INVESTIGATING THE In vitro REGENERATION VIGOUR OF Brassica juncea VAR. VARUNA AND ITS WHITE RUST TOLERANT MUTANT GENOTYPES: CONJUGATING THE CONVENTIONAL AND BIOTECHNOLOGICAL APPROACHES

Indian mustard (Brassica juncea (L.) Czernj. Cosson) is an economically significant oilseed crop across the globe with well-known nutritive values. It ranks third among the oilseed crops in the world and second in India. White rust, caused by Albugo candida, is a devastating disease of Brassicaceae family impeding the yield of Indian mustard by up to sixty percent worldwide. One way to overcome this problem is to develop transgenic resistant varieties. Different genotypes in Brassica are known to require different protocols for efficient regeneration protocol which becomes a prerequisite for taking up any genetic improvement plan through transgenic approaches. In this study, we evaluated the regeneration potential of B. juncea check white rust susceptible variety Varuna and its two white rust tolerant mutant genotypes (C66, C69). Of the various hormonal combinations tested, all the genotypes responded best in the presence of MS+ 0.05mg/l dinitrophenylhydrazine + 1.0 mg/l 6-benzylaminopurine for shoot initiation while further development of shoots were best stimulated by 1.0 mg/l 6-benzylaminopurine and rooting response was best on half strength MS+ 2.0 mg/l Indole-3-butyric acid. The regenerated plants were successfully grown to maturity and selfed seeds were harvested. Henceforth, the efficient regeneration protocol optimized here will help us to further genetically transform the B. juncea var. Varuna and its genotypes with white rust resistance genes deploying durable resistance against A. candida. We believe, this study will widen the scopes of biotechnology for sustaining the Indian mustard yield against white rust.