Optimizing callus induction and proliferation for Agrobacterium-mediated transformation of Brachypodium distachyon

Brachypodium distachyon has emerged as the model species for important temperate grass crops such as wheat and barley and the genome of the B. distachyon community inbred line Bd21 has been sequenced. Methods for tissue culture and Agrobacterium-mediated transformation have been developed for this model grass as a resource for reverse genetics and functional genomic analyses. In order to obtain a high quantity and quality of compact embryogenic callus (CEC) in B. distachyon, it is important to examine and optimize the optimal concentration of the auxin 2,4-D (dichlorophenoxyacetic acid) to use in both callus induction and callus proliferation media. Here, we investigated the effects of different concentrations of 2,4-D on callus induction and callus proliferation of B. distachyon Bd21. Our results showed that 2.5 mg l–1 2,4-D is an optimal concentration to use for both callus induction and proliferation, although 5.0 mg l–1 may also be used for callus proliferation. Additionally, the suitability of hygromycin or bialaphos as selectable markers was examined and results indicated that hygromycin is significantly more efficient than bialaphos when using the Agrobacterium-mediated transformation system