A shoot regeneration protocol effective on diverse genotypes of sunflower (Helianthus annuus L.)

We describe a protocol, and several experiments that helped lead to its development, for sunflower regeneration. Important factors for sunflower regeneration were explant age, cytokinin type and concentration, basal medium, and explant source. We could not induce shoot regeneration from the explants derived from mature tissues including leaf, petiole, and stem. However, use of juvenile explants such as embryo meristem and primordial leaf tissues allowed routine regeneration of 17 different sunflower genotypes. High frequency of shoot regeneration was achieved with these explants taken from seedlings up to 5 d after germination. Explant age was less critical for embryo meristem explants than for primordial leaf tissues. Of the four basal media tested, MS and B5 media produced higher shoot-regeneration frequencies than did Anderson and woody plant media. The highest shoot-regeneration frequency was obtained with MS medium supplemented with 2 mu M BA and without auxin. Addition of 1 mu M naphthalene-acetic acid to the medium significantly reduced both the percentage of explants producing shoots and average number of shoots per explant. Regenerated shoots were grown to maturity in a greenhouse.