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Summary: The trade‐off between yield and quality, a major problem for the production of fleshy fruits, involves fruit expansive growth and sugar metabolism.Here we developed an integrative model by coupling a biophysical model of fleshy fruit growth processes, including water and carbon fluxes and organ expansion, with an enzyme‐based kinetic model of sugar metabolism to better understand the interactions between these two processes. The integrative model was initially tested on tomato fruit, a model system for fleshy fruit.The integrative model closely simulated the biomass and major carbon metabolites of tomato fruit developing under optimal or stress conditions. The model also performed robustly when simulating the fruit size and sugar concentrations of different tomato genotypes including wild species. The validated model was used to explore ways of uncoupling the size–sweetness trade‐off in fruit. Model‐based virtual experiments suggested that larger sweeter tomatoes could be obtained by simultaneously manipulating certain biophysical factors and transmembrane transports.The integrative fleshy fruit model provides a promising tool to facilitate the targeted bioengineering and breeding of tomatoes and other fruits. [ABSTRACT FROM AUTHOR]

Fleshy fruits are very varied, whether in terms of their composition, physiology, or rate and duration of growth. To understand the mechanisms that link metabolism to phenotypes, which would help the targeting of breeding strategies, we compared eight fleshy fruit species during development and ripening. Three herbaceous (eggplant, pepper, and cucumber), three tree (apple, peach, and clementine) and two vine (kiwifruit and grape) species were selected for their diversity. Fruit fresh weight and biomass composition, including the major soluble and insoluble components, were determined throughout fruit development and ripening. Best-fitting models of fruit weight were used to estimate relative growth rate (RGR), which was significantly correlated with several biomass components, especially protein content (R =84), stearate (R =0.72), palmitate (R =0.72), and lignocerate (R =0.68). The strong link between biomass composition and RGR was further evidenced by generalized linear models that predicted RGR with R -values exceeding 0.9. Comparison of the fruit also showed that climacteric fruit (apple, peach, kiwifruit) contained more non-cellulosic cell-wall glucose and fucose, and more starch, than non-climacteric fruit. The rate of starch net accumulation was also higher in climacteric fruit. These results suggest that the way biomass is constructed has a major influence on performance, especially growth rate. [ABSTRACT FROM AUTHOR]

The cuticle is composed of cutin and cuticular waxes, and it is the first protective barrier to abiotic and biotic stresses in fruit. In this study, we analysed the composition of and changes in cuticular waxes during fruit development in nectarine (Prunus persica L. Batsch) cultivars, in parallel with their conductance and their susceptibility to Monilinia laxa. The nectarine waxes were composed of triterpenoids, mostly ursolic and oleanolic acids, phytosterols, and very-long-chain aliphatics. In addition, we detected phenolic compounds that were esterified with sugars or with triterpenoids, which are newly described in cuticular waxes. We quantified 42 compounds and found that they changed markedly during fruit development, with an intense accumulation of triterpenoids during initial fruit growth followed by their decrease at the end of endocarp lignification and a final increase in very-long-chain alkanes and hydroxylated triterpenoids until maturity. The surface conductance and susceptibility to Monilinia decreased sharply at the beginning of endocarp lignification, suggesting that triterpenoid deposition could play a major role in regulating fruit permeability and susceptibility to brown rot. Our results provide new insights into the composition of cuticular waxes of nectarines and their changes during fruit development, opening new avenues of research to explore brown rot resistance factors in stone fruit. [ABSTRACT FROM AUTHOR]

The development of a new organ is the result of coordinated events of cell division and expansion, in strong interaction with each other. This study presents a dynamic model of tomato fruit development that includes cell division, endoreduplication, and expansion processes. The model is used to investigate the potential interactions among these developmental processes within the context of the neo-cellular theory. In particular, different control schemes (either cell-autonomous or organ-controlled) are tested and compared to experimental data from two contrasting genotypes. The model shows that a pure cell-autonomous control fails to reproduce the observed cell-size distribution, and that an organ-wide control is required in order to get realistic cell-size variations. The model also supports the role of endoreduplication as an important determinant of the final cell size and suggests that a direct effect of endoreduplication on cell expansion is needed in order to obtain a significant correlation between size and ploidy, as observed in real data. [ABSTRACT FROM AUTHOR]

* Background One of the key goals of fruit biology is to understand the factors that influence fruit growth and quality, ultimately with a view to manipulating them for improvement of fruit traits. * Scope Primary metabolism, which is not only essential for growth but is also a major component of fruit quality, is an obvious target for improvement. However, metabolism is a moving target that undergoes marked changes throughout fruit growth and ripening. * Conclusions Agricultural practice and breeding have successfully improved fruit metabolic traits, but both face the complexity of the interplay between development, metabolism and the environment. Thus, more fundamental knowledge is needed to identify further strategies for the manipulation of fruit metabolism. Nearly two decades of postgenomics approaches involving transcriptomics, proteomics and/or metabolomics have generated a lot of information about the behaviour of fruit metabolic networks. Today, the emergence of modelling tools is providing the opportunity to turn this information into a mechanistic understanding of fruits, and ultimately to design better fruits. Since high-quality data are a key requirement in modelling, a range of must-have parameters and variables is proposed. [ABSTRACT FROM AUTHOR]

Summary: The concentrations of sugars in fruit vary with fruit development, environment and genotype. In general, there were weak correlations between the variations in sugar concentrations and the activities of enzymes directly related with the synthesis or degradation of sugars. This finding suggests that the relationships between enzyme activities and metabolites are often non‐linear and are difficult to assess. To simulate the concentrations of sucrose, glucose, fructose and sorbitol during the development of peach fruit, a kinetic model of sugar metabolism was developed by taking advantage of recent profiling data. Cell compartmentation (cytosol and vacuole) was described explicitly, and data‐driven enzyme activities were used to parameterize equations. The model correctly accounts for both annual and genotypic variations, which were observed in 10 genotypes derived from an interspecific cross. They provided important information on the mechanisms underlying the specification of phenotypic differences. In particular, the model supports the hypothesis that a difference in fructokinase affinity could be responsible for a low fructose‐to‐glucose ratio phenotype, which was observed in the studied population. [ABSTRACT FROM AUTHOR]

Monitoring of fruit growth is a measurement widely used in physiology and agronomy studies. This is normally done from detached fruits, which can lead to erroneous results when fruits grow asynchronously in clusters as occurs in blueberry plants ( Vaccinium spp .). The aim of this communication is to develop a simple allometric model for estimating blueberry weight from diameter measurements. In three growth seasons, weight and diameter of a total of 416 fruits were measured from four field-grown blueberry cultivars. The obtained data set was then randomly divided resulting in 200 data for calibrating model and 216 for validating. Prior to calibration procedure, the use of cultivar-specific models or a common model for four cultivars was evaluated by Analysis of Covariance between logarithm transformed diameter and cultivar/season variables. From analysis, no interactive effect was observed, so a common allometric model was constructed, giving a power functional relationship between berry diameter and weight. The allometric model was validated with the independent data, giving errors ranging from 4.7% to 6.9%. Residuals showed a random dispersion pattern. Our results showed that a common model was adequate for providing a reliable means of estimating blueberry fruit weight of different cultivars. [ABSTRACT FROM AUTHOR]

Knowledge of the genetic control of sugar metabolism is essential to enhance fruit quality and promote fruit consumption. The sugar content and composition of fruits varies with species, cultivar and stage of development, and is controlled by multiple enzymes. A QTL (quantitative trait locus) study was performed on peach fruit [Prunus persica (L.) Batsch], the model species for Prunus. Progeny derived from an interspecific cross between P. persica cultivars and P. davidiana was used. Dynamic QTLs for fresh weight, sugars, acids, and enzyme activities related to sugar metabolism were detected at different stages during fruit development. Changing effects of alleles during fruit growth were observed, including inversions close to maturity. This QTL analysis was supplemented by the identification of genes annotated on the peach genome as enzymes linked to sugar metabolism or sugar transporters. Several cases of co-locations between annotated genes, QTLs for enzyme activities and QTLs controlling metabolite concentrations were observed and discussed. These co-locations raise hypotheses regarding the functional regulation of sugar metabolism and pave the way for further analyses to enable the identification of the underlying genes. In conclusion, we identified the potential impact on fruit breeding of the modification of QTL effect close to maturity. [ABSTRACT FROM AUTHOR]

The decline in xylem flow during the late growth stage in most fruits may be due either to a decrease in the water potential gradient between the stem bearing the fruit and the fruit tissues or to a decrease in the hydraulic conductivity of xylem vessels, or both. In this study, we analysed changes in xylem flows to the mango Mangifera indica L. fruit during its development to identify the sources of variation by measuring changes in the water potential gradient and in the hydraulic properties of the fruit pedicel. The variations in xylem and transpiration flows were estimated at several stages of mango fruit development from the daily changes in the fresh mass of detached and girdled fruits on branches. The water potential gradient was estimated by monitoring the diurnal water potential in the stem and fruit. The hydraulic properties of the fruit pedicel were estimated using a flow meter. The results indicated that xylem flow increased in the early stages of fruit development and decreased in the late stage. Variations in xylem flow were related to the decrease in the hydraulic conductivity of xylem vessels but not to a decrease in the water potential gradient. The hydraulic conductivity of the fruit pedicel decreased during late growth due to embolism caused by a decrease in the fruit water potential. Further studies should establish the impact of the decrease in the hydraulic conductivity of the fruit pedicel on mango growth. [ABSTRACT FROM AUTHOR]

Citrate is one of the most important organic acids in many fruits and its concentration plays a critical role in organoleptic properties. The regulation of citrate accumulation throughout fruit development, and the origins of the phenotypic variability of the citrate concentration within fruit species remain to be clarified. In the present study, we developed a process-based model of citrate accumulation based on a simplified representation of the TCA cycle to predict citrate concentration in fruit pulp during the pre- and post-harvest stages. Banana fruit was taken as a reference because it has the particularity of having post-harvest ripening, during which citrate concentration undergoes substantial changes. The model was calibrated and validated on the two stages, using data sets from three contrasting cultivars in terms of citrate accumulation, and incorporated different fruit load, potassium supply, and harvest dates. The model predicted the pre and post-harvest dynamics of citrate concentration with fairly good accuracy for the three cultivars. The model suggested major differences in TCA cycle functioning among cultivars during post-harvest ripening of banana, and pointed to a potential role for NAD-malic enzyme and mitochondrial malate carriers in the genotypic variability of citrate concentration. The sensitivity of citrate accumulation to growth parameters and temperature differed among cultivars during post-harvest ripening. Finally, the model can be used as a conceptual basis to study citrate accumulation in fleshy fruits and may be a powerful tool to improve our understanding of fruit acidity. [ABSTRACT FROM AUTHOR]

Fruit physiology is strongly affected by both fruit temperature and water losses through transpiration. Fruit temperature and its transpiration vary with environmental factors and fruit characteristics. In line with previous studies, measurements of physical and thermal fruit properties were found to significantly vary between fruit tissues and maturity stages. To study the impact of these variations on fruit temperature and transpiration, a modelling approach was used. A physical model was developed to predict the spatial and temporal variations of fruit temperature and transpiration according to the spatial and temporal variations of environmental factors and thermal and physical fruit properties. Model predictions compared well to temperature measurements on mango fruits, making it possible to accurately simulate the daily temperature variations of the sunny and shaded sides of fruits. Model simulations indicated that fruit development induced an increase in both the temperature gradient within the fruit and fruit water losses, mainly due to fruit expansion. However, the evolution of fruit characteristics has only a very slight impact on the average temperature and the transpiration per surface unit. The importance of temperature and transpiration gradients highlighted in this study made it necessary to take spatial and temporal variations of environmental factors and fruit characteristics into account to model fruit physiology. [ABSTRACT FROM AUTHOR]

Fruit development, from its early stages, is the result of a complex network of interacting processes, on different scales. These include cell division, cell expansion but also nutrient transport from the plant, and exchanges with the environment. In the presence of nutrient limitation, in particular, the plant reacts as a whole, by modifying its architecture, metabolism, and reproductive strategy, determining the resources available for fruit development, which in turn affects the overall source-sink balance of the system. Here, we present an integrated model of tomato that explicitly accounts for early developmental changes (from cell division to harvest), and use it to investigate the impact of water deficit and carbon limitation on nutrient fluxes and fruit growth, in both dry and fresh mass. Variability in fruit response is analyzed on two different scales: among trusses at plant level, and within cell populations at fruit level. Results show that the effect of stress on individual cells strongly depends on their age, size, and uptake capabilities, and that the timing of stress application, together with the fruit position on the plant, is crucial in determining the final phenotypic outcome. Water deficit and carbon depletion impacted either source size, source activity, or sink strength with contrasted effects on fruit growth. An important prediction of the model is the major role of symplasmic transport of carbon in the early stage of fruit development, as a catalyst for cell and fruit growth. [ABSTRACT FROM AUTHOR]

Abstract: The present study aimed to clarify the relationship between sugars and vitamin C in fruit. The objective was to determine whether vitamin C content was regulated by sugar content due to the role of sugar as a precursor for vitamin C. During summer, maximal content in sugar and vitamin C were found in both genotypes tested Solanum lycopersicon ‘Cervil’ and ‘Levovil’. During autumn, fruit pruning increased fruit size and hexose content but fruit vitamin C content did not increase. Therefore sugar substrate was not limiting for vitamin C synthesis during autumn. We demonstrated for two cultivars, ‘Cervil’ and ‘Levovil’, with different sugar accumulation profiles during ripening, that sugar content was not determinant in the regulation of vitamin C content. The strong correlation observed between sugars and vitamin C in ‘Cervil’ was due to their concomitant increase during fruit ripening. [ABSTRACT FROM AUTHOR]

Throughout tomato domestication, a large increase in fruit size was associated with a loss of dry matter and sugar contents. This study aims to dissect the contributions of genetic variation and the physiological processes underlying the relationships between fruit growth and the accumulation of dry matter and sugars. Fruit quality traits and physiological parameters were measured on 20 introgression lines derived from the introgression of Solanum chmielewskii into S. lycopersicum, under high (HL, unpruned trusses) and low (LL, trusses pruned to one fruit) fruit load conditions. Inter- and intra-genotypic correlations among traits were estimated and quantitative trait loci (QTL) for size, composition, and physiological traits were mapped. LL increased almost all traits, but the response of sugar content was genotype-dependent, involving either dilution effects or differences in carbon allocation to sugars. Genotype×fruit load interactions were significant for most traits and only 30% of the QTL were stable under both fruit loads. Many QTL for fresh weight and cell or seed numbers co-localized. Eleven clusters of QTL for fresh weight and dry matter or sugar content were detected, eight with opposite allele effects and three with negative effects. Two genotypic antagonistic relationships, between fresh weight and dry matter content and between cell number and cell size, were significant only under HL; the second could be interpreted as a competition for carbohydrates among cells. The role of cuticular conductance, fruit transpiration or cracking in the relationship between fruit fresh weight and composition was also emphasized at the genetic and physiological levels. [ABSTRACT FROM PUBLISHER]

Many quantitative trait loci (QTLs) for quality traits have been located on the tomato genetic map, but introgression of favourable wild alleles into large fruited species is hampered by co-localizations of QTLs with antagonist effects. The aim of this study was to assess the growth processes controlled by the main QTLs for fruit size and composition. Four nearly isogenic lines (NILs) derived from an intraspecific cross between a tasty cherry tomato (Cervil) and a normal-tasting large fruit tomato (Levovil) were studied. The lines carried one (L2, L4, and L9) or five (Lx) introgressions from Cervil on chromosomes 1, 2, 4, and 9. QTLs for fruit size could be mainly associated with cell division processes in L2 and L9, whereas cell expansion was rather homogeneous among the genotypes, except Cervil for which the low expansion rate was attributed to low cell plasticity. The link between endoreduplication and fruit size remained unclear, as cell or fruit sizes were positively correlated with the cell DNA content, but not with the endoreduplication factor. QTLs for fruit composition reflected differences in water accumulation rather than in sugar accumulation, except in L9 for which the up-regulation of sucrose unloading and hexose transport and/or starch synthesis was suggested. This may explain the increased amount of carbon allocated to cell structures in L9, which could be related to a QTL for fruit texture. In Lx, these effects were attenuated, except on fruit size and cell division. Finally, the region on top of chromosome 9 may control size and composition attributes in tomato, by a combination of QTL effects on cell division, cell wall synthesis, and carbon import and metabolism. [ABSTRACT FROM PUBLISHER]

This work proposed a model of tomato growth adapted from the Fishman and Génard model developed to predict carbon and water accumulation in peach fruit. The main adaptations relied on the literature on tomato and mainly concerned: (i) the decrease in cell wall extensibility coefficient during fruit development; (ii) the increase in the membrane reflection coefficient to solute from 0 to 1, which accounted for the switch from symplasmic to apoplasmic phloem unloading, and (iii) the negative influence of the initial fruit weight on the maximum rate of active carbon uptake based on the assumption of higher competition for carbon among cells in large fruits containing more cells. A sensitivity analysis was performed and the model was calibrated and evaluated with satisfaction on 17 experimental datasets obtained under contrasting environmental (temperature, air vapour pressure deficit) and plant (plant fruit load and fruit position) conditions. Then the model was used to analyse the variations in the main fluxes involved in tomato fruit growth and accumulation of carbon in response to virtual carbon and water stresses. The conclusions are that this model, integrating simple biophysical laws, was able to simulate the complex fruit behaviour in response to external or internal factors and thus it may be a powerful tool for managing fruit growth and quality. [ABSTRACT FROM PUBLISHER]

A carbon-based model is described of the source-sink relationships of a stem bearing fruits in space and time and focusing on growth variability along the branch. The novelty of the model comes from the aggregation of physiological processes taking into account spatial aspects. The stem is represented as a set of compartments (metamers) connected to source (leafy shoots) and sink (fruits) compartments. Each leafy shoot forms one compartment. The fruit consists of three compartments involved in translocation (cytoplasm), structure (cell wall) and storage (vacuole). Physiological processes considered are photosynthesis, respiration of fruits and leaves, translocation of assimilates and fruit growth. Assimilate production is regulated by sink strength. Carbon translocation between two compartments depends on the gradient of assimilate concentration. The gradient induces carbon translocation from the most to the least concentrated compartment, except for the vacuole compartment into which translocation is possible whatever the concentration gradient. Fruit growth, in terms of fresh weight, results from the phloem water supplied to the fruit according to the concentration gradient between the fruit and the stem. The model is calibrated for peach trees by comparing observed and simulated fruit dry and fresh weights for a shoot with normal fruit load. The model simulates variability between peach fruits and the effect of contrasting fruit loads. According to this model, photosynthesis increases and assimilate concentrations in leaves and phloem decrease with decreasing leaf:fruit ratio as reported in the literature. Simulated concentrations of assimilates in the phloem range from 2 to 14%. Simulated concentration gradients and specific mass transfer for peach trees range from 0.05 to 0.17 g cm−3m−1and from 0 to 3 g cm−2h−1, respectively, and are of the same order of magnitude as those reported for various other tree species. The model is used to analyse the effect of fruit position relative to the leaves. Copyright 1999 Annals of Botany Company [ABSTRACT FROM AUTHOR]

Abstract: To check if bunch trimming improves quality traits of banana, its effect on the dry matter content of the pulp and peel of two banana cultivars (Grande Naine, and a hybrid named Flhorban 924) were investigated during fruit growth. For both cultivars, bunches with six hands (controls) were compared with trimmed bunches with only two hands at two fruit development stages, one early fruit pruning treatment at 160 degree days (dd) and one late fruit pruning treatment at 540 dd. Early bunch trimming increased fruit weight by more than 25%. An allometric relationship of type Y = aX b was found between fruit and pulp dry weight, in which the coefficients mainly depended on the cultivar concerned. In the allometric relationship between the weight of water in the fruit and the pulp, coefficient b was the same in the two cultivars. During fruit growth, the dry matter content of the pulp and peel increased rapidly between 160 and 600 dd, then continued to increase, but more slowly, to reach maximum at between 600 and 800 dd depending on the cultivar, and finally declined slowly until the end of growth. The early bunch trimming treatment led to an increase of 1g100g−1 in the dry matter content of the peel. However, the dry matter content of the pulp was not affected by bunch trimming irrespective of when the treatment was carried out. In conclusion, this common cultivation practice did improve fruit weight but had no significant impact on the dry matter content of the banana pulp at harvest. [Copyright &y& Elsevier]