Genetic and cyto-histological analyses in Olea europaea L. cultivars in parent-child kinship

Modern olive breeding points to a plant model characterized by low vigour, high productivity, and resistance to biotic and abiotic stresses, all traits required by the intensive and superhigh-density (SHD) systems of olive tree growing. The Italian Don Carlo and FS-17 Favolosa stand out among the new cultivars that are being tested. They were obtained not by breeding but by mass selection from two seedling populations of the Frantoio cultivar (maternal parent). Here, a multidisciplinary approach was used to determine the paternal parent of Don Carlo and FS-17, and then to investigate the inheritance of interesting traits such as fruit cell dimensions and oil content in these cultivars. Microsatellites were applied in phylogeny and kinship analyses, along with two functional markers previously developed on OeACP1 and OeACP2 genes. Ascolana Tenera cultivar was identified as the paternal parent of both new cultivars. This result was also supported by the analysis of the self-incompatibility group of the new cultivars and their most likely paternal parents. Light and electron microscopy [Cryo Scanning Electronic Microscopy (CRYO-SEM), Electronic Scanning Microscopy (E-SEM), and Transmission Electron Microscope (TEM)] techniques were used to analyze the fruit development concerning oil accumulation. Significant differences in cuticle thickness, size and shape of mesocarp and exocarp cells, and oil content were detected among cultivars. Our results suggested that the rearrangement of the traits studied led to an improved progeny compared to the parents. FS-17 exhibited an oil storage efficiency higher than Frantoio. Don Carlo showed fruit traits and oil content almost intermediate between the parents, making it a dual-purpose cultivar.