Fig 5 - uploaded by Christopher E. Buddenhagen
Content may be subject to copyright.
Estimated risk of Synchytrium endobioticum introduction to currently uninfected regions via potato seed and ware tuber trade, based on epidemic simulation. Risk was evaluated based on the log of the mean of the number of times a municipality became infected in each of 20 timesteps (seasons). Means were calculated across 1000 simulations of spread. In the initial conditions for this scenario analysis, only Khulo municipality in Adjara starts with the pathogen, as the only municipality with confirmed pathogen presence to our knowledge. Simulations assume no recovery or control measures within infected areas. The inset network diagram (right) represents the underlying network structure in one simulation with β = 0.4 as a dispersal parameter. Differences in the network structure and number of links associated with each value of β
Source publication
CONTEXT
Potato is an essential food staple and a critical crop for rural livelihoods in the Republic of Georgia, where many phytosanitary risks threaten production.
OBJECTIVE
The objectives of this study were, first, to characterize the current seed and ware potato transaction network, value chain, varietal adoption, and phytosanitary risks for Ge...
Citations
... The cultivation of healthy potato seed is based on the in vitro apical meristem method, which is recognized as a successful approach in the world. The quality of potato seed material is one of the main factors for its yield [4], Multiple reproduction in the open field causes various types of potato diseases in which viral infections are one of the leading reasons for the degeneration of sustainable potato seed production [5]- [8] and economic losses due to their negative impacts on yield and tuber quality [9], [10]. 40 species of viruses were known which can infect potatoes worldwide [11]. ...
Potato seed production remains a problem in Georgia. Large farmers prefer imported elite seed, which is quite expensive, while small farmers use low-quality seed produced on their plots, which may be infected with viruses. To assure potato production and supply of high-healthy planting material effective ways of eliminating viral infection must be developed. This study was conducted to evaluate the effect of thermotherapy with the combination of apical meristem culture on the four potato varieties "Picasso", "Raya", "Santé" and 'Arizona" infected with Potato virus M (PVM) in Georgia. Tree types of temperature: 33 0 C, 36 0 C, 39 0 C with combination of 2, 3 and 4 h exposure were used for thermotherapy on the four potato varieties "Picasso", "Raya", "Santé" and "Arizona" infected with Potato virus M. After 27 days Enzyme-linked immune sorbent assay (ELISA) were used to evaluate the virus infection rate. The most effective result (100% virus eradication) was obtained by temperature-36 0 C with 2h exposure during 27 days for potato varieties "Picasso" and "Raya". Results show that on treatment 36 0 C/4h during 27 days was effective for potato varieties "Sante" and "Arizona". Sprouts generated on 39 0 C with 4h exposure started to degrade due to heat. Based on the results virus free potato accessions were added collection of Biotechnology Center.
... When natural disasters destroy local infrastructure, there is particular risk that new pathogens will be introduced to the region; emergency needs make it difficult to implement effective sanitary measures (Lantagne et al., 2014). Informal seed exchange is a common practice globally that can disseminate infected plant material among neighbors and through entire regions (Delaquis et al., 2018;Andersen et al., 2019;Andersen Onofre et al., 2021;Nduwimana et al., 2022). The increase in international trade and e-commerce has also facilitated pathogen spread. ...
... represents an interesting challenge. For species in a virome that are new to a region and offer a substantial threat, reducing seed levels to zero is key, along with tracking the potential spread of new species through seed systems, evaluating management strategies, and understanding how farmers may adapt to the new disease scenario (McQuaid et al., 2016;Almekinders et al., 2019;Andersen et al., 2019;Ferris et al., 2020;Andersen Onofre et al., 2021;Nduwimana et al., 2022). Movement of at least a limited amount of contaminated plant materials might be inevitable in some cases, although indexing programs and implementation of new diagnostic tools based on HTS could help limit new introduction of viruses and other plant pathogens. ...
Virome analysis via high-throughput sequencing (HTS) allows rapid and massive virus identification and diagnoses, expanding our focus from individual samples to the ecological distribution of viruses in agroecological landscapes. Decreases in sequencing costs combined with technological advances, such as automation and robotics, allow for efficient processing and analysis of numerous samples in plant disease clinics, tissue culture laboratories, and breeding programs. There are many opportunities for translating virome analysis to support plant health. For example, virome analysis can be employed in the development of biosecurity strategies and policies, including the implementation of virome risk assessments to support regulation and reduce the movement of infected plant material. A challenge is to identify which new viruses discovered through HTS require regulation and which can be allowed to move in germplasm and trade. On-farm management strategies can incorporate information from high-throughput surveillance, monitoring for new and known viruses across scales, to rapidly identify important agricultural viruses and understand their abundance and spread. Virome indexing programs can be used to generate clean germplasm and seed, crucial for the maintenance of seed system production and health, particularly in vegetatively propagated crops such as roots, tubers, and bananas. Virome analysis in breeding programs can provide insight into virus expression levels by generating relative abundance data, aiding in breeding cultivars resistant, or at least tolerant, to viruses. The integration of network analysis and machine learning techniques can facilitate designing and implementing management strategies, using novel forms of information to provide a scalable, replicable, and practical approach to developing management strategies for viromes. In the long run, these management strategies will be designed by generating sequence databases and building on the foundation of pre-existing knowledge about virus taxonomy, distribution, and host range. In conclusion, virome analysis will support the early adoption and implementation of integrated control strategies, impacting global markets, reducing the risk of introducing novel viruses, and limiting virus spread. The effective translation of virome analysis depends on capacity building to make benefits available globally.
... In this study, we simulate epidemic risk across the south Florida avocado landscape, with the relative likelihood of spread between two locations described by a gravity model. Gravity models are commonly used in agent-based and epidemic modeling to evaluate the movement of pests and pathogens (Andersen, 2019;Andersen Onofre et al., 2021;Jongejans et al., 2015;Rauch, 2016;Xing et al., 2020). In our gravity model, orchards with higher host (avocado tree) density and closer proximity to other orchards are at higher risk for pathogen spread and establishment. ...
CONTEXT: When emerging pathogens threaten global food security, collective action for disease management is
key for protecting food systems. We evaluate how the informal exchange of information about epidemic and
economic outcomes can influence the management decisions of individuals and the resulting epidemics, in the
context of the avocado laurel wilt epidemic in south Florida.
OBJECTIVES: In scenario analyses, we addressed how socioeconomic networks, laurel wilt epidemic networks,
policy incentive structures, and social behaviors combine to influence (a) information exchange across this re-
gion, (b) growers’ decisions about disease management, and (c) epidemic spread and yield loss. We identified the
scenarios in which regional avocado health fared best.
METHODS: We built an agent-based model to simulate laurel wilt epidemic expansion and establishment across
south Florida over a 10-year period. The model used parameters specific to patterns observed and quantified
from the laurel wilt epidemic in south Florida. Based on the locations and sizes of avocado orchards there, we
simulated disease expansion and information dissemination through multilayer socioeconomic and epidemic
networks and evaluated the effects of “carrot” and “stick” policy incentive structures and behaviors like “stub-
bornness” in decision making. Scenarios were simulated for multiple parameters across a 10-year time period,
and the regional health of avocado and management decisions of growers were analyzed.
RESULTS AND CONCLUSIONS: Increased social connections led to lower regional crop health due to increased
exchange of information reinforcing selection of less expensive but less effective management choices. This in-
formation exchange was particularly impactful during the lag phase of epidemic expansion, when the cost of
disease management outweighed the cost of disease. Managers who were resistant or “stubborn” against
adopting these less expensive and less effective management strategies, particularly during the lag phase of
epidemic expansion, contributed to greater regional health. In these scenarios, growers responded more to
policies which penalized individuals than to policies which rewarded individuals.
SIGNIFICANCE: By quantifying varying degrees of stubbornness, and how growers may weight past experiences
and new information, we represented key aspects of decision making and its many influences on regional col-
lective action in this novel agent-based model. The model demonstrates the caveats of information exchange
across social networks during epidemics, and the valuable role that policy makers and informed educators can
have, particularly during the lag phase of epidemic expansion. Decision makers and stakeholders must under-
stand the influences of information exchange to overcome the challenges of collective action for crop health.
... This is why the small-holder, subsistence-oriented farmer households rely mainly on community-level informal seed systems for their native crops (Bisht 2021;Elia and Santamaria 2013;Lanka et al 2017;Velázquez-Salazar et al 2021). On the other hand, local seed movements could also create risks for seed borne pathogen spread (Onofre et al 2021). There are also organizations that initiate and help to maintain breeding programs (Maretta et al 2021) and encourage farmers to multiply their own seeds, promote seed exchanges, and foster the establishment of an independent seed sector (Kliem and Sievers-Glotzbach 2021;Sacchi et al 2019). ...
... In some regions, earlier indiscriminate use of pesticides has caused resistance development in insect pets, and creating additional challenges for plant protection (Velmourougane and Bhat 2017). Also, plant disease risks may threat crop yields (Onofre et al 2021). Therefore, it is important to increase farmers knowledge on correct practices of use of plant protection chemicals, and also to establish appropriate inspection system for spraying materials, equipment and practices (Fang and Zhu 2014). ...
... Also, producers' associations and NGOs are expected to transfer knowledge and technical support to farmers (Sacchi et al 2019;Tobin and Glenna 2019). It has been suggested that better knowledge would help to reduce use of chemical inputs (Tawk et al 2019) and would help to select better varieties and seeds for cultivation (Onofre et al 2021;Bisht 2021). ...
This study reviews the current information on the crop value chains that support biodiversity and analyses their critical endogenous and exogeneous factors. The study uses a systematic literature review approach.
... Potatoes are produced on an area of 25,000 hectares with annual consumption of 55 kg per capita. The yields, range from 8.6 to 12.6 tons/ha, vary greatly across the country due to the wide variability of agroecological zones and farming practices (data from 2015-2020), which is signi cantly lower than the average rate in developed countries (50-60 tons/ha) (Kelsey et al., 2021). ...
Potato is an important commodity in Georgia, but the average yields are considerably low (12 t/ha) mainly due to bacterial diseases. During 2020-2021, 73 samples of diseased potato tubers and stems were collected from fields and storage facilities, in different locations in Georgia. Following microbiological and biochemical tests, 54 strains (74%) were gram-negative, facultative anaerobic, oxidase negative, catalase-positive, they developed at 37 o C and in 5% NaCl, non-fluorescent on King´s B medium, and produced cavities on CVP, thus indicating they were either Dickeya or Pectobacterium spp. Twenty-seven out of selected 33 strains were identified as Dickeya spp. using conventional PCR and 21 of them were further characterized as D. solani (using TaqMan RT-PCR). According to the present research, D. solani is the major pathogen associated with potato soft rot and black leg in different regions of Georgia. The most prevalent species in Europe, P. brasiliense , as well as D. dianthicola have not been detected in the current research.
... Disease modeling may be used to evaluate the likely effects of management, like addressing the problem of seed degeneration (Jones et al. 2010;Thomas-Sharma et al. 2017). Spatial epidemic components such as seed trade networks (Andersen Onofre et al. 2021;Andersen et al. 2019;Buddenhagen et al. 2017;Delaquis et al. 2018;McQuaid et al. 2017) may also be valuable elements of more refined management performance mapping. ...
... The benefits from management performance mapping may be enhanced if maps and VOI calculations are updated with new information sources as they become available in an adaptive management scheme (Bennett et al. 2018;Shea et al. 2014). Empirical data can be supplemented with models, expert opinion, and local knowledge (Andersen Onofre et al. 2021;Petsakos et al. 2018;Tulloch et al. 2014) to help users understand changes in factors including pesticide resistance, new varieties, and new management such as irrigation. Projects may expand because of new stakeholder priorities and new situations on the ground. ...
Policymakers and donors often need to identify the locations 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-benefit locations, but often actions are needed with limited information. The value of information (VOI) in this context is formalized by evaluating the results of decision making guided by a set of specific information compared with the results of acting without considering that information. 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 the use of recursive partitioning, XGBoost, and Bayesian network models to characterize the relationships among 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 management performance areas would often provide more benefits than would random selection of target areas. We illustrate how assessing the VOI can contribute to targeted development programs and support a culture of continuous improvement for interventions.
... absoluta) as the main pest of tomato. Late blight was reported than one of the most important disease of Potato in the Republic of Georgia by Onofre et al. (2021). This disease could be a common to Solanaceae plants family. ...
To assess the phytosanitary practices of tomato producers in the West Region of Cameroon, a survey was carried out with 90 producers from 3 subdivisions , Nde, Noun and Menoua. The survey aimed to evaluate the impacts of education level, phytosanitary practices, the chemicals used and their management on tomato yield and on the environment. The results showed that 98% of tomato growers are male, aged 30-40 years old. More than 50% producers reached the high school and 71% did not receive any training in pesticides use and handling. F1 hybrids (63%) are the main varieties cultivated. The main tomato diseases recorded were caused by fungi (42%), insects (39%) and nematodes (13%). Plants are destroyed by these agents at different growth stages: leaves (35%), fruits (29%) and stems (26%) are the most affected. The producers commonly use chemical pesticides, to control pest and diseases. Dithiocarbamates (47%) and Chloronitrile (18%) are the main fungicide families used while Avermectins (45%) and Pyréthrinoids (32%) are the main insecticide. The producers estimated that the protective effectiveness range from 25 to 100%. To optimize the effectiveness of the pesticides, they are applied several times, alternated and mixed with different active ingredients. The majority of these producers (95%) does not use the recommended personal protective equipment (PPE) and throw the packaging wastes at the treatment sites thereby causing environmental hazards. Based on our findings, the phytosanitary practices of tomato producers in the West region of Cameroon are worrying and potentially harmful for both human health and the environment. Urgent measures need to be taken to raise awareness on pesticides use and handling to tomato producers, not only to reduce their incidence on the environment and soil ecosystem, but also to increase tomato yield.
... Thus, one can predict the potential effects on seed security of quality seed sourcing, disease invasion risk, and surveillance objectives. By simulation of potential scenarios of seed systems shocks, this approach can be used to predict the downstream effects on seed health and supply, potentially building on analyses of cropland connectivity (Andersen et al., 2019;Andersen Onofre et al., 2021;Buddenhagen et al., 2017Buddenhagen et al., , 2022Garrett, 2021;Xing et al., 2020). One caveat to keep in mind in evaluating the results is that only a portion of the complete network is reported in studies such as this; a complete census of the networks Figure 10. ...
Seed system network analysis can reveal exchange connections between stakeholders and test scenarios such as those of seed systems shocks. We investigated the seed exchange network structure, disease surveillance risk, and gender contribution in Burundi, under two banana disease risk scenarios. Two sites where banana bunchy top disease (BBTD) is endemic in Cibitoke Province were compared with a site free of the disease in Gitega Province. All sites had formal seed interventions using community nurseries. A quantitative survey on seed sharing was done followed by a qualitative evaluation through focus group discussions. Banana seed sourcing options were fewer in the disease-free site, which also had higher cultivar diversity. Most farmers sourced seed informally within a three-kilometer radius. Seed sharing within and between villages was based on social and family linkages, especially for women. The interaction between the formal system and informal seed exchange was more active where new cultivars, or better seed quality was expected. The BBTD endemic region had lower seed quality assessment stringency. Farmers used both direct mother plant assessment and seed source reputation in seed evaluation. The formal banana seed systems are sources of new varieties, and trusted for clean seed but the informal system was still used as a main source of seed, especially local cultivars. Assessing disease surveillance scenarios shows women in a weaker position for healthy seed acquisition. Identifying the roles of individuals in seed systems can support decision processes for seed interventions in vegetatively propagated crops.
... High-quality seed potato is crucial for successful potato cultivation (Onofre et al., 2021). Viral diseases are one of the primary reason for degeneration of seed potatoes and thus constitute a major constraint for sustainable potato production (Awasthi and Verma, 2017;Priegnitz et al., 2019;Wasilewska-Nascimento et al., 2020). ...
Certain viruses dramatically affect yield and quality of potatoes and have proved difficult to eradicate with current approaches. Here, we describe a reliable and efficient virus eradication method that is high throughput and more efficacious at producing virus-free potato plants than current reported methods. Thermotherapy, chemotherapy, and cryotherapy treatments were tested alone and in combination for ability to eradicate single and mixed Potato virus S (PVS), Potato virus A (PVA), and Potato virus M (PVM) infections from three potato cultivars. Chemotherapy treatments were undertaken on in vitro shoot segments for four weeks in culture medium supplemented with 100 mg L⁻¹ ribavirin. Thermotherapy on in vitro shoot segments was applied for two weeks at 40°C (day) and 28°C (night) with a 16 h photoperiod. Plant vitrification solution 2 (PVS2) and cryotherapy treatments included a shoot tip preculture followed by exposure to PVS2 either without or with liquid nitrogen (LN, cryotherapy) treatment. The virus status of control and recovered plants following therapies was assessed in post-regeneration culture after 3 months and then retested in plants after they had been growing in a greenhouse for a further 3 months. Microtuber production was investigated using in vitro virus-free and virus-infected segments. We found that thermotherapy and cryotherapy (60 min PVS2 + LN) used alone were not effective in virus eradication, while chemotherapy was better but with variable efficacy (20–100%). The most effective result (70–100% virus eradication) was obtained by combining chemotherapy with cryotherapy, or by consecutive chemotherapy, combined chemotherapy and thermotherapy, then cryotherapy treatments irrespective of cultivar. Regrowth following the two best virus eradication treatments was similar ranging from 8.6 to 29% across the three cultivars. The importance of virus removal on yield was reflected in “Dunluce” free of PVS having higher numbers of microtubers and in “V500’ free of PVS and PVA having a greater proportion of microtubers > 5 mm. Our improved procedure has potential for producing virus-free planting material for the potato industry. It could also underpin the global exchange of virus-free germplasm for conservation and breeding programs.
... Examples of such practices are positive selection (i.e., selecting the best plants for seed mother plants; Gildemacher et al., 2011;Priegnitz et al., 2020), rogueing (i.e., removing diseased or affected plants; Broadbent et al., 1950), and the seed plot technique (i.e., small plot dedicated only to seed production; Bryan, 1983). The seed-Health model can contribute to understanding how host resistance, seed replacement and on-farm management practices affect seed degeneration, and to evaluating the performance of combinations of management practices using scenario analysis in different environments before establishing experiments (Andersen Onofre et al., 2021;Garrett and Xing, 2021;Thomas-Sharma et al., 2017). The combination of the ISH approach with the use of the seedHealth model could identify the effectiveness of practices to manage seed degeneration. ...
CONTEXT
Studies in the Andes have demonstrated that seed degeneration of potato occurred in experimental conditions, but was negligible in farmers' conditions. There are two hypotheses for this difference: (1) farmers cultivate resistant varieties, or (2) they use on-farm practices that can manage seed degeneration. Farmers may replace some of the seed saved from their fields with outside seed, but it is an open question what level of benefit farmers experience from partial replacement.
OBJECTIVES
The objective of this study was to investigate the role of the cultivated varieties, the on-farm seed management practices, and seed replacement in potato seed degeneration. Moreover, this study evaluated the potential effect of partial replacement of the farmers' seed lot each season with healthy seed, compared to less frequent nearly full replacement, in simulations.
METHODS
We surveyed farmers in the Cotopaxi province, Ecuador, in 2008, 2010, and 2018, and performed a study on the incidence of pathogens and pests in farmers' seed lots in 2018. We also evaluated the potential effects of the timing of replacement of farmers' seed lots by healthy seed to manage degeneration, applying the seedHealth model.
RESULTS AND CONCLUSIONS
We found that farmers experience no or only slow degeneration in their varieties. Analysing yield data reported by farmers to detect degeneration, we did not detect yield declines. The type of variety and year of data collection explained the variation in yield. These results seem to confirm the hypothesis that varieties cultivated in the Andes are resistant to the impact of seed degeneration on yield, and that seed degeneration depends on the agroecological conditions present within a cropping season or year. Because we did not find an impact on yield, we hypothesized that on-farm practices affect seed-borne pathogens and pests causing seed degeneration. We identified multiple on-farm practices playing a role in the process of seed degeneration: they either slowed down or accelerated this process depending on the seed-borne pathogen and pest causing seed degeneration. Our scenario analyses using the seedHealth model showed how replacing farmers' seed lots by healthy seed could usefully reduce seed degeneration compared to using the same amount of seed to periodically replace nearly all seed in a season. Our results showed that on-farm practices are also critical drivers in the process of seed degeneration.
SIGNIFICANCE
This study demonstrated the importance of considering on-farm seed management practices (i.e., use of cultivated varieties) to strengthen seed systems interventions aiming to manage potato seed degeneration. Additionally, this study showed the potential of partially replacing farmers' seed with healthy seed as an alternative when complete seed replacement is not an option.
