Organellar genome analysis of rye (Secale cereale) representing diverse geographic regions

Rye (Secale cereale) is an important diploid (2n = 14, RR) crop species of the Triticeae and a better understanding of its organellar genome variation can aid in its improvement. Previous genetic analyses of rye focused on the nuclear genome. In the present study, the objective was to investigate the organellar genome diversity and relationships of 96 accessions representing diverse geographic regions using chloroplast (cp) and mitochondrial (mt) DNA PCR-RFLPs. Seven cpDNA and 4 mtDNA coding and noncoding regions were amplified using universal cpDNA and mtDNA primer pairs. Each amplified fragment was digested with 13 different restriction enzymes. mtDNA analysis indicated that the number of polymorphic loci (20) was low and genetic differentiation (GST) was 0.60, excluding the outgroups (hexaploid wheat, Triticum aestivum, 2n = 6x = 42, AABBDD; triticale, xTriticosecale Wittmack, 2n = 6x = 42, AABBRR). cpDNA analysis revealed a low level of polymorphism (40%) among the accessions, and GST was 0.39. Of the 96 genotypes studied, 70 could not be differentiated using cpDNA PCR-RFLPs even though they are from different geographic regions. This is most likely due to germplasm exchange, indicating that genotypes might have a common genetic background. Two cpDNA and 3 mtDNA fragments were significantly correlated to the site of germplasm collection. However, there was no clear trend. These results indicate that the level of organellar polymorphism is low among the cultivated rye genotypes. The cpDNA and mtDNA PCR-RFLP markers used in the present study could be used as molecular markers in rye genetics and breeding programs.