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Rain-induced fruit cracking is a major problem in sweet cherry cultivation. Basic research has been conducted to disentangle the physiological and mechanistic bases of this complex phenomenon, whereas genetic studies have lagged behind. The objective of this work was to disentangle the genetic determinism of rain-induced fruit cracking. We hypothesized that a large genetic variation would be revealed, by visual field observations conducted on mapping populations derived from well-contrasted cultivars for cracking tolerance. Three populations were evaluated over 7–8 years by estimating the proportion of cracked fruits for each genotype at maturity, at three different areas of the sweet cherry fruit: pistillar end, stem end, and fruit side. An original approach was adopted to integrate, within simple linear models, covariates potentially related to cracking, such as rainfall accumulation before harvest, fruit weight, and firmness. We found the first stable quantitative trait loci (QTLs) for cherry fruit cracking, explaining percentages of phenotypic variance above 20%, for each of these three types of cracking tolerance, in different linkage groups, confirming the high complexity of this trait. For these and other QTLs, further analyses suggested the existence of at least two-linked QTLs in each linkage group, some of which showed confidence intervals close to 5 cM. These promising results open the possibility of developing marker-assisted selection strategies to select cracking-tolerant sweet cherry cultivars. Further studies are needed to confirm the stability of the reported QTLs over different genetic backgrounds and environments and to narrow down the QTL confidence intervals, allowing the exploration of underlying candidate genes.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières; In crops, optimizing target traits in breeding programs can be fostered by selecting appropriate combinations of architectural traits which determine light interception and carbon acquisition. In apple tree, architectural traits were observed to be under genetic control. However, architectural traits also result from many organogenetic and morphological processes interacting with the environment. The present study aimed at combining a FSPM built for apple tree, MAppleT, with genetic determinisms of architectural traits, previously described in a bi-parental population. We focused on parameters related to organogenesis (phyllochron and immediate branching) and morphogenesis processes (internode length and leaf area) during the first year of tree growth. Two independent datasets collected in 2004 and 2007 on 116 genotypes, issued from a ‘Starkrimson’ × ‘Granny Smith’ cross, were used. The phyllochron was estimated as a function of thermal time and sylleptic branching was modeled subsequently depending on phyllochron. From a genetic map built with SNPs, marker effects were estimated on four MAppleT parameters with rrBLUP, using 2007 data. These effects were then considered in MAppleT to simulate tree development in the two climatic conditions. The genome wide prediction model gave consistent estimations of parameter values with correlation coefficients between observed values and estimated values from SNP markers ranging from 0.79 to 0.96. However, the accuracy of the prediction model following cross validation schemas was lower. Three integrative traits (the number of leaves, trunk length, and number of sylleptic laterals) were considered for validating MAppleT simulations. In 2007 climatic conditions, simulated values were close to observations, highlighting the correct simulation of genetic variability. However, in 2004 conditions which were not used for model calibration, the simulations differed from observations. This study demonstrates the possibility of integrating genome-based information in a FSPM for a perennial fruit tree. It also showed that further improvements are required for improving the prediction ability. Especially temperature effect should be extended and other factors taken into account for modeling GxE interactions. Improvements could also be expected by considering larger populations and by testing other genome wide prediction models. Despite these limitations, this study opens new possibilities for supporting plant breeding by in silico evaluations of the impact of genotypic polymorphisms on plant integrative phenotypes.

The genetic relationships between behavior and digestive efficiency were studied in 860 chickens from a cross between two lines divergently selected on digestive efficiency. At 2 weeks of age each chick was video-recorded in the home pen to characterize general activity and feeding behavior. Tonic immobility and open-field tests were also carried out individually to evaluate emotional reactivity (i.e. the propensity to express fear responses). Digestive efficiency was measured at 3 weeks. Genetic parameters of behavior traits were estimated. Birds were genotyped on 3379 SNP markers to detect QTLs. Heritabilities of behavioral traits were low, apart from tonic immobility (0.17–0.18) and maximum meal length (0.14). The genetic correlations indicated that the most efficient birds fed more frequently and were less fearful. We detected 14 QTL (9 for feeding behavior, 3 for tonic immobility, 2 for frequency of lying). Nine of them co-localized with QTL for efficiency, anatomy of the digestive tract, feed intake or microbiota composition. Four genes involved in fear reactions were identified in the QTL for tonic immobility on GGA1.

Chantier qualité GA; All salmonid species investigated to date have been characterized with a male heterogametic sex-determination system. However, as these species do not share any Y-chromosome conserved synteny, there remains a debate on whether they share a common master sex-determining gene. In this study, we investigated the extent of conservation and evolution of the rainbow trout (Oncorhynchus mykiss) master sex-determining gene, sdY (sexually dimorphic on the Y-chromosome), in 15 different species of salmonids. We found that the sdY sequence is highly conserved in all salmonids and that sdY is a male-specific Y-chromosome gene in the majority of these species. These findings demonstrate that most salmonids share a conserved sex-determining locus and also strongly suggest that sdY may be this conserved master sex-determining gene. However, in two whitefish species (subfamily Coregoninae), sdY was found both in males and females, suggesting that alternative sex-determination systems may have also evolved in this family. Based on the wide conservation of sdY as a male-specific Y-chromosome gene, efficient and easy molecular sexing techniques can now be developed that will be of great interest for studying these economically and environmentally important species.

International audience; Genetically determined differences among honeybee workers are known to contribute to task specialisation. To investigate the genetic component of olfactory learning we used proboscis extension conditioning to record individual performance, and a patriline-level analysis to separate the variance in learning performance into its different components. We found that the among-patriline within-colony component (solely genetic) explained 11.2% of the variance in acquisition performance and 6.5% of the variance in resistance to extinction. While environmental effects appeared to be the main source of variation, our results confirm that olfactory learning has a significant genetic basis. If colonies benefit from genetic differences among workers in task expression thresholds, colonies might also benefit from genetic differences in cognitive performance among workers by influencing task performance.

The management of gastrointestinal strongyle infestations in ruminants relies mostly on anthelmintics. Only three chemical families are available, and gastrointestinal strongyles resistance is increasing. The resistance mechanisms are relatively well known for benzimidazoles (involving one gene with two alleles), whereas the genetic determinism of the resistance to macrocyclic lactones or imidazothiazoles (levamisole) is still poorly understood, but probably involves multigenic regulation. A double approach (candidate genes and transcriptomic) is proposed for levamisole resistance and the first results are presented. It is very important to understand resistance mechanisms to reduce their occurrences. Examples with benzimidazoles are presented to describe interactions between the type of genetic mechanism and the speed with which resistance appears and expands, the efficacy of selective pressure by treatments, and the role of refugia., La gestion des infestations du tube digestif par les strongles chez les ruminants est essentiellement assurée par les traitements anthelminthiques. Seules trois familles chimiques sont disponibles et des phénomènes de résistance à ces produits sont apparus chez les strongles gastro-intestinaux. Les mécanismes de résistance concernant la famille des benzimidazoles sont relativement bien établis (un gène avec deux allèles est impliqué), alors que pour la famille des lactones macrocycliques ou celle des imidazothiazoles (lévamisole), les déterminismes génétiques, encore peu connus, sont sans doute multigéniques. Une double approche («gènes candidats» et transcriptomique) est proposée pour le lévamisole et les premiers résultats sont présentés. La compréhension des mécanismes d’action est très importante pour tenter de réduire l’apparition de résistance. Des exemples concernant les benzimidazoles sont utilisés pour décrire l’interaction entre le type de mécanisme de résistance et la vitesse d’apparition et de diffusion de la résistance, l’efficacité des pressions sélectives par les traitements et le rôle des refuges., Cabaret Jacques, Charvet Claude, Fauvin Aymeric, Boudsocq-Silvestre Anne, Sauve Christine, Cortet Jacques, Neveu Cédric. Strongles du tractus digestif des ruminants : mécanismes de résistance aux anthelminthiques et conséquences sur leur gestion. In: Bulletin de l'Académie Vétérinaire de France tome 162 n°1, 2009. pp. 33-38.

Highlight This research successfully used image-based spectral indices acquired in the field to assess variability of response to drought in a tree mapping population and to detect the related genetic determinisms., Genetic studies of response to water deficit in adult trees are limited by low throughput of the usual phenotyping methods in the field. Here, we aimed at overcoming this bottleneck, applying a new methodology using airborne multispectral imagery and in planta measurements to compare a high number of individuals. An apple tree population, grafted on the same rootstock, was submitted to contrasting summer water regimes over two years. Aerial images acquired in visible, near- and thermal-infrared at three dates each year allowed calculation of vegetation and water stress indices. Tree vigour and fruit production were also assessed. Linear mixed models were built accounting for date and year effects on several variables and including the differential response of genotypes between control and drought conditions. Broad-sense heritability of most variables was high and 18 quantitative trait loci (QTLs) independent of the dates were detected on nine linkage groups of the consensus apple genetic map. For vegetation and stress indices, QTLs were related to the means, the intra-crown heterogeneity, and differences induced by water regimes. Most QTLs explained 15−20% of variance. Airborne multispectral imaging proved relevant to acquire simultaneous information on a whole tree population and to decipher genetic determinisms involved in response to water deficit.

There are different strategies for producing fodder crops without irrigation under Mediterranean climate conditions. One strategy is to avoid the drought period by using annual plants such as cereals or Italian ryegrass. Another strategy is to use perennial forage species highly resistance to drought such as Dactylis glomerata or Festuca arundinaceae. The advantage of the second strategy is a rapid growth when favourable conditions come back after summer and good ground cover, which limits erosion. Summer dormancy, defined as an absence of growth in summer despite irrigation, is a very effective adaptation to drought which has been observed in cocksfoot. Nevertheless, summer dormancy in cocksfoot is associated with low vegetative productivity. The objective of this study is to analyse the genetic and eco-physiological determinisms of summer dormancy and vegetative growth in cocksfoot. For this purpose, the progeny between a summer dormant genotype from the variety Kasbah and a summer active genotype from the variety Medly is studied. The first results show that despite an expected negative correlation (r = −0.40) between summer dormancy and vegetative plant growth, genotypes exist with the same summer dormancy level as the genotype of Kasbah and a higher vegetative productivity than the genotype of Medly. These results are promising for the development of new cocksfoot varieties combining both summer dormancy and high vegetative productivity. The genomic regions implied in the variation of these traits are under study and should be useful for breeding.

In apple (Malus x domestica Borkh), as in many fruiting crops, fruit maintenance vs abscission is a major criteria for production profitability. Growers routinely make use of chemical thinning agents to control total fruit load. However, serious threats for the environment lead to the demand for new apple cultivars with self-thinning properties. In this project, we studied the genetic determinism of this trait using a F1 progeny derived from the cross between the hybrid INRA X3263, assumed to possess the self-thinning trait, and the cultivar ‘Belre`ne’. Both counting and percentage variables were considered to capture the fruiting behaviour on different shoot types and over three consecutive years. Besides low to moderate but significant genetic effects, mixed models showed considerable effects of the year and the shoot type, as well as an interaction effect. Year effect resulted mainly from biennial fruiting. Eight Quantitative Trait Locus (QTL) were detected on several linkage groups (LG), either independent or specific of the year of observation or the shoot type. The QTL with highest LOD value was located on the top third of LG10. The screening of three QTL zones for candidate genes revealed a list of transcription factors and genes involved in fruit nutrition, xylem differentiation, plant responses to starvation and organ abscission that open new avenues for further molecular investigations. The detailed phenotyping performed revealed the dependency between the self-thinning trait and the fruiting status of the trees. Despite a moderate genetic control of the self-thinning trait, QTL and candidate genes were identified which will need further analyses involving other progenies and molecular investigations.

An indirect phenotyping method was developed in order to estimate the susceptibility of rubber tree clonal varieties to Corynespora Leaf Fall (CLF) disease caused by the ascomycete Corynespora cassiicola. This method consists in quantifying the impact of fungal exudates on detached leaves by measuring the induced electrolyte leakage (EL%). The tested exudates were either crude culture filtrates from diverse C. cassiicola isolates or the purified cassiicolin (Cas1), a small secreted effector protein produced by the aggressive isolate CCP. The test was found to be quantitative, with the EL% response proportional to toxin concentration. For eight clones tested with two aggressive isolates, the EL% response to the filtrates positively correlated to the response induced by conidial inoculation. The toxicity test applied to 18 clones using 13 toxinic treatments evidenced an important variability among clones and treatments, with a significant additional clone x treatment interaction effect. A genetic linkage map was built using 306 microsatellite markers, from the F1 population of the PB260 x RRIM600 family. Phenotyping of the population for sensitivity to the purified Cas1 effector and to culture filtrates from seven C. cassiicola isolates revealed a polygenic determinism, with six QTL detected on five chromosomes and percentages of explained phenotypic variance varying from 11 to 17%. Two common QTL were identified for the CCP filtrate and the purified cassiicolin, suggesting that Cas1 may be the main effector of CCP filtrate toxicity. The CCP filtrate clearly contrasted with all other filtrates. The toxicity test based on Electrolyte Leakage Measurement offers the opportunity to assess the sensitivity of rubber genotypes to C. cassiicola exudates or purified effectors for genetic investigations and early selection, without risk of spreading the fungus in plantations. However, the power of this test for predicting field susceptibility of rubber clones to CLF will have to be further investigated.

Heat shocks effective for the production of triploid brown trout (Salmo trutta ) were optimized: 28 °C shocks lasting 10 to 15 minutes and applied 5 minutes after fertilization induce very high rates of triploidy (close to 100%) without causing much mortality; they can therefore be proposed for mass production of triploid brown trout. Female homogamety in that species is also demonstrated from analysis of gynogenetic progenies and progenies of sex-inverted females. Although the efficiency of masculinizing hormonal treatments requires further improvement, production of all-female sterile populations is now possible in this species promising for European sea-farming.

La lignée «75/59» sélectionnée en Allemagne fédérale à partir du croisement «Atom» x «Bubjekosoko» montre une aptitude à la parthénocarpie naturelle, facultative, de niveau élevé, s’exprimant à toute époque de l’année. Neuf essais ont été réalisés, dans des conditions variées (serre verre ou plastique, chauffée ou froide, champ) à des époques de l’année différentes. Après un traitement avec castration sans pollinisation, les fruits sans graines qui se développent sont d’aspect et de poids comparables à ceux issus de fleurs pollinisées manuellement, quels que soient le type de culture et l’époque de l’année, à l’exception d’un essai où les fruits sont plus petits, ce qui traduit une sensibilité de l’expression de la parthénocarpie aux facteurs du milieu, sans que l’on puisse savoir, dans ce cas précis, quels facteurs du milieu sont en cause. Des fleurs de «75/59» laissées en fécondation libre donnent en mélange des fruits sans graines (de 34 à 94% dans nos essais) et des fruits avec graines. Quand il y a ainsi compétition entre fruits avec ou sans graines à l’intérieur d’un bouquet et/ou d’une plante, celle-ci se fait au détriment des fruits sans graines, qui sont alors significativement plus petits que les fruits avec graines issus du même traitement. La parthénocarpie de «75/59» est récessive. Les tests d’allélisme ont montré qu’elle n’était due ni au gène pat (parthenocarpic) présent chez «Montfavet 191», ni au gène pat-2 de «Severianin». La parthénocarpie de «75/59» serait sous le contrôle de 3 gènes récessifs au moins, et plus probablement 4 ou 5 gènes, dont nous faisons l’hypothèse qu’ils sont indépendants et à action additive. Ces résultats sont discutés et comparés avec ceux obtenus par d’autres auteurs., Line "75/59", bred in West Germany from the cross between Atom" x "Bubjekosoko" shows an aptitude for high level, natural but facultative parthenocarpy at all times of the year. Nine experiments were carried out under varying conditions (glass or plastic houses, heated or unheated, open field) and at different periods of the year. After treatment involving emasculation without pollination, the appearance and weight of the seedless fruits which developed were comparable to those of the seeded fruits issued from hand-pollinated flowers, regardless of cultivation type or period of year. The findings for one experiment differed, in that the seedless fruits were smaller this indicates susceptibility of parthenocarpy expression to environmental factors. Notwithstanding, in the present case, it is not possible to identify which environmental factors are involved. Open pollinated flowers of "75/59" set a mixture of both seedless fruits (from 34 to 94% in our experiments) and seeded fruits. When both seeded and seedless fruits compete on a single inflorescence andlor plant, the seedless fruits suffer and in this case are significantly smaller than the seeded fruits issued from the same treatment. The parthenocarpy of "75/59" is recessive. The allelism tests revealed that this is not due to the pat (parthenocarpic) gene present in "Montfavet 191" neither is it due to the pat-2 gene in "Severianin". The parthenocarpy of "75/59" would appear to be controlled by 3 recessive genes at least, and more probably, by 4 or 5 genes. We are of the opinion that these genes act independantly and that their effect is cumulative. These results are discussed and compared to those obtained by other authors.

Pour étudier le déterminisme génétique de la résistance à des conditions de milieu défavorables, et notamment tester l’hypothèse qu’elle est due essentiellement à l’action de gènes non additifs, nous avons utilisé le caractère « ponte de femelles vierges de Tribolium castaneum du 7e au 11e jour (première période) et du 11e au 15e jour (deuxième période) de la vie adulte, les animaux étant placés dans le milieu d’élevage standard (S) ou dans un milieu fortement dégradé (D). Dans une première expérience, nous avons créé trois groupes constitué chacun de 600 femelles puis de 3 filles de chacune dans la succession de milieux suivante, respectivement S.S., S.D., D.D. (première et deuxième période). La ponte en milieu dégradé est inférieure de 60 p. 100 à celle en milieu standard. L’héritabilité n’est pas modifiée significativement par la période ou le milieu de ponte. Par contre, quelle que soit la période ou le milieu, l’héritabilité calculée par corrélation entre les 3 pleines sœurs (0,33) est significativement supérieure à celle calculée par régression des filles sur la mère (0,22) ce qui peut être dû à des effets génétiques non additifs et /ou un effet milieu commun chez les filles. Dans une deuxième expérience, nous avons sélectionné les animaux à l’aide d’un indice avec restriction permettant d’augmenter la ponte en milieu dégradé (Pd) en deuxième période sans modifier celle en milieu standard (Ps) en première période. Si, comme prévu, la sélection familiale n’a eu d’effet ni sur Ps, ni sur Pd, la sélection réciproque récurrente, contrairement à nos hypothèses, n’a eu aucun effet sur Pd et a fait augmenter Ps. Les deux principales conclusions de ces expériences sont, d’une part que les gènes à effet additif sont identiques en milieu standard ou dégradé, d’autre part qu’il est impossible de conclure catégoriquement à l’existence de gènes de résistance agissant par dominance., With the aim of studying the genetic determinism of the resistance to unfavourable environmental conditions and in particular to verify the hypothesis according to which it is mainly depending on the action of non additive genes, we used the trait « egg laying of virgin females of Tribolium Castaneum » from day 7 to 11 (first period) and from day 11 to 15 (second period) of adult life. The animals were kept either in a standard medium (S) or in a highly conditioned medium (C). The first experiment involving three groups of six hundred females plus three daughters of each was made in the following media, S-S, S-C, C-C (first and second period). The egg laying in the conditioned medium was 60 p. 100o lower than in the standard medium. The heritability was not significantly affected by the egg laying period or environment. Conversely, the heritability calculated by the correlation between the three full sibs (0.33) significantly exceeded that calculated by daughter-dam regression (0.22). This might be due to non additive genetic effects and /or to common environmental effect in the daughters. In the second experiment, we selected the animals using an index with restriction to increase the egg laying in conditioned medium (Lc), in the second period, without modifying that of the standard medium (Ls), in the first period. As foreseen, the family selection did not affect either Ls or Lc whereas the reciprocal recurrent selection, contrary to our hypothesis, had no influence on Lc and increased Ls. It may be concluded from these experiments on the one hand that the additive genes are the same in standard or conditioned media and on the other that it is impossible to draw a definitive conclusion on the existence of resistance genes acting by dominance.

International audience; An analysis of the variation of the number of pyloric caeca in hatchery-reared brown trout showed that :- the sex of the animals has no significant influence;- an important part of variability is caused by additive genetic factors (approximate heritability 0.4);[br/]- there is a maternal effect which inheres to the size of eggs; alevins hatched from large eggs tend to have high numbers of caeca (correlation + 0,5)- lastly, the joined action of that maternal factor and other genetic and environmental factors apparently includes interactive effects; further studies on that point would be useful.; L'analyse de la variation du nombre de caeca pyloriques chez la Truite fario élevée en pisciculture a montré que :- le sexe des animaux n'a aucune influence significative;- une part importante de variabilité est d'origine génétique additive (héritabilité approximative 0,4);- il existe un effet maternel inhérent à la taille des oeufs, les alevins issus de gros aeufs tendant à avoir des nombres de caeca élevés (corrélation +0,5);- enfin, l'action conjointe de ce facteur maternel et des autres facteurs génétiques et environnementaux semble comporter des effets interactifs dont l'étude plus approfondie serait utile.