Peter Kromann

Potatoes for Sustainable Global Food Security

Potato is the third most important food crop in terms of global consumption, and it has been highly recommended by the Food and Agriculture Organization of the United Nations as a food security crop as the world faces a growing population and related problems with food supply. This paper presents data on global potato production, consumption, malnutrition, and hunger; information which helps pinpoint where the resource-poor and hungry live and how the potato and international agricultural research could help improve food security and livelihoods in developing countries. The International Potato Center has used such a targeting exercise to focus its research for development and develop its new strategic plan, in which five out of the six objectives are related to potato.

Biological control agents: from field to market, problems, and challenges

Global food security is vulnerable due to massive growth of the human population, changes in global climate, the emergence of novel/more virulent pathogens, and demands from increasingly discerning consumers for chemical-free, sustainably produced food products. Bacterium-based biological control agents (BCAs), if used as part of an integrated management system, may satisfy the above demands. We focus on the advantages, limitations, problems, and challenges involved in such strategies.

Rainfall Thresholds as Support for Timing Fungicide Applications in the Control of Potato Late Blight in Ecuador and Peru

Accumulated rainfall thresholds were studied in seven field experiments conducted in Ecuador and Peru for their value in timing applications of fungicide to control potato late blight, caused by Phytophthora infestans. Fungicide regimes based on accumulated rainfall thresholds ranging from 10 to 70 mm were compared with calendar spray schemes of every 5 or 7 days. Very low thresholds of 10 to 20 mm gave similar levels of control and resulted in similar number of sprays as did calendar spraying. However, neither low thresholds nor calendar sprays were effective in protecting susceptible potato genotypes in over half of the experiments. Thresholds of 25 to 50 mm of rainfall led to reduction in the number of sprays needed to protect resistant cultivars but also resulted in high levels of disease on susceptible cultivars. We conclude that timing fungicide sprays based on accumulated rainfall thresholds could be a successful component of integrated management strategies that include cultivars with moderate or high levels of resistance. The simplicity of measuring accumulated rainfall means that the technology can potentially be used by resource-poor farmers in developing countries.

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.

Identification of mVOCs from Andean Rhizobacteria and Field Evaluation of Bacterial and Mycorrhizal Inoculants on Growth of Potato in its Center of Origin

Food security (a pressing issue for all nations) faces a threat due to population growth, land availability for growing crops, a changing climate (leading to increases in both abiotic and biotic stresses), heightened consumer awareness of the risks related to the use of agrichemicals, and also the reliance on depleting fossil fuel reserves for their production. Legislative changes in Europe mean that fewer agrichemicals will be available in the future for the control of crop pests and pathogens. The need for the implementation of a more sustainable agricultural system globally, incorporating an integrated approach to disease management, has never been more urgent. To that end, the Valorizing Andean Microbial Diversity (VALORAM) project (http://valoram.ucc.ie), funded under FP7, examined the role of microbial communities in crop production and protection to improve the sustainability, food security, environmental protection, and productivity for rural Andean farmers. During this work, microbial volatile organic compounds (mVOCs) of 27 rhizobacterial isolates were identified using gas chromatography/mass spectrometry (GC/MS), and their antifungal activity against Rhizoctonia solani was determined in vitro and compared to the activity of a selection of pure volatile compounds. Five of these isolates, Pseudomonas palleroniana R43631, Bacillus sp. R47065, R47131, Paenibacillus sp. B3a R49541, and Bacillus simplex M3-4 R49538 trialled in the field in their respective countries of origin, i.e., Bolivia, Peru, and Ecuador, showed significant increase in the yield of potato. The strategy followed in the VALORAM project may offer a template for the future isolation and determination of putative biocontrol and plant growth-promoting agents, useful as part of a low-input integrated pest management system.

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.

Review of Potato Biotic Constraints and Experiences with Integrated Pest Management Interventions

Potato (Solanum spp.) ranks third in importance as a single food crop worldwide. Late blight, caused by Phytophthora infestans, is considered to be the most important single biotic constraint of potato, but degeneration of vegetative planting material, caused primarily by a complex of viruses, potentially causes even greater yield losses. Arthropod pests are also important, with the primary problems on a global scale being the potato tuber moth complex (Phthorimaea operculella, Symmetrischema tangolias and Tecia solanivora), leaf miner fly (Liriomyza huidobrenis), Colorado potato beetle (Leptinotarsa decemlineata), and Andean potato weevil (Premnotrypes spp.). Potato is one of the most pesticide-demanding agricultural crops and health risks related to pesticide use in potato production are high, especially in developing countries where protective clothing is generally not used. Experiences with potato integrated pest management (IPM) interventions have been multiple, but some of the most promising for disease management involve efforts to integrate the use of resistant cultivars, fungicides (for late blight) and capacity building of farmers. Interventions for arthropod pests rely less on host resistance and focus more on sustaining biodiversity and habitat management, as well as technological innovations to improve on-farm management, for example, cultural management practices and biological control. It is concluded that farmer capacity building is one of the most important elements needed to improve potato IPM in developing countries and that farmer acceptance of new technologies is best achieved through their understanding of the economic, ecological and practical benefits of the new technologies.

Can Andean potatoes be agronomically biofortified with iron and zinc fertilizers

AimsThe aim of this study was to investigate the proof-of-concept that Andean potato (Solanum tuberosum L., Andigenum Group) can be agronomically biofortified with iron (Fe) and zinc (Zn) fertilizers.MethodsGreenhouse and field experiments were conducted in the Ecuadorian Andes with varying rates of foliar and soil applied Fe and Zn fertilizers to investigate the potential resulting increase in tuber Fe and tuber Zn concentrations.ResultsThe study showed that simple fertilizer practices enhancing Zn supply to potato plants can increase tuber Zn concentrations. The rate of increase of tuber Zn following Zn fertilization was similar across cultivars. A concomitant negative effect of high rates of Zn applications on yield was not seen, and a maximum Zn application level for increasing tuber Zn concentration was not identified. A positive tuber yield effect was seen at one field site. High rates of foliar Zn application reached a 2.51-fold tuber Zn increase, and high rates of soil Zn application a 1.91-fold tuber Zn increase. The experiments showed no positive correlation between Fe fertilization and Fe concentration in tubers. Moreover, the study showed a strong effect of site on the concentration of Fe and Zn in tubers, and the tuber mineral concentrations across sites and treatments were negatively correlated with tuber yield.ConclusionsThe results confirmed the proof of concept that Andean potato cultivars can be agronomically Zn-biofortified with foliar and soil applied Zn fertilizers. Tuber Fe concentrations of Andean potatoes were not increased with Fe fertilization.

Epidemic Network Analysis for Mitigation of Invasive Pathogens in Seed Systems: Potato in Ecuador

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 approach for evaluating the epidemiological role of nodes in seed networks, and apply it to a regional potato farmer consortium (Consorcio de Productores de Papa [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 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. However, women had a smaller amount of the market share for seed tubers and ware potato. Understanding seed system networks provides input for scenario analyses to evaluate potential system improvements. [Formula: see text] Copyright

Evaluation of host susceptibility, pathogen aggressiveness and sporangial survival in soil as factors affecting incidence of potato tuber infection by Phytophthora infestans in Ecuador

Incidence of potato tuber infection by Phytophthora infestans is low in Ecuador. Factors considered to potentially affect the incidence of tuber infection include pathogen aggressiveness, host resistance, direct suppression from biological and chemical characteristics of soil acting on pathogen propagules, and exclusion resulting from soil structure and high ridging. In this study, we tested the hypothesis that low incidence could be due to reduced pathogen aggressiveness and/or low host susceptibility by comparing several pathogen isolates and commonly grown potato cultivars from Ecuador with isolates and cultivars from Europe, where tuber blight is known to be a problem. Additionally, in Ecuador, whole tubers and slices of common varieties were inoculated with local isolates of P. infestans to test for potential infection under Ecuadorian conditions. All isolates, regardless of origin, caused tuber infection. The aggressiveness of isolates varied, but this was both between and among Ecuadorian and Swedish isolates and it was not possible to establish a clear difference in the degree of infection based on isolate origin, or origin of potato variety. In general, we found no evidence to suggest that low aggressiveness of the pathogen or extreme resistance of the host explains low incidence of tuber blight in Ecuador. Therefore, we conclude that low incidence of tuber blight in Ecuador is probably caused by soil factors. Furthermore, exclusion due to soil structure and high hilling may play an important role as a preliminary soil infectivity study demonstrated that P. infestans sporangia were infective in six Ecuadorian field soils for at least 15 days.