Comparison of genetic gains of mass and clonal selection of grapevine

Abstract

The genetic variability among and within ancient grapevine varieties is a basis for the innovation in wine sector in the future. Therefore, genetic variability should be preserved and simultaneously evaluated through the most efficient methods.

The present study uses the theories of mixed models and of quantitative genetics to demonstrate the potential of intravarietal genetic variability for selection purposes. The case study reports to the second step of selection of the Touriga Nacional variety carried out in a large field trial containing 195 genotypes (a representative sample of the intravarietal variability). This trial is located at Vila Nova de Fozcoa (demarcated Douro/Port region in Portugal) and was planted according to a randomized complete block design with 5 replicates. During 14 years (1989 to 2002), the yield behaviour of seven individual clones (the top ranked according to the yield average of the 14 years) was compared with the behaviour of groups of clones.

The results showed that the estimates of the generalized broad-sense heritability of yield per year ranged from 0.36 to 0.87. For a confidence level of 95%, the genetic gains obtained with the selection of groups of clones were always above zero, except in one year. Analyzing the behaviour of individual clones, in some years their predicted genotypic effects were higher than those obtained for the groups of clones but, in other years, were lower. The precision in the prediction of genetic effects was always higher when groups of clones were selected.

It is concluded that the selection will be more efficient and stable when based on the utilization of the intravarietal variability and when a group of clones is selected (mass/polyclonal selection).