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.

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.

Durante dos ciclos de cultivo, en 1985-86 y 1988-89, se investigaron los efectos de los principales virus sobre el rendimiento de papa en la sierra central del Perú a 3,200 msnm. Se utilizaron los cultivares mejorados Yungay y Mariva (Solanum tuberosum ssp. andigena x Solanum tuberosum spp. tuberosum) determinándose que los virus PLRV y PVY transmitidos por los áfidos, reducen hasta la mitad el rendimiento de una población originada en tubérculos-semilla sanos, en tanto que los virus transmitidos por contacto y sus combinaciones entre ellos, solamenteocasionaron una reducción significativa del rendimiento en el caso de poblaciones de baja densidad de siembra. Mientras más largos los estolones del cultivar, la densidad debía ser más baja para que se manifestara el efecto de los virus. En este trabajo se discuten la utilidad de los métodos empleados y su eficiencia para detectar los mecanismos de transmisión de los virus.Aceptado para publicación: agosto 29, 1996

Agroscope's working programme 2014-17 aims at providing specific solutions for key challenges of Swiss crop production. The competitiveness of crop production and a healthy environment are overarching objectives. The critical context exacerbated by population growth and scarcity of land reserves requires ecological intensification: increasing yields and food quality per invested resource unit while avoiding undesirable side effects on the environment. This effort shall be supported by a strengthened guidance by ecological principles and the use of new technologies. An intensive and continuous knowledge exchange between practitioners and research representatives is needed in order to facilitate that feasible problem solutions evolve based on increasingly comprehensive and precise research data.

Interest in urban agriculture (UA) has considerably increased during the last decade. Research has shown that UA can have several positive impacts on the social and environmental health of a city. Increasingly, the question of the role of professional farmers is raised. The Food Urbanism Initiative (FUI; see www. foodurbanism. org/lausanne) explicitly looks at this via its use of Lausanne, Switzerland as a case study site. In the first phase, the research team assessed the population's attitude towards UA by means of a public survey. It concludes that although UA is not the most important publicly perceived urban issue, it is well supported. Presently, the case study work includes the assessment of the existing physical opportunities and the possible various typologies of urban farming that could apply to the site. Current research is investigating the potential of urban farming for professional farmers. Additionally, the success of a series of city initiated pilot projects (micro community plots/plantages, traditional family gardens, sheep keeping and the pedagogic farm of Rovereaz Domain) reinforces the importance of UA and its implementation via diverse methods. However, the FUI Lausanne urban analysis so far indicates that although there are many potential sites for UA, many of them are small, privately-owned, and disconnected parcels. There are serious constraints for traditional professional farming in urban areas as far as economic and agronomic aspects are concerned, leaving agricultural production in urban areas to be tended by urban "gardeners" or quasi-professionals. Principal issues concern both the legal limits to professional farming and restrictions related to the scale of a successful agricultural operation. Urban and peri-urban farmers may have increased opportunities for commercialisation and partnerships with urban population. Consequently, the FUI challenge is to find the most applicable array of realistic UA project typologies while at the same time doing so with an expanded notion regarding the future role of professional, semiprofessional and "hobby" farmers.

As with the other two research programmes Agroscope (AgriMontana and NutriScope), ProfiCrops began in 2008 and will end in March 2014. To bring the programme to a close, several events were organised and a series of articles were published in Recherche Agronomique Suisse from July 2013 onwards. This last article presents an assessment of ProfiCrops, based on standard project review criteria: efficiency, effectiveness, relevance and added-value. Important lessons-learnt are drawn from the implementation of the research programme. It is, however, a partial assessment, due to the lack of sufficient data. The scope of the strategic objectives formulated at the beginning of the programme made the evaluation more complex than anticipated. Efficiency has been impacted by the mismatch between objectives and resources. A notable example of this is the availability of scientists' time and its allocation across specific programme activities. However, several tangible results were obtained, such as: a list of more than 300 solutions, interdisciplinary exchanges in favour of project participants and the programme, a reinforced state of mind towards interdisciplinarity, an improved understanding of the meaning of innovation for Agroscope and the creation of new partnerships. Most of these results would not have been produced without the programme.