Simulation of the effect of fruit thinning on peach quality

A model of fruit quality described by fruit weight, percent dry material and sugar content was developed for peach. The application of the model is restricted to shoots bearing fruits considered as independent units. It is composed of three sub-models describing the dry matter, the fresh matter and the sugars accumulation, respectively. The inputs are the temperature, the global radiation and the intensity and date of fruit thinning. The first submodel considers three compartments: the one-year-old stem, the leafy shoots and the fruits. It simulates the carbon assimilation, the respiration, the carbon storage and the growth of leaves and fruits. The carbon partitioning is based on organ demands and priority rules. The second sub-model computes the fresh weight of fruits from their dry weight through allometric relationships. In the third sub-model, the assimilates supplied to the fruit are partitioned in sucrose, sorbitol, glucose and fructose. The rates of change of these sugars are depending on supply, transfer functions between them, and use for respiration and synthesis of insoluble material. The effect of different periods and levels of thinning was analysed. As noticed in experiments, the fruit thinning increases the fruit weight, and the dry material and sugars concentrations in the flesh of the fruit. The fruit weight and sucrose concentrations are the parameters of fruit quality the most sensitive to thinning.