Mitochondrial genome of rapeseed (Brassica napus L.). 1. Intraspecific variation of mitochondrial DNA

Abstract

Restriction endonuclease analysis was carried out for mitochondrial (mt) DNAs of 27 accessions of rapeseed (Brassica napus L.) to detect intraspecific variation of the mitochondrial genome. MtDNA isolated from green leaves was digested with ten endonucleases and was electrophoresed using agarose slab gel. Mt genomes of the 27 accessions were classified into two major types, each of which was further divided into three subtypes based on the length differences in the restriction fragments of mtDNAs. In total, six mt genome types (type Ia, Ib, Ic, IIa, IIb and IIc) could be identified. To analyze the relationship between the mt genome types and the cytoplasmic male sterility (cms) induction, restriction fragment patterns of two male sterile cytoplasms, namely, nap cms and pol cms, were compared with those of the normal cytoplasm. The mt genome of the nap cytoplasm was found to be either of Ia, Ib and Ic types, whereas the pol cytoplasm carried the type IIb mt genome. Mitochondrial linear plasmid DNA was also observed in several accessions, but the relationship between its presence and the cms trait could not be established.