A Multidisciplinary Approach for the Assessment of the Last Surviving ‘Marrone di Chiusa Pesio’ Chestnut Trees in the Piemonte Region (Italy)

Chestnut orchards are a multifunctional resource, providing not only fruit or wood but also playing a role in the conservation of mountain and hillside landscapes. In the Piemonte Region, Italy, a rich genetic heritage of chestnut genotypes has contributed to considerable biodiversity and environmental value. The study aimed to valorize an important example of the chestnut agrobiodiversity in the Piemonte Region by focusing on the ‘Marrone di Chiusa Pesio’ (MCP) cultivar (cv). A multidisciplinary approach was applied, involving genetic and morphological analyses, Visual Tree Assessment (VTA), and phytochemical and nutritional profiling. The plant census provided identification and geolocation of 187 MCP specimens; the 20 most representative trees were genetically analyzed, and then, through the VTA, their morpho-functional status was evaluated. The nutraceutical properties and phytochemical composition were assessed by measuring the total polyphenol content (TPC), antioxidant capacity (AOC), and other phytochemical classes through spectrophotometric and chromatographic methods. The results showed significantly higher TPC values (ranged from 36.51 ± 1.60 mgGAE/100 g of dried weight—DW to 103.14 ± 1.24 mgGAE/100 g DW) compared to other ‘Marrone-type’ cultivars, along with high levels of key phenolic markers, bioactive compounds, and nutritional substances. These included tannins (about 22–28 mg/100 g DW) and cinnamic acids (about 23–25 mg/100 g DW), followed by flavonols, benzoic acids, organic acids, monoterpenes, vitamin C, and catechins, listed in order of predominance. A Principal Component Analysis (PCA) was performed to observe the distribution of the samples and their correlations based on the chemical composition. The results confirmed the interesting phytochemical properties of the ‘Marrone di Chiusa Pesio’ nuts, together with their good morphological and functional properties. Given the ongoing genetic erosion of Castanea sativa cultivars, due to cultivation abandonment and climate change, the main factors contributing to the progressive loss of biodiversity worldwide, the presented approach aimed to provide an overview of the conservation status of the local agrobiodiversity. This study highlighted the value of a local chestnut cultivar, presenting the low conservation status of the few remaining specimens. The goal was to define the significant phenotypic variation regarding MCP in the considered area due to environmental variations, which may be of interest in its genetic adaptation to climate change. The study may potentially encourage the development of strategies for actively conserving the forest agrobiodiversity and hillside ecosystem services in the highly diverse landscapes of the Alpine valleys.