Clonal variation for shoot ontogenetic heteroblasty in maritime pine (Pinus pinaster Ait.)

Pine seedling shoots undergo sharp heteroblastic changes during the early ontogenetic stages. The rate of these changes has been seen to vary between species and provenances within species, but there is a marked lack of information about its genetic control at the lower hierarchical levels. We used clonal replicates of maritime pine to determine broad-sense heritability of shoot ontogenetic heteroblasty and its correlation to rooting ability. We applied a simple ontogenetic index based on the proportion of basal nodes with secondary needles in rooted cuttings of 15 clones from 9 environmentally contrasting origins. We found a high clonal heritability for shoot ontogenetic index and a moderately high heritability for rooting ability, but both genetic and phenotypic correlations between these two traits were weak and non-significant. These results indicate that both developmental phenomena are genetically controlled, but not strictly associated in this species.