Grk je autohtona sorta vinove loze značajna danas za vinogradarsto Lumbarde i
okolnog područja na otoku Korčule. Jedna je od rijetkih sorata vinove loze s funkcionalno
ženskim cvijetom, što kod uzgoja ove sorte uzrokuje određene teškoće vezane uz
oplodnju i razvoj bobica u grozdu. Sorta je specifična po pojavi malih, besjemenih bobica
(lokalni naziv „pasoline”) koje se u grozdu nalaze zajedno sa znatno većim bobicama koje
sadrže sjemenke. Udio pojedininog tipa bobica unutar grozda vrlo je varijabilan. Ovim
istraživanjem nastojalo se utvrditi koji su uzroci pojave besjemenih bobica kod sorte Grk
vezani uz građu i razvitak muškog i ženskog gametofita, utvrditi utjecaj različitih sorata
oprašivača na broj sjemenih bobica u grozdu te utvrditi varijacije kvalitete grožđa i vina
uzrokovane različitim udijelima besjemenih bobica (pasolina). Analizom muškog
gametofita utvrđeno je nepostojanje pora za klijanje na sporodermi peludi sorte Grk. Iz
toga razloga pelud ove sorte je sterilna iako se razvoj gameta odvija normalno te zrelo
peludno zrno sadrži dvije spermalne i jednu vegetativnu jezgru. Utvrđena je pravilna građa
sjemenog zametka te prisutnost pojedinačnih stanica ženskog gametofita u zrelom
stadiju. Embriji unutar sjemenoga zametka nastavljaju normalan razvoj kroz sve stadije
razvoja ili dolazi do propadanja sjemenih zametaka. Proces propadanja započinje kod
neoplođenih bobica veličine 4 mm.
Analiza utjecaja oprašivača na broj sjemenih bobica pokazuje da su najbolji
oprašivači bili sorte Pošip (27,68% sjemenih bobica u grozdu) i Plavac mali (26,95%
sjemenih bobica u grozdu) dok je najlošiji oprašivač sorta Chardonnay (9,73% sjemenih
bobica u grozdu). Analizom kvalitete mošta utvrđeno je da velike sjemene bobice sadrže
signifikantno veći sadržaj šećera u moštu i pH vrijednost mošta dok male besjemene
bobice imaju signifikantno veći sadržaj kiselina.
Organoleptičkom analizom vina nije utvrđena signifikantna razlika između
varijanata vina od 80% malih besjemenih bobica u grozdu i one sa 80% sjemenih bobica
u grozdu. Signifikantnih razlika nije bilo niti u parametrima osnovne kemijske analize vina
osim kod sadržaja pepela u korist vina sa podjednakim udjelom velikih sjemenih bobica i
besjemenih bobica (pasolina). U vinu dobivenom od 80% pasolina utvrđeno je
signifikantno najviše kafeinske, kumarinske i ferulinske kiseline te procijanidina B1 i
resveratrola.Grk is a native grapevine variety important for viticulture of the Lumbarda area on the
island of Korčula. It is one of the rare grape varieties with functionally female flower, which
causes certain difficulties in grape production associated with poor fertilization and the
development of the berry. Each cluster of this variety contains small, seedless berries
(local name pasoline) and large berries that contain seeds. The share of berries type
within the cluster is highly variable. This study attempts to identify the causes of poor
seedless berries development trough the analysis of structure and development of male
and female gametophyte, to determine the effect of different pollinator varieties on the
number of seeded berries in the cluster and to determine the impact of seedless berry
share on quality of grapes and wine. Lack of germination pores on pollen sporoderma was
found in the analysis. For this reason, the pollen of this variety is sterile, although the
development of gametes takes place normally and mature pollen grain contains two
sperms and a vegetative nucleus.
The structure of the ovule and the presence of individual cells of the female gametophyte
in the mature stage were regular. Embryos inside the ovule develop normally through all
the developmental stages, otherwise decay of the ovule takes place. The process of the
ovule decay begins in unfertilized berries which are 4 mm in size. The decline of ovules
caused by two processes: parthenocarpy and stenospermocarpy. Parthenocarpy occurs
in berries in which there has been no fertilization. The stenospermocarpy occurs with
berries where there has been a process of fertilization but cessation of ovul growth and its
degeneration was caused by unknown physiological factors within the plant. In embrio sac
of certain berries whose stigmas in the opening flower remained covered with flower cap,
there was deternin existence of the zygote in the phase of intensive elongation. Ther was
also obvious that both sinergide look identical and non-degenerate, indicating that there
was no penetration of the pollen tubes and no proper fertilization proces occured. This fact
potentially leads to a hypothesis that in vines can reach process of apomixis.
The analysis of the impact of pollinator variety on the number of seeded berries shows
that the best pollinators were the following varieties: Pošip (27.68% seeded berries in a
cluster) and Plavac mali (26.95% seeded berries in a cluster). The worst pollinator variety
was Chardonnay (9.73% seeded berries in a cluster). The analysis of the must quality
determined that the large seeded berries contain significantly higher sugar content and pH
value while the small seedless berries have significantly higher acid content.
A significant difference between varieties of wine made from 80% of small seedless
berries in the cluster and those made of 80% of the seeded berries in the cluster was not
found in the organoleptic analysis. A significant difference was not determined even in the
basic chemical composition of the wine except for ash content in the wine with equal
share of large seeded berries and seedless berries. Significantly the largest content of
caffeic, coumaric and ferulic acid, procyanidin B1 and resveratrol was found in the wine
made from 80% seedless berries
