• The enhanced fruit quality resulting from deficit irrigation is largely due to increased concentration, while the accumulation of specific polyphenols ( e.g. , rutin and naringenin chalcone) is metabolically driven. • Partial deficit irrigation has less effect on fruit quality traits compared to constant deficit irrigation applied during the whole tomato plant growth cycle. • Yield reduction caused by deficit irrigation results from both source and sink limitations. Therefore, irrigation strategies must be adjusted to optimize the size and activity of sink and source organs throughout the crop cycle to balance quality, yield, and water use efficiency. Drought is the most influential factor affecting the yield and quality of tomato crops, but the range of responses observed is considerable. In order to better understand this variability, industrial tomatoes (cv. H1311) were grown under four irrigation regimes: i) control that maintained soil water content at field capacity (Control: C), ii) 50 % reduction in water supply compared to the control from seedling to fruit harvest (deficit irrigation: DI), iii) 50 % reduction in water supply compared to the control from seedling to fruit mature green stage and then control irrigation during fruit ripening (DI-C), iv) control irrigation until fruit mature green stage and then a 50 % reduction in water supply (C-DI). Results showed that DI enhanced fresh fruit quality by increasing sugars, acids, polyphenols, and carotenoid contents, but most of these effects were attributable to higher dry matter content, as the dry matter concentration of these compounds was not affected or even reduced. Only naringenin, rutin and total polyphenol contents exhibited additive concentration and metabolic effects under DI, as their concentrations increased on both the fresh and dry mass bases. Both C-DI and DI-C treatments had less effect on fruit quality traits than DI. At the plant level, DI strongly reduced vegetative and reproductive development in similar proportions, as well as leaf area and photosynthetic capacity through both stomatal and non-stomatal factors. As a consequence, the commercial fruit yield was strongly reduced under DI, due to decreases in fruit number and fruit growth rate. Altogether, the results suggested that yield reduction resulted from both source and sink limitations under DI. Overall, because commercial fresh and dry yields per plant were similar in C and DI treatment, water removal during the ripening period (C-DI) remained the most competitive strategy in terms of WUE, whereas constant DI might be the most favorable for fresh fruit quality.
Aslani et al. (Wed,) studied this question.