Assessment of Ancient Carob Germplasm of Lebanon by Morphological Traits

Abstract

This study aimed to assess the ancient carob germplasm growing in Lebanon. A set of 59 old trees sampled from different locations across the country (between 0 and 554 m a.s.l.) were subject to morphological characterization by using 33 traits related to the tree, the leaf, the pod and the seed. Results revealed important morphological variability within the Lebanese carob germplasm. The most variable traits were the number of aborted seeds per pod, seed yield, pulp weight, pod weight and pod volume. Correlation analysis showed a negative correlation of both pod size and weight with seed yield, and a positive correlation between pod length and total seed weight. Evaluation of carob morphological characters and eco-geographic parameters revealed positive correlation of seed length, chord length and pod width with the longitude, in addition to a slight positive correlation of pod weight with latitude and longitude. Principal component analysis allowed extracting the most active and discriminant morphological variables, which were mainly represented by pod weight, width, length, thickness and shape, chord length, and individual seed weight and length. Cluster analysis revealed a clear differentiation between two main morphological groups; the first cluster was characterized by long and heavy pods and seeds, while the second cluster was distinguished by medium to small pods and seeds. Two eco-geographic sub-clusters could be differentiated, Mount Lebanon and the South, while the trees of Beirut and the North were dispersed in various subgroups. According to these results, the Lebanese carob germplasm might be a reservoir of genetic diversity that should be further investigated by complementary studies including flowering characteristics, pod chemical quality attributes and genetic analysis.