The aim of this study was to assess the influence of the application of mycorrhizal fungal inoculum on “Cabernet Sauvignon” (Vitis vinifera L.) leaf gas exchange, yield parameters, as well as grape berry composition, especially regarding phenolic compounds. The experiment was conducted over two years under natural vineyard conditions of the Zagreb wine-growing area, the continental region of Croatia. “Cabernet Sauvignon” grapevines were grafted on SO4 rootstock, both being commonly used in all wine production areas in Croatia. Results obtained demonstrated that symbiotic grapevines, in general, expressed improved leaf gas exchange parameters and higher yield parameters, especially regarding the number of clusters per vine. It should be emphasized that mycorrhizal fungi affected higher total flavan-3-ols, total anthocyanins, and total polyphenols in berry skin in both experimental years. Despite variation in some yield parameters, generally, it is possible to obtain higher yields together with the improved phenolic composition of grapes.

Since changes in temperature and precipitation have different effects on (a) all developmental stages of grapevines in most of the wine regions worldwide (i.e., on their phenological characteristics) and (b) different varieties, a comprehensive database of bioclimatic indices has been calculated and analysed for Croatian wine producing regions. The database consists of the average growing season temperature, growing degree‐days, Huglin index, dryness index and cool night index that are based on all available meteorological measurements as well as the outputs of regional climate models (RCMs) from the EURO‐CORDEX database. The horizontal grid spacing of 0.11° from the RCM ensembles enabled a fine‐scale determination of bioclimatic indices for the present and future climate in Croatia. In addition, statistical analyses (standard statistical parameters and Bayesian method) were carried out to examine trends in sugar content, total acidity and date of harvest. Calculations were performed for the present and future climate on the basis of data from seven selected vineyards/wineries and four varieties (‘Graševina’, ‘Plavac mali’, ‘Chardonnay’ and ‘Merlot’). The results show whether the part of Croatia that is suitable for grape cultivation in the present climate will continue to be favourable in the future within the Mediterranean area. In general, projections suggest further warming and drying of the climate in Croatia and an earlier harvest, with some variations among varieties that show latitude dependence. Projections for the future climate also suggest that the existing viticultural zoning will be much less adequate for the Croatian territory because it reduces the economically sustainable production of wine in certain areas.

Grapevine leaves are photosynthetically the most active green organs providing carbohydrates that are of utmost importance for the regular vine’s metabolism and growth. Moreover, leaves are the pioneers of fungal infections caused by B. cinerea, E. necator, and P. viticola. Plant response to these microorganisms mostly depends on the content and composition of phenolic compounds abundantly found in the leaf’s outer tissues (epidermis, cuticle, trichomes). In order to obtain a satisfactory quantity of phenolic compounds, an experiment was conducted towards optimizing a solid–liquid extraction method. Variables were as follows: the type of organic solvent, the sample weight, the extraction temperature, and the extraction time. The optimal conditions were obtained by applying the response surface methodology. Therefore, by using acetonitrile as the organic solvent, conducting a single-step extraction at the temperature of 48 °C during the time period of 2 h and 25 min with a solid-to-solvent ratio of 1:56 g mL−1 (178 mg of leaves powder and 10 mL of extraction solvent) the optimal content of phenolic compounds was obtained. This protocol is reliable, fast, and relatively easy to perform for the determination of the abovementioned compounds.

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Due to the short period of the grape fresh samples availability and their very complex analysis, appropriate grape samples storage is mandatory. In this study, samples were analyzed immediately after harvest and after storage at 220 8C. Frozen samples were thawed as follows: at the room temperature, in the microwave oven, in the refrigerator, and the skin was pulled off from the frozen grape berries. The freezing had a positive effect on the contents of anthocyanins and flavonol glycosides. These compounds are contained in cell vacuoles thus membrane degradation, throughout the freezing process, could enhance their extractability. The freezing had a negative effect on the content of the other polyphenols which can be bound to the cell wall. Among examined thawing methods, the most appropriate method was the peeling grape berry skin from the frozen berries samples with the receptacle. Suitable alternative to the aforementioned method could be the microwave thawing. Practical applicationOne of the most important groups of compounds contained in grape berries are polyphenolic compounds. These compounds significantly affect the quality of grapes and wine. They also have a positive impact on human health. Most of the grapes are being processed into wine, but it also has many other uses. Besides the table grapes, raisins, juices, jams, and wine distillates, currently, various cosmetic and pharmaceutical preparations made from grapes whose functioning is based on the effects of polyphenols are encounter on the market. Given the short period of availability of fresh grape samples and complex procedure of their analysis and processing, samples must be stored in an appropriate manner. This study reported the effect of freezing and applied thawing method on retentions of polyphenolics in grapes. The information obtained by this study is essential for the development of specific applications of the grape berries skins.