Identification of the core collection in Iranian almond germplasm: utilizing morphological traits and evaluating biochemical properties of the collection

Almond (Prunus dulcis Miller) is a major commodity with the highest nut production in the world. A core collection is of the utmost importance for fruit tree breeding programs from a managerial and economic perspective. In current study, an almond germplasm panel consisting of 228 genotypes was subjected to a comprehensive analysis for two years, which included 20 morphological and pomological traits. A curated ensemble of 28 almond genotypes or cultivars was precisely selected by applying stringent parameters through the use of the Power Core software, ultimately leading to the establishment of the novel almond core collection. It is noteworthy that this collection effectively contained 9.2% of quantitative traits and 3.5% of qualitative traits. In addition, variance difference (VD%) and mean difference (MD%) computations of quantitative and qualitative traits yielded values of 97.43% and 10.18%, respectively, thus indicating a profound degree of genetic variation in core collection. Moreover, the Shannon diversity index (H) pertinent to categorical traits demonstrated a substantial augmentation across all seven phenotypic factors. Cluster analysis indicated the core collection accessons were equally distributed among two distinct population groups. Furthermore, oil content measurement showed Ooil content ranged from 44.61% in genotype 151 to 62.72% in genotype C1, while fatty acid ranged from 60.20% in genotype K49 to 80.57% in Avizj, thereby indicating a metabolic variation in core collection germplasm. These results may provide valuable references and be conductive to the germplasm collection strategy, which may facilitate the improvement of almond in future breeding programs.