Tropical Maize (Zea mays L.) Genotypes Respond Differently to Agrobacterium-mediated Genetic Transformation
The current study was designed to evaluate and ascertain genetic transformability of regenerable genotypes using Agrobacterium-mediated transformation method and to identify genotype(s) which can be used as better transgene recipient in future research. The super virulent Agrobacterium strain EHA 101 harbouring the binary vector pNOVIPT1 carrying the 4 Kbp T-DNA region, which included the PSARK::IPT::NOST and PCMPS::PMI::NOST expression cassettes, was used to infect immature zygotic embryos harvested 16 days after pollination. The phosphomannose-isomerase gene was used as a marker to select transgenic events on Linsmaier and Skoog selection medium having 5 g/l mannose as a selective agent. Molecular analyses of transgenic plants were carried out using polymerase chain reaction, Southern blot and semi-quantitative reverse transcription polymerase chain reaction which, respectively, indicated the presence, stable integration and expression of the transgene. The study indicated genotype dependent response of tissue culture, proficient elite African tropical maize to Agrobacterium-mediated genetic transformation and possibility of enhancing the genetic basis of tropical maize through genetic engineering using Agrobacterium. Among the six maize genotypes tested, the CIMMYT inbred line CML216 and the Ethiopian open-pollinated variety Melkassa-2 produced normal and fertile transgenic plants and were identified for future use in genetic transformation aiming to overcome biotic and/or abiotic stresses of high priority in affecting maize production in the East and Central African region.