Morphological characterization of the 1-year-old shoots in tetraploid vs. diploid leccino olive ( <i>Olea Europaea</i> L.) cultivar

Abstract Polyploidization is known to cause changes in the ploidy levels of plant somatic cells that affect the morphological, physiological and chemical composition. The aim of this research was to investigate the effects of tetraploidization in olive. To do this, several characteristics of 1-year-old shoots of two olive genotypes were compared: the diploid cultivar Leccino (L), and its tetraploid mutant Leccino Compact (LC), considered a slow-growing genotype. LC differed significantly from L in the morphological characteristics, with higher values of diameter, dry mass and volume of the stem (46%, 103%, 102%, respectively), and higher area, mass and volume of the individual leaf (43%, 66%, 73%, respectively). LC also had thicker, longer and wider leaves (30%, 10%, 34%, respectively) and significantly lower leaf density (7%) and lower specific leaf area, leaf mass ratio and leaf area ratio (17%, 4%, 18%, respectively). Internode length and stem density were not significantly different. The results allowed us to thoroughly characterize the effects of tetraploidy on 1-year-old shoots in olive, and also suggest that the slow growth of LC is due to its lower leaf area per unit of total biomass, which reduces leaf area production and, consequently, light interception, resource availability and tree growth. These results will be useful for genetic improvement programmes and for planning further exploitation of tetraploidy in horticulture.