Influence of Agrobacterium strain, culture medium, and cultivar on the transformation efficiency of Vitis vinifera L.

Like most woody plants, grapevine is classically improved through vegetative methods or conventional breeding. Despite significant progress in genetic engineering, some cultivars of Vitis vinifera are recalcitrant to transformation. This study investigated factors involved in the response of V vinifera to transformation by Agrobacterium. Embryogenic cultures of several V vinifera cultivars (Portan, Danuta, Shiraz, and Chardonnay) were established on four solid media (GS1CA, C1P, C1+P, and C1A10) differing in mineral compounds, plant growth regulator type and level, and gelling agent. Embryogenic callus was cocultured with Agrobacterium tumefaciens (EHA105, AGL0, AGL1, LBA4404), Agrobacterium vitis (K252), or Agrobacterium rhizogenes (M) strains carrying the pBINm-gfp5-ER binary plasmid. It was shown that Agrobacterium strain, culture medium used for maintenance of embryogenic callus, and grapevine genotype play an important role in transformation efficiency. The supervirulent EHA105 A. tumefaciens and the wide host range A4 A. rhizogenes strains showed increased transformation efficiency compared to the widely used LBA4404 A. tumefaciens strain or the limited host range K252 A. vitis strain. Experiments showed that in order to produce highly competent embryogenic tissues, it was necessary to replace 2,4-D (2,4-dichlorophenoxyacetic acid) with NOA (beta-naphthoxyacetic acid) before the coculture with Agrobacterium. A transformation method suitable for several cultivars of V vinifera is described.