Diallel crossing (10x10) in Swiss stone pine. Juvenile-adult correlations and genetic gain for predicting forward selection

Abstract

Swiss stone pine (Pinus cembra) is a viable solution for afforestation in the
high mountain zone, at the upper limit of the forests, due to the species adaptation
ability to the limiting climatic conditions. The aim of this study was to analyse the
genetic variability, inheritance rate and juvenile-adult correlations, in a 26 years
full-sib (10x10 complete mating design) trial, in order to predict the genetic gain of
forward selection. In the spring of 2023, measurements and evaluations were carried
out for all the existing trees, for Survival rate (Sr), growth (Diameter as breast
height- Dbh, Trees' height- Th, Trees' volume- Tv) and quality traits (Forks, stem
slenderness- Ss, branches' diameter- Bd, branches' finesse- Bf, defoliation- Def).
The 90 cross-pollinated (CP) families registered 50% of Sr whereas the other 10 selfcross-pollinated (consanguineous) registered just 11% of Sr, and the majority of those
trees are dominated and face extinction in the next years. Juvenile-adult correlations
were highly significant (p<0.001), indicating that early selection (at the age of 14
years) might be efficient. At the trial age, based on the medium to high heritabilities,
the forward selection of the best 10% individual trees from the top 20 of the 90 CP
families, for Dbh, could be applied, which ensure at least 9.2% of genetic gain.