Biology subjects

Forbes, G.

Publications and source records attributed to Forbes, G..

6 recordsLinked to original sources

bioRxiv2018

Management performance mapping: the value of information for regional prioritization of project interventions

Policymakers and donors often need to identify the locations and settings where technologies are most likely to have important effects, to increase the benefits from agricultural development or extension efforts. Higher quality information may help to target the high-payoff locations. The value of information (VOI) in this context is formalized by evaluating the results of decision making guided by a set of information compared to the results of acting without taking the information into account. We present a framework for management performance mapping that includes evaluating the VOI for decision making about geographic priorities in regional intervention strategies, in case studies of Andean and Kenyan potato seed systems. We illustrate use of Bayesian network models and recursive partitioning to characterize the relationship between seed health and yield responses and environmental and management predictors used in studies of seed degeneration. These analyses address the expected performance of an intervention based on geographic predictor variables. In the Andean example, positive selection of seed from asymptomatic plants was more effective at high altitudes in Ecuador. In the Kenyan example, there was the potential to target locations with higher technology adoption rates and with higher potato cropland connectivity, i.e., a likely more important role in regional epidemics. Targeting training to high performance areas would often provide more benefits than would random selection of target areas. We illustrate how assessing the VOI can help inform targeted development programs and support a culture of continuous improvement for interventions.

ecology↗

bioRxiv2017

Health quality of seed potato and yield losses in Ecuador

Low potato productivity in Ecuador is partly attributed to the use of low quality seed tubers. However, seed health quality in Ecuador, and its interaction with altitude and yield has been poorly investigated. We surveyed 11 farmers fields in Ecuador in 2010 to determine incidence and severity of pathogens and pests affecting foliage and seed tubers, and to determine the influence of altitude and seed sources over seed health quality (pathogen and pest diversity in/on the seed tuber). Additionally, a field experiment was planted in CIP-Quito using assessed seed tubers collected from surveyed farmers fields, during 2010 and 2011, to determine yield responses to seed health quality. Results show that foliage was mainly affected by late blight and flea beetle damages while seed tubers were predominantly affected by black scurf, andean weevil damages, potato virus S and potato virus X. We found that seed health quality was similar among farmers seed sources, and detected that increase in altitude decreased seed-borne virus diversity. Only seed-borne pathogens and presence of mechanical damages were found to explain yield variation. Seed-borne pathogens affecting yield variation were black scurf on seed tubers, potato virus S, and potato yellow vein virus. However, these factors changed when regressions were performed per seed source or variety. The yield responses to seed health quality of each variety should be considered to fine-tune integrated pest management strategies.

ecology↗

bioRxiv2017

Global cropland connectivity: A risk factor for invasion and saturation by emerging pathogens and pests

The geographic pattern of cropland is an important risk factor for invasion and saturation by crop-specific pathogens and arthropods. Understanding cropland networks supports smart pest sampling and mitigation strategies. We evaluate global networks of cropland connectivity for key vegetatively-propagated crops (banana and plantain, cassava, potato, sweetpotato, and yam) important for food security in the tropics. For each crop, potential movement between geographic location pairs was evaluated using a gravity model, with associated uncertainty quantification. The highly-linked hub and bridge locations in cropland connectivity risk maps are likely priorities for surveillance and management, and for tracing intra-region movement of pathogens and pests. Important locations are identified beyond those locations that simply have high crop density. Cropland connectivity risk maps provide a new risk component for integration with other factors - such as climatic suitability, genetic resistance, and trade routes - to inform Pest Risk Assessment and mitigation.

ecology↗

bioRxiv2017

Pathogen mitigation in an Ecuadorian potato seed system: Insights from network analysis

Seed systems have an important role in the distribution of high quality seed and improved varieties. The structure of seed networks also helps to determine the epidemiological risk for seedborne disease. We present a new method for evaluating the epidemiological role of nodes in seed networks, and apply it to a regional potato farmer consortium (CONPAPA) in Ecuador. We surveyed farmers to estimate the structure of networks of farmer seed tuber and ware potato transactions, and farmer information sources about pest and disease management. Then we simulated pathogen spread through seed transaction networks to identify priority nodes for disease detection. The likelihood of pathogen establishment was weighted based on the quality and/or quantity of information sources about disease management. CONPAPA staff and facilities, a market, and certain farms are priorities for disease management interventions, such as training, monitoring and variety dissemination. Advice from agrochemical store staff was common but assessed as significantly less reliable. Farmer access to information (reported number and quality of sources) was similar for both genders. Women had a smaller amount of the market share for seed-tubers and ware potato, however. Understanding seed system networks provides input for scenario analyses to evaluate potential system improvements.

ecology↗

bioRxiv2017

Resistance genes in global crop breeding networks

Resistance genes are a major tool for managing crop diseases. The crop breeder networks that exchange resistance genes and deploy them in elite varieties help to determine the global landscape of resistance and epidemics, and comprise an important system for maintaining food security. These networks function as complex adaptive systems, with associated strengths and vulnerabilities, and implications for policies to support resistance gene deployment strategies. Extensions of epidemic network analysis can be used to evaluate the multilayer agricultural networks that support and influence crop breeding networks. We evaluate the general structure of crop breeding networks for cassava, potato, rice, and wheat, which illustrate a range of public and private configurations. These systems must adapt to global change in climate and land use, the emergence of new diseases, and disruptive breeding technologies. Principles for maintaining system resilience can be applied to global resistance gene deployment. For example, both diversity and redundancy in the roles played by individual crop breeding groups (public versus private, global versus local) may support societal goals for crop production. Another principle is management of connectivity, where enhanced connectivity among crop breeders may benefit global resistance gene deployment, but increase risks to the durability of resistance genes without effective policies regarding deployment.

genetics↗

bioRxiv2017

A risk assessment framework for seed degeneration: Informing an integrated seed health strategy for vegetatively-propagated crops

Pathogen build-up in vegetative planting material, termed seed degeneration, is a major problem in many low-income countries. When smallholder farmers use seed produced on-farm or acquired outside certified programs, it is often infected. We introduce a risk assessment framework for seed degeneration, evaluating the relative performance of individual and combined components of an integrated seed health strategy. The frequency distribution of management performance outcomes was evaluated for models incorporating biological and environmental heterogeneity, with the following results. (1) On-farm seed selection can perform as well as certified seed, if the rate of success in selecting healthy plants for seed production is high; (2) When choosing among within-season management strategies, external inoculum can determine the relative usefulness of incidence-altering management (affecting the proportion of diseased plants/seeds) and rate-altering management (affecting the rate of disease transmission in the field); (3) Under severe disease scenarios, where it is difficult to implement management components at high levels of effectiveness, combining management components can produce synergistic benefits and keep seed degeneration below a threshold; (4) Combining management components can also close the yield gap between average and worst-case scenarios. We also illustrate the potential for expert elicitation to provide parameter estimates when data are unavailable.

epidemiology↗