mutants). Throughout, specific mathematical topics of particular interest for the development of these ideas are detailed in separate boxes which can be read relatively independently of the main text.

National audience

The genetic control of maize kernel weight (KW) determination could be studied through its physiological and/ or compositional determinants. Our objective was to dissect the genetic control of maize KW by analyzing its physiological (KGR: kernel growth rate; KFD: kernel filling duration) and compositional (protein, oil, starch) determinants in a dentxflint Caribbean RIL population, which combines a broad genetic background with grains of high added value for industry. An additional objective was to determine the stability of the genetic control under contrasting growing conditions, for which soil nitrogen offer was modified across experiments. Heritability (H-2) values were high for KW (H-2 = 0.74) and intermediate for the other traits (from 0.62 to 0.42). Kernel weight had a strong correlation with KFD (r = 0.69), KGR (r = 0.60) and protein concentration (r = 0.56). Ten joint QTL with inconsistent effects across years and seven epistatic interactions were detected. Despite changes in effect size, most QTL were significant under both environments. Nine QTL were associated with variations in potential KW (KWP), mean KW, KGR and oil concentration, eight with variations in protein and starch concentration and seven with KFD. Epistatic interactions were related to regions with significant main effects. The most important finding was the existence of a common QTL for KWP, KGR and KFD on chromosome 5, for which there was no previous report. Results increased our knowledge on the genetic control of KW through its phenotypic and genetic correlation with KFD, confirming the need to explore different physiological strategies in different genetic backgrounds.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitièresData Availability: The relevant DOIs/accession numbers required to access raw data in Zenodo is: http://dx.doi.org/10.5281/zenodo.35030 (doi: 10.5281/zenodo.35030).; Water use efficiency (WUE) is a quantitative measurement which improvement is a major issue in the context of global warming and restrictions in water availability for agriculture. In this study, we aimed at studying the variation and genetic control of WUE and the respective role of its components (plant biomass and transpiration) in a perennial fruit crop. We explored an INRA apple core collection grown in a phenotyping platform to screen one-year-old scions for their accumulated biomass, transpiration and WUE under optimal growing conditions. Plant biomass was decompose into morphological components related to either growth or organ expansion. For each trait, nine mixed models were evaluated to account for the genetic effect and spatial heterogeneity inside the platform. The Best Linear Unbiased Predictors of genetic values were estimated after model selection. Mean broad-sense heritabilities were calculated from variance estimates. Heritability values indicated that biomass (0.76) and WUE (0.73) were under genetic control. This genetic control was lower in plant transpiration with an heritability of 0.54. Across the collection, biomass accounted for 70% of the WUE variability. A Hierarchical Ascendant Classification of the core collection indicated the existence of six groups of genotypes with contrasting morphology and WUE. Differences between morphotypes were interpreted as resulting from differences in the main processes responsible for plant growth: cell division leading to the generation of new organs and cell elongation leading to organ dimension. Although further studies will be necessary on mature trees with more complex architecture and multiple sinks such as fruits, this study is a first step for improving apple plant material for the use of water.

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Article de revue (Article scientifique dans une revue à comité de lecture); International audience; Accumulated 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.

International audience; Rapid and uniform seed germination is a crucial prerequisite for crop establishment and high yield levels in crop production. A disclosure of genetic factors contributing to adequate seed vigor would help to further increase yield potential and stability. Here we carried out a genome-wide association study in order to define genomic regions influencing seed germination and early seedling growth in oilseed rape (Brassica napus L.). A population of 248 genetically diverse winter-type B. napus accessions was genotyped with the Brassica 60k SNP Illumina genotyping array. Automated high-throughput in vitro phenotyping provided extensive data for multiple traits related to germination and early vigor, such as germination speed, absolute germination rate and radicle elongation. The data obtained indicate that seed germination and radicle growth are strongly environmentally dependent, but could nevertheless be substantially improved by genomic-based breeding. Conditions during seed production and storage were shown to have a profound effect on seed vigor, and a variable manifestation of seed dormancy appears to contribute to differences in germination performance in B. napus. Several promising positional and functional candidate genes could be identified within the genomic regions associated with germination speed, absolute germination rate, radicle growth and thousand seed weight. These include B. napus orthologs of the Arabidopsis thaliana genes SNOWY COTYLEDON 1 (SCO1), ARABIDOPSIS TWO-COMPONENT RESPONSE REGULATOR (ARR4), and ARGINYL-t-RNA PROTEIN TRANSFERASE 1 (ATE1), which have been shown previously to play a role in seed germination and seedling growth in A. thaliana.

Leptosphaeria maculans, the causal agent of stem canker of oilseed rape (Brassica napus), develops gene-for-gene interactions with oilseed rape, and four L. maculans avirulence (AVR) genes (AvrLm1, AvrLm2, AvrLm4, and alm1) were previously genetically characterized. Based on the analysis of progeny of numerous in vitro crosses between L. maculans isolates showing either already characterized or new differential interactions, this work aims to provide an overview of the AVR genes that may specify incompatibility toward B. napus and the related species B. juncea and B. rapa. Two novel differential interactions were thus identified between L. maculans and B. napus genotypes, one of them corresponding to a complete resistance to European races of L. maculans. In both cases, a single gene control of avirulence was established (genes AvrLm3 and AvrLm7). Similarly, a single gene control of avirulence toward a B. rapa genotype, also resistant to European L. maculans isolates, was demonstrated (gene AvrLm8). Finally, a digenic control of avirulence toward B. juncea was established (genes AvrLm5 and AvrLm6). Linkage analyses demonstrated that at least four unlinked L. maculans genomic regions, including at least one AVR gene cluster (AvrLm1-AvrLm2-AvrLm6), are involved in host specificity. The AvrLm3-AvrLm4-AvrLm7 region may correspond either to a second AVR gene cluster or to a multiallelic AVR gene.

Price reduction and environmental concerns advocate a lower use of nitrogen (N) fertilizer on the wheat (Triticum aestivum L.) crop. It is a common hypothesis that hybrids would be more valuable in stressed environments such as limited fertilizer conditions. The objective of this study was to assess heterosis and combining ability at two N levels. Seven winter wheat cultivars were used to produce a 7 × 7 diallel cross without the reciprocals. The 21 F1 hybrids and parental lines were tested in replicated plots over 2 yr without N fertilizer (NO) or with 150 kg N ha -1 (N+). The diallel analysis was conducted according to Griffing with year, genotype, and treatment as fixed effects. Mid-parent heterosis for grain yield was +12.2%** at NO and +8.9%** at N+ in 1997 and +1.7% ns at NO and -0.4% ns at N+ in 1998. This was directly related to high mid-parent heterosis for above-ground dry weight in 1997 (+11.2%** at NO and +10.9%** at N+) and low heterosis in 1998 (+1.2% ns at NO and + 0.0% ns at N + ). General (GCA) and specific (SCA) combining ability effects were always significant. The GCA/SCA ratio ranged from 3.6 to 14.8. The GCA x N level interaction was generally significant indicating different parental contributions at low or high N levels. The SCA x N level interaction was never significant. There was a tendency toward higher GCA/SCA ratio at NO than at N+. The choice of parents will be dependent upon the N level under which the new hybrids will be grown.

Identifying the genes controlling the variation of quantitative traits is a key goal for geneticists. Genetic loci underlying quantitative trait variation (QTL) have been mapped by traditional linkage mapping for years and positional cloning identified several QTLs. However linkage mapping is limited to the analysis of traits differing between two lines and the impact of genetic background on QTL effect has been underlined.Thanks to the increase in molecular markers, genome-wide association studies were then proposed to circumvent QTL limitations.[br/] ln tomato, a self-pollinated crop, we have shown that association studies are possible, using the admixed nature of cherry tomato genomes that limits the impact of population structure in such an approach.[br/] Nevertheless, the results might be restricted by linkage disequilibrium and allele frequency, which vary greatly along the genome. Multi-allelic Advanced Generation Inter-Cross (MAGIC) populations allow a wide range of variability to be analyzed and avoid dealing with population structure.

Identifying the genes controlling the variation of quantitative traits is a key goal for breeders. Genetic variations underlying quantitative traits (QTL) have been mapped by traditional linkage mapping for years and positional cloning identified several QTLs.[br/] However linkage mapping is limited to the analysis of traits differing between two lines and the impact of genetic background on QTL effect has been underlined. Thanks to the increase in molecular markers, genome-wide association studies were then proposed to circumvent QTL limitations. ln tomato, a self-pollinated crop, we have shown that association studies are possible, using the admixed nature of cherry tomato genomes that limits the impact of population structure in such an approach.[br/] Nevertheless, the results might be limited by linkage disequilibrium, which varies greatly along the genome. Multi-allelic Advanced Generation Inter-Cross (MAGIC) populations allow a wide range of variability to be analyzed and avoid dealing with population structure.

A sunflower line, XRQ, carrying the gene Pl5, which gives resistance to all French downy mildew races shows cotyledon-limited sporulation in seedling immersion tests; consequently, segregations in crosses with other downy mildew resistance sources were tested both by this method and by a secondary infection on leaves. Pl5 was found to segregate independently of Pl7 (HA338) but to be closely linked, or allelic, with Pl8 (RHA340). F3 and F4 progenies from a cross with a line containing Pl2 showed that Pl5 carries resistance to race 100 which segregates independently of Pl2. The Pl5 gene was mapped on linkage group 6 of the Cartisol RFLP map, linked to two RFLP markers, ten AFLP markers and the restorer gene Rf1. Tests with downy mildew race 330 distinguished Pl5 and Pl8, the first being susceptible, the second resistant, whereas both these genes were active against race 304 to which Pl6 (HA335) and Pl7 gave susceptibility. It is concluded that Pl5 and Pl8 are closely linked on linkage group 6 and form a separate resistance gene group from Pl6/Pl7 on linkage group 1. The origins of these groups of downy mildew resistance genes and their use in breeding are discussed.

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International audience; Post-translational protein modifications such as acetylation have significant regulatory roles in metabolic processes, but their relationship to both variation in gene expression and DNA sequence is unclear. We address this question in the Goto-Kakizaki (GK) rat inbred strain, a model of polygenic type 2 diabetes. Expression of the NAD-dependent deacetylase Sirtuin-3 is down-regulated in GK rats compared to normoglycemic Brown Norway (BN) rats. We show first that a promoter SNP causes down-regulation of Sirtuin-3 expression in GK rats. We then use mass-spectrometry to identify proteome-wide differential lysine acetylation of putative Sirtuin-3 protein targets in livers of GK and BN rats. These include many proteins in pathways connected to diabetes and metabolic syndrome. We finally sequence GK and BN liver transcriptomes and find that mRNA expression of these targets does not differ significantly between GK and BN rats, in contrast to other components of the same pathways. We conclude that physiological differences between GK and BN rats are mediated by a combination of differential protein acetylation and gene transcription and that genetic variation can modulate acetylation independently of expression.

The purpose of the present study was to map quantitative trait locus (QTLs) associated with percentage of seed protein, oil and fatty acids content under different conditions in a population of recombinant inbred lines (RILs) of sunflower. Three independent field experiments were conducted with well-, partial-irrigated and late-sowing conditions in randomized complete block design with three replications. High significant variation among genotypes is observed for the studied traits in all conditions. Several specific and non-specific QTLs for the aforementioned traits were detected. Under late-sowing condition, a specific QTL of palmitic acid content on linkage group 6 (PAC-LS.6) is located between ORS1233 and SSL66_1 markers. Common chromosomic regions are observed for percentage of seed oil and stearic acid content on linkage group 10 (PSO-PI.10 and SAC-WI.10) and 15 (PSO-PI.15 and SAC-LS.15). Overlapping occurs for QTLs of oleic and linoleic acids content on linkage groups 10, 11 and 16. Seven QTLs associated with palmitic, stearic, oleic and linoleic acids content are identified on linkage group 14. These common QTLs are linked to HPPD homologue, HuCL04260C001. Coincidence of the position for some detected QTLs and candidate genes involved in enzymatic and non-enzymatic antioxidants would be useful for the function of the respective genes in fatty acid stability.Key words: Sunflower, quantitative trait locus, simple sequence repeats, oil content, protein content, fatty acids.

International audience

International audience; Lignin content and composition are considered as mandatory traits of eucalyptus breeding programs, especially for pulp, paper, and bioenergy production. In this article, we used 33 Eucalyptus urophylla full-sib families of an 8 × 8 factorial design to provide estimates of genetic parameters for lignin- and growth-related traits. Secondly, from the sequencing of the 16 unrelated founders, we described the nucleotide and haplotype variability of cinnamoyl-CoA reductase (CCR), a candidate gene for lignin-related traits encoding the cinnamoyl-CoA reductase. Finally, we tested the association between CCR polymorphisms and trait variation using a mixed linear model. A high value of narrow sense heritability was obtained for lignin content (h² = 0.85) and S/G ratio (h² = 0.62) indicating that these traits are under strong genetic control. High levels of nucleotide (θπ = 0.0131) and haplotype (Hd = 0.958) diversity were detected for CCR. From an initial set of 152 biallelic single nucleotide polymorphisms (SNPs), a subset of 65 nonredundant loci was selected. Three intronic SNPs were found to be associated to the variation of S/G ratio after multiple testing correction. In the line of what has been obtained in forest trees, these SNPs explained between 2.45% and 2.87% of the genetic variance of the trait. This study demonstrates the interest of the candidate gene approach for quantitative trait nucleotide detection in Eucalyptus and paves the way to gene assisted selection of lignin composition in E. urophylla.

UMR 1334 AGAP : Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ ; Team AFFS ‘Architecture and Functioning of Fruit Species’ Contact: costes@supagro.inra.frPublication 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/256699; Although flowering in mature fruit trees is recurrent, floral induction can be strongly inhibited by concurrent fruiting, leading to a pattern of irregular fruiting across consecutive years referred to as biennial bearing. The genetic determinants of biennial bearing in apple were investigated using the 114 flowering individuals from an F1 population of 122 genotypes, from a ‘Starkrimson’ (strong biennial bearer)3‘Granny Smith’ (regular bearer) cross. The number of inflorescences, and the number and the mass of harvested fruit were recorded over 6 years and used to calculate 26 variables and indices quantifying yield, precocity of production, and biennial bearing. Inflorescence traits exhibited the highest genotypic effect, and three quantitative trait loci (QTLs) on linkage group (LG) 4, LG8, and LG10 explained 50% of the phenotypic variability for biennial bearing. Apple orthologues of flowering and hormone-related genes were retrieved from the whole-genome assembly of ‘Golden Delicious’ and their position was compared with QTLs. Four main genomic regions that contain floral integrator genes, meristem identity genes, and gibberellin oxidase genes co-located with QTLs. The results indicated that flowering genes are less likely to be responsible for biennial bearing than hormone-related genes. New hypotheses for the control of biennial bearing emerged from QTL and candidate gene co-locations and suggest the involvement of different physiological processes such as the regulation of flowering genes by hormones. The correlation between tree architecture and biennial bearing is also discussed.

Herbicides inhibiting Acetyl-CoenzymeA carboxilase (ACCase) and Acetohydroxyacid synthase (AHAS) are among the most widely used in France and in the world. Their intensive use selected resistant plants into weed populations. It was assessed that non-target-site resistance (NTSR) to herbicides inhibiting ACCase is prevalent on target-site resistance (TSR) in many black grass (Alopecurus myosuroides) populations which is a very harmful weed in the cereal fields. While TSR mechanisms are well know and understood, NTSR mechanisms have not been studied much by now. We tried to identify genes conferring NTSR to ACCase inhibitors and AHAS inhibitors into black grass thanks to a Suppressive Subtractive Hybridization (SSH) technology of analysis of the transcriptome. Characterization of NTSR involves a five steps process: to look for populations containing NTSR individuals, to characterize the phenotype of each individual of these populations, to set resistant and sensitive plants apart before and after the herbicide treatment into a freezer, to identify NTSR "candidate genes", and check the role of these genes in NTSR mechanisms. This work is about the first four steps of the process, which have been done with herbal material from different plants and populations because of the short time available. NTSR is an unforeseeable adaptive trait involving a large set of genes, and influenced by external factors. By characterizing the phenotype of many plants with several herbicides inhibiting ACCase and AHAS, we could assess that NTSR is a complex, polygenic and unforeseeable process. It relies on the accumulation of genes, each conferring a different level of resistance to each herbicide. An aim of this work is to identify some of these genes and to understand how they get involved in NTSR. We noticed that NTSR genes selected with herbicides inhibiting ACCase also encodes enzymes involved in NTSR to herbicides inhibiting AHAS. Different levels of expression or different sequences of NTSR genes both confer a level of resistance to the plants. Several biochemical functions seem to be involved, and two steps can be focused on: the perception of the herbicide and the transduction of the signal (regulators, kinases proteins), and the action of effectors (transport, response to stress, detoxification proteins). We could identify four NTSR "candidate genes": two of them are regulators, the other ones are effectors. A glycosyl transferase protein (GT) seems to be over expressed has a constitutive gene in resistant plants compared to sensitive plants, and a protein probably involved in response to oxidative stress is over expressed in resistant plants both before the herbicide treatment and as a result of the herbicide perception. We also identified many proteins putatively involved in a response to oxidative and environmental stresses.; Les herbicides inhibiteurs de l'Acétyle-CoenzymeA carboxylase (ACCase) et de l'Acétolactate synthase (ALS) sont parmi les plus répandus en France et dans le monde. Leur emploi intensif a sélectionné des plantes résistantes dans des populations d'adventices. Il a été montré que la résistance non liée à la cible aux inhibiteurs de l'ACCase (RNLC) est prédominante sur la résistance liée à la cible (RLC) dans de nombreuses populations de vulpin des champs (Alopecurus myosuroides), adventice très nuisible des cultures de céréales d'hiver. Or, si la RLC est relativement bien connue, peu d'études ont été menées à ce jour sur la RNLC. Nous avons cherché à identifier des gènes-candidats de RNLC aux inhibiteurs de l'ACCase et de l'ALS chez le vulpin des champs grâce à une technique d'analyse du transcriptome, l'hybridation soustractive suppressive (SSH). Le processus de caractérisation de la RNLC fait intervenir cinq étapes : la recherche de populations possédant des individus résistants, la caractérisation phénotypique des individus de cette population, le prélèvement de matériel végétal avant et après traitement sur des individus sensibles et résistants, l'identification de gènes-candidats de RNLC et la validation du rôle de ces gènes dans la RNLC. Ces travaux concernent les quatre premières étapes, réalisées sur du matériel végétal différent car le déroulement du processus complet sur une seule population nécessite un délai supérieur à six mois. La RNLC est un trait adaptatif imprévisible mettant en jeu un ensemble de gènes important et sous l'influence de facteurs externes à la plante. La caractérisation phénotypique de plante avec plusieurs herbicides inhibiteurs de l'ACCase et de l'ALS nous permet de définir la RNLC de complexe, polygénique, et imprévisible. Elle repose sur l'accumulation de gènes conférant chacun un niveau de résistance variable aux différents herbicides. Un objectif de cette étude est d'identifier ces gènes, et de comprendre leur implication dans la RNLC. Nous nous apercevons que les gènes de RNLC sélectionnés par des inhibiteurs de l'ACCase sélectionnés jusqu'à aujourd'hui codent pour des protéines également responsables de la RNLC aux inhibiteurs de l'ALS. Ce sont des différences d'expression et/ou de séquence des gènes de RNLC dans la plante qui sont à l'origine des niveaux de résistance observés. Parmi les gènes candidats identifiés, différentes fonctions biochimiques semblent intervenir à deux niveaux : la perception de l'herbicide et la transmission du signal reçu (protéines kinases), et la mise en action des effecteurs de la RNLC (protéines de transport, de réponse aux stress, de régulation de l'expression du génome). Nous avons identifié quatre gènes candidats de RNLC parmi lesquels deux gènes régulateurs et deux gènes effecteurs. Une glycosyl transferase (GT) semble être surexprimée de manière constitutive chez les plantes résistantes par rapport aux sensibles, et une proteine de réponse au stress oxydatif est surexprimée chez les résistants avant traitement et suite au traitement herbicide. De nombreuses protéines potentiellement impliquées dans la réponse aux stress oxydatif et environnement ont également été identifiées.

The genetic and environmental control of microfibril angle (MFA), the genetic correlations with other wood and growth traits, and therefore the implications for selection are poorly documented for Eucalyptus. Thus, the objectives of this study were to determine the spatial variation of the MFA, wood density (ρ) and stiffness (E); to determine the relationship between MFA and wood traits and finally to estimate the genetic and environmental control of wood and growth traits from clonal and progeny tests of Eucalyptus in Brazil and Congo. Conventional methods, resonance, X-ray diffraction and spectroscopy were combined to evaluate the wood properties. MFA variation accounted for 44 percent of the variation in specific modulus (E/ρ) of wood. The ρ was the prime determinant on wood stiffness and strength while the MFA played a secondary role. The heritability estimates were moderate to high for the MFA, ρ, E, Klason lignin (KL) and growth traits according to the spatial position and the experimental design. Genetic control of the MFA, ρ and E and their genetic correlations with KL and circumference of 1.3 meters of trees varied with age. The results suggest that tree with potential to grow fast are genetically more likely to produce low ρ and also to decrease the MFA for ensuring stiffness required for their development. Most wood properties were genetically negatively correlated with growth, although favorable genetic correlations between many wood traits were observed. Genetic and environmental correlations were sometimes of opposite signs according to the considered trait. This can be explained by the pleiotropic effect of genes and / or linkage disequilibrium. The implications of these findings for selection strategies are discussed according to the final use of Eucalyptus wood.; Le contrôle génétique et l'environnemental de l'angle des microfibrilles (MFA), les corrélations génétiques du MFA avec d'autres caractères du bois et de croissance, et par conséquent les implications pour la sélection sont très peu documentés pour les Eucalyptus. Les objectifs de cette étude étaient d'établir la variation spatiale du MFA, de la densité du bois (ρ) et de sa rigidité (E); de déterminer les relations entre MFA et propriétés du bois et enfin d'estimer le contrôle génétique et environnemental des caractères du bois et de la croissance dans le cadre de tests clonaux et de test de descendances d'Eucalyptus au Brésil et au Congo. Méthodes classiques, résonance, diffraction des rayons-X et la spectroscopie proche infrarouge ont été combinées pour évaluer les propriétés du bois. La variation du MFA représente 44% de la variation du module spécifique (E/ρ) du bois. La densité du bois est le principal déterminant de la rigidité et de la résistance du bois alors que le MFA joue un rôle secondaire. Les estimations de l'héritabilité sont de modéré à élevées pour le MFA, ρ, E, la lignine de Klason (KL) et les caractères de croissance, selon la position spatiale et le dispositif expérimental. Le contrôle génétique du MFA, ρ et E et leurs corrélations génétiques avec KL et la circonférence à 1.3 mètre des arbres varient avec l'âge. Les résultats suggèrent que les arbres à forte croissance sont génétiquement plus aptes à produire du bois de faible densité et un MFA plus faible pour assurer la rigidité du bois nécessaire à leur développement. La plupart des propriétés du bois sont génétiquement corrélées négativement avec la croissance, bien que corrélations génétiques favorables entre propriétés du bois sont observés. Les corrélations génétiques et environnementales sont parfois de signes opposés selon les caractères considérés. Ceci peut s'expliquer par l'effet pléiotropique des gènes et/ou par le déséquilibre de liaison. Les conséquences de ces résultats sur les stratégies de sélection sont discutées selon l'usage final du bois d'Eucalyptus.

Background Catabolite repression control (CRC) is an important global control system in Pseudomonas that fine tunes metabolism in order optimise growth and metabolism in a range of different environments. The mechanism of CRC in Pseudomonas spp. centres on the binding of a protein, Crc, to an A-rich motif on the 5' end of an mRNA resulting in translational down-regulation of target genes. Despite the identification of several Crc targets in Pseudomonas spp. the Crc regulon has remained largely unexplored. Results In order to predict direct targets of Crc, we used a bioinformatics approach based on detection of A-rich motifs near the initiation of translation of all protein-encoding genes in twelve fully sequenced Pseudomonas genomes. As expected, our data predict that genes related to the utilisation of less preferred nutrients, such as some carbohydrates, nitrogen sources and aromatic carbon compounds are targets of Crc. A general trend in this analysis is that the regulation of transporters is conserved across species whereas regulation of specific enzymatic steps or transcriptional activators are often conserved only within a species. Interestingly, some nucleoid associated proteins (NAPs) such as HU and IHF are predicted to be regulated by Crc. This finding indicates a possible role of Crc in indirect control over a subset of genes that depend on the DNA bending properties of NAPs for expression or repression. Finally, some virulence traits such as alginate and rhamnolipid production also appear to be regulated by Crc, which links nutritional status cues with the regulation of virulence traits. Conclusions Catabolite repression control regulates a broad spectrum of genes in Pseudomonas. Some targets are genus-wide and are typically related to central metabolism, whereas other targets are species-specific, or even unique to particular strains. Further study of these novel targets will enhance our understanding of how Pseudomonas bacteria integrate nutritional status cues with the regulation of traits that are of ecological, industrial and clinical importance.

International audience; Among forest trees, poplars are important components of riparian ecosystems and are now accepted by the scientific community as ideal model to study perennial plants. They offer several advantages as a model system, including rapid growth, ease of cloning, prolific sexual reproduction, small genomic size and facile transgenesis. Our work has the objective to contribute to the knowledge of the genetic control of bud set in black poplar (Populus nigra L.). For this purpose the genetic variability (CVg) and the broad-sense hereditability (H2), at individual and genotypic level, have been examined in a full-sib family of black poplar (POP5) and in different European natural populations of the same specie grown in a common garden experiment. The full-sib family was obtained from parents selected from the germplasm collection (DISAFRI – University of Tuscia) from Italian natural populations, diverging for phenology and other adaptive traits. The full-sib family was planted in two sites in Central (Viterbo 42°25’N, 12°05’E) and Northern Italy (Cavallermaggiore 44°42’N, 07°40’E). The european natural populations were sampled in 5 different countries and 820 genotypes, from 15 metapopulations were planted in a common garden study in Northern Italy (Savigliano 44°36’N, 07°37’E). A randomized block design was defined for the establishment of the experimental plantations in each site. Six complete blocks were used with one replicated genotype randomly assigned to each block. The phenological study has been realized on the basis of a protocol designed to monitor the six phenological phases of bud set in black poplar. Data analysis have allowed to decompose the contribution of the different phases to the dynamic of bud set. Four phases characterized the process (phase 2.5, phase 1.5, subprocess 1 and subprocess 2) and two phenological points were useful to compare different sites (50% of individuals in phase 2.5 and 1.5). Preliminary results of the bud set phenology in P. nigra natural population will be also presented and compared to the full-sib family data. These results will be discussed in relationship to the photoperiod and temperature trend introducing, in prospect, the utility of this work for genetic improvement and mapping of QTLs associated to bud set.

Energy intake and genetic background are major determinants of muscle fat content in most animals, including man. We combined genetic selection and dietary energy supply to study the metabolic pathways involved in genetic and nutritional control of fat deposition in the muscle of rainbow trout (Oncorhynchus mykiss). Two experimental lines of rainbow trout, selected for lean (L) or fat (F) muscle, were fed with diets containing either 10 or 23 % lipids from the first feeding, up to 6 months. At the end of the trial, trout exhibited very different values of muscle fat content (from 4·2 to 10·1 % wet weight). Using microarrays made from a rainbow trout multi-tissue cDNA library, we analysed the molecular changes occurring in the muscle of the two lines when fed the low-energy or high-energy diet. The results from microarray analysis revealed that eleven metabolism-related genes were differentially expressed according to the diet while selection resulted in expression change for twenty-six genes. The most striking observation was the increased level of transcripts encoding the VLDL receptor and fatty acid translocase/CD36 following both the high-fat diet and upward selection for muscle fat content, suggesting that these two genes are relevant molecular markers of fat deposition in the white muscle of rainbow trout.

International audience

Drought response of three Douglas-fir clones (slow, intermediate and fast growing) inhabiting two different climatic regimes in France was examined. We used the hydraulic conductivity and the percent loss of conductivity due to embolism from stems and branches as well as wood microdensity measurements to determine the role of genetics in the control of embolism in this species. Conductivity and tree-ring's microdensity variables (ring width: RW, mean ring density: MRD, minimum ring density: MID and maximum ring density: MAD) were compared in growth rings in all three clones during a typical year (2002) vs. an extremely dry year (2003). A new method was developed in order to assess axial hydraulic specific conductivity (Ks) within tree rings. The results show that branches are more resistant to embolism than stems, and that there are significant differences in embolism resistance among the clones between the two sites. Ks varied between years, sites and clones but the site exerted the most significant effect. Lartimache (more humid site during 2003) trees showed substantially higher Ks than those inhabiting Chassenoix (strongly affected by the 2003 heat and drought wave site). Wood analysis showed a significant year effect for all ring variables and a significant clone effect for all ring variables except for MAD, while the site effect was significant for MRD and MAD. The existence of a genetic control for the study traits indicates that Douglas-fir populations introduced in France may have a selection potential to face extreme climate events like the 2003 heat and drought wave.

The genetic control of tree ring growth in Douglas-fir in response to the drought and heat-wave that occurred in 2003 in Europe was studied with microdensity profiles in three clonal experiments located in three different French regions. The drought and heat-wave significantly affected Douglas-fir wood formation. The Chassenoix site (Northeast of Massif-Central) was more severely affected that the other two: the 2003 year-ring was narrower and less dense than in the other sites and than the previous (2002) and following (2004) year-rings in the same site: ring growth stopped earlier and latewood did not develop completely. The year-rings 2004 and 2002 were very similar in this site. There was a significant genetic control for all ring parameters in the three sites and during the three years. The heritability was highly variable between years and among sites, without any clear pattern in this variability, except in Chassenoix where it was slightly lower in the 2003 year-ring. Variables measuring the response of trees to the 2003 event, i.e., the difference in ring width between 2002 and 2003, or between 2003 and 2004, showed a very variable degree of genetic control, from very low to relatively high. Douglas-fir seemed plastic enough to acclimate to the drought and heat-wave and then to recover during 2004. Furthermore the level of heritability estimated demonstrates that Douglas-fir has an adaptive potential that could be useful for multi-generation long-term response., La réponse du douglas à la canicule de 2003 en France a été étudiée à l'aide de profils microdensitométriques obtenus sur des arbres de 3 tests clonaux situés dans 3 régions différentes. La canicule a significativement affecté la formation du bois du douglas. Les arbres du site de Chassenoix, situé dans le Morvan, ont réagi plus fortement que ceux des 2 autres : le cerne de l'année de la canicule est plus étroit et moins dense que le même cerne dans les 2 autres sites et plus étroit et moins dense que les cernes immédiatement antérieur (2002) et postérieur (2004) dans le même site ; la formation du bois s'est arrêtée plus tôt et le bois final ne s'est pas complètement développé. À Chassenoix, le cerne de l'année 2004 ressemble plus au cerne 2002 qu'au cerne 2003, ce qui traduit une récupération. Nous mettons en évidence un contrôle génétique significatif pour toutes les variables intra-cernes dans les 3 sites, pour les 3 années 2002, 2003 et 2004. Les héritabilités sont très variables entre caractères, sites et années, sans structure particulière, sauf à Chassenoix où ces héritabilités sont légèrement plus faibles durant l'année de la canicule. Des variables décrivant la réponse des arbres entre 2002 et 2003 puis 2003 et 2004 sont très irrégulièrement contrôlées génétiquement, avec des héritabilités allant de 0 à près de 0,5. Le douglas semble avoir été suffisamment plastique pour s'acclimater à la sécheresse et canicule puis pour récupérer en 2004 une croissance proche de celle de 2002. De plus, son potentiel génétique démontré par le niveau d'héritabilité estimé lui donne également une capacité adaptative multi-génération à plus long terme.

International audience; The genetic control of tree ring growth in Douglas-fir in response to the drought and heat-wave that occurred in 2003 in Europe was studied with microdensity profiles in three clonal experiments located in three different French regions. The drought and heat-wave significantly affected Douglas-fir wood formation. The Chassenoix site (Northeast of Massif-Central) was more severely affected that the other two: the 2003 year-ring was narrower and less dense than in the other sites and than the previous (2002) and following (2004) year-rings in the same site: ring growth stopped earlier and latewood did not develop completely. The year-rings 2004 and 2002 were very similar in this site. There was a significant genetic control for all ring parameters in the three sites and during the three years. The heritability was highly variable between years and among sites, without any clear pattern in this variability, except in Chassenoix where it was slightly lower in the 2003 year-ring. Variables measuring the response of trees to the 2003 event, i.e., the difference in ring width between 2002 and 2003, or between 2003 and 2004, showed a very variable degree of genetic control, from very low to relatively high. Douglas-fir seemed plastic enough to acclimate to the drought and heat-wave and then to recover during 2004. Furthermore the level of heritability estimated demonstrates that Douglas-fir has an adaptive potential that could be useful for multi-generation long-term response.; La réponse du douglas à la canicule de 2003 en France a été étudiée à l'aide de profils microdensitométriques obtenus sur des arbres de 3 tests clonaux situés dans 3 régions différentes. La canicule a significativement affecté la formation du bois du douglas. Les arbres du site de Chassenoix, situé dans le Morvan, ont réagi plus fortement que ceux des 2 autres : le cerne de l'année de la canicule est plus étroit et moins dense que le même cerne dans les 2 autres sites et plus étroit et moins dense que les cernes immédiatement antérieur (2002) et postérieur (2004) dans le même site ; la formation du bois s'est arrêtée plus tôt et le bois final ne s'est pas complètement développé. À Chassenoix, le cerne de l'année 2004 ressemble plus au cerne 2002 qu'au cerne 2003, ce qui traduit une récupération. Nous mettons en évidence un contrôle génétique significatif pour toutes les variables intra-cernes dans les 3 sites, pour les 3 années 2002, 2003 et 2004. Les héritabilités sont très variables entre caractères, sites et années, sans structure particulière, sauf à Chassenoix où ces héritabilités sont légèrement plus faibles durant l'année de la canicule. Des variables décrivant la réponse des arbres entre 2002 et 2003 puis 2003 et 2004 sont très irrégulièrement contrôlées génétiquement, avec des héritabilités allant de 0 à près de 0,5. Le douglas semble avoir été suffisamment plastique pour s'acclimater à la sécheresse et canicule puis pour récupérer en 2004 une croissance proche de celle de 2002. De plus, son potentiel génétique démontré par le niveau d'héritabilité estimé lui donne également une capacité adaptative multi-génération à plus long terme.

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International audience

Phenotypic plasticity and canalization are important topics in quantitative genetics and evolution. Both concepts are related to environmental sensitivity. The latter can be modeled using a model with genetically structured environmental variance. This work reports the results of a genetic analysis of adult weight in the snail Helix aspersa. Several models of heterogeneous variance are fitted using a Bayesin, MCMC approach. Exploratory analyses using posterior predictive model checking and model comparisons based on the deviance information criterion favor a model postulating a genetically structured heterogeneous environmental variance. Our analysis provides a strong indication of a positive genetic correlation between additive genetic values affecting the mean and those affecting environmental variation of adult body weight. The possibility of manipulating environmental variance by selection is illustrated numerically using estimates of parameters derived from the snail data set. Udgivelsesdato: DEC Phenotypic plasticity and canalization are important topics in quantitative genetics and evolution. Both concepts are related to environmental sensitivity. The latter can be modeled using a model with genetically structured environmental variance. This work reports the results of a genetic analysis of adult weight in the snail Helix aspersa. Several models of heterogeneous variance are fitted using a Bayesin, MCMC approach. Exploratory analyses using posterior predictive model checking and model comparisons based on the deviance information criterion favor a model postulating a genetically structured heterogeneous environmental variance. Our analysis provides a strong indication of a positive genetic correlation between additive genetic values affecting the mean and those affecting environmental variation of adult body weight. The possibility of manipulating environmental variance by selection is illustrated numerically using estimates of parameters derived from the snail data set.

DOI:10.1007/s00122-003-1196-1; absent

Seed weight and oil content are important properties of cultivated sunflower under complex genetic and environmental control, and associated with morphological and developmental characteristics such as plant height or flowering dates. Using a genetic map with 290 markers for a cross between two inbred sunflower lines and 2 years of observations on F3 families, QTL controlling seed weight, oil content, plant height, plant lodging, flowering dates, maturity dates and delay from flowering to maturity were detected. QTL detected were compared between the F2 and F3 generations and between the 2 years of testing for the F3 families in 1997 and 1999. Some of the QTL controlling seed weight overlapped with those controlling oil content. Several other co-localisations of QTL controlling developmental or morphological characteristics were observed and the relationships between the traits were also shown by correlation analyses. The relationships between all these traits and with resistance to Sclerotinia sclerotiorum and Diaporthe helianthi are discussed.

International audience