ASHS 2015 Annual Conference

In 1646 Giovanni Battista Ferrari provided the first known report of blood oranges in his Hesperides, relating that a missionary during his stay in the Philippines had observed the presence of an orange fruit characterized by red flesh (“purpurei coloris medulla”) and a grape-like savor (“quae uvam sapiat”). Later, Loureiro in Flora Cochinchinensis (1790), Gallesio in Traité du Citrus (1811), Risso and Poiteau in Histoire Naturelle des Orangers (1818-1822), and Inzenga (1815-1887) in Agrumi Siciliani described different types of orange characterized by red color in the fruit, which was also depicted in a picture by Bartolomeo Bimbi in the 18th century. Many authors agree that blood oranges have a Mediterranean origin, from ancient ‘Sanguinelli’ varieties, such as ‘Doppio Sanguigno’. Authoritative texts suggest a second, independent origin in Spain, from ‘Doblefina’, and a third from ‘Shamouti Orange’, referred to as ‘Shamouti Blood’ (Hodgson, 1967). The ‘Moro’ cultivar has long been the most highly pigmented commercial fruit, with deep red violet flesh, ripening from December to February. The ‘Tarocco’ variety, probably named for its shape like a spinning top, was discovered in the early 1900s in the area of Pedagaggi (Syracuse Province), but spread rapidly to Lentini and Francofonte (Syracuse) and south of Mount Etna, where the best conditions exist for the expression of its genetic potential. Thanks to the Citrus Experimental Station of Acireale, today called the Research Centre for Citriculture and Mediterranean Crops, and the University of Catania, ‘Tarocco’ has become ‘the King of Oranges’ in Sicily, with many clones differing in ripening season, shape (presence of a broad neck) and degree of pigmentation. More than 60 germplasm accessions exist, and more than 20 ‘Tarocco’ clones are now cultivated, supplying high quality fruits to markets from mid-December to mid-May. The anthocyanin development in the peel and the flesh of blood oranges, largely represented by cyanidin -3-glucoside and cyanidin-3-(6”malonil) glucoside, is cold-dependent. A transcriptional regulator gene, named Ruby, not expressed at all in blonde oranges, correlates with the amount of anthocyanin, but a molecular marker (LTR) located just upstream of Ruby is responsible for the presence of anthocyanin and the activation of Ruby. Molecular investigation confirms that the blood orange varietal group has a common origin (with pummelo and mandarin as parental species), providing pummelo the Ruby allele. Subsequently (cumulative) mutations were the exclusive genetic mechanism determining the variability of the group.