Inter-Species Comparative Analysis of Components of Soluble Sugar Concentration in Fleshy Fruits

Abstract

The soluble sugar concentration of fleshy fruit is a key determinant of fleshy fruit quality. It affects directly the sweetness of fresh fruits and indirectly the properties of processed products (e.g., alcohol content in wine). Despite considerable divergence among species, soluble sugar accumulation in a fruit results from the complex interplay of three main processes, namely sugar import, sugar metabolism, and water dilution. Therefore, inter-species comparison would help to identify common and/or species-specific modes of regulation in sugar accumulation. For this purpose, a process-based mathematical framework was used to compare soluble sugar accumulation in three fruits: grape, tomato, and peach. Representative datasets covering the time course of sugar accumulation during fruit development were collected. They encompassed 104 combinations of species (3), genotypes (30), and growing conditions (19 years and 16 nutrient and environmental treatments). At maturity, grape showed the highest soluble sugar concentrations (16.5–26.3 g/100 g FW), followed by peach (2.2 to 20 g/100 g FW) and tomato (1.4 to 5 g/100 g FW). Main processes determining soluble sugar concentration were decomposed into sugar importation, metabolism, and water dilution with the process-based analysis. Different regulation modes of soluble sugar concentration were then identified, showing either import-based, dilution-based, or import and dilution dual-based. Firstly, the higher soluble sugar concentration in grape than in tomato is a result of higher sugar importation. Secondly, the higher soluble sugar concentration in grape than in peach is due to a lower water dilution. The third mode of regulation is more complicated than the first two, with differences both in sugar importation and water dilution (grape vs. cherry tomato; cherry tomato vs. peach; peach vs. tomato). On the other hand, carbon utilization for synthesis of non-soluble sugar compounds (namely metabolism) was conserved among the three fruit species. These distinct modes appear to be quite species-specific, but the intensity of the effect may significantly vary depending on the genotype and management practices. These results provide novel insights into the drivers of differences in soluble sugar concentration among fleshy fruits.

Grapevine phenology in France: from past observations to future evolutions in the context of climate change

“…However, even if those stages are important to understand the growth cycle of the plant, much remains to be investigated with respect to grape maturity, which is fundamental to determine berry composition at harvest. Some studies have already begun to model the berry maturation process (García de Cortázar-Atauri et al, 2009b, Dai et al, 2016. Nevertheless, it will also be important to produce simplified tools (such as the GFV model) for future analysis of the impact of climate change on this phase which is fundamental to define harvest composition.…”

Grapevine quality: A multiple choice issue

“…The sugar concentration at maturity is a result of various processes, including sugar supply from the leaves, loading via phloem, metabolism in cells, transport into vacuole for storage (Lecourieux et al, 2014), and water dilution effect (Dai et al, 2016;Sadras et al, 2008). The complex nature of the sugar concentration hampers the identification of its genetic markers.…”

Disentangling the Effects of Water Stress on Carbon Acquisition, Vegetative Growth, and Fruit Quality of Peach Trees by Means of the QualiTree Model

“…Furthermore, it is worth noticing that the increasing of sugar concentrations in the fruit flesh induced by water stress was similar to the increase in dry matter content in the fruits, suggesting that the main process affected was the water inflow to the fruit (Génard et al, 2010 ) and not a larger sugar accumulation in the fruit. Dilution by water plays a relevant role in determining the concentration of soluble sugars (Génard et al, 2014 ; Dai et al, 2016 ) and it is known to be largely affected by environmental conditions and management practices (Kobashi et al, 2000 ).…”

“…Moreover, QualiTree represents the development of several fruit quality traits including size, flesh dry matter content and concentrations of various sugars. In QualiTree, fruit sugar content is described by a set of differential equations (Génard et al, 2003 ) that accounts for the three processes involved in the development of soluble sugars (sucrose, glucose, fructose, and sorbitol) within the fruit: sugar importation, metabolism and water dilution (Dai et al, 2016 ).…”