Simple and efficient genetic transformation of sorghum using immature inflorescences

Sorghum is an important cereal crop and has been grown in a wide range of environments from tropic to warm-temperate zones. Genetic improvement of this crop has been based on those traditional breeding methods, but there is a limited application of genetic transformation for sorghum improvement due to its recalcitrance to genetic manipulation in vitro. The current study aimed at development of immature inflorescences as a genetic transformation system for sorghum. Immature inflorescences of two sorghum elite lines were chosen as the explants for developing a new method for genetic transformation. Sorghum immature inflorescences were collected from plants at the flowering stage and co-cultured with virulent Agrobacterium tumefaciens strain LBA4404 containing one of the special gene constructs. Once co-cultivation was completed, the treated immature inflorescences were moved onto regeneration medium to induce development of shoot and root from the resulted embryogenic callus. This system was also amenable for the microprojectile bombardment (biolistic particle delivery system) method. Putatively transgenic plants were confirmed for the presence of transgene in the plants based on the molecular analysis of the T1 plants. All resulted transgenic plants were normal in morphology and fully fertile. The transformation system developed with the immature inflorescence is a simple and efficient method for sorghum transformation, which can speed up the process of engineering new varieties.