Agrobacterium-Mediated Transformation of Maize of Ukrainian Breeding

Since Ukraine is a powerful maize exporter in the world, screening genotypes susceptible to genetic transformation among those cultivated on its territory and the development of an effective technology for the transformation of maize of Ukrainian breeding are relevant. Precultivated immature maize embryos of nine genotypes (inbred lines and hybrids) were subjected to Agrobacterium-mediated transformation. Three strains of A. tumefaciens and three vector constructs, which contained the selective marker gene of neomycin phosphotransferase II, as well as the reporter genes of green fluorescent protein or β-glucuronidase, were used in the work. Transgenic plants were selected on nutrient media with paromomycin. For six genotypes, shoot regeneration was observed after transformation on selective media. The presence of transgenes in 43 clones obtained from four genotypes using all available vectors was revealed by the PCR method. The transformation frequency varied from 0 to 27% in individual experiments. A strong correlation was found between frequencies of the regeneration and the transformation between genotypes and donor plants of the same genotype. The use of the pCB271 vector, which contained monocot nucleotide sequences of gene expression regulation upstream of the selective marker gene, namely the intron of the maize hsp70 gene, significantly increased the frequency of shoot regeneration after transformation. Analysis of T1 generation plants revealed single-locus integration of transgenes into the plant genome. The proposed protocol of genetic transformation using paromomycin as a selective agent is effective in obtaining transgenic maize lines and hybrids of Ukrainian breeding. Three genotypes (inbred line DK232 and hybrids KP7×PRZh5 and KS277×RS15) were selected as the most susceptible among tested genotypes to Agrobacterium-mediated transformation and promising for further research on the production of transgenic maize plants.