ILTAB is known for its capacity to genetically transform recalcitrant tropical plants. ILTAB will continue its efforts in this area over the next years in agronomically important cultivars of cassava and rice and will develop expertise in plantain and sweet potato.

Objectives:

• to develop virus control in African and South American cassava cultivars
• to establish a routine cassava transformation system for transfer of other traits

Status of the project:

• A reproducible genetic transformation protocol has been established for the West African cassava cultivar TMS 60444 (considered an excellent model system due to its susceptibility to African cassava mosaic disease (ACMD)).
• Geminivirus resistance: this project is important for Africa, to combat ACMD, and for South America, as a protection against possible occurrence of the disease there. Several transgenic plant lines are showing resistance and will be transferred for field testing in Africa in late 2001.
• Other useful traits: in collaboration with CIAT and other laboratories; targets selected include bacterial blight resistance, whitefly resistance, and decreased post harvest deterioration.

Challenges:

• Transformation of multiple cassava cultivars (6 to 10): studies are ongoing and will continue mostly through the training of scientists from less developed countries (LDC) and through collaboration with other labs, as for example the virus resistance project conducted in collaboration with CIAT.
• Gene expression in cassava: we are lacking information on tissue-specific transgene expression in cassava, most especially with regard to tuberous roots. Such knowledge will be important for future cassava projects.

Collaborators:

• CIAT (Colombia) is our primary partner for cassava transformation. They carry the cassava mapping and gene libraries for cassava that promise to yield natural traits for bacterial and virus resistance, whitefly resistance, and tuber quality.
• INRA (Ivory Coast) will continue to be an effective partner. We currently have two students from this institute, and we plan to have one of our first field trials in Africa in this country in late 2001.
• Bath University (UK) will be the primary contact for post harvest deterioration and protein engineering.

Basic scientific interests:

Multiple gene transformation: We have begun multiple gene transformation on rice with some success, and we intend to pursue research on model plants, for example, research utilizing the three genes involved in the golden rice project in collaboration with IRRI.

Transfer of large “native” DNA inserts: We achieved such transfers with bacterial resistance in rice, and we intend to develop capabilities to transfer large (100-250 kb) intact DNA sequences such as those from BAC libraries carrying identified traits of agronomic interest. Collaboration with CIAT to transfer bacterial blight resistance to cassava in this manner has commenced. Such activity is related to multigene transformation and connects to our work on gene discovery in plantain (in collaboration with EMBRAPA or CATIE, see here under).

Recombination in transgenic plants: We have discovered a natural system that geminiviruses use to recombine among themselves. We intend to transfer this system to transgenes in plants in order to promote selectable marker gene deletion.

[Return to top]