A new approach for efficient regeneration of a recalcitrant genotype of sunflower (Helianthus annuus) by organogenesis induction on split embryonic

A new approach for shoot regeneration from split embryonic axes of Helianthus annuus var. RHA266, a poor responding genotype to in vitro culture, has been developed. The regeneration procedure is based on successive excision of the apical and axillary shoots originating from pre-existing meristems. This elimination process stimulates adventitious shoot bud formation in 80% of treated explants. Although newly induced buds were observed on hormone-free medium, higher rate of induction and bud development were obtained on medium containing 0.1 mg l(-1) BA. All regenerated plants were phenotypically similar to seed-derived RHA266 plants with no observed somaclonal variation, as assessed by AFLP analysis. The efficient shoot regeneration from newly formed meristematic cells should offer opportunities to genetically engineer economically important sunflower genotypes that have proven till now, to be recalcitrant towards other regeneration systems.