Evaluation of Morphological, Qualitative, and Metabolomic Traits during Fruit Ripening in Pomegranate (Punica granatum L.)

Pomegranate is characterized by several local accessions and cultivars widespread across different countries, each with different bio-agronomic features. Physiological and biochemical processes occur during fruit ripening, leading to changes in size, color, and flavor, improving the fruit's acceptability for the consumer. The aim of this study was to evaluate the changes in physico-chemical and nutritional traits of three Italian germplasm genotypes ('Santa Lucia', 'Di Benedetto', and 'Arborea') to determine the differences for these parameters both within the same cultivar during four ripening stages, and between individual cultivars in the same ripening stage. Morphological traits and fruit pigmentation showed variation during the ripening process, with higher values at the final stage. The highest fruit weight was detected in 'Di Benedetto' (392.19 g), while 'Arborea' displayed high juice content. Qualitative traits, such as soluble solids, increased until stage III, while titratable acidity values decreased during the ripening stage in 'Di Benedetto' and 'Arborea'. In all three accessions, a reduction in the total polyphenols up to the III ripening stage was observed. Metabolomic analyses using H-1-NMR (proton nuclear magnetic resonance) showed a variation in citric acid and sugar content according to the ripening stage and accession considered. This study found high variability in nutraceutical traits among the analyzed pomegranates. The three pomegranate genotypes showed significant differences in qualitative and metabolomic characteristics. Principal component analysis revealed the main traits that contribute to the positive and negative correlations with PC1 and PC2, highlighting the great variability in the investigated pomegranate genotypes.