Development of cytoplasmic male sterility-fertility restoration systems of variable origin in mustard – Brassica juncea

Abstract

Mustard (Brassica juncea) is the major edible oil crop of Indian subcontinent. Although substantial heterosis has been observed in intervarietal hybrids, no hybrid cultivar has been commercialised due to lack of suitable cytoplasmic male sterility (CMS) - fertility restoration system. CMS has been engineered by combining seven cytoplasms of different wild species with B. juncea nucleus following the synthesis of sexual or somatic hybrids and their repeated backcrossings. These alloplasmics, in general, have delayed flowering, high female fertility and mild to severe leaf chlorosis in some (Oxyrrhina, Moricandia). Chlorosis rectification has been achieved through protoplast fusion. Fertility restoring genes for CMS (Trachystoma) B. juncea and (Moricandia) B. juncea have been introgressed following allosyndetic recombination. Restored F1 hybrids possess more than 90% fertility. Sterility inducing ogu cytoplasm was also transferred from B. napus to B. juncea sexually and the resulting CMS was improved through protoplast fusion. It was also observed that CMS having genetically constituted mitochondrial genome and least diverged from cultivated species have minimal floral abnormalities and are amenable to fertility restoration.