Assessment of the water stress effects on peach fruit quality and size using a fruit tree model, QualiTree

- A middle-late maturing peach cultivar was successfully implemented into QualiTree.
- QualiTree was able to adequately simulate the effects of water stress on fruit growth.
- Fructose, glucose and sorbitol contents in the fruit flesh were well simulated.
- Water stress increased sugar contents in the fruit flesh.

Low water availability has increased the use of regulated deficit irrigation strategies in fruit orchards. However, these water restrictions may have implications on fruit growth and quality. The current paper assesses the suitability of an existing fruit tree model (QualiTree) for describing the effects of water stress on peach fruit growth and quality. The model was parameterised and calibrated for a mid-late maturing peach cultivar ('Catherine'). Mean and variability over time of fruit and vegetative growth were consistent with observed data on trees submitted to full irrigation or to regulated deficit irrigation. The relative root mean square errors of the model for growth ranged between 0.09 and 0.31.Sugar contents in fruit flesh were fairly well simulated, except for sucrose, which was overestimated. The relative root mean square errors of the model ranged from 0.01 to 0.40 for fructose; from 0.04 to 0.05 for glucose; from 0.21 to 0.41 for sucrose and from 0.09 to 0.28 for sorbitol. Water stress reduced leafy shoot growth up to 23% and fruit final size up to 49% when compared to the well-watered control. However, sugar contents in the flesh increased with water stress, up to 70% in the case of glucose. Simulations showed that a severe water stress during stage III of fruit development decreased fruit sizes by 22%, when compared to the control, whereas it enhanced sugar accumulation in the fruit flesh, up to 70% in the case of glucose and fructose. Therefore, these simulations showed that QualiTree might be useful in the design of innovative horticultural practices.