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Siobain Duffy Investigates Evolution of Crop Diseases

Scientists examining symptoms at a different small stakeholder farm, outside Nampula, MZ

Cassava Mosaic symptoms -- this plant isn't even that badly infected! © Siobain Duffy Siobain Duffy, a Rutgers University evolutionary virologist, is investigating the root of viral disease in cassava crops in East Africa. Cassava, also known as yuca, manioc, or tapioca, is a starchy tuber that is a staple crop in sub-Saharan Africa, providing “nearly 40% of the calories consumed in Africa,” says Duffy. “But diseases caused by [viruses] perennially limit cassava production on small producer or subsistence farms.” Understanding cassava disease epidemics, then, is crucial for East African food security. Duffy is part of a multinational research team that will contribute to that cause with the support of a Bill and Melinda Gates Foundation/Department for International Development grant to study cassava disease epidemics.

Duffy, along with Malawian graduate student Willard Mbebe (who is matriculating at University of Witwatersrand, South Africa but conducting his research at Rutgers), will study the diversity and evolutionary dynamics of the two whitefly-transmitted viruses responsible for the two cassava diseases. “We don’t know yet whether the viruses causing the two diseases are equally diverse, or whether they evolve at the same speed, and in the same ways,” says Duffy. Although plant breeders engineer cassava plants for better disease resistance, “it could be that evolvability [of one or both viruses] makes them able to overcome or adapt to resistance bred into cassava plants.”

The Natur-Park Südgelände is an abandoned rail yard in Berlin has become a refuge in the city for native plants and animals. © Charles NilonThe project is collaborative – Duffy and Mbebe work with scientists from seven East African countries, the UK, and North Carolina. Duffy has already attended meetings in Tanzania and Mozambique, and is involved in all aspects of the project, from fieldwork to analysis to environmental planning. “I’ll be back [in Tanzania] this summer to help collect samples of diseased cassava and the whiteflies that vector the two kinds of viruses,” she says.

While this project allows Duffy to expand on her larger research interests of emerging RNA- and DNA-based viruses, she was originally drawn to the work because of its humanitarian value. Citing an example of a 1997 famine in Uganda, Duffy says, “these diseases can directly lead to human deaths, and I want to be part of sustainable and durable solutions.” “It allows me to use my evolutionary background to help increase food security in East Africa,” she says.

March 2014