Effect of potential crop on vine water constraint

Fermentative maceration in white wine production, involving extended contact with grape skins and seeds, has gained interest in recent years. The impact of this winemaking technique on wine composition and sensory properties remains underexplored.

Volatile sulphur compounds are a group of impact odorants with low odour thresholds that can contribute both positively and negatively to wine aroma. The varietal thiols, 3MH and 3MHA, are known to contribute positive tropical aromas to white wines and are most abundant in Sauvignon Blanc wines. The group of compounds contributing negative aromas are known as reductive sulphur compounds (RSCs) as they add a reductive aroma of asparagus, cooked vegetables and rotten egg to wines. All these compounds play a part in and are a result of the sulphur pathway in the yeast cell during fermentation and therefore attempting to increase the concentration of the varietal thiols may directly influence the concentration of the RSCs. The varietal thiols and the low molecular weight RSCs are highly volatile and therefore their sensory perception can change rapidly over time.

Forest fires in the vicinity of vineyards have significantly increased in the last decade and are a concern for grapegrowers and winemakers in many wine producing countries. The fires cause smoke drift throughout vineyards which cannot be avoided and may result in the production of wines described as ‘smoke tainted’. Such wines are characterized by undesirable sensory characters described as ‘smoky’, ‘burnt’, ‘ash’ aromas and flavours, and also may cause a lingering, unpleasant ashy aftertaste [1; 2].

Most vineyards are grafted and include a variety (Vitis vinifera) grafted over a wild Vitis rootstock (hybrids of V. berlandieri, riparia and rupestris). Grape berry quality at harvest depends on a subtle balance between acidity and the concentrations of sugars, polyphenols and precursors of aroma compounds. The mechanisms controlling the balance of sugars/acids/polyphenols are influenced by the abiotic environment, in particular nitrogen supply, and interact with the genotypes of both the scion variety and the rootstock. Previous work suggests that some of the effects of water stress are in fact linked to a nitrogen deficiency driven indirectly by the reduction of water absorption.

In vitro culture makes it possible to carry out specific studies that would not be possible with whole plants grown in the field or in a greenhouse. Cryopreservation allows long-term preservation without metabolic changes in the plant material and cryotherapy can be efficient in virus elimination, which is a major scientific challenge.
The preculture media of cryopreservation protocols were evaluated on three Croatian grape varieties with different antioxidants (salicylic acid, ascorbic acid and glutathione). The highest growth in vitro was achieved on the medium with the addition of glutathione and the lowest with the addition of salicylic acid.