Using AFLPs to determine phylogenetic relationships and genetic erosion in durum wheat cultivars released in Italy and Spain throughout the 20th century

Characterization of germplasm by DNA-markers provides a tool for precise germplasm identification and a quantitative assessment of genetic diversity. The genetic structure of the durum wheat germplasm grown in the Mediterranean basin varies largely from traditional landraces and cultivars characterized by a high versatility, to the modern varieties characterized by high yield potential, wide adaptation, and commercial end-use quality. The objective of this study was to assess the phylogenetic relationships among 24 durum wheat cultivars selected from relevant germplasm obtained at different periods in Italy and Spain, and to quantify the genetic erosion caused in durum wheat by breeding activities during the last century in these two countries.Genetic similarity between cultivars was studied by AFLP markers through the calculation of the Dice’s coefficient. The results showed a high degree of genetic similarity between the old Spanish cultivars and the collection of Italian cultivars, suggesting that wheat could have been introduced in the Iberian Peninsula via Italy. Genetic diversity estimates based on AFLP data confirmed the maintenance of genetic diversity with time since the values of Polymorphic Information Content were 0.27 for old cultivars (released before 1945), 0.28 for intermediate cultivars (released between 1950 and 1985) and 0.29 for modern cultivars (released between 1988 and 2000). These results indicate that genetic variability in Italian and Spanish durum wheat seems to have been maintained quite constant throughout the breeding process over the last century.