Jorge Andrade-Piedra

Quantifying the Rate of Release and Escape of Phytophthora infestans Sporangia from a Potato Canopy

ABSTRACT A means for determining the rate of release, Q (spores per square meter per second), of spores from a source of inoculum is paramount for quantifying their further dispersal and the potential spread of disease. Values of Q were obtained for Phytophthora infestans sporangia released from an area source of diseased plants in a potato canopy by comparing the concentrations of airborne sporangia measured at several heights above the source, with the concentrations predicted by a Lagrangian Stochastic simulation model. An independent estimate of Q was obtained by quantifying the number of sporangia per unit area of source at the beginning of each sampling day by harvesting diseased plant tissue and enumerating sporangia from these samples. This standing spore crop was the potential number of sporangia released per area of source during the day. The standing spore crop was apportioned into time segments corresponding to sporangia concentration measurement periods using the time trace of sporangia sampled above the source by a Burkard continuous suction spore sampler. This apportionment of the standing spore crop yielded potential release rates that were compared with modeled release rates. The two independent estimates of Q were highly correlated (P = 0.003), indicating that the model has utility for predicting release rates for P. infestans sporangia and the spread of disease between fields.

Simulation of Potato Late Blight in the Andes. I: Modification and Parameterization of the LATEBLIGHT Model

ABSTRACT LATEBLIGHT, a mathematical model that simulates the effects of weather, host growth and resistance, and fungicide use on asexual development and growth of Phytophthora infestans on potato foliage, was modified so that it can be used in the Andes and, eventually, worldwide. The modifications included (i) the incorporation of improved equations for the effect of temperature on lesion growth rate (LGR) and sporulation rate (SR); (ii) the incorporation of temperature-dependent latent period (LP); and (iii) the use of experimentally measured parameters of LGR, SR, and LP for specific potato cultivars and pathogen lineages. The model was parameterized for three Peruvian potato cultivars (Tomasa, Yungay, and Amarilis) infected with isolates of a new clonal lineage of P. infestans that is currently predominant in Ecuador and Peru (EC-1).

Multi-stakeholder platforms for linking small farmers to value chains: evidence from the Andes

Value chains linked to urban markets and agro-industry present new opportunities for adding value and raising rural incomes. Small farmers, who produce small volumes, struggle to enter these markets. A lack of trust among value chain actors increases transaction costs and short-circuits innovation. This paper explores how multi-stakeholder platforms have been used to address these problems in potato-based value chains in Bolivia, Peru and Ecuador. It uses the Institutional Analysis and Development (IAD) framework to understand how platforms work. Differences in characteristics of the value chains, the participating actors and institutional arrangements have led to the emergence of two types of platforms. The first type brings traders, processors, supermarkets and others together with farmer associations and research and development (R&D) organizations to foster the development of new market opportunities through commercial, institutional and technological innovation. The second type is structured around geographically delimited supply areas, meshing farmers and service providers to address market governance issues in assuring volumes, meeting quality and timeliness constraints and empowering farmers. Evidence from these cases indicates that platforms that bring stakeholders together around value chains can result in new products, processes, norms and behaviours that benefit poor farmers, which could not have been achieved otherwise.

Qualification of a Plant Disease Simulation Model: Performance of the LATEBLIGHT Model Across a Broad Range of Environments.

ABSTRACT The concept of model qualification, i.e., discovering the domain over which a validated model may be properly used, was illustrated with LATEBLIGHT, a mathematical model that simulates the effect of weather, host growth and resistance, and fungicide use on asexual development and growth of Phytophthora infestans on potato foliage. Late blight epidemics from Ecuador, Mexico, Israel, and the United States involving 13 potato cultivars (32 epidemics in total) were compared with model predictions using graphical and statistical tests. Fungicides were not applied in any of the epidemics. For the simulations, a host resistance level was assigned to each cultivar based on general categories reported by local investigators. For eight cultivars, the model predictions fit the observed data. For four cultivars, the model predictions overestimated disease, likely due to inaccurate estimates of host resistance. Model predictions were inconsistent for one cultivar and for one location. It was concluded that the domain of applicability of LATEBLIGHT can be extended from the range of conditions in Peru for which it has been previously validated to those observed in this study. A sensitivity analysis showed that, within the range of values observed empirically, LATEBLIGHT is more sensitive to changes in variables related to initial inoculum and to weather than to changes in variables relating to host resistance.

Simulation of potato late blight in the andes. II: Validation of the LATEBLIGHT model

ABSTRACT LATEBLIGHT, a mathematical model that simulates the effect of weather, host growth and resistance, and fungicide use on asexual development and growth of Phytophthora infestans on potato foliage, was validated for the Andes of Peru. Validation was needed due to recent modifications made to the model, and because the model had not been formally tested outside of New York State. Prior to validation, procedures to estimate the starting time of the epidemic, the amount of initial inoculum, and leaf wetness duration were developed. Observed data for validation were from field trials with three potato cultivars in the Peruvian locations of Comas and Huancayo in the department of Junín, and Oxapampa in the department of Pasco in 1999 and 2000 for a total of 12 epidemics. These data had not been used previously for estimating model parameters. Observed and simulated epidemics were compared graphically using disease progress curves and numerically using the area under the disease progress curve in a confidence interval test, an equivalence test, and an envelope of acceptance test. The level of agreement between observed and simulated epidemics was high, and the model was found to be valid according to subjective and objective performance criteria. The approach of measuring fitness components of potato cultivars infected with isolates of a certain clonal lineage of P. infestans under controlled conditions and then using the experimental results as parameters of LATEBLIGHT proved to be effective. Fungicide treatments were not considered in this study.

Linking Smallholders to the New Agricultural Economy: The Case of the Plataformas de Concertación in Ecuador

Abstract This article examines the challenges of linking smallholders to high-value food markets by looking at the experience of the Plataformas programme in the Ecuadorian Sierra. Multiple evaluation methods are employed to ensure identification of program impact. The findings suggest that the programme successfully improved the welfare of beneficiary farmers, as measured by yields and gross margins. These benefits are achieved through improving the efficiency of agricultural production and through selling at higher prices. No significant secondary health or environmental effects were found. Overall, the programme provides clear evidence that combining production support with facilitating market access can be successful.

Use of Phosphonate to Manage Foliar Potato Late Blight in Developing Countries

Twenty phosphonate products found in the agrochemical market in Ecuador and Peru were evaluated in bioassays for the control of foliar potato late blight, caused by Phytophthora infestans. Eight phosphonate products were evaluated in 16 field experiments done in Peru, Ecuador, Kenya, and Nepal. A meta-analysis across locations involving 71 combinations of potato genotype by site and year demonstrated a significant relationship between phosphonate application rate and efficacy for controlling late blight on potato foliage. The meta-analysis revealed that phosphonate rates of approximately 2.5 g a.i./liter provided efficacy similar to that of the conventional contact fungicides mancozeb and chlorothalonil used at similar rates. At rates higher than 2.5 g a.i./liter, the efficacy of phosphonate was superior to the contact fungicides. Overall, late blight control by phosphonate appeared relatively stable in field experiments across locations. An analysis of field experiments and 64 combinations of potato genotype by site and year showed no correlation between the susceptibility level of potato genotypes and efficacy of phosphonates. The cost of both phosphonate compounds and contact fungicides varied greatly among the countries of the field study; however, in Kenya, control with phosphonate was clearly less expensive than with mancozeb.

Technical and Economic Analysis of Aeroponics and other Systems for Potato Mini-Tuber Production in Latin America

Producing large quantities of high quality mini-tubers at low cost is essential for an economically viable supply of seed potatoes. Here we systematize the technical and economic aspects of aeroponics and provide a benchmark comparison of this technology with other mini-tuber production systems as developed in Latin America: conventional, semi-hydroponics, and fiber-cement tiles technology. Research methodologies included: 3-year registration of cash flows and production registers of aeroponics, economic and technical surveys, in-depth inquiry with managers of technologies. Results show that aeroponics as promoted by the International Potato Center (CIP) has several advantages, including high multiplication rates (up to 1:45), high production efficiency per area (> 900 mini-tubers per m2), savings in water, chemicals and/or energy, and positive economic indicators. The fiber-cement tiles technology from Brazil is also shown to be highly efficient and slightly more robust compared to aeroponics. Preconditions for the successful adoption of the different technologies in developing countries are discussed.ResumenLa producción de grandes cantidades de mini-tubérculos de alta calidad y a bajo precio es esencial para un abastecimiento económicamente viable de semilla de papa. Aquí sistematizamos aspectos técnicos y económicos de aeroponía y se compara la línea de base de esta tecnología con otros sistemas de producción de mini-tubérculos que han sido desarrollados en América Latina: tecnología convencional, semi-hidroponía, tejas de fibrocemento. Metodologías de investigación incluyeron: registro de flujo de caja y registro de producción de aeroponía durante 3 años, encuestas económicas y técnicas, indagación en detalle con gerentes de tecnologías. Los resultados demuestran que la aeroponía tal como lo promueve el Centro Internacional de la Papa (CIP) tiene múltiples ventajas, entre ellas tasas altas de multiplicación (hasta 1:45), eficiencia alta de producción por área (> 900 mini-tubérculos por m2), ahorros en agua, químicos y/o energía, y indicadores económicos positivos. También se demuestra que la tecnología de tejas de fibrocemento de Brasil es muy eficiente y ligeramente más robusta comparada con aeroponía. Se discuten las condiciones previas para una adopción exitosa de las diferentes tecnologías en países en vía de desarrollo.

Preemergence Infection of Potato Sprouts by Phytophthora infestans in the Highland Tropics of Ecuador

Experiments were conducted to determine whether preemergence infection of potato sprouts by Phytophthora infestans occurs in the highland tropics of Ecuador. In three separate experiments in the field, P. infestans was identified on the preemerged sprouts of 49, 5, and 43% of tubers, respectively, which had been removed from soil prior to emergence. Tubers had been planted within 10 m of approximately 300-m2 plots with mature potato plants severely infected with late blight. Infection potential of potato sprouts also was evaluated in the greenhouse by applying 10-ml sporangial suspensions (50 and 250 sporangia/ml) daily for 10 days to the soil surface of pots planted with sprouted seed potato tubers. The daily inoculation rate of 50 sporangia/ml (15.9 × 103 sporangia/m2) resulted in sprout infection in 100% of inoculated pots and roughly corresponded to the sporangial deposition accumulated over 24 h in the field. Deposition had been measured at 1 m from a severely infected potato plot. Our study demonstrated the potential for preemergence infection of potato sprouts by P. infestans in the highlands of Ecuador, where year-round aerial inoculum is present. Preemergence infection is consistent with high levels of disease sometimes seen in recently emerged potato fields. These experiments indicate a need to reconsider disease management approaches.

Knowledge management for pro-poor innovation: the Papa Andina case

Papa Andina began as a regional research program focusing on the Andean potato sectors of Bolivia, Ecuador and Peru, but later shifted its focus to facilitating pro-poor innovation. To accomplish this shift, a number of approaches were developed to foster innovation, by facilitating mutual learning and collective action among individuals and groups with differing, often conflicting, interests. This paper explains why and how Papa Andina shifted its focus from conducting research to facilitating innovation, and describes two approaches that Papa Andina developed to facilitate mutual learning and innovation: the ‘participatory market chain approach’ and ‘horizontal evaluation’. Differing local circumstances and beliefs shaped the work of local teams, and rivalry among the teams stimulated creativity and innovation. Participatory evaluations helped individuals recognize and appreciate differences and build shared knowledge across the teams. After describing the case, the paper discusses the implications for knowledge management and innovation theory, and for the potential use of Papa Andinas approaches in other settings.