In vitro preliminary evaluation of the low vigour olive F2 ‘Koroneiki’ progenies

Olive (Olea europaea L. subsp. europaea) is one of the most ancient, cultivated, and economically crucial fruit crops in the Mediterranean area. Many of the cultivated genotypes showed a high level of morphological and biological variation of agronomic characteristics. One of the most suitable agronomic characteristics is that of low vigour, a trait that is useful for new intensive-managed orchards. Among international olive germplasm, the Greek self-fertile cultivar ‘Koroneiki’ is close to the commercial ideal habit showing medium-low vigor and constant bearing, whilst maintaining commercially acceptable fruit yield and oil quality. The Department SAAF in the university of Palermo has raised a F2 progeny, derived from the selfing of ‘Koroneiki’, to obtain a wide range of interesting genotypes showing low vigor and new architectural compact traits, including dwarf or “brachytic habit”. In plant breeding, in vitro culture represents an important tool to multiplicate large numbers of selected genotypes when compared to traditional propagation techniques. In this work, the preliminary results of in vitro shoot proliferation and rooting of F2 ‘Koroneiki’ genotypes, are presented. Single-node woody explants of dwarf and semi-dwarf genotypes were collected from the field, sterilized, and in vitro cultured. For branching of lateral buds, two types of culture media (OM and WPM), two types of cytokinin (zeatin and meta-topolin), and three types of hormone concentrations (control, 2 and 1:1 mg L-1) were evaluated. Rooting factors include two types of basalt salts (including vitamins) at half strength (OM and WPM), two types of auxins (IBA and NAA), and three levels of PGR concentration (control, 1:1, 2:2 mg L-1). Results showed great variability among the F2 progenies, and many clones were obtained. Interestingly, low vigor and dwarf traits are maintained in all in vitro stages. Results are useful for future selection and breeding programs.