Long-term impact of deficit irrigation on the physical quality of berries in 'Crimson Seedless' table grapes.

BACKGROUND

In table grapes, berry firmness influences consumer acceptance so it is important to avoid berry shattering and dehydration during their post-harvest life. Since studies of irrigation effects on table grape quality are comparatively rare, sensory evaluation aimed to identify high-quality berries obtained under different deficit irrigation treatments. A 3-year study examined the effects of deficit irrigation strategies on some physical quality attributes at harvest, after 28 days of cold storage at 0 °C and after an additional shelf-life period of 3 days at 15 °C. Control vines were irrigated to ensure non-limiting water conditions (110% of crop evapo-transpiration), while both regulated deficit irrigation treatment (RDI) and partial root-zone drying (PRD) treatments applied 35% less water post-veraison. The null irrigation treatment (NI) only received natural precipitation (72% less water than control vines).

RESULTS

Total yield and physical quality at harvest were not significantly affected by RDI or PRD. Only severe deficit (NI) decreased berry size, and this treatment had the most dehydrated berries and the worst sensory scores post-harvest. After cold storage, increased berry shattering of the PRD treatment was correlated with lower leaf xylem abscisic acid (ABA) concentration at the time of harvest. Overall quality, especially stem browning, determined the shelf-life, and longer storage duration tended to diminish treatment differences.

CONCLUSIONS

Only NI clusters showed lower quality than their irrigated counterparts. Neither RDI nor PRD had any noticeable effect on berry quality at the end of cold storage and shelf-life, with the slight differences detected between these treatments related to stem browning and dehydration. Sensory results were similar in RDI and PRD, which provided grapes that were more acceptable to consumers than the control. Thus, it is possible to decrease irrigation of table grapes without adversely affecting the physical quality of the berries.