Agro-morphological and molecular diversity analysis of new cytoplasmic male sterile lines in Indian cauliflower for their use in hybrid breeding

Abstract

Cauliflower is a typical thermo-sensitive crop, highly responsive to heterosis for yield and stress tolerance. A diverse set comprising of 24 cytoplasmic male sterile (CMS) lines, developed across different maturity groups of Indian cauliflower, using refined Ogura, Can(napus) and Tour sterile cytoplasms was studied to understand the morphometric and molecular changes. The established Ogura-based CMS line of ‘84 series’ (in the nuclear background of snowball cauliflower) was used as an immediate source for conversion of fertile early- and mid-maturity groups lines. Observations on 18 agro-morphological traits revealed significant differences among the CMS lines, however they could not distinguish different CMS systems. The CMS system significantly reduced the floral traits (19) in almost all the transformed lines irrespective of the maturity group, however, the reduction was maximum in CMS line Tour(CMS 394–41–5) having Tour sterile cytoplasm. This CMS line had a peculiar feature of ‘gripping phenomena’ for the style which drastically reduced flower size and eventually seed yield. These CMS lines showed variation with 11 mtDNA markers and 36 genomic simple sequence repeats (gSSR), and of these, BnTR1 perfectly-identified Can(napus) and Tour CMS systems. This is the first detailed report on the extent of diversity observed in 24 new CMS lines developed using three diverse sterile cytoplasms in the nuclear background of different maturity groups of Indian cauliflower. The information will be of immense significance for immediate use in hybrid breeding and/or use as an immediate source of CMS trait for tropical cauliflowers in other regions.