S01 - Session O6 - Organelle genome-based markers in deciphering mitonuclear conflict displaying floral malformations and distinguishing cytoplasm types in snowball cauliflower

Authors: Saurabh Singh *, Shyam Sundar Dey, Reeta Bhatia, Raj Kumar

Snowball cauliflower ( Brassica oleracea var. botrytis L.) is an important member of the cole group of vegetables grown in the Indian subcontinent. The cultivation of hybrids is remunerative in cauliflower and cytoplasmic male sterility (CMS) is an important genetic mechanism for hybrid breeding. The CMS in angiosperms is mainly the consequence of mitonuclear intergenomic conflict and different cytoplasms are associated with an array of floral deformities. Therefore, it is essential to distinguish different cytoplasm types in cauliflower. Mitotype-specific mt-DNA markers are instrumental in differentiating cytoplasm types in angiosperms. The prevalence of autoplasmic and alloplasmic mitonuclear intergenomic incompatibilities yields complex floral malformations. In this context, the utility of mitochondrial-DNA markers was illuminated in determining cytoplasm types in snowball cauliflowers and revealed the epistatic effects of mitonuclear conflict affecting floral phenotypes. The genomic DNA isolation of cauliflower cytolines was done by CTAB method. PCR amplification with the primers specific to orf-138 revealed the presence of Ogura cytoplasm in the CMS lines of Indian cauliflower. The mt-SSRs BnTR4 and orf125 indicated the polymorphism within the orf-138 sequence. The InDels (insertion/deletions) of 51 nucleotides were found to be linked with such cytoplasmic genetic variations as revealed by polymorphic sequence analysis. The influence of the cytoplasm on varying nuclear genetic backgrounds caused floral deformities, such as reduction in the size of the petals and sepals, fused flowers, splitting of the style, flowers devoid of non-functional stamens, and conversion of stamens to petaloid structures. These deformities caused dysplasia of floral reproductive organs and reduced the nectar volume and seed yield. The current investigation has identified useful markers to identify cytoplasmic lines with floral malformations. The study opened new horizons to develop ideal CMS lines and making hybrid breeding in cole vegetables remunerative to improve the economic status of farmers.