The importance of fruit cuticle in water relations and firmness has been suggested through studies of the long-shelf life delayed fruit deterioration (dfd) tomato genotype. We tested the hypothesis that dynamic cuticle properties and composition affect tomato fruit transpiration and firmness and are influenced by environmental water availability, using dfd and two normally softening fruit cultivars, Ailsa Craig (AC) and M82, grown under control and water stress (WS) conditions. The effect of WS was also assessed following fruit detachment. WS increased fruit firmness, cuticle load, and the expression of cuticle biosynthetic genes, while reducing cuticle permeability and fruit transpiration rate in AC and M82, but not in dfd fruit. This study supports a direct relationship between fruit cuticle properties, transpiration and firmness, and provides insights into the adaptation of tomato genotypes to environments where water is scarce.
During the return phase, we studied the effect of abscisic acid (ABA) deficiency on cuticle formation along orange fruit development and maturation. We also tested whether postharvest ABA treatment can regulate cuticle properties and composition in citrus fruit and hence control fruit quality after detachment. In agreement with the results obtained with tomato fruit, orange fruit cuticle properties are regulated along maturation process and dependent on ABA content. Thus, ripening stage and preharvest conditions are more important factors determining postharvest behaviour than the water stress conditions applied after fruit detachment. We found these results especially relevant for the agricultural industry, since we claim that adjusting preharvest watering regime it is possible to regulate cuticle metabolism and properties and hence the postharvest behaviour of tomato and citrus fruit, two of the most important crops in the world.
In overview, we can learn from our results that water deficient regime conditions can improve tomato fruit quality after harvest through the modulation of cuticle-related molecular pathways. In addition, we found that ABA-deficiency is a factor increasing cuticle permeability and hence fruit weight loss in orange and tomato fruits. An innovative perspective of our project is considering the water stress growing conditions as a tool to improve fruit quality after harvest. Our experimental water deficient regime was able to increase the synthesis of cuticle components and hence reduce the transpiration rate and weight loss of the harvested tomatoes, which showed a better external appearance, fruit firmness and less decay. Therefore, such conditions led to increased tomato quality and reduced food waste. More research is needed to set up the related parameters, but our results will help to develop new strategies aimed to control fruit quality and shelf life of fleshy fruit in a harmful environment in which water is a scarce resource.
