Phenotypic divergence of grapes using productive cycle

Abstract

Classifying vines regarding the number of days required to complete de productive cycle and the duration of intermediate phenologic phases are essential for genetic improvement programs, implementation of cultivation techniques and handling of the grape harvest. The objective of this study was to evaluate the access phenotypic divergence of grapes from the germplasm collection by the Agronomic Institute - IAC. Evaluations were performed for 4 years of production, from 2012 to 2015, when the plants were 4 years old. The training system applied the espalier, at a 2.0 x 1.0 m spacing between lines and plants, respectively. The IAC's grape germplasm collection comprised 110 varieties of the 'Vitis vinifera', 'Vitis labrusca' species and inter-specific hybrids grafted into the IAC 766 rootstocks, being 3 plants per each variety. After the pruning of the main vine phonologic phases, the number of days was evaluated using the scale proposed by Eichhorn and Lorenz. Two evaluations a week were carried out until the flowering, and afterwards one evaluation was performed a week, the period between pruning and the beginning of sprouting, full flowering with 50% flowers opened, beginning of maturation (veraison) and maturation (harvest), visually mature fruits and content of soluble solids above 14 degrees Brix. Multivariate analysis, such as the correlation between varieties, analysis of the main components (PCA) and methods of non-weighted arithmetic means (UPGMA) was applied to classify the phenotypes according to the productive cycle. A relation was found between the sprouting and the flowering phases, as well as the starting maturation and maturation. The first two components explained 81% of the total variability, being that the starting maturation and maturation were the best variables to study the divergence of vine phenotypes. Also, combining the UPGMA method and the PCA analysis that distinguished three groups, allowed us to divide the phenotypes into 25 processes, 75 median and 10 late varieties, according to their productive cycle. It was possible to conclude that the techniques used to study the genetic diversity applied to phenologic characters were effective to evaluate the vines phenotypic divergence, and therefore, the multivariate analysis may be used to guide future vine improvement programs.