Regeneration systems at high frequency from high oleic Helianthus annuus L. genotypes

A rapid and efficient regeneration system via direct organogenesis from two high oleic sunflower genotypes has been developed. Explants of longitudinal bisected shoot apices of 10 days old seedlings were incubated on two different shoot induction media. Shoots from meristem adjacent tissue regenerated within 3 weeks, without a callus phase. The best shoot regeneration (63\%) was observed with SIM2 medium containing Murashige and Skoog (MS) salts 4.3 g L-1 myoinositol 0.56 mM, thiamine-HCl 0.30 muM, glycine 26.64 muM, nicotinic acid 4.1 muM, pyridoxine-HCl 2.4 muM, sucrose 3\% and 6-benzyl-aminopurine (BAP) 0.44 muM. A high rooting efficiency (60-90\%) was achieved independent of genotype and rooting media. Considering sunflower as a recalcitrant species, although some differences in the organogenetic response of the genotypes, over 50\% of the explants were able to induce direct organogenesis and regenerate whole viable plants. Acclimatized plantlets showed further development reaching the flowering stage and seed production. This regeneration system may be of special value for genetic transformation experiments using biological vectors or direct gene delivering methods like microinjection or particle Lynn.