Comparative phenological evaluation of white wine vine varieties grown in Bulgaria

A comparative phenological evaluation of a group of 32 vine varieties for white wines has been carried out. It has been found through the application of cluster analysis, PCA and factor analysis that, depending on the duration of the separate phenophases and periods in days, the studied varieties are grouped into four clusters. The phenological indicators are transformed into three factors, with a different degree of influence on the grouping of varieties, which explain 74% of the total variation. The most important for the grouping of varieties are the phenophase berry growth, and the periods flowering – berry softening and berry softening – technological maturity. In order to increase the efficiency of selection, it is advisable to cross varieties for white wines characterized by optimal phenological parameters, and belonging to clusters most remote from each other