Abstract

As a novel method of identifying S and N cytoplasms in onion, a mitochondrial DNA based marker cytochrome b (cob) was used to cytoplasmically characterize Indian onion populations. The oligonucleotides amplified 414 bp DNA for S-cytotype and 180 bp for N-cytotype in open-pollinated populations, namely, Punjab Naroya, Punjab Selection, Punjab White, PRO-6, PBR-4 and P-266. Out of the 200 seedlings screened in each population, 19 in Punjab Naroya, 15 in Punjab Selection and 5 in Punjab White showed amplification of 414 bp revealing S-cytoplasmic proportion of 9.5, 7.5 and 2.5%, respectively. While PRO-6, PBR-4 and P-266 showed amplification of 180 bp only, indicating the absence of S-cytoplasm. The results suggest that Punjab Naroya, Punjab Selection and Punjab White can be exploited for development of male sterile (A) and maintainer (B) lines, while PRO-6, PBR-4 and P-266 can be utilized to isolate maintainer and restorer (R) lines. The study establishes a rapid method of cytoplasm identification in onion, which is pre-requisite to developing CMS lines. In contrast to 4–8 years taken by conventional approach used in India, this technique identifies cytoplasm within 15 days of sowing and proves its practical efficacy for future onion F1 breeding in the country.