Plant transformation systems have been developed using several different approaches, and the development of reliable and efficient transformation systems is still one of the most important breakthroughs in molecular biology and biotechnology of rice. However, there are many cultivars in rice and transformation efficiency is dependent on the cultivar. The conventional Agrobacterium-mediated rice transformation system using secondary calli requires 14-16 weeks for establishing transgenic plantlets, and it is thought that somaclonal variation through the Tos17 retrotransposon occurs during the tissue culture stage. Here, we modified an Agrobacterium-mediated transformation system in rice cultivar Dongjin, adding an endosperm removal step that is critical to transformation frequency and changing the Agrobacterium strain and media composition. This method increased transformation efficiency and stability. These results will provide valuable information for scientists to use a reliable and efficient rice transformation system.

• Se-Youn Han(Molecular Breeding Division, National Academy of Agricultural Science, RDA) These authors contributed equally to this work.
• Dongjin Shin(Molecular Breeding Division, National Academy of Agricultural Science, RDA) These authors contributed equally to this work.
• Seok-Jun Moo(lecular Breeding Division, National Academy of Agricultural Science, RDA) These authors contributed equally to this work.
• Seon-A Jeon(lecular Breeding Division, National Academy of Agricultural Science, RDA)
• Myung-Ok Byun(lecular Breeding Division, National Academy of Agricultural Science, RDA)
• Beom-Gi Kim(lecular Breeding Division, National Academy of Agricultural Science, RDA) Corresponding author