Despite the economic and ecological importance of the carob tree, few studies are available on the morphological characterization and chemical composition of carob in Algeria. This has resulted in the lack of selection of commercial cultivars of high seed and sugar content. The present study aims to assess the diversity of 11 wild and 1 cultivated carob populations in various regions of Algeria, characterized by diverse geographical and climatic conditions. The final objective is to assess the diversity of neglected carob plants that exhibit superior fruit quality traits and/or are well adapted to different pedoclimatic conditions. The current study focuses on analyzing pod and seed diversity by investigating 12 morphological and 5 physiochemical traits. The analysis of variance revealed significant differences between populations (p < 0.001) for all traits studied, indicating high morphological and chemical variability among these carob populations. Principal component analysis (PCA) was employed to study the relationship between these traits and the geographical origin. High seed yields characterized wild populations, whereas cultivated populations were rich in sugar. Based on morphological traits of pods, seeds and chemical compositions, a hierarchical clustering grouped the carob populations into four groups. The findings of this study represent a significant advancement towards establishing effective cultivar breeding programs in Algeria. They demonstrate that the germplasm examined in this research exhibits an optimal level of morphological and chemical diversity, which is instrumental in the identification of specific traits of both commercial and environmental significance.

Carob (Ceratonia siliqua L. Fabaceae) is a species of significant economic, ecological, and cultural importance in the Mediterranean region. It is valued for its adaptability to various environments and wide-ranging agricultural and industrial applications. Despite its potential, the genetic characterization of this species in Algerian territories has received little attention to date. The present study aims to decipher carob’s genetic structure and diversity in Algeria. This study presents a comprehensive morphological characterization of 39 Algerian carob accessions based on pod traits and molecular genotyping using eight nuclear and three chloroplast SSR markers across different geographical locations and environmental conditions. The morphological analysis revealed a discrete differentiation among accessions, primarily influenced by their area of origin. The genetic analysis identified 38 unique genotypes. Allelic richness indicated high polymorphism, with an average of 3.81 alleles and 5.36 genotypes for nuclear SSR markers. Chloroplast SSR markers showed lower variability but provided insights into population structure. Genetic analysis revealed distinct genetic clusters aligned with geographical and bioclimatic regions, supported by minimum spanning network analysis that showed the genetic flow patterns among accessions. Discriminant analysis of principal components identified five optimal sub-population groups, highlighting a genetic structure linked with different bioclimatic conditions. These findings evidence the complex genetic diversity of Algerian carob germplasm and offer valuable insights for the sustainable exploitation of carob genetic resources.