Plant viruses decrease food production and economic yields in many tropical crops. Two virus groups, potyviruses and geminiviruses, are both dominant and emerging in the tropics. For logistical reasons, we will concentrate our efforts on the geminiviruses for which ILTAB has accumulated significant information and knowledge over the last decade. Future interests will range from disease diagnostics to control and will include taxonomy, biology, and epidemiology.

Objectives:

• molecular characterization of geminiviruses
• control of geminiviruses in a variety of crops, including tomato, cotton, and cassava

Status of the project:

• Molecular characterization: this has been underway for several years and will continue as databases grow as a result of research worldwide. ILTAB is a recognized authority in this field and is the home of GeminiNET, the geminivirus network.
• Biology of geminiviruses: ongoing projects have resulted in the cloning of geminiviruses infecting cassava, tomato, and cotton. Research has shown that recombination and synergism are inherent dynamic components of geminivirus infections and are potentially dangerous because they contribute to the emergence of novel geminiviruses.
• Molecular studies: research on geminivirus replication has increased our understanding of replication specificity within the geminiviruses.
• Geminivirus recombination: recent studies have begun to elucidate the molecular mechanism responsible for genetic recombination in geminiviruses. This knowledge will allow better control strategies to be devised.
• Geminivirus control: replication-related, pathogen-derived resistance strategies are being used to develop a wide range of control strategies for geminiviruses. Plants are under production, and laboratory and field tests will be completed within twelve months.

Challenges:

• Wide range control of geminiviruses through transgenics: we have two methods under development involving the G5 and the N-Rep proteins.
• Exploitation of the molecular mechanism for recombination: we need to demonstrate its usefulness in transgenic plants.

Collaborators:

• Mahyco in India for biotechnological control of tomato, okra, and cotton geminiviruses.
• Dr. Otim-Nape at NARO in Uganda for Ugandan cassava viruses.
• Dr. Sangare at INRA, Ivory Coast for West African viruses.

Basic scientific interests:

Understand how geminiviruses replicate at the molecular level and how geminiviruses interact with host factors.

Future developments:

We are in the process of developing collaborative projects using Arabidopsis to investigate and isolate host factors that are important for geminivirus replication. Similarly, we are developing plans to access structural data for several viral proteins including those essential for virus replication.

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