Search

International audience

Proceedings of the 7. International Conference on Integrated Fruit Production at Avignon (France), 27-30/10/2008; International audience; Improving 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.

International audience

International audience

National audience

National audience

International audience; Aims: This study aimed at assessing the functional linkage among seed traits (including seed number, seed weight), berry growth and berry sugar and acid concentration by adapting a mathematical growth function with parameters having biological importance. Methods and results: The evolution of berry diameter of Cabernet- Sauvignon was satisfactorily fitted to a bi-phasic growth function with six parameters. Correlations between the parameters and berry characteristics, including time of skin color change, seed number, seed weight, final berry size and chemical composition, were analyzed. Results showed that berry growth within a bunch deviated according to seed number, which positively related to parameters describing diameter increment (D1) and initial growth rate (GRini) during the first rapid growth phase, but not related to any parameters involved in the second growth phase. The time of skin color change was negatively associated with mean seed weight, and coincided with growth parameter DABmax that denotes the time when growth rate is maximum during the second rapid growth phase. Sugar concentration was negatively correlated to final berry fresh weight (BFW), seed fresh weight (SFW), GRini and diameter increment during the second rapid growth phase (D2). Path analysis further revealed that the negative effects of SFW and D2 were indirectly mediated via BFW and GRini. Conclusions: We thus conclude that seed affects berry growth and exerts its influence only during the first growth phase via modifying the parameters D1 and GRini. The time of colour change is also affected by seed, and might not be a good indicator of growth restoration after the lag phase. Sugar concentration is linked to final berry size, specific berry growth parameters and seed weight, for the last mainly in an indirect manner. Significance of the study: This study, integrating the analysis of berry growth and composition with a mathematical growth function, provides a valuable approach for deeper understanding of the functional associations among seed traits, berry growth and berry sugar and acid concentration at the berry level. Keywords: fruit growth analysis, seed, sugar, Vitis

National audience

International audience; The effects of cuticular crack surface area and inoculum density on the infection of nectarine fruits by conidia of Monilinia laxa were studied using artificial inoculations with conidial suspensions and dry airborne conidia during the 2004 and 2005 seasons, respectively. Additionally, the effect of ambient humidity on fruit infection was evaluated in the 2005 experiment. An exploratory analysis indicated that (i) ambient humidity did not significantly explain the observed variability of data, but that (ii) the incidence of fruit infection increased both with increasing inoculum density and increasing surface area of cuticular cracks. The product of these two variables represented the inoculum dose in the cracks, and was used as a predictor of fruit infection in the model. Natural infection in the orchard was observed to increase throughout the season in both 2004 and 2005. The relationship between the probability of fruit infection by M. laxa and the artificially inoculated dose in the cuticular cracks was well described by a logistic regression model once natural inoculum density was taken into account (pseudo R2 = 65%). This function could be helpful for estimating the risk of fruit infection at harvest based on fruit size and natural inoculum density

National audience

Contact: wery@supagro.inra.fr; National audience

National audience; Integrated Fruit Production (IFP) calls for an adaptation of production processes to improve crop quality and environmental safety. This approach gives priority to alternative methods of pest control. Our study investigates the potential of management scenarios that integrate chemical, biological (inundative release of Harmonia axyridis ladybirds) and cultural (nitrogen fertilization and winter pruning) pest control methods for the peach tree-aphid system. We used a modeling approach to address this question. We defined 108 management scenarios, which were based on theoretical pest control strategies combined with control variables relative to pest control and cultural practices. Then, we performed model simulations of these scenarios and studied the relationships between control variables and model outputs referring to agronomical, economical, sanitary (pest), and sustainability performance. Results showed that ‘agronomical performance’ was largely controlled by ‘agronomical practices’, while ‘pest performance’ was largely controlled by ‘pest control practices’.

International audience

International audience

International audience; The number of cells and the mean cell volume in the mesocarps of fruits from peach genotypes with different percentages of the genome of Prunus davidiana, a wild, related, species, were evaluated. The mesocarp mass varied greatly between the four groups of genotypes. The mean cell volume and the number of cells were negatively correlated within each group. This correlation can be interpreted as a relationship of competition between cells. In order to describe the type of competition in the different groups, we tried to adjust a model of competition for resources proposed by Lescourret and Génard (Ecoscience 10:334–341, 2003). To estimate the values of the three parameters of the model for the different groups, we applied model selection. Within nested models, we identified a single best model with six parameter values. This model was roughly accurate, but it allowed us to describe the general relationship for each group. The parameter values revealed a strong and under-compensating density-dependence effect for all groups. The percentage of P. davidiana genome appeared to influence the maximal number of cells and the strength of the competition, but no effect was found on the maximal mean volume of cells

International audience

Carbon allocation within a plant depends on complex rules linking source organs (mainly shoots) and sink organs (mainly roots and fruits). The complexity of these rules comes from both regulations and interactions between various plant processes involving carbon. This paper presents these regulations and interactions, and analyses how agricultural management can influence them. Ecophysiological models of carbon production and allocation are good tools for such analyses. The fundamental bases of these models are first presented, focusing on their underlying processes and concepts. Different approaches are used for modelling carbon economy. They are classified as empirical, teleonomic, source-sink or based on transport and chemical/biochemical conversion concepts. These four approaches are presented with a particular emphasis on the regulations and interactions between organs and between processes. The role of plant architecture in carbon partitioning is also discussed and the interest of coupling plant architecture models with carbon allocation models is highlighted. The link between roots, shoots and reproductive compartments is analysed through a model developed for peach trees, describing carbon transfer within the plant, and based on source-sink and Munch transport theory. On this basis, the consequences of fruit load or plant pruning on fruit and vegetative growth can be evaluated.

International audience; Fruit quality at harvest is a complex trait, including size, overall flavour (taste and texture) and visual attractiveness (colour, shape), which depend on both genotype and environment. The improvement of fresh product quality is slowed down by this complexity. It is expected that the development of process-based models and their integration in ecophysiological models should facilitate quality management, provided that integration properly accounts for interactions among biological processes. Here we describe some process-based models developed on peach and tomato fruits, which predict final fruit size and composition in primary compounds. Perspectives of integration of such models are discussed.

National audience

The effects of light environment, leaf-to-fruit ratio, and 'initial' fruit size on processes involved in mango fruit quality were investigated at the branch level, for a better understanding of the heterogeneity of mango fruit quality within a tree. This approach required analysing (i) the source/sink balance at the branch level, (ii) the water relations between branch and fruit, and (iii) the accumulation of sugars, organic acids and minerals in the flesh. Three models were derived from experimental data. They simulated fruit growth in water and dry matter content and storage of biochemical and mineral compounds in fruit flesh. The changes introduced in the original versions of these models are detailed. These models were integrated in a global model predicting individual fruit size and gustatory quality (i.e. sweetness and sourness). The global model of mango quality has been tested satisfactorily against experimental data of fruit size, sweetness and sourness. The global model at the branch level was then scaled up at the tree level. It predicted accurately the variability of mango quality observed within a tree by taking into account the fruit light environment, the 'initial' fruit size and the leaf-to-fruit ratio. The model was able to predict the distribution of fruit size and harvest date of a tree using as inputs the full bloom date of the orchard and distributions of 'initial' fruit size, light environment branches and competition for assimilate supply. These simulations showed that this model could have practical applications to manage fruit quality and plan harvest and marketing.

Fruit quality at harvest is a complex trait, including size, overall flavour (taste and texture) and visual attractiveness (colour, shape), which depend on both genotype and environment. The improvement of fresh product quality is slowed down by this complexity. It is expected that the development of process-based models and their integration in ecophysiological models should facilitate quality management, provided that integration properly accounts for interactions among biological processes. Here we describe some process-based models developed on peach and tomato fruits, which predict final fruit size and composition in primary compounds. Perspectives of integration of such models are discussed.

A theory of fruit climacteric ethylene emission was developed and used as the basis of a simulation model called ETHY. According to the theory, the biosynthetic pathway of ethylene is supplied by ATP and is regulated by 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase. The conjugation of ACC with malonate to form MACC was taken into account as a way to decrease the availability of ACC. Because of the seasonal increase of fruit volume, the dilution of biochemical compounds used in ETHY was taken into account. Finally, the ethylene diffusion across the skin was considered. The theory took into account the effect of temperature and O(2) and CO(2) internal concentrations on ethylene. The model was applied to peach (Prunus persica) fruit over 3 years, several leaf:fruit ratios, and irrigation conditions. An adequate ethylene increase was predicted without considering any increase in respiration during the ripening period, which suggests that the respiratory climacteric may not be required for ripening. Another important result of this study is the high sensitivity of ETHY to the parameters involved in the calculation of ACC oxidase and ACC synthase activities, ATP production, and skin surface and permeability. ETHY was also highly sensitive to changes in fruit growth and temperature.

International audience

To determine the effects of assimilate and water supply on the determination of mango fruit quality, the seasonal variations of minerals, acids and sugar concentrations were investigated over two successive years. To manipulate the assimilate supply, selected branches were girdled to provide ratios of 10, 25, 50 and 100 leaves per fruit. Irrigation was managed to provide two types of water supply treatments. Fruit growth rate was greater when increasing the leaf:fruit ratio. Structural dry matter content and total dry matter content of flesh were higher in fruit with higher leaf:fruit ratios. Treatments had no effect on the structural to total dry matter ratio of flesh. Potassium and magnesium to structural dry weight ratios were not affected by treatments, whereas the calcium to structural dry weight ratio was higher in the flesh of fruit grown under low leaf:fruit ratios. Low assimilate supply increased the ratios of malle and citric acid to structural dry weight. This treatment had little effect on acid concentrations. Glucose and fructose to structural dry weight ratios were higher when assimilate supply was lower. Low leaf:fruit ratios increased fructose concentration but not glucose concentration. Irrigation treatment strongly affected fructose concentration. Sucrose concentration, based either on structural dry matter or on fresh matter, was significantly increased by higher leaf-to-fruit ratios. When the fruit was close to maturity, levels of sucrose storage and starch breakdown were positively correlated with assimilate supply. Levels of starch breakdown were correlated with irrigation supply. The effects of these treatments on sugar concentrations may change fruit taste.

For the last 5 years, research has been undertaken on associations of coffee and shade trees in Central America to promote coffee agroforestry systems in the region and to improve coffee farmers' incomes through diversification (timber production), production of high quality coffee and payment of incentives for environmental services in order to compensate for the low coffee prices of recent years. Field measurements have been undertaken to study and model partitioning of light, nutrients and water between coffee and trees, and impacts of shade trees on microclimate, coffee physiology and quality. Farm surveys have also been done to study farmer coffee agroforestry practices and changes in agricultural management in face of the persistent coffee crisis. These results show that shade creates more favorable microclimatic conditions for coffee cultivation by decreasing leaf temperature of up to 4°C under sub-optimal conditions of low altitude (< 700 m) and by up to 2°C under optimal conditions (> 1100 m). Under sub-optimal conditions, the presence of shade trees reduces coffee heat stress, enhances coffee growth and productivity with an adequate shade level in the range of 20-40%. These results also show that coffee transpiration is lower under shade trees (Eucalyptus deglupta or Terminalia ivorensis) or artificial shade than in full sun. These results demonstrate that beneficial effects of shade are not limited to sub-optimal conditions as the presence of shade improves coffee quality, irrespective of the ecological conditions, via a lengthening of the maturation period of coffee berries (up to 6 weeks under shade trees in sub-optimal conditions, and up to 3-4 weeks under artificial shade in optimal conditions). This translates into better bean filling, larger bean size, improved biochemical composition and higher cup quality. Coffee beverage from sun-grown coffee is bitter and more astringent than that from shade-grown ones. Furthermore, beverage acidity and preference are higher for coffee produced under artificial shade or timber trees compared to full sun conditions. Consequently, shade trees improve both the productivity and quality under sub-optimal conditions. Under optimal conditions, the reduction of coffee productivity (~20%) observed with shade can be economically compensated by a decrease in alternate production pattern and a premium paid for higher coffee quality. The farm survey indicates that shade level and tree density are generally too high in coffee farms for a good compromise between an acceptable reduction in coffee productivity and a diversification of revenues from sales of timber products. Changes in farmers' practices vary according to ecological conditions and coffee prices at farm gate. In optimal conditions where high prices are rewarding coffee quality, the farmers remain strongly focalized on producing coffee, although cutting costs without compromising too much plantation productivity. On the other hand, the role of trees is been reinforced in sub-optimal lowlands as sales of timber are representing up to 80% of coffee incomes. These results highlight the fact that beneficial effects of shade are not limited to sub-optimal conditions and that payments for environmental services provided by coffee agroforestry systems are starting to take place in the Central America. Still, additional research is needed to model the effects of agroforestry practices on microclimate, resource partitioning, coffee physiology, productivity and quality in order to provide adequate recommendations for extension services and farmers on the selection and management of associated shade trees according to ecological conditions.

International audience

International audience

With the financial assistance of the European Union (ICA4-CT-2001-10071), research has been undertaken for the last 3 years on coffee and tree associations in Central America (www.casca-project.com). Its purpose is to promote coffee agroforestry systems in the region and to improve farmer's income through diversification (timber production), production of high quality coffee and payment of incentives for environmental services in order to compensate the current low coffee prices. Intensive measurements have been undertaken to model light and water partitioning between coffee and trees. The impact of shade trees on microclimate, coffee physiology and quality has also been investigated. Especially under sub-optimal conditions, the results show that tree shade creates more favorable microdimatic conditions for coffee and improves coffee photosynthesis. They demonstrate that coffee transpiration is lower under tree shade (Eucalyptus deglupta or Terminalia ivorensis) than in full sun. Nevertheless, they indicate that water competition can take place during the last weeks of the dry season. These results demonstrate that adequate shade (20-40%) decreases coffee productivity by 15-25%. However, this lower productivity can be financially compensated by an increased proportion of larger beans suitable for export and the premium paid for higher cup quality. Indeed, shade lengthens by up to 6 weeks the maturation of coffee berries resulting in better bean filling and beverage quality. These investigations indicate that modelling the effects of agroforestry practices on microclimate, resource partitioning, coffee physiology, productivity and quality is required to provide adequate recommendations for selecting and managing associated trees according to local ecological conditions. (Texte intégral)

International audience

International audience

International audience

A la Réunion, avec l'augmentation constante de la production de mangues, les professionnels des filières fruitières souhaiteraient une caractérisation plus complète de la qualité des fruits, qui ne se limiterait pas aux critères dits d'attractivité, afin de mieux maîtriser les différentes étapes de la qualité entre le verger et l'assiette. Chez le manguier, il existe une variabilité importante de la production et de la qualité des fruits au sein d'un même arbre. De nombreux critères (calibre, coloration, qualité gustative, et aromatique) sont reliés plus ou moins directement à la croissance du fruit. La croissance des fruits résulte de l'accumulation d'eau et d'assimilats carbonés. Elle est donc principalement influencée par l'alimentation hydrique et carbonée du fruit. La disponibilité des assimilats dépend d'une part de leur production au niveau des feuilles, qui est fonction de l'environnement lumineux et de l'activité photosynthétique foliaire, et d'autre part de leur répartition, qui est liée à la position du fruit, par rapport aux feuilles et aux autres fruits, et à sa force de puits. La disponibilité hydrique et carbonée influe sur la qualité des fruits, par son action sur les apports d'eau et de nutriments, et son effet sur la maturation et le métabolisme du fruit. Les objectifs du travail de thèse sont les suivants: - étudier l'influence de la fourniture en assimilats et de la disponibilité en eau sur la croissance de la mangue, - étudier les relations entre la croissance en calibre et l'élaboration de la qualité gustative du fruit chez le manguier, - étudier la relation entre croissance, maturation et élaboration de la qualité aromatique de la mangue. D'un point de vue scientifique, ce travail permettra de formaliser les résultats et de les intégrer à un modèle de croissance du fruit. L'objectif finalisé est d'apporter des recommandations techniques afin d'envisager une maîtrise au champ de la qualité des fruits. Une première expérimentation a été menée en intervenant sur la charge en fruits du rameau "porteur" afin d'étudier l'influence de l'alimentation carbonée sur la croissance et l'élaboration de la qualité des mangues. Nous réalisons une décortication annulaire à la base du rameau (constitué de bois, feuilles assimilatrices et fruits en croissance) pour éviter les transferts d'assimilats avec le reste de l'arbre et obtenir alors un fonctionnement autonome pour les flux de carbone. Les premiers résultats montrent que la croissance en calibre des fruits placés en conditions contrastées d'alimentation carbonée (nombre de feuilles par fruit respectivement de 10, 25, 50, 100 et 150) est dépendante du traitement puisqu'à maturité leur poids est respectivement de 180, 260, 375, 515 et 565 g. L'accumulation d'eau et de matière sèche (MS) est maximale pour les fruits du traitement 100 (pas de différences avec le 150). Les sucres solubles contenus dans la pulpe de mangue sont principalement du glucose, fructose et saccharose. Ce dernier s'accumule beaucoup plus lentement chez les fruits en condition de faible alimentation (25 feuilles par fruit).

International audience

International audience