Molecular characterization of genetic variability and structure of olive (Olea europaea L.) germplasm collection analyzed by agromorphological traits and microsatellite markers

Abstract

We studied 200 trees belonging to 20 accessions of cultivated olive (O. europaea L.) from 4 regions of origin, evaluated by means of agromorphological traits and simple sequence repeat (SSR) markers. The agromorphological traits showed high variation between genotypes and significant correlation coefficients were obtained among the values recorded in two consecutive years, 2013 and 2014. The maximum coefficient of variation for the quantitative agronomic traits was observed in fruit weight wet (13.45%), while the lowest was found in stone width (3.18%). Fruit shape index, leaf length, leaf width, and lenticel size also showed variability. With both DNA-based and agromorphological descriptors, higher levels of variability were found. Genetic variation observed among the olive germplasm at the DNA level was higher than that of the agromorphological traits, indicating the efficiency of SSR markers for detecting genetic diversity among olive genotypes and their relationships. The lack of consistency between the relationship studies performed with molecular and morphological markers could indicate that each marker system measures different aspects of olive genetic variability. Molecular data obtained by SSR markers together with morphological and agronomical characterization of olive trees confirmed the high diversity and their potential use for olive breeding.