Genetic and environmental variation of internodal and whorl branch formation in a progeny trial of <i>Picea abies</i>

Abstract

Abstract Progenies from a natural stand of Picea abies planted on a forest site with heterogeneous growth conditions were characterized for genetic and environmental control of internodal and whorl branch formation and lammas growth. The progenies studied were 27 years old from seed and planted in a randomized complete block experiment. Internodes and whorls studied were located in the top section of the trees. Significant genetic variation (p<0.01) was found for a number of internodal and whorl branches. Block means for the length of internodes, a strong indicator for the site index in respective blocks, were correlated strongly with branch dimensions (r≥0.90), intermediately with the frequency of lammas growth (r=0.81) and number of branches in whorls (r=0.68), and only weakly with the number of internodal branches per length unit of internode (r=0.25). A strong environmental effect on branch dimensions was supported by the relative size of variance components. The results show that the environmental effect expressed by site index dominates the control of branch dimensions, while the number of branches is under stronger genetic control in P. abies.