Relative Leaf Expansion Rate as an Indicator of Compensatory Growth of Defoliated Vines (Vitis vinifera L. cv. Prokupac)

Defoliation is a common practice in vineyards, with numerous benefits for vine microclimate conditions, andit can significantly improve the composition of grapes. In addition, early defoliation reduces the active leafarea, which affects the modifications of the source-sink balance and decreases whole-vine photosynthesis.The reaction of grapevines to early defoliation is to mitigate the effects through compensatory growth,resulting in more lateral shoots with a greater number of leaves. In this study, we evaluate the use of nondestructiveand continuous measurements of mean and lateral leaf area on the same shoots for the purposeof monitoring leaf area development and calculating relative leaf expansion rate (RLER) during activegrowth. The results show that the grapevine’s ability to recover its leaf area after defoliation dependsmainly on the time of defoliation. Vines defoliated early had time to compensate for the removed leaves byproducing a greater number of lateral shoots with more leaves, resulting in a larger total leaf area. Witha decrease in shoot growth during vegetation, the recovery ability decreases, and compensatory growthis therefore not enough to restore the reduced leaf area. Based on the value of RLER, it is shown that, ifdefoliation is performed in the period of intensive shoot growth, it retards the emergence of new shootsand leaves over several days, followed by a period of regrowth. Very slow or no growth of shoots and leavesoccurred with defoliation after the véraison stage

Genetic characterization and relationships of traditional grape cultivars from Serbia

Reference genetic profiles were generated for 12 traditional grapevine cultivars of Serbia through a genotyping approach that included the "core set" of 9 SSR markers for genetic identification and further 13 common microsatellites for strengthening genetic relationship analysis. Consistent matching with SSR markers of grapevines cultivated in neighbouring countries or maintained in European germplasm collections was found for most of the genotypes, suggesting possible synonyms and revealing that 'Muskat Krokan' corresponds to 'Muscat fleur d’Oranger' and two 'Tamjanika' cultivars are identical to 'Moscato Giallo' and 'Moscato Rosa'. When compared with germplasm representing the classical eco-geographic grouping of grapevine cultivars, Serbian non-Muscat genotypes clustered within the Convar pontica subconvar balcanica taxon thus supporting their indigenous origin.

REACTION OF TABLE GRAPE VARIETIES TO LOW WINTER TEMPERATURES

The aim ofthis study was toinvestigate theresistanceof winter buds to lowwinter temperatures oneighttablevarieties of differentripening time. The study was conducted during vine dormancy at three testing dates during winter i.e. over the last ten days of the three winter months of December, January and February. At the first, second and third dates, the air temperature in the freezing chamber was reduced to - 15oC, -20oC, and -10oC, respectively.The analysis of the average values for the study period shows that Muscat Hamburg and Smederevo Muscat had the lowest and highest average percentage of completely frozen buds (48.97% and 58.84%, respectively). The average values for partly frozen buds ranged from 29.17 % in Afuz-Ali to 33.11 % in Muscat Hamburg. The evaluation of the data on unfrozen buds suggests that the average values were within the range of 11.15 % (Smederevo Muscat) to 17.91 % (Muscat Hamburg)

Changes in leaf water status in grapevine graftlings treated with growth regulators

The effect of foliar application of plant growth regulators, paclobutrazol (1000 mg/L), chlorcholine chloride (200 mg/L) and gibberellic acid (100 mg/L) on leaf water status in grapevine graftlings of cv Cardinal was investigated. After stratification and waxing, young vines were planted into vegetation pots and grown in a glasshouse. Foliar treatments were applied once, twice or three times during the vegetative period, starting on 25 July and every 15 days thereafter. Values of total water potential (Tl) and of relative water content (RWC) were measured over the same period. Results indicate a tendency of increased TL values in leaves of plants repeatedly treated with a growth inhibitor paclobutrazol (-1.18 Mpa) compared with untreated (-1.36 Mpa) as well as plants treated twice with gibberellic acid (-1.37 Mpa). RWC in leaves was significantly increased in the second half of the vegetative period when paclobutrazol was applied twice (78%) in comparison with control (75%). Values of both investigated indices point to a more favorable water status of plants treated during the vegetative period with growth inhibitors compared with untreated and plants treated with gibberellic acid