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Characterization of the Virus × Temperature Interaction in Secondarily Infected Potato Plants Using EPIVIT. Lukas Bertschinger, Institute of Plant Sciences, Swiss Federal Institute of Technology (ETH), Universitätstr. 2, 8092 Zürich, Switzerland, Current address: Swiss Federal Research Station for Fruit-Growing, Viticulture and Horticulture, Fruit-Growing Department, CH-8820 Wädenswil, Switzerland; Ernst R. Keller, and Cesare Gessler. Institute of Plant Sciences, Swiss Federal Institute of Technology (ETH), Universitätstr. 2, 8092 Zürich, Switzerland. Phytopathology 85:815-819. Accepted for publication 9 January 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-815.

The model EPIVIT, designed for contact- and aphid-transmitted viruses of tuber crops, simulates the percentage of infected tubers harvested from a potato field. It includes a module for tuber infection of plants with a tuberborne (secondary) infection (efficiency of autoinfection). This module postulates a monomolecular function for the relation between the efficiency of autoinfection and developmental heat, providing a theoretical basis for understanding how an infectious, systemic virus and the environment, represented by temperature, are interacting. The module was calibrated with temperature and autoinfection data obtained with the modern potato cultivar Yungay (Solanum tuberosum ssp. tuberosum × S. tuberosum ssp. andigena) in five contrasting environments in Peru. Model estimates for potato X potexvirus (PVX), Andean potato mottle comovirus (APMV), potato Y potyvirus (PVY), or potato leafroll luteovirus (PLRV) were obtained. They were more accurate when temperature-sensitive growth rates were used for heat accumulation than with constant accumulation rates. The bell-shaped relationships obtained between heat accumulation rates and apparent temperature differed for each virus, with optimum heat accumulation rates at 28ºC for PVY, and between 18 and 28ºC, 20 and 25ºC, and 23 and 28ºC for PLRV, PVX, and APMV, respectively. With PLRV and PVY data, high precision levels (P < 0.05) were only obtained when the parameter trigger developmental heat was included. This parameter represents a threshold amount of developmental heat accumulated any time temperature fluctuates into the range between developmental cardinal temperatures, before heat becomes effective for the efficiency of autoinfection. This calibration supports EPIVIT’s assumptions regarding the influence of temperature on virus behavior in the host plant. With complete verification of this model component, validation is still needed for final confirmation of the model, as well as an elucidation of the biological mechanisms that underlie efficiency of autoinfection and virus behavior at different temperatures by analytical research.

Additional keywords: beta-function, epidemiology, G × E interaction, model parametrization, model tuning.