Analysis of phyllometric parameters efficiency in discrimination of Croatian native V. vinifera cultivars

The aims of this study were to achieve correct cultivar classification of leaf samples by using phyllometric parameters to determine the performance of parameters applied as the discriminant criteria and to determine the minimal number of leaf parameters needed to accurately classify leaf samples within cultivars. Seventy-nine phyllometric parameters were measured/calculated on 360 leaf samples from eleven grapevine cultivars, gathered during several years, from different growing conditions and with some differences in the sampling methods applied. Stepwise discriminant analysis was used to rank the phyllometric parameters according to their efficiency in the discrimination of cultivars. A series of discriminant analyses was performed with successive introduction of new parameters as discriminatory elements until 100 % correct classification of leaf samples into the correct cultivar was achieved. This was achieved using only the seven highest ranking phyllometric parameters from the stepwise discriminant analysis. Additionally, canonical discriminant analysis was performed to evaluate the differences between cultivars in the same parameters. This study represents a model for analysis of the efficiency of different ampelometric parameters for discrimination of V. vinifera cultivars.

Reproductive potential of the functionally female native Croatian grapevine 'Grk bijeli'

A native Croatian grapevine 'Grk bijeli', sharing a parent-offspring relationships with 'Tribidrag' (aka 'Zinfandel'), is grown exclusively on the Adriatic island of Korčula. It is one of the grape cultivars with female-only functional flowers, causing reduced fertilisation and leads to problems in grape production and wine quality. A typical cluster of 'Grk bijeli' at maturity contains fully developed seeded berries, in addition to a highly variable proportion of undersized seedless berries. The aim of this study was to identify the cause of the reduced reproduction potential of 'Grk bijeli' in order to establish a better growing environment for improved yield and grape quality. 'Grk bijeli' female gametophyte develops normaly and at maturity contains both egg and central cell, together with two synergid cells and three antipodal cells. On the other hand, 'Grk bijeli' pollen grains show developmental deviations. Specifically, most of the pollen grains undergo the first pollen mitosis and contain one vegetative cell and one generative cell, while 20 % of ungerminating grains also accomplish the second pollen mitosis, giving rise to two sperm cells and one vegetative cell. Morover, 'Grk bijeli' pollen has acolporate morphology, which prevents germination and contributes to reduced reproduction. Furthermore, fertilisation after pollination with other varieties results in various degrees of ovule abortion depending on the pollinator, revealing Croatian cultivars 'Plavac mali crni' and 'Pošip bijeli' as favourable varieties. Although this study describes a highly valuable cultivar of local importance, it also contributes to fundamental knowledge of grapevine reproductive biology and offers a strategy for improvement of wine production and oenological performance of semi-fertile varieties in general

Differences in chemical composition of 'Plavac mali' grape berries

Evaluation of differences in yield and quality of grapevine is often based on the random samples of berries harvested on the same date. Due to differences in ripeness of berries from the same cluster, and among berries from different clusters of the same vine, the determined differences among examined treatments (clones, agricultural practices etc.) based on random berry samples may be over- or underestimated. The aims of this study were to determine: (1) differences among three 'Plavac mali' clones in the proportion of berries of different density classes (sugar concentration level) using the flotation method; (2) differences in berry weight and chemical composition among density classes of the same clone, and (3) differences between clones of the same density class. Significant differences were determined for all observed characteristics, among different berries density classes and clones. The results obtained indicate that berry samples used to compare different clones should be, to the greatest possible extent, at the same level of ripeness, as this significantly effects chemical composition. This can be achieved using the density separation of berries with the simple flotation method presented in this study. The presented results could be useful in the future improvement of clonal selection methodology as well as in improvement of sampling strategy for other types of researches

Cryopreservation and cryotherapy of grapevine (Vitis vinifera L.)

This study aimed at testing the efficiency of a droplet-vitrification cryopreservation protocol in eliminating selected grapevine viruses. The cryopreservation protocol led to approximately 50 % recovery with cultivar 'Portan' and five international cultivars tested, but very low recovery was noted with Croatian cultivars. GFLV and GLRaV-3, two (economically important grapevine) viruses were eliminated in a high percentage (up to 100 %) of plants regenerated from cryopreserved shoot tips. Virus sanitation was observed as well in samples before liquid nitrogen exposure. Genetic stability of plants regenerated after cryopreservation was studied using AFLP markers. Polymorphic fragments were observed in non-cryopreserved and cryopreserved samples treated with PVS2 solution, the number of which increased with increasing durations of exposure to PVS2 solution

Ampelographic and genetic characterization of Croatian grapevine varieties

Before the Phylloxera (Daktulosphaira vitifoliae) crisis in Croatia more than 400 grape varieties were under cultivation. Today their number is drastically decreased. Recently, many efforts in the preservation of grapevine biodiversity were undertaken: detailed inventory of varieties in different wine-growing regions, establishing of national and regional collections and their systematic ampelographic and genetic characterisation. This paper shows results of multiannual ampelographic and genetic research concerning Croatian grapevines considered as autochthonous varieties. After identification, many synonyms and homonyms were detected and unique genotypes were selected. Basic data of them are shown: description (according to OIV descriptors) and genetic profiles (9 SSR loci), growing area and status of vulnerability. Also, genetic relationship based on the shared allele distance is computed from SSR data. Results show certain level of similarity among varieties, and classify Croatia as important gene-pool in Europe. Some additional accessions which were detected and introduced into collections recently are still being investigated and characterized so that the here presented list of Croatian native grapevine cultivars is not final

Viral Diversity in Autochthonous Croatian Grapevine Cultivars

A survey was conducted on nine autochthonous grapevine cultivars grown along the Croatian coastal region. In total, 48 vines (44 from germplasm collection, 4 from vineyards) originating from 23 sites were tested for 26 viruses using molecular methods. Results revealed high infection rates with Grapevine leafroll-associated virus 3 (GLRaV-3); Grapevine virus A (GVA, both 91.7%); Grapevine fleck virus (GFkV, 87.5%); and Grapevine rupestris stem pitting-associated virus (GRSPaV, 83.3%). Other detected viruses were: Grapevine fanleaf virus (GFLV); Grapevine leafroll-associated viruses 1, 2, and strains of 4 (GLRaV-1, GLRaV-2, GLRaV-4); Grapevine viruses B, D, F (GVB, GVD, GVF); Grapevine red globe virus (GRGV); Grapevine vein feathering virus (GVFV); Grapevine Syrah virus 1 (GSyV-1); and Grapevine Pinot gris virus (GPGV). No virus-free vine was found. Mixed infections were determined in all vines, the number of viruses in a single vine ranged from three to nine. GLRaV-3 variant typing confirmed presence of group I, II, and III. Four vines with leaf deformation and mottling were positive for GPGV. Seven viruses (GLRaV-4-like group, GVD, GVE, GVF, GRGV, GSyV-1, and GVFV) were detected for the first time in Croatia. This survey confirmed the deteriorated sanitary status of autochthonous Croatian grapevine cultivars