PCR amplification in the mitochondrial genomes of the hau CMS line and its maintainer. The hau CMS mitotype and the normal mitotype coexisted in both the hau CMS line 00-6-102A (A) and its maintainer line 00-6-102B (B), but were substoichiometrically different in these cytotypes. Different PCR cycles (25, 30, 35) were used to amplify these different open reading frames. Primer pairs P1, P2 and P3 targeted the hau CMS mitotype-specific sequences orf288, orf325 and orf170, respectively, whereas P4, P5 and P6 targeted its maintainer line (normal) mitotype-specific sequences. All PCR reactions used 50 ng mtDNA as template. The PCR assay indicated that the hau CMS mitotype and normal mitotypes coexisted in Brassica juncea, but the content was substoichiometrically different form the two cytoplasm types. M: DNA ladder.