Published online by Cambridge University Press: 16 March 2011
Woad (Isatis tinctoria L.) was introduced in Europe in ancient times to produce indigo, a natural blue pigment used mainly for dyestuff. This species was cultivated in Portugal until the beginning of the 20th century, especially in the inner North and South. A set of nine inter-simple sequence repeat (ISSR) markers generated 177 reproducible fragments, of which 171 were polymorphic. The mean number of fragments/accession was 111, ranging between 100 (Portugal-Coimbra) and 124 (Poland). The total polymorphism observed was 0.3272, the average polymorphism was 0.1784 and the gene differentiation between accessions was 0.4546. Polymorphism ranged between 53.8% (Austria) and 73.1% (Belgium). The genetic relationship among woad accessions was obtained with unweighted pair group method with arithmetic mean dendrogram based on a molecular marker, clearly clustering the woad accessions according to their geographic origin. The genetic diversity observed in this collection shows that there is a considerable potential for its improvement and that ISSR could be used to evaluate intra- and inter-accession similarities in I. tinctoria species.