Leaf water potential and sap flow as indicators of water stress in Crimson ‘seedless’ grapevines under different irrigation strategies

Vitis vinifera L. cv. Crimson Seedless is a late season red table grape developed in 1989, with a high market value and increasingly cultivated under protected environments to extend the availability of seedless table grapes into the late fall. The purpose of this work was to evaluate leaf water potential and sap flow as indicators of water stress in Crimson Seedless vines under standard and reduced irrigation strategy, consisting of 70 % of the standard irrigation depth. Additionally, two sub-treatments were applied, consisting of normal irrigation throughout the growing season and a short irrigation induced stress period between veraison and harvest. 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 can potentially be used to signal differences in the transpiration rates, which may be suitable for improving irrigation management strategies while preventing undesirable levels of water stress. Although all four irrigation strategies resulted in the production of quality table grapes, significant differences (p ≤ 0.05) were found in both berry weight and sugar content between the standard irrigation and reduced irrigation treatments. Reduced irrigation increased slightly the average berry size as well as sugar content and technical maturity index. The 2-week irrigation stress period had a negative effect on these parameters

Impact of berry size at harvest on red wine composition: a winemaker's approach

Producción CientíficaBACKGROUND: A classical postulate of viticulture declares that small grape berries produce the best red wines. The popularity of this postulate among winemakers leads them to consider berry size at harvest as a tool to measure the grape’s potential to obtain great red wines. To address this issue, two vineyards from the same cultivar and subjected to the same physiological conditions during growing were selected for their difference in average grape berry size at harvest. Grapes from both origins were characterized and used for red winemaking by the same way. Release of volatile compounds and phenolic compounds during the alcoholic fermentation was monitored, and the finished wines were chemically characterized. RESULTS: Larger grapes have a lower theoretical surface-to-volume ratio but have thicker skins and a greater proportion of skins (m/m). Wines made from grapes with a greater proportion of skins contain higher amounts of phenolic compounds, terpenes, volatile acids, acetate esters and polysaccharides. CONCLUSION: According to the results, it seems that grape skin extraction is more related to skin proportion than to berry size. Thus not always smaller grapes produce darker red wines.This work was supported by CONICYT-Chile (FONDECYT 3150322, FONDECYT 11160510, FONDECYT 1140882 and FONDEQUIP EQM-130129)

Isolation and characterisation of a melon cDNA clone encoding phytoene synthase.

A cDNA clone (MEL5), encoding a protein homologous to phytoene synthase (PSY), has been isolated from a climacteric melon fruit cDNA library, using the tomato cDNA clone TOM5 [34] as a heterologous probe. MEL5 hybridised to a transcript of 1.65 kb which suggested that the 1.36 kb clone, isolated originally, was not full-length. The missing 5 end was isolated by a reverse transcriptase-polymerase chain reaction (RT-PCR)-based method. This enabled the full sequence of the protein to be deduced and the cleavage site of the transit peptide for chromoplast import to be predicted. Northern analysis of RNA extracted from fruit samples of different ripening stages as well as from roots, leaves and flower petals was used to examine the expression pattern of the corresponding mRNA. The transcript corresponding to MEL5 is present at low quantities in unripe (green) fruit, reaches its highest levels when the fruit turns from green to orange and persists at lower levels during later ripening stages. A similar transcript was also detected in flower petals and in trace amounts in leaves and roots. Genomic Southern analysis indicates that the clone is homologous to a low-copy-number gene family. Sequence analysis showed a high degree of conservation among plant PSYs