COMPARATIVE STUDIES OF SOME WHITE WINE CULTIVARS IN THE SUB-REGION OF BELGRADE AND NIŠ

In two wine-growing areas with different climatic characteristics 12 cultivars intended for the production of white wines were studied. The climatic characteristics include: mean annual air temperatures, mean vegetation air temperatures, heliothermal coefficient, hydrothermal coefficient and active temperatures sum from the moment of the growth of shoots to their full maturity for each studied cultivar. Elements of buds fruitfulness (6 features in total), yield, cluster mass, sugar quantity and grape quality were observed in both localities. In the vineyards of Grocka and Kutina high yielding varieties Ugni blanc and Dimyat can be grown with great success. Italian Riezling produced higher yields and better quality of unfermented grape juice in the vineyards of Grocka in comparison with the vineyards of Kutina. Pinot blanc in both localities was characterized by high yield, but the quality of unfermented grape juice was better in the vineyards of Grocka. Variety Rkaciteli produced high yield and good quality of unfermented grape juice in the experimental period in the vineyards of Kutina.

studies of a greater number of cultivars in collection plantings under the same or similar ecological conditons have numerous advantages (C o l a p e t r r a, 1987). As a rule, a cultivar of wide adaptibility has high genetic potential and in favorable ecological conditions produces high yields and in unfavorable produces lower yields and grapes of poor quality. That is the reason that favorability and soil, as well as a complex of adequate agrotechnical measures taken by man intentionally with regard to the needs of a plant, are the key factors of success in grape production. (S i v č e v, 1997). Optimal loading of vines with fruitful buds according to B o n d a r e n k (1989) is directly dependent on the harmonious relationship between ecological factors. F r e g o n i et al., (1992) determined favorability of growing for the three most represented wine cultivars: Barbera, Croatina and Malvasia di Candida aromatica in the area of Val Tidone, based on interdependence of yield, quality of unfermented grape juice and wine, sum of air temperatures expressed in Winkler's index, altitude, terrain exposition and type of soil. According to B r a v d o (2001), vine foundation and locality also have significant influence on the concentration of free and bound monoturpenes, as well as other aromatic substances in unfermented grape juice and wine.
Simultaneous growing of greater number of vine cultivars on one locality enables better use of climate and soil and contributes to more efficient resistance to limiting factors of the environment. In this paper 12 white wine cultivars were studied, grown in two different localities with the aim of comparing and recommending them based on climatic characteristics and their 12 features.

Material and Method
The studies were conducted in the collective plantings of the Faculty of Agriculture, University of Belgrade, "Radmilovac" (λ=44º 45´ N, ϕ=20º 35´ E, H=135 m) and Viticulture and Wine Production Center of Niš, Institute of Agricultural Studies "Srbija" (λ=43º 61´ N, ϕ=22º 32´ E, H=200 m). The lot on experimental farm "Radmilovac" is situated on a mild slope, rows are distributed in southeast-northwest direction. The planting distance is 3 x 0.75 m, the training system is double-branched cordone with mixed cutting applied. The hilly terrain, semiarid and mildly warm climate on a carbonate geological foundation enabled the formation of rigosoil. The soil structure is nutty to clotty. According to its mechanical contents, it is clay to sandy clay, of good permeability and high absorption power. Nitrogen is present only in the field soil layer (0.10-0.15%), averagely provided with available potassium and poorly provided with easily available phosphorus.
The experimental lot of the Viticulture and Wine Production Center is situated on a slope with medium slant up to 5º, the rows are directed southeastnorthwest. The distance between the rows is 2.5 x 1.3 m (planting in the "nest") with the exception of cultivars Dimyat and Rkaciteli where the distance is somewhat larger 2.8 x 1.5 m. The training system is single-branched cordone with mixed cutting applied. The mechanical contents of the soil is heavier relative to the soil at Experimental Station "Radmilovac", which is confirmed by lower value pH=5.5 and the absence of carbonates; it is heavy rigosoil. The surface layer of the soil is well provided with humus (3.15%) and the quantity gradually decreases with depth. The quantity of potassium in the surface layer of the soil is 24.6 g/100g a.d.s. 4 and decreases with depth. The surface layer of soil is poorly supplied with phosphorus and it appears only in traces in deeper layers.
The studies were conducted at Wine Production Center of Niš in the period from 1993 to 1995. Cultivars of three main ecological-geographical groups were included in the study: Fruitfulness of buds and shoots was determined applying standard methods for the following features. The yield of grapes was determined per vine and calculated per unit of area. Apart from the yield, the number of clusters per vine was measured and average grape mass was calculated. Sugar contents was determined based on the thickness of unfermented grape juice, the contents of total acids by neutralization with N/4 NaOH. The quantity of sugar per hectare was determined per hectare based on grape yield, percentage of unfermented grape juice and sugar percentage in unfermented grape juice.

Results and Discussion
Comparative results of the elements of climate are shown in table 1   Air temperature tendency in Belgrade and Niš for the period of 20 years (1982-2001), graph. 1, indicates increase of mean annual and mean vegetation temperatures, which is in accordance with the forecast climatic changes (H o u g h t o n, 1991). In the last decade of the second millenium air temperature fluctuations for successive years in both Belgrade and Niš are significant, which is a risk factor for grapevine. We can conclude that, when analyzing climatic conditions, main meteorological elements tendencies must be analyzed at the same time.
Hydrothermal coefficient was calculated separately for the periods April-June and July-October (1996)(1997)(1998)(1999)(2000)(2001). It indicates redistribution of precipitation in the vineyards of Grocka: maximum in September (R=87.8 mm) is more prominent than the spring maximum. Intensive summer precipitation (R=88.8 mm) is also noticeable in these vineyards. Mean values for the studied features of fruitfulness, for the experimental period, are shown in special tables for the Experimental Station "Radmilovac" (tab. 2a) and Viticulture and Wine Production Center Niš (tab. 2b), so that comparisons may be made within a locality and among them by cultivars. Data indicate that burdening of vines with fruitful buds in Radmilovac ranges from 20 to 30, and in Niš from 15 to 20, which is a consequence of different vegetation potential and growing system. This produced effects on the share of fruitful shoots, which is on the level of mean values for all cultivars 58.5% in Radmilovac and 84.3% in Niš. Productivity of buds was greater in Radmilovac (174.0 g) in comparison with the productivity of buds in Niš (154.6 g). Cultivars with higher buds productivity value in the vineyards of Grocka were: Kujundžuša, Dimyat, Ugni Blanc, Ocatac Blanc and Malvasia Istriana, and in Niš: Dimyat, Bayan Chirey, Ugni Blanc, Rkaciteli and Hungarian Riezling (C v e t k o v ć , 1998).
N a k a l a m i ć and G a r i ć (1995) point out that in the vineyards of Orahovac, in the phase of growing fertility, Riesling Italico gave the best results with mixed cutting and with the length of arches of 10-12 buds and burdening of vines-28-30 buds.
Significant differences were observed in the grape yield per year and mean values for the experimental period in both locations per cultivar. The following cultivars are prominent in both localities: Ugni Blanc, Kujundžuša, Dimyat and Ocatac Blanc. Ugni Blanc belongs to ecological-geographical group subconvarietas Iberica and Dimyat, Kujundžuša and Vugava to ecologicalgeographical group subconvarietas Balcanica. Pinot blanc, Müller-Thurgau, Muscat blanc and Riesling Italico are the cultivars which produce excellent results in both localities and which made high contents of sugar in unfermented grape juice in the experimental period. According to E i b a c h (1990) external factors: climate or grapevine growing method were not exclusive factors of grape quality. As early as in 1927, Sartorius established negative correlation between the yield and contents of sugar in unfermented grape juice, known as the relationship between quality and quantity. B ä d e r (quoted by Eibach) showed that this relation is not the same in all cultivars, correlation is more prominent between the contents of sugar in unfermented grape juice and cluster mass in comparison with the contents of sugar in unfermented grape juice and number of clusters per vine.
Sugar quantity was calculated per hectare in accordance with the yield. On average, sugar quantity at the Experimental Station "Radmilovac" was 2640 kg/ha and in Viticulture and Wine Production Center Niš 2168 kg/ha. If we compare this with the values of heliothermal and hydrothermal coefficient we can notice that the climatic conditions in the vineyards of Grocka are favorable relative to the vineyards of Kutina. High fertility and adaptability to different ecological conditions is the characteristic of cultivar Ugni Blanc, which is confirmed by the results of G a l e t (1979) and M e l i t a F a z i n i ć (1987). Cultivar Bayan Chirey produced high yields in the studied conditions, but it matures late and collects little sugar in unfermented grape juice, which is the reason why it is not recommended for propagation in the regions of Serbia. Elementi rodnosti okaca (ukupno 6 obeležja), prinos, masa grozda, količina šećera i kvalitet grožđa praćeni su u oba lokaliteta. Sorte sa visokom vrednošću produktivnosti okaca u gročanskom vinogorju su: Kujundžuša, Smederevka, Juni blan, Bugava i malvazija bela, a u Nišu: Smederevka, Bajan širej, Juni blan, Rkacitel i Sremska zelenika.