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 © 2017 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

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 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.

Ralstonia solanacearum: A new threat to potato production in Serbia

A survey of ware potatoes (a total of 1127 samples) from localities in Serbia during two consecutive years resulted in detection and identification of R. solanacearum in 17 tuber samples. The monitoring detected the causal agent of bacterial wilt and brown rot of potato in three districts of Vojvodina province. In 2011, the infection by R. solanacearum was confirmed in 7 samples of ware potato tubers (varieties - Saturna, Pirol, Hermes, Panda) in West Backa and South Backa Districts. In 2012, the infection by R. solanacearum was confirmed in 10 potato tuber samples (Lady Claire, Desiree, Panda, Red Fantasy and Vineta varieties) from two districts: South Backa and Central Banat. Bacterial strains obtained from positive samples were identified as R. solanacearum biovar 2 using PCR/RFLP analysis, pathogenicity test on tomato transplants, and nutritional, enzymatic and biovar determination tests. To our best knowledge, these are the only findings of R. solanacearum infection in ware potatoes in Serbia. R. solanacearum was not detected in tomato or any other host plant tested in this study. Furthermore, the bacterium was not found in any of the water samples tested, including those originating from areas in which the bacterium was found in ware potato samples.

First Report of the Pale Potato Cyst Nematode Globodera pallida from Slovenia

The potato cyst nematodes (PCN) Globodera rostochiensis (Woll.) Behrens and G. pallida (Stone) Behrens are considered the most important nematode threat to potato production worldwide, and they are subject to strict quarantine regulations in many countries. The first report of the PCN in Slovenia dates back to 1971, when a single cyst of G. rostochiensis was detected (3). In the last decade, G. rostochiensis was detected several times, mainly in the central and northern parts of the country (2). Interceptions of G. pallida in imported consignments of ware potato were made several times, but had not been detected in soil in Slovenia. Therefore, the country was declared as a protected zone for G. pallida in the European Union by the national authorities in 2003. During the official PCN systematic survey in autumn 2011, the pale potato cyst nematode, G. pallida, was found in a soil sample. Two viable cysts were extracted and the nematode species was identified. The posterior part of the cysts containing eggs and juveniles were used for morphometrical analysis, while the anterior parts were used for DNA extraction and molecular analyses. The ribosomal internal transcribed spacer (ITS) region was amplified using ITS5 and PITSp4 primers and detected in real-time PCR using ABI7500 (Applied Biosystems, Life Technologies, Carlsbad, CA,) (1). Also, the ribosomal DNA region that extends from the 3′ end of the 18S ribosomal subunit and includes all of ITS1, 5.8S, and ITS2, to the 5′ end of the 28S ribosomal subunit, was used to generate a DNA sequence. The sequence obtained was compared with those from several Globodera species, revealing unequivocal similarity to G. pallida. The infested soil sample originated from a ware potato field near Ivancna Gorica, central Slovenia. Subsequently, an additional 69 samples were taken from the surroundings and viable G. pallida cysts were found in another five samples taken from two neighboring fields (one of grassland and the other of clover). Three fields, totaling 1.9 ha, were declared as G. pallida-infested. The eradication of the pest will take place by enforcing strict phytosanitary measures. Ware potatoes originating from areas where the pests occur is considered to be the most probable pathway for the introduction of G. pallida in Slovenia. A ware potato processing facility is situated in very close proximity to the infested fields. The waste waters from potato tuber washing were discharging onto the grassland, never used for potato or other field crop production in which the G. pallida infestation was found. The facility processes imported ware potato from several European and non-European countries. This case demonstrates that ware potato may pose a serious risk for the introduction of such pests, and should be therefore subjected to more intensive phytosanitary inspection. References: (1) J. Bacic et al. Russ. J. Nematol. 16:63, 2008. (2) S. Širca et al. Phytopathol. Mediterr. 49:361, 2010. (3) G. Urek et al. Nematology 5:391, 2003.