Molecular and morphological characterization of Crataegus L. species (Rosaceae) in southern Syria

The systematics of the genus Crataegus (Rosaceae) have been considered problematic owing to the fact that hybridization, introgression, polyploidy and apomixis may occur in this genus. A study of the Crataegus species from the Arab mountains, Sweida Province, Syria, has been undertaken based on both plastid DNA sequences (trnL‐trnF, psbA‐trnH) and morphological data. In the investigated region, three morphologically distinguishable Crataegus species: C. azarolus var. aronia L., C. × sinaica Boiss. ssp. sinaica and C. monogyna var. monogyna Jacq. were investigated. Crataegus azarolus can be clearly distinguished morphologically from C. monogyna by the colour, size and structure of fruits, the number of pyrenes, the flowering and ripening time, the density of thorns, the tree shape and also the leaf shape. According to our morphological data, in Syria, C. × sinaica is variable and could represent a hybrid of C. azarolus × C. monogyna; the cpDNA sequence analysis showed sequences corresponding to C. monogyna as the plausible mother of the hybrid.