Analysis of the Genetic Structure of a Barley Collection Using DNA Diversity Array Technology (DArT)

Garlic (Allium sativum L.) is a vegetatively propagated species that has been used as a culinary and medic-inal plant and it is a source of sulphur-containing compounds. Our objectives are to assess S-alk(en)yl cysteine sulphoxide (SACS) content and to characterise genotypically, a set of 135 accessions, which have previously been assigned standard morphological descriptors. HPLC was used to assay the amount of sulphur-containing compounds, while AFLP was used as the genotyping platform. The 286 different informative AFLP fragments identified across the collection were subjected to principal component anal-ysis. Eight clusters were obtained: two consisted exclusively of A. sativum L. var. ophioscorodon clones; four clusters grouped together both non-bolting and semi-bolting clones (all classified as var. sativum); the remaining two contained only non-bolting types. AFLP genotyping successfully differentiated var. ophioscorodon from var. sativum clones. Semi-bolters were not distinguished from the non-bolting clones. A K-clustering analysis generated similar outcomes. However, a model-based approach identified some heterogeneity within bolting accessions. Strict correlation between the geographical origin of clones and the clusters to which they belonged was not observed. The SACS content, important for the taste and the protective health benefits of the bulbs, was analysed for the whole set. Clones of two non-bolting clusters contained significantly greater amounts of SACSs than the remaining ones. The non-bolter and semi-bolter clusters produced low amounts of SACS, so they are not locally adopted genotypes. This is the first report on variation between alliin:methiin ratio. The ratio varied between clusters too. The analysis of SACS content provided some insight into the genetic basis of this important end-use trait, and this can be further used for efficient conservation of garlic genotypes.