Harnessing heterosis in Brassica juncea (L.) Czern. & Coss.: Challenges in commercial hybrid production and future strategies

Abstract

India relies on imports to meet nearly 70 % of its edible oil demand, underscoring an urgent need to improve domestic oilseed productivity. Rapeseed-mustard (Brassica juncea (L.) Czern. & Cosson), the second-largest oilseed crop in India, has experienced a yield plateau due to the exhaustion of genetic variability in conventionally bred varieties. Heterosis breeding through hybrid development offers the most promising strategy to break this stagnation, yet commercialisation remains critically dependent on efficient pollination control systems, primarily cytoplasmic male sterility (CMS). A key challenge is the “biological penalty” imposed during CMS background conversion, wherein the combining ability and heterotic potential of superior genotypes may not remain intact, necessitating rigorous re-evaluation of converted lines. Public-sector brassica hybrids have largely failed to exceed the commercial heterosis threshold of 25–35 %. This review examines the fundamental requirements for hybrid development, the historical progression of breeding systems and the current status of major CMS systems (Ogura, Moricandia, Tournefortii and others) deployed in India, along with the challenges hindering adoption. The regulatory approval of the genetically engineered hybrid DMH-11-utilising the Barnase-Barstar system marks a significant milestone, offering stable and precise pollination control independent of alien cytoplasm constraints with a demonstrated 28–37 % yield advantage. Future strategies must focus on broadening the genetic base through alien introgression, developing defined heterotic pools and integrating genomic selection, gene editing and marker-assisted selection (MAS) with conventional breeding to achieve self-sufficiency in edible oil production.