title: Incomplete Infection of Secondarily Infected Potato Plants - an Environment Dependent Underestimated Mechanism in Plant Virology.
abstract: 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.
authors.affiliation: Agroscope, Institute of Plant Production SciencesNyon/Wädenswil, Switzerland; Programa de Investigaciones en Papa, Instituto Nacional de Investigación Agraria y Agroindustrial, Ministerio de AgriculturaLima, Peru; Institute for Integrative Biology, Department of Environmental Systems Science, Swiss Federal Institute of Technology (ETZ)Zürich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Bertschinger
authors.affiliation: Agroscope, Institute of Plant Production Sciences Nyon/Wädenswil, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Bühler
authors.affiliation: Agroscope, Institute of Plant Production Sciences Nyon/Wädenswil, Switzerland.
authors.forename: Brice
authors.initials: B
authors.lastname: Dupuis
authors.affiliation: School of Life Sciences and Facility Management, Zürich University of Applied Sciences Wädenswil, Switzerland.
authors.forename: Brion
authors.initials: B
authors.lastname: Duffy
authors.affiliation: Institute for Integrative Biology, Department of Environmental Systems Science, Swiss Federal Institute of Technology (ETZ) Zürich, Switzerland.
authors.forename: Cesare
authors.initials: C
authors.lastname: Gessler
authors.affiliation: International Potato Center Lima, Peru.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Forbes
authors.affiliation: Institute for Agricultural Science, Department of Environmental Systems Science, Swiss Federal Institute of Technology (ETZ) Zürich, Switzerland.
authors.forename: Ernst R
authors.initials: ER
authors.lastname: Keller
authors.affiliation: Programa de Investigaciones en Papa, Instituto Nacional de Investigación Agraria y Agroindustrial, Ministerio de AgriculturaLima, Peru; School of Agriculture, Forest and Food Sciences, Bern University of Applied SciencesZollikofen, Switzerland.
authors.forename: Urs C
authors.initials: UC
authors.lastname: Scheidegger
authors.affiliation: Centre for Crop Systems Analysis, Plant Sciences, Wageningen University and Research Wageningen, Netherlands.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Struik
keywords: autoinfection; climate change; epigenetics; food security; gene-silencing; plant viruses; seed degeneration; seed potato systems