SUSTAINED ROOT CULTURE FOR GENERATION AND VEGETATIVE PROPAGATION OF TRANSGENIC ARABIDOPSIS-THALIANA

Excised roots of wild-type and nitrate-reductase deficient mutant Arab idopsis thaliana (L.) HEYNH. can be propagated as sustained root cultu res in liquid medium. Culture initiation from a single seedling requir ed a two-day indoleacetic acid treatment at 0.05 mg/l concentration. I ndoleacetic acid facilitated subculture but was not essential for sust ained growth. This procedure has allowed the clonal propagation of roo ts derived from individual wild-type and mutant seedlings for more tha n 21 months. The cultured roots retained their shoot regeneration abil ity; however, a controlled desiccation treatment was required to resto re it to the level of freshly excised roots. The chromosome number rem ained diploid and no evidence for the accumulation of recessive mutati ons was observed. The cultured roots are competent for Agrobacterium-m ediated transformation. The sustained root culture technology allowed the maintenance of transgenic tissues in which expression of a dominan t, seed-lethal gene (seed-specific pea vicilin promoter fused to dipht heria toxin A chain gene) precluded generative propagation.