Utilization of sucrose during cocultivation positively affects Agrobacterium-mediated transformation efficiency in sugar beet (Beta vulgaris L.)

Authors: SONGÜL GÜREL, MUHAMMET ÇAĞRI OĞUZ, FERZAT TURAN, KEMAL KAZAN, CANAN YÜKSEL ÖZMEN, EKREM GÜREL, ALİ ERGÜL

Abstract: 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.

Keywords: Sugar beet, genetic transformation, cocultivation, plant growth regulators

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