Cassava Transformation and Friable Embryogenic Callus Development

At CIAT, genetic transformation of cassava is being used as a tool to support conventional breeding programs. The aim has so far focused on genes (such as those for pest resistance) not yet available in cassava germplasm, although the modification of metabolic pathways (like starch modification and b-carotene content) to improve cassava is also sought. Transgenic plants, and cell lines, containing genes for pest resistance, starch modification and herbicide tolerance, are now being produced. Molecular tests for gene expression, and preliminary bioassays to test efficacy of protection against cassava stemborer were carried out this year. We observed low levels of protection. However, more bioassays with younger larvae have to be done to confirm observations.

Transformation is now being achieved with friable embryogenic callus or FEC, and using a model, and farmer preferred cultivars. We have established FEC cell lines for four cultivars, two of which are for the North Coast, one for the inter-Andean valleys of Colombia, and a cultivar used as a model in transformation. We have therefore set up a system for scaling up cassava transformation at CIAT. Experiments are done 2-3 times a month, using Agrobacterium or biolistics, with at least four cultivars (TMS 60444, SM 1219-9, CM 2306-4, and M Col 2215).