Potential of QualiTree, a virtual fruit tree, to study the management of fruit quality under biotic and abiotic constraints

QualiTree is a generic fruit tree object-based model in which the effects of management practices on the development of fruit quality are explicitly modelled. It considers a large range of fruit quality traits important for growers, retailers and consumers, including: fruit size, the proportion of total mass consisting of fruit flesh, flesh dry matter content, flesh concentrations of various sugars, and sweetness, a linear combination of sugar concentrations. Though parsimonious in terms of 3D representation of the plant architecture, it is able to express a high degree of within-tree variability of fruit quality criteria. QualiTree has been successfully tested using several datasets. A range of peach cultivars - from very-early to late - has been parameterised into QualiTree. Simulation studies show the potential of QualiTree to predict how fruit quality profiles may change under various levels of biotic and abiotic stress, which will become common within the context of global change. We simulated patterns of foliar attacks by parasites and showed that reductions in fruit quality were lower when attacks were late in the season. Other simulation studies indicated that severe water stress during stage III of fruit development decreased fruit size whereas it dramatically enhanced sugar accumulation in the fruit flesh, especially in the case of glucose and fructose. Hence, QualiTree might be useful in the design of innovative horticultural practices combining regulated deficit irrigation strategies and plant-mediated control of pests.