Modeling Fruit Growth And Sugar Accumulation And Optimizing Irrigation Scheduling For Improving Water Use Efficiency And Fruit Quality Of Tomato

With the development of social economy and the improvement of living standard, the consumers are paying more and more attention to the fruit quality because the tomato yield has met their demand. Irrigation is one of the most important measurements applying to regulate tomato yield and fruit quality, since it plays a key role in the fruit water and carbon balance. In this study, two years of regulated deficit irrigation experiments were conducted on big fresh tomato in the solar greenhouse of Shiyanghe experimental station of China Agricultural University from 2011 to 2013, and a consecutive deficit irrigation experiment was conducted on cherry tomato "Cervil" and big fresh tomato "Levovil" in a glass greenhouse in Avignon, France in 2014. The responses of plant growth, eco-physiological characteristics, water consumption, and yield and fruit quality to water deficit were analyzed based on these experiments. Combining the data from these experiments and the collected data from previous experiments, empirical statistical models were developed to simulate the water-yield-quality relations for tomato, and a process-based fruit growth and sugar accumulation coupled model was also established. Besides, optimal irrigation decision-making methods were evaluated. The main results are outlined as follows:(1) Water deficit decreased the plant water potential, leaf stomatal conductance and transpiration rate, but didn’t affect the leaf photosynthesis rate significantly. Water deficit prolonged the terminal leaflet growth period but not the fruit growth period. Water deficit reduced the leaflet growth rate and final length as well as the fruit growth rate and size. Water deficit decreased the tomato plant biomass including the fruits dry mass and the vegetation dry mass, but its effects on the dry mass partition among stem, leaf, truss and fruit depended on the genotypes.(2) Tomato yield and fruit quality were not significantly influenced by the moderate water deficit (reducing 1/3 full irrigation amount) during Stage II (first fruit set to first fruit ripening) or Stage III (first fruit ripening to the end of harvest) or consecutive mild water deficit (reducing 1/9 full irrigation amount) during Stage Ⅱ and Stage Ⅲ stages. Tomato yield was significantly reduced by the severe water deficit (reducing 2/3 full irrigation amount) at Stage II or Stage III or by the consecutive mild-to-moderate or more water deficit (reducing 2/9 or more full irrigation amount) during Stage Ⅱ and Stage Ⅲ stages, but the fruit quality attributes like soluble solids, reducing sugars, organic acids, sugar/acid ratio, vitamin C, lycopene, fruit firmness and color index were increased in varying degrees.(3) The empirical statistical models describing the water-yield-quality relations were evaluated with 4 years’ experimental data. Minnas model was recommended for water-yield relation simulation. Multiplicative model was recommended to simulate the relations of water with soluble solids, reducing sugars, and sugar/acid ratio and fruit firmness, and Additive model was used to simulate the relations of organic acids, vitamin C, color index and comprehensive quality index.(4) Sugars accumulation model for tomato fruit (TOM-SUGAR) was developed based on the SUGAR model and it performed well on the simulation in the sugars accumulation of tomato fruits from different experiments. The relative root mean square errors (RRMSE) of soluble sugars content and starch content were 17.9% and 18.7 for "Cervil" respectively, and 14.7% and 28.0% for "Levovil" respectively. The RRMSE of soluble sugars concentration and starch concentration were 21.3% and 21.0% for "Cervil" respectively, and 15.4% and 31.5% for "Levovil" respectively.(5) The tomato fruit growth and sugar accumulation coupled model was developed by integrating the fruit growth model developed by Genard et al. (1998) and TOM-SUGAR. The coupled model simulated well the fruit fresh mass, dry mass, soluble sugars content, starch content, soluble sugars concentration and starch concentration with the RRMSE of 13.0%,12.9%,15.2%,22.9%,19.1% and 26.7% for "Cervil" respectively and of 18.9%,18.6%,12.8%,24.6%,14.1% and 30.5% for "Levovil" respectively.(6) An optimal irrigation decision-making method with the goal of maximum benefit was developed by considering the water-yield-quality-price relations for tomato. Another optimal irrigation decision-making method was also built with goal programming method considering the water-yield-quality relations for tomato. The optimal irrigation scheduling was achieved by solving these two models under different cases, providing useful guidances for the water management in the production of high quality tomato.