VARIATION AMONGST BRASSICA-JUNCEA CULTIVARS FOR REGENERATION FROM HYPOCOTYL EXPLANTS AND OPTIMIZATION OF CONDITIONS FOR AGROBACTERIUM-MEDIATED GENETIC-TRANSFORMATION

Twelve cultivars of Brassica juncea grown in different agroclimatic re gions of the world were tested for their ability to regenerate in vitr o from hypocotyl explants and, accordingly, were divided into three gr oups. One group of cultivars regenerated on MS medium supplemented wit h 2,4-D, BAP and with NAA, BAP combinations; another group regenerated only on MS with 2,4-D, BAP; and the third group showed very low regen eration on both of these combinations. Inclusion of silver nitrate in the medium was essential for high frequency of regeneration. In genera l, Indian cultivars were more responsive than the cultivars of CIS and Australian origin. Using the media optimal for regeneration and an Ag robacterium-based binary vector carrying hpt and gus-intron genes, con ditions for genetic transformation of B. juncea hypocotyl explants wer e optimized. Transformation frequencies, identified by GUS staining at the initial stages of growth, were lower on MS medium with 2,4-D, BAP than on MS with NAA, BAP. Plants resistant to 20 mug/ml hygromycin we re regenerated at a frequency of 11-36% from hypocotyl explants and we re shown to be transformed by Southern blotting, GUS staining and prog eny analysis.