Pomological diversity of the Italian blood orange germplasm

Abstract Blood oranges have been cultivated in Italy since the early 19th century. Growers and breeders were able to identify and collect many somatic mutants, which differed in their major pomological traits, such as fruit size and firmness, pulp and peel pigmentation, and ripening period. Recently, in the framework of a genetic resource conservation program, most of the accessions collected at CREA in recent decades were planted in a single block to evaluate their characteristics. The presence of many selections in the same block, of the same age and grafted on the same rootstock is extremely important for a reliable characterization of the pomological characters, particularly pigmentation, which is strongly influenced by both the environment and the rootstock. The collection consists of 88 genotypes, including old lines and nucellar selections. Some commercial Tarocco, Moro and Sanguinello varieties were also included in the collection to facilitate comparison among clones. Moreover, the pomological features of 20 elite Tarocco clones cultivated nearby in the same experimental station were used as a further reference. The pomological characterization, based on 13 traits and performed in two consecutive years, revealed significant variability. Some genotypes showed strong year-to-year variability, mainly in fruit pigmentation, probably due to different climatic conditions during winter. Similarly, other traits such as fruit size, total soluble solids and acidity also varied among and within the varietal groups. These findings have a potential utility in identifying promising clones, which might fulfil the growing market needs such as higher anthocyanin content and longer shelf life.