terclim by ICS banner
IVES 9 IVES Conference Series 9 Yield formation and grape composition: more than meets the eye 

Yield formation and grape composition: more than meets the eye 


Fruit quality in grapes is not well defined but is often depicted as correlating inversely with crop yield. Both fruit yield and composition, however, are made from distinct components that interact in complex ways. Reproductive growth of grapevines extends over two growing seasons. Inflorescences initiated in buds during the previous year differentiate flowers and set and develop berries during the harvest year. Compensation mechanisms ensure that changing one yield component typically results in a less than proportional change in yield. For example, reducing the number of berries per vine may increase berry size. Nevertheless, warm temperatures and ample water during budbreak or bloom will increase both the number and size of berries, and increase or decrease berry sugar while decreasing acidity. Moreover, the time of fruit set and the number of seeds, rather than yield, may drive the time of ripening onset. By that time, berry size is effectively predetermined and can no longer be manipulated by cultural practices. Ripening starts with berry softening and is followed by sugar accumulation, acid breakdown and, finally, anthocyanin accumulation in dark-skinned grapes. Like yield components, these processes can be modified by altering the size and density of the canopy, which changes the fruit-zone microclimate. Unlike vegetative and reproductive growth, fruit composition is much more responsive to temperature than to water supply. This presentation will give an overview of yield formation and grape ripening, and discuss some key environmental and viticultural factors that lead to differences in harvest yield and fruit composition.


Publication date: June 13, 2024

Issue: Open GPB 2024

Type: Article


Markus Keller1*
1 Washington State University, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350, USA

Contact the author*


grapevine, yield components, water stress, temperature, Vitis


IVES Conference Series | Open GPB | Open GPB 2024


Related articles…


The phenolic compounds of red wines represent a source of numerous benefits for human health, which is why they are a constant subject of scientific research. Winemaking in Serbia has a growing economic significance, with particularly autochthonous varieties included [1]. This research identifies and quantifies phenolic compounds of Serbian red varietal wines of Prokupac and Black Tamjanika varieties. Quantification of the level of phenolics has been conducted, including molecular tannins [(+)-catechin, (-)-epicatechin, procyanidin dimers B1, B2, B3, B4], molecular anthocyanins, and the mean degree of polymerization of tannins by HPLC by UV detection, total antioxidant capacity via spectrophotometric methods and chromatic characteristics via CIELAB.

Mechanistic insights into the bioavailability of oleocanthal and oleacein from olive oil in presence of wine active peptides and amino acids

Oleocanthal (OC) and oleacein (OL) are highly bioactive secoiridoids found in olive oil at elevated concentrations, especially when it is produced from unripe olives (Olea europaea L.). Both compounds have been correlated with strong activities against serious diseases through recent clinical trials. The most important clinical trials have been performed in patients against chronic lymphocytic

Understanding sweetness of dry wines: first evidence of astilbin isomers in red wines and quantitation in a one-century range of vintages

The gustatory balance of wines relies on sweetness, bitterness and sourness. In dry wines, sweetness does not result from the presence of residual sugar as in sweet wines, but is due to other non-volatile compounds. Such taste-active compounds are released during winemaking, by grapes, yeasts or oak wood and belong numerous chemical families [1]. Beyond this diversity, stereochemistry of molecules can also influence their sensory properties [2]. However, the molecular determinants associated with this taste have only been partially elucidated. Astilbin (2R, 3R) was recently reported to contribute to wine sweetness [3]. As its aglycon contains two stereogenic centers, three other stereoisomers may be present: neoisoastilbin (2S, 3R), isoastilbin (2R, 3S), and neoastilbin (2S, 3S). These compounds have already been observed in natural products, but never in wine. This work aimed at assaying their presence for the first time in wines as well as their taste properties.The isomers were synthesized from astilbin and purified by semi-preparative HPLC.

The challenge of quality in sulphur dioxide free wines: natural polyphenol alternatives

Sulphur dioxide (SO2) seems indispensable in winemaking because of its properties. However, a current increasing concern about its allergies effects in food product has addressed the international research efforts on its replacement. This supposes a sufficient knowledge of its properties and conditions of use. Several studies compared SO2 properties against new alternatives that are supposed to overcome SO2 disadvantages. Firstly, the state of art on SO2 wine replacements is revised, and secondly, the last promising results using natural enriched polyphenol extracts are shown.

Oligosaccharides in red wines: could their structure and composition be influenced by the grape-growing

Oligosaccharides have only recently been characterized in wine, and the information on composition and content is still limited. In wine, these molecules are mainly natural byproducts of the degradation of grape berry cell wall polysaccharides. Wine oligosaccharides present several physicochemical properties, being one relevant factor linked to the astringency perception of wines (1,2). A terroir can be defined as a grouping of homogeneous environmental units based on the typicality of the products obtained. This notion is particularly associated with wine, being the climate and the soil two of the major elements of terroir concept.