Variabilité de la croissance et de la qualité chez la pêche (Prunus persica L Batsch) et liaison entre croissance et qualité

— La croissance de la pêche a été décrite par un modèle de croissance déterministe à 2 phases. Les courbes de croissance cumulée et de vitesse de croissance de 120 fruits ont été comparées par analyse en composantes principales sur les paramètres du modèle. Les différences entre fruits sont importantes pendant la deuxième phase de croissance. Après récolte, les qualités gustative (composition biochimique) et commerciale (fermeté et coloration) de chaque fruit ont été analysées. Le pH est peu variable; l'acidité, l'indice réfractométrique et la teneur en sucres forment un ensemble de descripteurs intercorrelés qui séparent les fruits selon un gradient de qualité gustative et de fermeté auquel est liée la coloration jaune. Les autres paramètres de la coloration sont liés entre eux et sont non corrélés au groupe précédent. La relation entre croissance et qualité a été analysée par analyse factorielle des correspondances sur variables instrumentales. Les fruits mûrs précocement et ceux ayant un diamètre élevé à l'issue de la première phase ont des taches de couleur rouge violacé alors que l'orange et une chrominance plus élevée caractérisent les autres fruits. Les fruits ayant une deuxième phase de croissance importante et caractérisés par une vitesse maximale de croissance élevée et tardive sont plus sucrés, moins acides et ont une fermeté plus faible. La variation de la luminance n'est pas liée à celle de la croissance.— Variability of peach (Prunus Persica L Batsch) growth and quality, and relationships between growth and quality. The individual fruit growth of the peach (Suncrest cultivar), was studied by modelling growth curves based on cheek-diameter measurements. Our model assumed that peach fruit growth; was divided into 2 phases. The first one described the pit growth and the first part of the flesh growth; the second described the second part of the flesh growth (fig 1). The fit of the model was good (fig 2). The growth curves were compared using a particular principal component analysis (PCA) working on the model parameters. The differences between fruits were highest during the second phase (fig 3). The curves were grouped into classes using a cluster analysis running on PCA factors (fig 4). At harvest, quality data, ie pH, soluble solids, sucrose, reducing sugars, citric and malic acids, flesh firmness and skin color, were recorded. Quality variation among fruits was studied using a correspondence analysis and a cluster analysis. The pH did not vary (table I). Acidity, sugars and soluble solids were correlated and described a gustatory gradient (fig 5). Firmness and yellow color were correlated with this gradient. Other color descriptors were correlated to each other and described a coloration gradient which was independent from the gustatory one (fig 6). Four groups of peach fruits were individualized (figs 5, 6). For most quality descriptors, between-class differences were high (table II). The relationship between growth and quality was studied using a canonical correspondence analysis. The peach diameter in April was not correlated with quality (table IV). Growth was more correlated with gustatory quality and firmness than with coloration (tables I and III). Early mature fruits with a high cheek diameter at the end of the first phase had a large amount of purple. The other fruits had a large amount of orange and a high chrominance (fig 9). In fruits with both a significant second growth phase and a high and late maximal growth rate the highest soluble solids and sucrose content and the lowest citric acid content and firmness were found (fig 8). Luminance was not correlated with growth

Heritability of the queen brood post-capping stage duration in Apis mellifera mellifera L

The short duration of the post-capping stage of the honey bee is considered as a good trait to select for breeding honey bees resistant to Varroa jacobsoni. One way to operate is to apply this selection to queens, since this character is expressed in the 3 castes. To predict the efficiency of such a selection, we estimated: (1 ) the heritability of this character through daughter-queen to mother-queen regression and intra-class correlation in a population of Apis mellifera mellifera colonies in France; and (2) the regression between daughter-workers to mother-queens. The heritabilities obtained with these methods were 0.31 ± 0.10 and 0.22 ± 0.25 respectively. The worker capped period was positively correlated with the mother-queen period (r = 0.59), suggesting that queen selection could be efficient at obtaining workers with short capping durations. As the reduction of worker capping period can induce a decrease in the Varroa mite populations, selection for short-capping-duration queens to obtain Varroa-resistant strains is discussed

Heritability of the queen brood post-capping stage duration in Apis mellifera mellifera L

The short duration of the post-capping stage of the honey bee is considered as a good trait to select for breeding honey bees resistant to Varroa jacobsoni. One way to operate is to apply this selection to queens, since this character is expressed in the 3 castes. To predict the efficiency of such a selection, we estimated: (1 ) the heritability of this character through daughter-queen to mother-queen regression and intra-class correlation in a population of Apis mellifera mellifera colonies in France; and (2) the regression between daughter-workers to mother-queens. The heritabilities obtained with these methods were 0.31 ± 0.10 and 0.22 ± 0.25 respectively. The worker capped period was positively correlated with the mother-queen period (r = 0.59), suggesting that queen selection could be efficient at obtaining workers with short capping durations. As the reduction of worker capping period can induce a decrease in the Varroa mite populations, selection for short-capping-duration queens to obtain Varroa-resistant strains is discussed

Heritabilite de la duree d'operculation du couvain de reine chez Apis mellifera mellifera L.

National audienc

Vignoid, a plant-pathogen model to highlight the interactions between plant growth, powdery mildew, crop management and climate. A sensitivity analysis

National audienc

Using sensitivity analyses to identify and optimize key parameters of sharka management strategy

National audienc

Résistance de l'abeille domestique Apis mellifera à l'acarien parasite Varroa destructor : comportement et électroantennographie

International audienc

Evaluation of technical scenarios for the peach-brown rot system using a virtual fruit model simulating quality and storage potential

National audienceImproving fruit quality while reducing pesticide and water use supports both consumers’ requirements and environmental and health concerns. This objective promotes some alternative technical scenarios that use more cultural than chemical control for pest management. Our study focused on the peach-brown rot system (Monilinia laxa). It aims at determining sets of cultural options providing an optimal trade-off between revenue build-up, consumers’ requirements and environmental impacts. We used a modelling approach to simulate technical scenarios by using a virtual fruit model describing the seasonal changes in peach fruit quality traits during final swelling under the influence of climatic, biotic and cultural factors. We defined 243 virtual scenarios based on agronomical and epidemiological inputs (time and intensity of thinning, irrigation, cultivar choice and disease control). Virtual scenarios were evaluated on a multi-criteria profile of performance integrating storage potential, organoleptic and environmental factors, according to different objectives of profitability, water saving and no pathogen entry (cuticular crack) on fruits. Scenarios including water stress during final swelling are promising while requiring an evolution of market standards