Origin of tetraploid cultivated asparagus landraces inferred from nuclear ribosomal DNA internal transcribed spacers’ polymorphisms

Abstract

AbstractThe genus Asparagus includes a group of wild species that are closely related to the cultivated Asparagus officinalis (2n = 2× = 20). The narrow genetic background present in the asparagus cultivars shows the importance of asparagus landraces and the wild related species. The study of both genetic resources becomes necessary to facilitate their effective use in the breeding programmes. ‘Morado de Huetor’ (MH) and ‘Violetto d’Albenga’ (VA) are tetraploid asparagus landraces (2n = 4× = 40) cultivated in Spain and Italy, respectively, and whose origin remains unknown. To discover the origin of these landraces, a phylogenetic study was conducted based on restriction fragment length polymorphism (RFLP) of nuclear ribosomal DNA (nrDNA). The sequence of the two internal transcribed spacers (ITS) flanking the nrDNA5.8S gene (ITS1‐5.8S‐ITS2) were analysed for RFLP in 11 populations including both landraces (MH and VA), A. officinalis (wild and cultivated) and a group of closely related wild species (Asparagus maritimus, Asparagus prostratus, Asparagus pseudoscaber and Asparagus tenuifolius) with a European distribution. Restriction fragment patterns of both cultivated asparagus (2×) and two populations of A. maritimus (6×) from the Adriatic Sea area were present in the MH landrace. However, VA showed a similar pattern to A. officinalis. This study revealed that MH seems to be a hybrid between A. officinalis and A. maritimus that may have occurred in the Adriatic Sea region where hybridisations between cultivated diploid and wild species may have taken place. The origin of another tetraploid landrace (VA) might have had a similar origin but followed a different evolutionary path. Therefore, these landraces constitute a valuable genetic resource that could be used to enlarge the genetic background of modern cultivars. The ploidy levels of the populations employed in this study were analysed and levels not described previously were detected: A. maritimus (12×), A. tenuifolius (6×) and A. pseudoscaber (2×).