Total phenolic contents and antioxidant activities of pulp, seed and skin of 22 grape varieties (7 white and 15 red) grown in the Marmara region of Turkey were determined (common, registered or candidate cultivars). The total phenolic contents of grape pulp, seed and skin parts ranged from 9.26 to 62.29, from 162.29 to 326.18 and from 96.61 to 167.42 mg gallic acid equivalents/100 g fresh weight, respectively. Seasonal changes were noticeable in the total phenolic contents and antioxidant activities of different grape parts. The antioxidant activity of grape seeds of registered or candidate cultivars was the highest, followed by skins and pulps. The antioxidant activities of grape skins were higher in red varieties than in white varieties. The results indicated that registered and candidate red or white grape cultivars may have high amounts of phenolics and possess a superior antioxidant activity in comparison to popular cultivars, such as Bilecik İrikarası, Hamburg Misketi, Alfons and Isabella.

The main purpose of this study is to determine the contents of 3 major phenolic compounds (gallic acid, catechin, and epicatechin) in 22 different grape cultivars/hybrids obtained from 2 different breeding programs. Additionally, changes in these phenolic components in the grape leaves of some resistant/tolerant species were determined in relation to powdery and downy mildew diseases in viticulture. The skin, pulp, and seeds of grape berries were analysed over two years, while changes in the phenolic contents of grape leaves were determined before and after these diseases for two years. The major phenolic contents of new hybrids/cultivars were compared with those of popular cultivars in different parts of the grapes, and significant differences in phenolic contents were found among hybrids/cultivars and different grape parts. Variations in the contents of phenolics in grape seeds, skins, and pulp were high, but seeds contained higher levels of these phenolics than pulp and skin. Analyses of the relationship between two viticultural diseases and phenolic changes in resistant/tolerant cultivars in relation with the susceptible “Italia” cultivar revealed that an increase in the content of the phenolic compounds was found after powdery mildew disease. Hybrids/cultivars with high phenolic contents are recommended to develop new superior cultivars, which are resistant to grape fungal diseases, in breeding programs.

Clonal selection is an important tool for grapevine genetic improvement and high-quality production. Clonal selection has been carried out for 70 yr in Turkey and is being continued with different grape cultivars and rootstocks. In this study, 16 clones belonging to nine grape cultivars were selected by the Atatürk Central Horticultural Research Institute for study over 3 yr. Vines were characterised using standard ampelographic descriptors and the data obtained were transformed into numerical scores for analysis of genetic similarity. Although all the clones studied could be uniquely identified, there was much less variation between clones of a particular cultivar than there was between cultivars.

IntroductionIt is known that grapes are among the most important fruits for human health and their importance arises not only from nutritional value but also their natural phenolic compounds (Baydar, 2006a). Phenolic compounds are plant secondary metabolites that constitute one of the most common and widespread groups of substances in plants (Whiting, 2001). Plants need phenolic compounds for pigmentation, growth, reproduction, resistance to pathogens, and many other functions (Oksana et al., 2012). Plant phenolics are secondary metabolites that encompass several classes of structurally diverse natural products (Lattanzio et al., 2006). Secondary metabolites apparently act as defense (against herbivores, microbes, viruses, or competing plants) and signaling (to attract pollinating or seed-dispersing animals) compounds, as well as protecting the plant from ultraviolet radiation and oxidants (Swain, 1977;Kutchan, 2001). Phenolics are known to inhibit the feeding of many insects and have demonstrated toxicity (Grayer et al., 1992). The first stage of the defense mechanism of plants involves rapid

Different grape cultivars of Vitis species have been cultivated in Turkey since ancient times. A large proportion of these cultivars cannot be cultivated in the humid regions of the country due to downy mildew (Plasmopara viticola) and powdery mildew (Uncinula necator or syn. Erysiphe necator) diseases. Cultivars resistant to these diseases can generally grow without any or fewer fungicide applications. However, there are also differences in the resistance level of cultivars. In particular, Vitis vinifera cultivars, the most widely cultured species, are most affected by these diseases. Thirteen V. vinifera cultivars, eight V. labrusca cultivars and six interspecific cultivars were used in this study, for a total of 27 cultivars. The resistance of cultivars against downy mildew and powdery mildew was determined over two years with natural infection and artificial inoculation applications. Generally, all cultivars showed more resistance to downy mildew, while they also showed lower resistance to powdery mildew. The evaluation based on species found V. vinifera to be the most sensitive. While interspecific cultivars were found to be most resistant to downy mildew, V. labrusca cultivars were the most resistant to powdery mildew. Among cultivars of the same species, however, differences in terms of resistance were observed. These differences can be used in breeding studies in order to obtain new, disease-resistant cultivars, which may be grown commercially to comply with good agricultural practices (GAP) or organic viticulture in the future.