Transcriptomic analysis of dwarf vs. tall olive genotypes of the F2 'Koroneiki' progeny cultured in vitro

The olive tree (Olea europaea L.) is a paramount fruit species globally, particularly in the Mediterranean region, owing to its ecological and nutritional benefits. Over time, numerous breeding initiatives have been undertaken by both public institutions and commercial enterprises to identify genotypes suitable for high-density orchard systems. One of the most intriguing agronomic attributes is the characteristic of reduced tree size. Within the international olive germplasm, the Greek self-fertile cultivar ‘Koroneiki’ closely aligns with the ideal habitus, exhibiting moderate vigour and consistent bearing, while upholding commercially acceptable fruit yield and oil quality. The Department SAAF in the University of Palermo has raised an F2 progeny, derived from the selfing of ‘Koroneiki’, segregating for a wide range of interesting genotypes showing low vigour and new architectural compact traits, including dwarf or “brachytic habit”. In plant breeding, in vitro culture represents an important tool for numerous applications, including the multiplication of selected genotypes and the chance to understand better molecular pathways involved in the variability of some morphological traits. This work presents a promising protocol for in vitro shoot proliferation and rooting of F2 ‘Koroneiki’ genotypes and the preliminary transcriptomic analysis of two genotypes exhibiting contrasting plant height and vigour traits (dwarf vs. tall). For the transcriptional analysis mRNA was extracted from the apex to the first node and the roots. Bioinformatics techniques were employed to identify the genetic difference between dwarf vs. tall plants. The reconstruction and labeling of RNA sequences were done with de novo transcriptome assembly and annotation followed by identifying the biological significance of these transcripts through Gene Ontology (GO) analysis. The analysis unveiled compelling and valuable insights for comprehending olive plant vigour and juvenility pathways, thereby holding promise for future breeding programs.