Optimization of <i>Agrobacterium tumefaciens</i>-Mediated Genetic Transformation of Maize

Immature embryos of inbred maize (Zea mays) lines (H8183, H8184, and H8185) were used for Agrobacterium infection. We used the β-glucuronidase gene (GUS) as the target gene and the glufosinate resistance gene (bar) as the selection marker. We conducted research on several aspects, such as different genotypes, coculture conditions, screening agent concentrations, and concentrations of indole-3-butytric acid (IBA), 6-benzylaminopurine (6-BA), and ascorbic acid (Vc) in the differentiation medium. We optimized the genetic transformation system, and the obtained results indicated that among the three lines studied, the induction rate of H8185 was the highest at 93.2%, followed by H8184, with H8183 having the lowest induction rate (80.1%). The best coculture method was that using the N6 coculture medium layered with a sterile filter paper. Using orthogonal analysis, we found that the optimal combination of the three factors in the differentiation medium was A₃ (1 mg mL⁻¹ IBA), B₃C₁ (1.6 mg mL⁻¹ 6-BA), and D₃ (1.5 mg mL⁻¹ Vc). Through GUS staining analysis, Bar test-strip analysis, and polymerase chain reaction, five transgenic plants were finally obtained. This study established the optimal conditions for genetic transformation in maize.