Length polymorphism in the ribosomal DNA intergenic spacers of Lens species

Analysis of the ribosomal DNA (rDNA) intergenic spacers (IGS) (i.e., the IGS of 18S, 5.8S and 24S rDNA, and the NTS or non-transcribed spacer of 5S rDNA) of lentil cultivars and landraces (L. culinaris spp. culinaris) showed to have very low intraspecific length variability. PCR products of approximately 3200 bp were obtained from all cultivated materials; no significant electrophoretic differences were found between them. However, observable intraspecific polymorphism increased with the digestion of PCR-amplified IGSs by the restriction endonucleases BspHI, StuI and BstBI. This was also the case when specific PCR primers designed to amplify a particularly variable segment of the IGS were used. This segment includes two families of short, tandemly arranged, repeated sequences. Both methods revealed differences between some of the cultivated materials, yielding genetic markers that might be useful in further genetic mapping and breeding studies. Several NTS amplification products were observed in each plant, ranging from approximately 300 to 900 bp in the cultivated lentil. Differences between L. culinaris spp. culinaris and its related wild species (including the wild ancestor of the cultigen, L. culinaris spp. orientalis) were observed in the total length of their IGSs, the restriction patterns of the latter, and in their NTS variants. Additional key words: genetic markers, IGS, legumes, lentil, NTS.