At Mediterranean regions and particularly in southern Portugal, it is imperative to identify grape varieties more adapted to warm and dry climates in order to overcome future climatic changes. Two Vitis vinifera genotypes, Aragonez (syn. Tempranillo) and Trincadeira, were selected to assess their physiological responses to soil water stress. Vines were subjected to four irrigation regimes: irrigated during all phenological cycle, non-irrigated during all phenological cycle, non irrigated until veraison, irrigated after veraison. Predawn leaf water potential was much higher in Trincadeira than Aragonez in non-irrigated plants. This result is in accordance with its higher stomatal control efficiency in this variety (Trincadeira). Photosynthetic capacity (A max at saturating light intensity) decreased due to stomatal and biochemical limitations under water stress. However, recovery capacity of leaf water status after irrigation was faster in Trincadeira. Yield and yield x Brix increased when irrigation occurred after veraison, particularly in Trincadeira. These results show that Trincadeira presents a drought adaptation than Aragonez. Ratio of variable to maximum fluorescence F v /F m and total leaf chlorophyll related with leaf water potential for both species. Reflectance Normalized Difference Vegetation Index (NDVI 705 ), Red Edge Inflexion Point Index and Photochemical Reflectance Index were related with irrigation treatment. Relative water content and specific leaf area were similar between varieties. In conclusion, we suggested that there is variation among the genotypes and the main physiological parameters for variety selection, for drought, were leaf water potential, stomatal conductance and reflectance indexes.

Season long plant-based measurement of water stress and transpiration were studied under field conditions for Crimson grapevine subject to two irrigation regimes with two sub-treatments consisting of normal irrigation throughout the growing season and a short irrigation induced stress period between veraison and harvest aimed at accelerating fruit maturity and thus increasing fruit market value. Leaf water potential measurements coherently signaled crop-available water variations caused by different irrigation treatments, suggesting that this plant-based method can be reliably used to identify water-stress conditions. The use of sap flow density data to establish a ratio based on a reference 'well irrigated vine' and less irrigated vines showed the ability to signal differences in the transpiration rates, which may be suitable for use in automated irrigation systems to improve irrigation management strategies while preventing undesirable levels of water stress. The impacts of the four different irrigation strategies on post-harvest grape quality attributes was studied, and although all implemented irrigation strategies guaranteed the production of quality table grapes, significant differences (p≤0.05) were found in both berry weight and sugar content between the

R E S U M OTodos os frutos sofrem perdas de qualidade desde o momento da colheita até ao seu consumo. A utilização de quitosano como revestimento edível tem sido uma alternativa no tratamento pós-colheita de uva de mesa com bons resultados. Tendo em consideração que a preparação de revestimentos à base deste biopolímero é realizada em solução de ácido acético, pretendeu-se avaliar se a aplicação do referido ácido terá alguma influência nas características físico-químicas da uva de mesa durante o período de conservação a 1 °C e HR de 95%. Do presente estudo conclui-se que a modalidade de ácido acético apresentou pior comportamento que a modalidade controlo e que para além disso não se verificaram interferências negativas deste ácido na solução de quitosano. A conservação de uva de mesa foi facilmente conseguida até aos 14 dias de conservação em frio com a utilização do revestimento edível à base de quitosano na concentração de 0,8%. Palavras-chave: pós-colheita, qualidade, vida útil, Vitis vinifera L. A B S T R A C TAll fruits suffer quality loss from the time of harvest to their consumption. The use of chitosan as edible coating has been considered as an alternative postharvest treatment with good results in table grape. Considering that coatings based in this biopolymer are prepared in acetic acid solution, it was intended to assess whether the application of the acetic acid has an influence on the physicochemical characteristics of table grapes during their conservation period at 1º C and 95% RH.From the present study, it is concluded that the acetic acid alone has a worse performance than the control mode. However, no negative interference of the acetic acid was found in the chitosan solution. The postharvest conservation of table grapes may be easily achieved even after 14 days of cold storage with the use of a chitosan-based edible coating at a concentration of 0.8%.

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