Understanding the phenotypic variability of the olive 'Galega vulgar' fruits and oil-related traits across environments

'Galega vulgar', a genetically diverse variety, is the main olive tree variety across Portugal, being broadly cultivated across distinct environments. 'Galega vulgar' is presently being replaced by higher-yielding, although lower-quality, foreign varieties and efforts must be made to counteract this tendency, and to more efficient explore 'Galega vulgar' to the profit of olive tree producers, and the remaining market stakeholders. For that, in the present research, an evaluation of the influence of genetic and environmental factors and their interactions in the phenotypic variability of 'Galega vulgar' was performed, focused mainly on important traits to olive stakeholders (namely, fruit-related traits such as fruit and flesh weight and flesh-to-stone ratios and oil-related traits), towards the selection of the best representatives of the variability found. A three-year in-situ detailed agronomic characterization was conducted taking advantage of a previously defined 'Galega vulgar' collection composed of 595 trees from 95 clones, cultivated across all the Portuguese geographical districts where 'Galega vulgar' has representativeness (10 districts), considering thirteen phenotypic traits. The environment was the main contributor to the phenotypic variability observed on the 'Galega vulgar' variety. Significant differences for almost all the analysed traits were detected across years, trees, and geographical districts, with significant district-by-clone interactions. Of the two most frequent clones, clone C002 was the most stable across the geographical districts under study. The present work provides information on the phenotypic variability of 'Galega vulgar' important fruit and oil related traits across different environments, of utmost importance from the conservation, breeding, resilience, and production perspectives, considering the pressing need to adapt to climate change effects. In addition, since a significant geographic district x clone interaction was observed, the generated knowledge may now contribute to a better adjustment of the right clone for the right region in what respects new orchards establishment. A set of 'Galega vulgar' trees, primarily identified as belonging to the same clones, was selected due to their 'residual' phenotypic variability. These trees will contribute to broadening the genetic basis of a previously defined ex-situ conservation base 'Galega vulgar' collection of trees, to be trialled in a comparative field experiment, under the same environmental conditions. These experiments are needed for a more precise evaluation of the genetic potential of this variety, towards future genetic studies to clarify the complex genetic control of traditional olive breeding targeted traits and to develop molecular selection tools to support precision olive breeding.