Direct embryogenesis in the genus Helianthus and RAPD analysis of obtainedclones

A rapid and efficient regeneration system via somatic embryogenesis from le af discs and stem segments has been developed for four sunflowers species ( Helianthus spp.). The effect of different combinations of growth regulators , explant source and genotype on the embryogenic response of five wild sunf lower species was evaluated. Maximum frequency of somatic embryogenesis was achieved in the presence of 5.5 mu M indolacetic acid (IAA) and 5.3 mu M z eatine (ZA) irrespective of the genotype. Leaf explants performed superior to stem segments. The species showed a marked difference in their re,regene ration potential with the highest percentage of 62% embryogenic explants in the case of H. giganteus followed by H. maximiliani (15%). From H. nuttall ii and H. tuberosus 8% embryogenic explants were obtained while only callus or root formation was observed with H, grosesserratus. Shoots rooted spont aneously while embryogenic structures had to be treated with naphtylacetic acid (NAA). Thirty five randomly selected regenerated clones were analyzed with eleven 10-mer primers to verify genomic stability using RAPD-PCR on an average of 114 markers per clone. No polymorphisms could be detected betwe en the clones and their parents. This regeneration system may be of value f or application in genetic transformation with Agrobacterium tumefaciens or microparticle gun of the wild sunflower species.