Development of highly efficient genetic transformation protocols for table grape Sugraone and Crimson Seedless at low Agrobacterium density

Highly efficient genetic transformation protocols and the regeneration of transgenic plants of Sugraone and Crimson Seedless grapevines (Vitis vinifera L.) were achieved from embryogenic calli co-cultured with low Agrobacterium tumefaciens densities. The sensitivity of embryogenic cultures to kanamycin, as well as the effect of Agrobacterium strains, C58(pMP90) or EHA105, and the bacterial concentration (0.06 or 0.2 at Optical Density OD600) on transformation efficiency were studied. Embryogenic cultures showed different kanamycin sensitivities and the total suppression of embryo differentiation at 20 and 50 mg/l kanamycin for Crimson Seedless and Sugraone, respectively. sgfp gene expression was evaluated in callus co-cultured with each bacterial strain. Although GFP transient expression was higher with A. tumefaciens EHA105 in both cultivars at the beginning of the culture, there were no significant differences 28 days post-inoculation. However, the concentration of Agrobacterium did affected transformation efficiency: 0.06 OD600 being more effective for the transformation of Crimson Seedless and 0.2 OD600 for Sugraone. By following the optimised procedure, 21 and 26 independent transgenic plants were generated from Sugraone and Crimson Seedless respectively, three to five months post-infection. PCR analyses were carried out to verify the integration of the sgfp and nptII genes into grapevine genome and the stable integration of the sgfp gene was confirmed by Southern blot.