Modeling the vacuolar storage of malate shed lights on pre- and post-harvest fruit acidity

Background: Malate is one of the most important organic acids in many fruits and its concentration plays a critical role in organoleptic properties. Several studies suggest that malate accumulation in fruit cells is controlled at the level of vacuolar storage. However, the regulation of vacuolar malate storage throughout fruit development, and the origins of the phenotypic variability of the malate concentration within fruit species remain to be clarified. In the present study, we adapted the mechanistic model of vacuolar storage proposed by Lobit et al. in order to study the accumulation of malate in pre and postharvest fruits. The main adaptation concerned the variation of the free energy of ATP hydrolysis during fruit development. Banana fruit was taken as a reference because it has the particularity of having separate growth and post-harvest ripening stages, during which malate concentration undergoes substantial changes. Moreover, the concentration of malate in banana pulp varies greatly among cultivars which make possible to use the model as a tool to analyze the genotypic variability. The model was calibrated and validated using data sets from three cultivars with contrasting malate accumulation, grown under different fruit loads and potassium supplies, and harvested at different stages. Results: The model predicted the pre and post-harvest dynamics of malate concentration with fairly good accuracy for the three cultivars (mean RRMSE = 0.25-0.42). The sensitivity of the model to parameters and input variables was analyzed. According to the model, vacuolar composition, in particular potassium and organic acid concentrations, had an important effect on malate accumulation. The model suggested that rising temperatures depressed malate accumulation. The model also helped distinguish differences in malate concentration among the three cultivars and between the pre and post-harvest stages by highlighting the probable importance of proton pump activity and particularly of the free energy of ATP hydrolysis and vacuolar pH. Conclusions: This model appears to be an interesting tool to study malate accumulation in pre and postharvest fruits and to get insights into the ecophysiological determinants of fruit acidity, and thus may be useful for fruit quality improvement. (Résumé d'auteur

COMMENT DÉTERMINER LE STADE DE RÉCOLTE DES FRUITS CLIMACTÉRIQUES DESTINÉS À L'EXPORT ? APPLICATION A UNE NOUVELLE VARIÉTÉ DE BANANE DESSERT

Le CIRAD a mis au point une méthode innovante basée sur la règle des sommes thermiques qui permet de déterminer le stade optimal de récolte des nouvelles variétés de bananes destinées à l'export. Les essais ont été menés sur une nouvelle variété créée par le CIRAD, la Flhorban 916, et sur une variété témoin, la Cavendish. Elles ont été implantées sur 2 sites caractérisés par des conditions pédoclimatiques différentes. Le stade de récolte de Flhorban 916 a été évalué en déterminant son zéro physiologique puis l'IFC qui procure à ses fruits une DVV optimale. Ce stade de récolte a enfin été expérimenté dans les conditions réelles de la filière Cavendish. Les résultats montrent que le stade de récolte optimal de la nouvelle variété est de 700 degrés.jour calculé avec zéro physiologique de 16,7°C. Fiable et facile d'utilisation, cette technique permet au CIRAD de proposer sur le marché européen un produit répondant aux impératifs propres à la filière d'exportation actuelle. Son intérêt majeur est d'être applicable à toutes nouvelles variétés de fruits climactériques destinés à n'importe quel circuit d'export

Review of banana green life throughout the food chain: From auto-catalytic induction to the optimisation of shipping and storage conditions

International audienceBanana green life (GL) is the time between harvesting and the start of natural ripening. GL could be considered as a major quality criterion, as it defines whether or not a fruit is suitable for export and marketing. The ending of GL, when climacteric crisis occurs, is characterized by autocatalytic ethylene production. Ethylene synthesis and regulation are described. The main methods for determining GI are based on detecting the CO2 peak or a decrease in green pigments, using a spectrometer (NDVI) for the latter. Temperatures during fruit growth and Black Sigatoka disease are the main pre-harvest factors affecting GL. The former can be managed by applying the thermal sums concept and the latter by adequate field practices. The effects of the main exogenous storage parameters (storage temperature, relative humidity, concentration of ethylene and O-2/CO2 ratio in the atmosphere) could be modelled in some cases. The most effective solutions for extending GL rely on either developing coatings using new preservative compounds, or designing packaging capable of controlling the temperature, CO2/O-2 ratio and ethylene concentrations in the environment close to the fruits. It was demonstrated that 1-MCP is not relevant for increasing GL. A global and integrated approach involving the overall optimization of pre- and post-harvest factors needs to be applied to maintain green fruit until voluntary/artificial ripening is induced

Management of post-harvest fruit quality for ecologically intensified banana cropping systems

International audienc

ERK2 activation in arteriolar and venular murine thrombosis: platelet receptor GPIb vs. P2X.

The functional significance of extracellular signal-regulated kinase 2 (ERK2) activation was investigated during shear induced human platelet aggregation (SIPA) in vitro and during shear controlled thrombosis in vivo in intestinal arterioles and venules of wild type (WT) and transgenic (TG) mice with platelet-specific overexpression of human P2X(1) (TG). The conclusions are that P2X(1) and ERK2 both participate in shear stress controlled thrombosis, but ERK2 activation is initiated predominantly via GPIb-VWF interactions

A Process-Based Model of TCA Cycle Functioning to Analyze Citrate Accumulation in Pre- and Post-Harvest Fruits.

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

Decision tree scoring system to guide selection for consumer preference in sweetpotato breeding trials

Background Previously, a lexicon and protocol for quantitative descriptive analysis (QDA) was established for the Uganda sweetpotato breeding program. The implication of QDA scores for priority sensory attributes on consumer preference should be determined to interpret results efficiently and make decisions effectively. This study aimed to develop a gender-responsive decision tree to obtain an overall sweetpotato eating quality score to facilitate demand-led targeted breeding selection. It focused on Kamuli and Hoima districts (Uganda) and uses pre-lease advanced clones (‘NKB3’, ‘NKB105’, ‘NKB135’, ‘D11’, and ‘D20’), released varieties (‘NASPOT 8’, ‘NAROSPOT 1’), and landraces (‘Muwulu-Aduduma’, ‘Umbrella’). Results Including boiled sweetpotato sensory characteristics, namely mealy, sweet taste, sweetpotato smell, firm and not fibrous in breeding design would benefit end-users, especially women given their role in varietal selection, food preparation and marketing. ‘D20’, ‘NASPOT 8’ and ‘NAROSPOT 1’ were most liked in both districts. ‘NKB3’ and ‘D11’ were the least liked in Hoima, while ‘Muwulu-Aduduma’ was the least liked in Kamuli. There was a positive correlation between color and overall liking (R2= 0.8) and consumers liked the color (average rating ≥ 6 on 9-point hedonic scale) of all genotypes. Threshold values (average rating on 11-point scales) for consumer acceptability were identified (sweet taste=6, sweetpotato aroma and flavor=6, firmness=3, and mealiness=4). A regression decision tree tool was created to calculate an eating quality selection index when screening lines in breeding programs using the values. Conclusion Decision trees that include consumer needs and gender considerations would facilitate demand-led breeding and make varietal selection in sweetpotato breeding programs more effective