Plant Cell Rep (2012) 31:999–1007 DOI 10.1007/s00299-011-1218-4 O R I G I N A L P A P E R Highly efﬁcient sorghum transformation Guoquan Liu • Ian D. Godwin Received: 15 November 2011 / Revised: 19 December 2011 / Accepted: 19 December 2011 / Published online: 11 January 2012 The Author(s) 2012. This article is published with open access at Springerlink.com Abstract A highly efﬁcient microprojectile transforma- tion system for sorghum (Sorghum bicolor L.) has been developed by using immature embryos (IEs) of inbred line Tx430. Co-bombardment was performed with the neomy- cin phosphotransferase II (nptII) gene and the green ﬂuo- rescent protein (gfp) gene, both under the control of the maize ubiquitin1 (ubi1) promoter. After optimization of both tissue culture media and parameters of microprojectile transformation, 25 independent transgenic events were obtained from 121 bombarded IEs. The average transfor- mation frequency (the total number of independent trans- genic events divided by the total number of bombarded IEs) was 20.7% in three independent experiments. Trans- genic events were conﬁrmed by both PCR screening and Southern hybridization of genomic DNA from primary transgenics (T0). More than 90% of transformants were fertile and displayed normal morphology in a containment glasshouse. Co-transformation rate of the nptII and gfp genes was 72% in these experiments. The segregation of nptII and gfp in T1 progenies was observed utilizing ﬂuo- rescence microscopy and geneticin selection of seedlings indicating both were inherited in the T1 generation. The transformation procedure, from initiating IEs to planting putative transgenic plantlets in the glasshouse, was com- pleted within 11–16 weeks, and was approximately three- fold more efﬁcient than the previously reported best sorghum transformation system. Communicated by P. Lakshmanan. G. Liu I. D. Godwin (&) School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia e-mail: i.godwin@uq.edu.au Keywords Sorghum bicolor transformation Tissue culture Transgenic plants Microprojectile Copper sulfate Introduction Sorghum [Sorghum bicolor (L.) Moench], the ﬁfth most important cereal after wheat, rice, maize and barley, plays a unique role in food security and renewable energy (Belton and Taylor 2004). Sorghum is a drought-tolerant crop, which can grow in marginal areas not suitable for the other cereals. It is widely used for food especially in Africa and India, and for animal consumption (grain and stover) and as a biofuel energy source in Americas and Australia. Genetic engineering has the potential to have a great inﬂuence on improving sorghum yield and digestibility (Gurel et al. 2009). However, sorghum has been widely considered as a recalcitrant major crop in terms of tissue culture and genetic transformation (Grootboom et al. 2010). In fact, sorghum transformation has lagged far behind published efﬁciencies of rice (Hiei and Komari 2008), maize (Ishida et al. 2007) and barley (Ibrahim et al. 2010), even though it has been almost two decades since the ﬁrst study on transgenic sorghum was published (Casas et al. 1993). Microprojectile transformation and Agrobacterium-medi- ated transformation are two main approaches that have been utilized to obtain transgenic sorghum. The ﬁrst report of successful transgenic sorghum was published by using par- ticle bombardment in 1993 and a transformation efﬁciency of 0.286% was achieved (Casas et al. 1993). Seven years later, the ﬁrst Agrobacterium-mediated transgenic sorghum was reported (Zhao et al. 2000) at 2.12% efﬁciency. Since then, several more reports have been published (Zhao and Tomes 2003; Williams et al. 2004; Gao et al. 2005b; Nguyen et al. 123