Morphological and molecular characterization of Croatian carob tree (Ceratonia siliqua L.) germplasm

The results of morphological and AFLP variability of 120 plants of carob tree (Ceratonia siliqua L.), collected from 12 different locations (10 biological replicates for each location) on the coast and islands of the southern Croatian Adriatic, indicate high molecular and morphological variability among these carob populations. Analysis of molecular variance revealed significant differences among populations (26.07%; p < 0.001; a = 0.05). Out of the total variability, 22.49% refers to the variability among, and 77.51% within populations. UPGMA and STRUCTURE analysis based on AFLP genetic data clustered carob populations into three main groups representing three real genetic populations. UPGMA analysis based on morphological traits of leaves, pods, and seeds clustered carob populations into five groups. Mantel test showed significant correlation between morphological and genetic data (r = 0.58, p < 0.001; a = 0.05). According to the high genetic and morphological variability, the germplasm collection in the analysis could represent an important genetic pool for future breeding programmes. The goal of future research should be the conservation of C. siliqua in its natural habitats, and the establishment of gene banks of genetic resources with the purpose of creating new carob cultivars in breeding programmes.