Cluster architecture of old, neglected Croatian grapevine varieties (Vitis vinifera L.)

Abstract

Grape cluster architecture is an important trait affecting fruit composition and yield. Damage caused by gray mold (Botrytis cinerea) is directly related to cluster density and some other environmental factors. The aim of this study was to quantify characteristics of fully mature clusters of eleven old Croatian grapevine varieties (Vitis vinifera L.) which so far have not been phenotypically described in detail, and to examine Botrytis cinerea disease severity on their grapes under field conditions. Eight variables that describe the appearance of clusters were quantified in three consecutive years including cluster weight, length, width, volume, compactness, rachis weight, number of berries and single berry weight. Two-factor analysis of variance provided estimates of varietal and annual differences. Significant differences among eleven old Croatian varieties for all cluster traits were determined. Results suggest diverse cluster morphology within the old Croatian varieties revealing three variety groups by PCA analysis and their varying degrees of sensitivity to Botrytis. These phenotypic data on cluster structure represent a basis for future research, such as QTL analysis or assessment of productivity of these varieties.