Agrobacterium-mediated transformation of sorghum and analysis of putative transposable element-induced mutants in sorghum

Plant biotechnology has become a powerful tool to complement the traditional methods of plant improvement. Several methodologies have been developed to identify and clone agronomically important genes and to transfer genes from any living organism to plants. This work encompasses the study of two methodologies related to the identification and transferring of genes in sorghum. The first part reports the development of a protocol for sorghum transformation via Agrobacterium tumefaciens. It is demonstrated that Agrobacterium-mediated transformation is a feasible technique for the genetic transformation of sorghum. Sorghum transgenic plants were produced via Agrobacterium tumefaciens, and the transformation evidenced by Southern blot analysis of T0 and T1 plants, detection of GUS activity, and production of T1 plants resistant to hygromycin. Immature embryos of sorghum were very sensitive to Agrobacterium, and embryo death after co-cultivation was considered the limiting step to increase the transformation efficiency. Key factors were the co-cultivation medium, the use of a genotype and an explant with good tissue culture response, and the addition of Pluronic F-68 to the inoculation medium. Sorghum transformation via Agrobacterium is still not a routine technique, but it seems to have good potential once the protocol is further refined and improved. The second part of the thesis describes the analysis of several putative transposable element-induced mutants in sorghum identified in a Candystripe population, and the identification of endogenous transposable elements in sorghum derived from the cs1 family. Lastly, a likely involvement of a transposable element in the susceptibility of Colby to Periconia circinata is discussed