Marker-trait association approaches unravel the genetic determinism of fruit quality traits in a collection of blood oranges

M. Di Guardo, S. Seminara, S. Bennici, C. Catalano, F. Ferlito, A. Giuffrida, G. Las Casas, M. Caruso, G. Distefano, S. La Malfa, A. Gentile
Sweet orange [Citrus sinensis (L.) Osbeck] is the most important species belonging to the genus Citrus. Italy is the main world producer of blood oranges, a group of cultivars characterized by the synthesis and accumulation of anthocyanins in the flesh and sometimes also in the peel. The main cultivars of blood oranges include ‘Sanguinello’, ‘Moro’ and ‘Tarocco’. Blood orange cultivars are characterized by a high rate of spontaneous mutation leading to the identification of hundreds of selections (mainly for ‘Tarocco’) differing in plant and/or fruit traits of agronomical interest (e.g., harvesting period, fruit quality, yield). To characterize the variability within this varietal group and to detect molecular markers linked to traits of interest a wide germplasm collection of sweet oranges was phenotyped for the most important traits related to fruit quality and resequenced using Illumina technology (coverage of 40X). The germplasm collection includes mainly blood oranges (84 ‘Tarocco’, 13 ‘Sanguinello’ and 4 ‘Moro’) and 16, among blond oranges and minor blood oranges as reference. Phenotyping was carried out during 2 harvesting seasons (2021-2022 and 2022-2023) sampling fruits monthly from December to March to evaluate the evolution of fruit size and weight, juice production, TSS, TA, pH and anthocyanin content up to maturity ripening, while peel and flash color, peel thickness, and central axis diameter were assessed only at physiological maturity. Resequencing Illumina data were employed to genetically characterize the germplasm collection through the detection of structural variants (SVs). Genotypic and phenotypic data were integrated into a genome-wide association study (GWAS) employing the structural variants (SVs) used as molecular markers to avoid the bias represented by the high rate of SNPs originated by chimeric mutations in sweet orange. Results allowed the identification of candidate genes linked to fruit and peel weight, anthocyanins, sugar/acid ratio and juice content. The identification of molecular markers linked to these traits will enable the set-up of marker-assisted breeding programmes for the detection of new selections characterized by superior traits.
Di Guardo, M., Seminara, S., Bennici, S., Catalano, C., Ferlito, F., Giuffrida, A., Las Casas, G., Caruso, M., Distefano, G., La Malfa, S. and Gentile, A. (2024). Marker-trait association approaches unravel the genetic determinism of fruit quality traits in a collection of blood oranges. Acta Hortic. 1412, 329-336
DOI: 10.17660/ActaHortic.2024.1412.49
https://doi.org/10.17660/ActaHortic.2024.1412.49
Illumina sequencing, Citrus sinensis, SNP, anthocyanins
English

Acta Horticulturae