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Title:   Author  item
                                            ANDRADE-PIEDRA, JORGE - CORNELL UNIVERSITYitem
                                            FORBES, GREGORY - INTL POTATO CENTERitem
                                            SHTIENBERG, DANI - ARO VOLCANI CENTERitem
                                            Grunwald, Niklaus

                                                         - *Nik*item
                                            CHACON, MARIA - INTL POTATO CENTERitem
                                            TAIPE, MARCO - INTL POTATO CENTERitem
                                            HIJMANS, ROBERT - UC BERKELEYitem
                                            FRY, WILLIAM - CORNELL UNIVERSITY
  Submitted to: Phytopathology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 8/5/2005
                                    Publication  Date: 11/15/2005
                                    Citation: Andrade-Piedra, J.L., Forbes, G.A., Shtienberg, D., Grunwald, N.J., Taipe, M.V., Hijmans, R.J., Fry, W.E. 2005. Qualification of a plant disease simulation model: performance of the lateblight model across a broad range of environments. Phytopathology. 95:1412-1422.Interpretive Summary: LATEBLIGHT is a computer model that simulates the effect of biological and physical factors on asexual development of the potato late blight disease. The model was tested over a wide range of environments to assess how well it performs. Data from 32 fungicide-free epidemics observed in Ecuador, Mexico, Israel, and the USA in 13 potato cultivars were compared with model predictions using graphical and statistical tests. For the simulations, a level of host resistance was assigned to each cultivar based on general categories reported by local investigators. Based on the results from this study, it was concluded that LATEBLIGHT can be extended from the range of conditions in Peru for which it has been previously validated to those observed in this study. Thus LATEBLIGHT can be used to simulate epidemics in both sub-temperate and highland tropical environments. Further analysis showed that LATEBLIGHT is more sensitive to changes in variables related to initial inoculum and to weather than to changes in factors relating to host resistance.
                                Technical Abstract: The concept of model qualification, i.e., discovering the domain over which a validated model may be properly used, was illustrated with LATEBLIGHT, a mathematical model that simulates the effect of
weather, host growth and resistance, and fungicide use on asexual development and growth of Phytophthora infestans on potato foliage. Late blight epidemics from Ecuador, Mexico, Israel, and the United States involving 13 potato cultivars (32 epidemics in total) were compared with model predictions using graphical and statistical tests. Fungicides were not applied in any of the epidemics. For the simulations, a host resistance level was assigned to each cultivar based on general categories reported
by local investigators. For eight cultivars, the model predictions fit the observed data. For four cultivars, the model predictions overestimated disease, likely due to inaccurate estimates of host resistance. Model predictions were inconsistent for one cultivar and for one location. It was concluded that the domain of applicability of LATEBLIGHT can be extended from the range of conditions in Peru for which it has been previously validated to those observed in this study. A sensitivity analysis showed that, within the range of values observed empirically, LATEBLIGHT is more sensitive to changes in variables related to initial inoculum and to weather than to changes in variables relating to host resistance.


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