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Improving the health of vegetatively-propagated crops: better integration of disease management strategies for seed produced on-farm
S. THOMAS-SHARMA (1), J. Andrade-Piedra (2), M. Carvajal Yepes (3), J. Hernandez Nopsa (1), P. Kromann (2), J. Legg (4), J. Yuen (5), G. Forbes (6), K. Garrett (1). (1) Kansas State University, Manhattan, KS, U.S.A.; (2) International Potato Center, Quito, Ecuador; (3) International Center for Tropical Agriculture, Cali, Colombia; (4) International Institute of Tropical Agriculture, Dar es Salaam, Tanzania; (5) Swedi

Pathogen build-up in vegetative planting material (seed degeneration) is a major problem for food staples in many developing countries. Since certified seed of good health status continues to remain scarce and/or expensive for much of the immediate future in these regions, improving the health of on-farm seed is critical. We developed a framework that integrates various management strategies available to minimize seed degeneration in five major food security crops: potato, sweetpotato, cassava, yam, and banana. Variability in biological and environmental elements was incorporated through stochastic model components and the likelihood of a range of potential outcomes was studied. As expected, the application of disease management strategies mitigated the risks associated with season-to-season variability in disease-conducive weather. We identified scenarios in which positive selection can be as effective as certified seed usage, especially if the rate of success in selecting healthy plants is high. Also, when choosing between within-season management strategies, those that directly reduce the proportion of infected seeds/plants can be particularly effective. Models are being validated with experimental results for the five crops, globally. By integrating results from field experiments and expert elicitation in Bayesian belief networks, we are now developing decision support systems to maximize efficacy of management strategies in crop- and region-specific scenarios.

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