Phenotypic and Nutritional Diversity Reveal Elite Accessions of Berberis darwinii Supporting Berry Breeding and Functional Food Applications

Berberis darwinii is a native Chilean berry distributed across contrasting agro-ecological zones, highlighting its broad ecological amplitude and agronomic relevance. The objective of this study was to identify productive, functional, and balanced elite accessions of B. darwinii by integrating phenotypic, fruit quality, nutritional, and antioxidant traits under contrasting water availability. Ninety-six accessions were evaluated in a common-garden experiment over two consecutive growing seasons (irrigated and rainfed) for morphological, productive, and fruit quality traits. Substantial variation was observed in plant height, shoot number, leaf area, and spine density. Across seasons, some accessions combined high yields (up to 8.5 t ha−1), fruit diameters exceeding 8 mm, and elevated soluble solids (up to 33 °Brix). Because water regime, season, and plant age were not experimentally separated, these contrasts indicate adaptive performance under contrasting water availability rather than direct irrigation effects. Functional analyses revealed high biochemical diversity, with total polyphenols reaching 18,168.7 mg GAE 100 g−1 dry weight, anthocyanins up to 5747.7 mg cyanidin-3-glucoside 100 g−1 dry weight, and ORAC values up to 35.4 mmol Trolox 100 g−1 fresh weight. Multivariate analyses supported the selection of elite candidates for low-input domestication and functional ingredient development. This integrated common-garden framework links intra-specific phenotypic variation with phenolic/antioxidant diversity, supporting trait-based selection and interpretation of stress-associated secondary metabolism.