Genetic relationships between terminal shoot length, number of flushes and height in a 4-year-old progeny test of Pinus brutia Ten.

• Key message In this study, genetic variation in polycyclic growth was investigated in a young Pinus brutia Ten. study in Turkey. The number of flushes was partially under additive genetic control and was moderately correlated with the tree height at age 4. • Context Pinus brutia is the most economically important tree species in Turkey. Previous limited studies suggested that its cyclic shoot elongation pattern can be useful for selecting seed sources for breeding and conservation of genetic resources. • Aims Understand the degree of genetic control of terminal shoot growth, number of flushes, and total tree height at early ages and assess the genetic relationships between the traits to guide decisions for breeding and gene conservation. • Methods Open-pollinated progenies of 188 trees from eight different seed sources were tested in three locations in the Aegean region of Turkey. Variance components, heritability and additive genetic correlations were estimated for tree height, terminal shoot length, and number of flushes. • Results Traits were moderately under genetic control at the family. Terminal shoot length explained 76% of the variation in tree height. A strong genetic correlation (0.96) was found between tree height and terminal shoot length, while the number of flushes had a moderate genetic correlation with height (0.59). Northern seed sources tended to display less height growth, partially due to fewer flushes and lower shoot length. • Conclusion Shoot elongation in the species is partially under additive genetic control and could be useful to select for early height in breeding programs.