Variability in the pod and seed parameters and nuclear DNA content of Tunisian populations of <Emphasis Type="Italic">Ceratonia siliqua</Emphasis> L.

The carob tree (Ceratonia siliqua L.) is widely used in arid and semi-arid areas of Mediterranean countries for industrial, agricultural and ornamental purposes. We wished to determine the variability of its morphological parameters in relation to its exploitation for commercial purposes. Thirteen cultivated and 15 spontaneous populations of C. siliqua from various edapho-climatic zones of Tunisia were compared to determine the variation in pod and seed parameters, for trees growing in situ, and in 2C nuclear DNA content (determined by flow cytometry), for seedlings grown from seeds collected in situ. Analysis of variance showed significant differences (P < 0.0001) between sites for fresh weight, length, width, internal and external thickness of pods, the pod length/width ratio, percentage of viable seeds and seed fresh weight. The mean pod fresh weights (range 8.63–36.03 g) of cultivated C. siliqua were significantly greater than those of spontaneous trees (7.70–19.39). Similarly, for other morphological characters (pod length, width and thickness and seed weight), the cultivated trees showed the highest mean values: 19.46 cm, 2.22 cm, 0.91 cm and 0.20 g, respectively. How this variability could be exploited for agronomic and commercial purposes is discussed. The variation of the examined morphological characters was not correlated with the quantity of DNA, since there were no significant differences in nuclear DNA content among the cultivated or spontaneous individuals. The mean 2C nuclear DNA content was 1.20–1.30 pg, indicating the trees to be diploid (2n = 24).