An RTB project has recently got underway to identify the main causes of “seed degeneration” in roots, tubers and bananas, and develop simple tools to help small farmers manage the problem, and increase production of those vital crops

Virus-induced deformation of potato – Wilmer Pérez/CIP

Virus-induced deformation of potato – Wilmer Pérez/CIP

(31 January 2013) During his years working in the Andes region, it occurred to plant pathologist Greg Forbes that researchers weren’t doing enough to solve a pervasive problem: the diseases that degenerate seed potatoes and significantly diminish harvests.

“It is evident to anyone working in potato that seed degeneration is important,” said Forbes, who is now based at the International Potato Center (CIP) China Center for Asia and the Pacific. “On a global scale, it has got to be one of the biggest obstacles to productivity for small holders.”

Greg Forbes, CIP China

Forbes is consequently pleased to be leading an international effort to find solutions to that problem as the coordinator of a cross-cutting project within Roots, Tubers and Bananas (RTB), a CGIAR Research Program. He and his colleagues will study the diseases that damage planting material in cassava, potatoes, sweetpotatoes, yams and bananas, and develop tools to help researchers and farmers across the tropics to mitigate their impact, and thereby improve production.

Because roots, tubers and bananas are vegetatively propagated, diseases are passed from one generation to the next more easily than in plants that produce seeds through sexual reproduction. Forbes explained that whereas industrialized nations have largely solved the problem of seed degeneration through “clean seed systems,” attempts to establish such systems in developing countries have had limited success. The RTB project aims to find a more balanced approach that combines the use of resistant varieties and the promotion of on-farm practices and clean seed systems that are appropriate for local conditions.

“We’ve done some research around teaching small farmers a very simple technique called positive selection, which just involves selecting clean looking mother plants to take seed from. It’s very simple, but the farmers that did it got, on average, a 20 percent yield increase. It’s an imperfect control technique, but it gives you an idea of the ubiquitous reduction of productivity that seed degeneration causes,” Forbes said.

Potato mop-top virus – Wilmer Perez

Forbes and two-dozen colleagues from the United States, Latin America, Europe and Africa will meet in Arusha, Tanzania from February 5 to 8 to organize their work in coming years. Their goals include identifying the main diseases that cause seed degeneration in the RTB crops and regions, and modeling how factors such as resistance, on-farm management and local weather conditions affect them. Specialists on different RTB crops from Biodiversity International, CIP, the International Center for Tropical Agriculture (CIAT), the International Institute of Tropical Agriculture (IITA), Kansas State University and other institutions will work on the project at their research centers, but will feed their data into one analysis. Their plan is to develop simple models to predict seed degeneration under different conditions and guidelines to manage the problem.

“We hope to make specific recommendations about what kind of strategies should be promoted on national or regional levels to help small farmers to improve their management of these diseases, which will increase their production,” said Forbes.