Thesis

Seed-transmitted diseases as constraints for potato production in the tropical highlands of Ecuador

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  • TIERRA VIVA scientific & cultural mediation
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Abstract

Viruses have been considered as the main source of potato tuber-seed degeneration in the Andes. In Ecuador, surveys carried out in the major potato growing area show an astonishing low virus incidence (total average PLRV<3%, PVY<3%, PYVV<2%, altitude 2800-3700m). Similar results obtained by other scientists in other countries, suggest that the importance of those viruses for potato production in the tropical highlands has been overemphasized.

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... Table 3). 294 Fankhauser (2000) reported similar results about incidence of black scurf when sampling tubers of the 295 varieties INIAP-Gabriela and INIAP-Esperanza in the province Chimborazo (78% incidence). Incidence of 296 the Andean potato weevil was also high (46.4%) ...
... ( Table 3), but approximately 50% less than previously 297 reported by Fankhauser (2000) (88% incidence). These results may indicate that management strategies to 298 control R. solani proposed by local organizations are not working, or are not being adopted by farmers since 299 the incidence of black scurf remain stable from 1998 to 2010, when Fankhauser (2000) and our group did 300 the surveys. Our experience suggest a poor adoption of the management strategies by farmers, and points 301 out the need of strengthening local extension services (Parsa et al. 2012). ...
... 319Surveys performed in Peru during 1985-1987 and in Ecuador in 1998 also found that both of these viruses 320 were predominant in farmers' fields(Bertschinger et al. 1990;Fankhauser 2000). On the contrary, recent 321 research points out to a high incidence of PVY in the varieties INIAP-Fripapa and Superchola(Gomez et 322 al. 2015), but such contrast might be influenced by the seed source. ...
Preprint
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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.
... Cassava mosaic geminiviruses (CMGs) and Cassava brown streak viruses (CBSVs) are major causes of degeneration in East Africa (Legg et al. 2015), while viruses associated with cassava frogskin disease are the main causes of degeneration in South America (Carvajal-Yepes et al. 2014). For potato, viruses are a major cause of seed degeneration around the world (Thomas-Sharma et al. 2016), while latent tuber infections of the bacterial wilt pathogen, Ralstonia solanacearum, are a major problem in tropical and subtropical countries (Mwangi et al. 2008), and the fungal pathogen Rhizoctonia solani is a problem at high altitudes in the Andes (Fankhauser 2000). ...
... Weather is a critical factor determining the rate of seed degeneration. Viral degeneration of seed potato is lower at high altitudes (Rahman and Akanda 2008), due at least in part to lower virus and vector activity (Fankhauser 2000), and higher rates of reversion or lower autoinfection efficiency (Bertschinger 1992). In a fine-scale forecasting model of potato viruses, Bertschinger et al. (1995) used daily temperature measurements to determine host growth rates and vector dynamics, predicting the number of infected progeny seed. ...
Preprint
Full-text available
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.
... Additionally, depending on the geographic region, fungi, bacteria, nematodes, phytoplasmas, and insects can also play important roles in potato seed degeneration (Thomas‐Sharma et al. 2016). In high-elevation potato production regions of Ecuador, Rhizoctonia solani is a major cause of seed degeneration (Fankhauser 2000) whereas, in many other tropical and subtropical countries, Ralstonia solanacearum is a major concern (Mwangi et al. 2008). Adding to this complex etiology, the rate of degeneration is also highly variable across geographical regions. ...
... A key point to consider for potato seed systems is virus transmission mechanisms. As a case in point, PVX and Andean potato mottle comovirus are transmitted by contact whereas others such as PVY, PLRV, and PYVVare vectored by aphids (Fankhauser 2000). Networks could include both spread through seed transactions and spread based on the spatial proximity of farm pairs (as a proxy for the probability of vector movement between a pair). ...
Article
Full-text available
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 .
... Cassava mosaic geminiviruses (CMGs) and Cassava brown streak viruses (CBSVs) are major causes of degeneration in East Africa (Legg et al. 2015), while viruses associated with cassava frogskin disease are the main causes of degeneration in South America (Carvajal-Yepes et al. 2014). For potato, viruses are a major cause of seed degeneration around the world (Thomas-Sharma et al. 2016), while latent tuber infections of the bacterial wilt pathogen, Ralstonia solanacearum, are a major problem in tropical and subtropical countries (Mwangi et al. 2008), and the fungal pathogen Rhizoctonia solani is a problem at high altitudes in the Andes (Fankhauser 2000). ...
... Weather is a critical factor determining the rate of seed degeneration. Viral degeneration of seed potato is lower at high altitudes (Rahman and Akanda 2008), due at least in part to lower virus and vector activity (Fankhauser 2000), and higher rates of reversion or lower autoinfection efficiency (Bertschinger 1992). In a fine-scale forecasting model of potato viruses, Bertschinger et al. (1995) used daily temperature measurements to determine host growth rates and vector dynamics, predicting the number of infected progeny seed. ...
Article
Full-text available
Pathogen buildup 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 be synergistic 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 empirical data are unavailable. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
... Studies done in traditional Andean potato seed systems over the past 30 years found considerably less than 100% of tubers infected with potato viruses. This was true for viruses that are transmitted by contact (potato potexvirus X (PVX), potato Andean mottle comovirus (APMoV)) or vectored by aphids [potato potyvirus Y (PVY) and potato leafroll luteovirus (PLRV)] (Bertschinger et al., 1990b;Fankhauser, 2000;Haan, 2009;Pérez Barrera et al., 2015). In these studies, PVX, which singly does not cause severe yield loss, was frequently found in relatively high incidence, while PVY and PLRV, which can cause severe yield loss, were generally rare Scheidegger et al., 1996;Pérez Barrera et al., 2015). ...
... However, genetic variability for systemic tuber infection in primarily infected plants has been reported, as shown for PLRV (Syller, 1991(Syller, , 1994(Syller, , 2003Difonzo et al., 1994) or PVY (Gibson, 1991). Also, the results of various virus incidence surveys reported for a wide variety of potato genotypes in the Andes (Monasterios dela Torre, 1966;Fankhauser, 2000) point at genetic variability, even if survey data are not a compelling proof for genetic variability with regard to systemic tuber infection factors. Nonetheless, the surveys strongly support the hypothesis that reduced autoinfection may occur in many Andean potato genotypes and that autoinfection may constitute a general mechanism of virus-host pathosystems under Andean conditions. ...
Article
Full-text available
The common assumption in potato virus epidemiology is that all daughter tubers produced by plants coming from infected mother tubers (secondary infection) will become infected via systemic translocation of the virus during growth. We hypothesize that depending on the prevalent environmental conditions, only a portion of the daughter tubers of a plant that is secondarily infected by viruses may become infected. To test this hypothesis experimental data from standardized field experiments were produced in three contrasting environments at 112, 3280, and 4000 m a.s.l. in Peru during two growing seasons. In these experiments, the percentage of infected daughter tubers produced by seed tubers that were infected with either potato potexvirus X (PVX), potato Andean mottle comovirus (APMoV), potato potyvirus Y (PVY) (jointly infected with PVX) or potato leafroll luteovirus (PLRV) was determined. Incomplete autoinfection was found in all cases, as the percentage of virus infected daughter tubers harvested from secondarily infected plants was invariably less than 100%, with the lowest percentage of infection being 30%. Changing the growing site to higher altitudes decreased autoinfection for all viruses. Therefore, the assumption of complete autoinfection of secondarily infected plants were rejected, while the hypothesis of environmentally dependent incomplete autoinfection was accepted. The findings help explain the occurrence of traditional seed management practices in the Andes and may help to develop locally adapted seed systems in environments of the world that have no steady access to healthy seed tubers coming from a formally certified seed system. The results obtained almost three decades ago are discussed in light of most recent knowledge on epigenetic regulation of host plant – virus interactions which allow for speculating about the underlying biological principles of the incomplete autoinfection. A research roadmap is proposed for achieving explicit experimental proof for the epigenetic regulation of incomplete autoinfection in the pathosystem under study.
... The relative importance of degenerative pathogens and pests varies between geographic regions, and soilborne pathogens and pests that readily become seedborne can contribute significantly towards degeneration (Fig. 2). For example, in a study in the high-altitude production areas of the Ecuadorian Andes, significant yield reduction was attributed to Rhizoctonia solani, found at an incidence of up to 78% in farmers' seed, while the generally important viruses PLRV and PVY were at an incidence of <3% (Fankhauser, 2000). At lower altitudes in many tropical and subtropical countries, Ralstonia solanacearum, the cause of bacterial wilt, is an important component of degeneration with an incidence of up to 36% in tubers from some farms in Kenya (Mwangi et al., 2008). ...
... (Thiele, 1999). Studies in the Andes have shown that potato viruses are sometimes found at very low incidences in potato landraces or varieties that have been exposed to natural conditions for untold generations (Bertschinger et al., 1990;Fankhauser, 2000). Low levels of seed degeneration at high elevations could be because of reduced multiplication of vector and/or pathogen, which could limit disease spread. ...
Article
Full-text available
Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long-standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of seed produced by specialized growers that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. The success of certified seed in developed countries has concentrated the research and development agenda on the establishment of similar systems in developing countries. Despite these efforts, certified seed has had little penetration into the informal seed systems currently in place in most developing countries. Small-scale farmers in these countries continue to plant seed tubers acquired through the informal seed system, i.e. produced on-farm or acquired from neighbors or local markets. Informal seed tubers frequently have poor health status, leading to significant reductions in yield and/or market-value. Here we emphasize the need to refocus management efforts in developing countries on improving the health status of seed tubers in the informal system by integrating disease resistance and on-farm management tools with strategic seed replacement. This ‘integrated seed health strategy’ can also prolong the good health status of plants derived from certified seed, which would otherwise be diminished due to potential rapid infection from neighboring fields. Knowledge gaps, development challenges and impacts of this integrated seed health strategy are discussed.This article is protected by copyright. All rights reserved.
... The pathogen can survive in infected tubers, plant debris and volunteer plants. Infection of tubers can occur but is rarely observed (Oyarzún et al., 2005, Kromman et al., 2008, or even absent (Fankhauser, 2000) when tuber diseases had been prospected. These have been attributed to soil supressiveness due to physical/chemical properties (Oyarzun et al., 2011, Villamarin et al., 2011 and/or microbial antagonism . ...
Thesis
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Potato is one of the most import food crops in Ecuador. It is produced mostly by small scale farmers. Late blight is the main disease that affects the yield of the crop in the country. The development of resistant potato varieties is a major goal in the breeding program conducted by INIAP. The genetic diversity within the P. infestans population was studied. Despite the lack of sexual recombination, there is ample genetic variability within the Ecuadorian clonal population of the pathogen. Disease assays revealed that only very few resistant clones are available in Ecuador and that new sources of resistant clones are badly needed. Alternatives for improving and speeding up potato breeding in Ecuador are discussed based on the current legal framework.
... Nonetheless, although Ecuadorian andisols are likely to contain biotic and abiotic P. infestans suppressing factors, we found that sporangia remained viable in the six Ecuadorian soils for at least 15 days when using a concentration of 2 x 10 4 sporangia per cubic centimeter soil and differences among soils could not clearly be associated with organic matter, pH or aluminum. Moreover, it is worth noting that incidence of the soil borne pathogen Rhizoctonia solani is high in Ecuadorian potato fields (Fankhauser, 2000). ...
Article
Full-text available
Abstract: 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.
... Nonetheless, although Ecuadorian andisols are likely to contain biotic and abiotic P. infestans suppressing factors, we found that sporangia remained viable in the six Ecuadorian soils for at least 15 days when using a concentration of 2 x 10 4 sporangia per cubic centimeter soil and differences among soils could not clearly be associated with organic matter, pH or aluminum. Moreover, it is worth noting that incidence of the soil borne pathogen Rhizoctonia solani is high in Ecuadorian potato fields (Fankhauser, 2000). ...
Book
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In a general sense, this manual is a second edition of the Manual de Producción de Semilla de Papa de Calidad usando Aeroponía1 [Manual on Quality Seed Potato Production using Aeroponics]. The most significant differences from the first edition are that, on one hand, this version was prepared by a team of researchers who have worked with this technology and, on the other hand, it includes lessons from more than ten years of work with aeroponics in various countries of Latin America and Africa. Also, this time the information is more detailed, so that it can serve as a more effective guide for those who are interested in the topic.
Chapter
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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. © Springer Science+Business Media Dordrecht 2014. All rights are reserved.
Article
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En el período 1985-87 se investigó la incidencia de siete virus de papa: PVX, PVS, APMV, APLV, PLRV, PVY y SB-22 en campos y tubérculossemillas comunes de cultivares nativos y mejorados de agricultores de la Sierra Central y Sierra Sur del Perú. Como nativos se consideró el complejo de cultivares de las especies Solanum goniocalyyx, S. chaucha y S. tuberosum ssp. andigena, que son las mas sembradas en las zonas referidas. En general, las muestras resultaron muy infectadas (promedios de 62 a 98% de infección de virus por lote/por zona). PVX fue el virus de mayor incidencia (37-82%), seguido por PVS (19-53%); la incidencia promedio de PLRV y PVY fue de 0.7-6.8%. En particular, PLRV resultó muy difundido en lotes de cultivares nativos (24%). La incidencia del virus denominado SB-22 fue particularmente alta (39%) en el cultivar Ccompis (S. tuberosum ssp. andigena) lo mismo que el APLV (25%) en el cultivar Huayro (S. chaucha). Para APMV se determinó, en las zonas investigadas, una incidencia mediana (3-13%). La incidencia de PVX y PVS fue significativamente mas alta en cultivares mejorados que en cultivares nativos, mientras que la situación con PLRV y PVY fue a la inversa. En Cusco se investigó la incidencia de los virus en campos de papa plantados con tubérculossemillas distribuidos antes de 1986 por proyectos de desarrollo rural y en campos plantados con tubérculos-semillas de agricultores procedentes de ferias, vecinos, y otros. No se encontró diferencias significativas entre ambas categorías. Se discuten los resultados en relación a su relevancia para la producción de tubérculos-semillas de alta calidad fitosanitaria.
Article
Se utilizó ELISA en la modalidad de doble capa de anticuerpo, para detectar los virus PLRV, PVY, PVX y PVS en brotes de tubérculos de los cultivares Andinita y Granola en el estado de Mérida. Se evaluaron las clases de semilla Genética, Básica, Registrada, Certificada Nacional (N), y tipo pasilla para Andinita, incluyendo además Certificada Importada (I) para Granola. En el estado de Lara los cultivares fueron Kennebec en las clases Genética, Certificada (N) y Certificada (I) y Sebago con Básica y Certificada (I). Para cada clase se evaluaron 50 tubérculos, a nivel de laboratorio. De cada tubérculo se tomó el brote apical y uno lateral de aproximadamente 1 cm. de longitud. Los resultados de laboratorio indicaron que el virus detectado con mayor frecuencia para Granola fue el PVS. Se observó la mayor incidencia en la clase Certificada (N) y Certificada (I). El PVS y la infección doble PVX + PVS fueron los más frecuentes en Kennebec y Sebago. La mayor incidencia de PVS fue en Certificada (I) para ambos cultivares y la infección doble PVX + PVS fue en Certificada (I) de Sebago. En Andinita no se detectó ninguno de los cuatro virus.Aceptado para publicación : agosto 29, 1996
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With recent data on competition of plants in the field an attempt is made to give a summary of the literature, dealing with the influence of virus diseases on yield. It is theoretically possible, that up to a certain percentage the diseases have no effect on the yield. It is even possible, if planting is too dense, or if the diseased plants start tuberization before the healthy plants, and if the healthy plants have a longer vegetation period than the diseased neighbours, that slightly higher yields might be obtained.
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Methods used to test for virus infection in potato samples from South America are described and the incidence of infection in the samples is recorded. Samples were classified according to provenance, ploidy, altitude of collection, and as weed or cultivated forms to investigate the influence of these factors. The advantages of maintenance of potato collections as seed lines are discussed with special reference to prevention of spread of introduced viruses. Die bei der Untersuchung auf Virusbefall bei Kartoffelmustern aus Südamerika angewendeten Methoden werden beschrieben. Es wird über den Umfang der Infektion durch die Kartoffelviren X(PVX), S(PVS) und Y(PVY) und den nekrotischen Tabakrippenbräune-Stamm von Virus Y(TVN) in 784 Mustern berichtet, ebenso über das Auftreten von Blattroll in 241 Mustern (Tabelle 1). Um den Einfluss verschiedener Faktoren zu untersuchen, wurden die Muster eingeteilt nach Herkunft (Tabelle 1), Ploidiestufe (Tabelle 2), Höhenlage der Herkunftsorte (Tabelle 3) oder nach dem Gesichtspunkt, ob es sich um wilde beziehungsweise unkrautartige oder kultivierte Formen handelte (Tabelle 4). Die Vorteile der Aufrechterhaltung von Kartoffelsammlungen als Samen-Familien werden besprochen, besonders in bezug auf die Verhütung der Ausbreitung von eingeschleppten Viren. L’auteur décrit les méthodes utilisées pour détecter les infections virologiques dans les échantillons de pommes de terre en provenance de l’Amérique du Sud et rapporte l’importance de l’infection par les virus X (PVX), S (PVS), Y (PVY) et par la souche du virus Y causant la nécrose nervienne du tabac (TVN), dans 784 échantillons, et en même temps l’importance de l’infection par le virus de l’enroulement dans 241 échantillons (Tableau 1). Pour déterminer l’influence de ces facteurs, les échantillons ont été classés suivant la provenance (Tableau 1), l’état ploïdique (Tableau 2), l’altitude du prélèvement (Tableau 3), et le fait qu’il s’agit de formes cultivées ou sauvages et adventices (Tableau 4). L’auteur discute de l’opportunité de conserver les collections de pommes de terre sous forme de lignées en semences dans le but particulier d’empêcher l’extension des virus introduits.