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    Development of an efficient plant regeneration system in sunflower (Helianthus Annuus L.)
    (1998) Gürel, Ekrem; Kazan, Kemal
    With the aim of developing an efficient plant regeneration system from cells or tissues of sunflower (Helianthus annuus L.)', we compared several regeneration protocols using different explant types and hormonal combinations. Somatic embryogenesis could be induced on cotyledon explants, especially from the basal (proximal) portion of the cotyledons, but genotypic vairation appeared to be the most critical factor for both somatic embryo and root production. Such a variation was more prominent when 10 different sunflower cultivars were compared for shoot production from shoot-tip explants. Further refinement of the culture conditions may be neceassary to improve the efficiency of somatic embryo production. Thin cell layers from hypocotyl segments were not found to be successful for plant regeneration.
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    Evaluation of various sunflower (Helianthus annuus L.) genotypes for Agrobacterium tumefaciens-mediated gene transfer
    (1999) Gürel, Ekrem; Kazan, Kemal
    In this work, 10 sunflower (Helianthus annuus L.) genotypes were evaluated for their suitability for Agrobacterium tumefaciens-mediated gene transfer based on detection of a reported gene expression (GUS). A number of factors including the type of shoot-tip explant (split vs. intact), bacterial strain/binary vector combinations and wounding intact shoot-tips by particle bombardment were examined. Genotypes showed significant differences in their transformation efficiencies ranging from 0.0 to 82.7% GUS positive explants, hybrid genotypes being more responsive to Agrobacterium infection than inbred lines. Use of split shoot-tip explants did not increase the transformation efficiency over intact explants but the AGL-1/pKIWI strain/vector combination was more effective than the LBA4404/pTOK233 combination. Wounding explants by particle bombardment prior to inoculations with Agrobacterium had no positive effect on transformation.
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    Utilization of sucrose during cocultivation positively affects Agrobacterium-mediated transformation efficiency in sugar beet (Beta Vulgaris L.)
    (2019) Gürel, Songül; Oğuz, Muhammet Çağrı; Turan, Ferzat; Kazan, Kemal; Özmen, Canan Yüksel; Gürel, Ekrem; Ergül, Ali
    Sugar beet (Beta vulgaris L.) is one of the most important industrial crops throughout world. With the availability of suitable genetic transformation technologies, the yield, quality, and stress tolerance of sugar beet could be improved significantly. However, low transformation efficiencies seriously limit the application of molecular technologies to the genetic improvement of sugar beet. With the aim of improving gene transfer techniques for sugar beet, the effect of different sucrose concentrations during cocultivation on the initial Agrobacterium-mediated transformation efficiencies in sugar beet was tested. To develop an efficient experimental system through which the effect of sucrose could be tested, first, a prolific regeneration system was optimized by testing the effect of different plant growth regulators on in vitro regeneration and rooting efficiencies from sugar beet cotyledonary node explants. The highest mean number of regenerated shoots per explant was obtained when the cotyledonary node explants excised from young seedlings were grown on MS medium supplemented with 1.0 mg/L 6-benzylaminopurine. Using this regeneration system, the effect of different concentrations of sucrose included in the cocultivation medium on the initial genetic transformation efficiencies observed in T0 plants was tested using an Agrobacterium tumefaciens strain carrying the pBin19/35S:GUS-INT construct. The inclusion of 4.5% sucrose in the cocultivation medium resulted in significantly higher transformation (34.09%) and expression efficiencies (22.72%), confirmed by polymerase chain reaction and β-glucuronidase assays, respectively, in regenerated T0 seedlings. If translated into stably inherited transformation efficiencies, these findings could contribute to the success of genetic transformation studies in sugar beet and other crops recalcitrant to Agrobacterium-mediated transformation.