Morphological characteristics of an ex-situ collection of Tunisian wild cardoon (Cynara cardunculus L. var. sylvestris) and evaluation of its inulin content

Tunisian wild cardoon (Cynara cardunculus L. var. sylvestris (Lamk.) Fiori) germplasm is an important source of genetic variability to be conserved and exploited for crop improvement. The objectives of the present study are to explore morphologic diversity and evaluate inulin content in wild cardoon germplasm. Eight ecotypes from six different regions in the North of Tunisia were assessed from each locality. Fourty-eight ecotypes of wild cardoon were evaluated in randomized block with four replications. A high diversity was shown in the ex-situ collection regardless of their geographical origins. Statistically significant differences were found between ecotypes for 13 morphological characteristics which indicate a wide genetic diversity. The relationship among the ecotypes and characteristics was analyzed using principal component analysis (PCA). The two first axes of the PCA explain 58.47% of the total variance. The first component (39.61%) is dominated positively by length of leaf stalk, depth of leaf stalk, length of the longest lobe, length of spines at leaf, length of spines at lobes, and width of the longest lobe, while the second component (18.86%) is positively dominated by the length of spines of outer bracts. To valorize this germplasm, inulin content in leaves and roots collected at vegetative and flowering stages was evaluated. The average of inulin content varied between ecotypes from 1.57 to 27.46 mg/100 g FM. Results showed that roots of wild cardoon were richer in inulin than leaves. Likewise, inulin content increased more at the flowering stage than at the vegetative stage. At vegetative stage, ecotype from Beni Amor registered the highest inulin content in its leaves while ecotype from Siliana (SN) showed the highest content in its roots at the vegetative stage. At flowering stage, inulin content for both organs (leaves and roots) was the highest in individuals from Ain Berda1 (AB1). These characterizations can be useful for a plant breeding program to develop cultivars rich in inulin.