First author: Departamento de Protección de Cultivos, Instituto de Agricultura Sostenible (IAS), Consejo Superior de Investigaciones Científicas (CSIC), Apartado 4084, 14080 Córdoba, Spain; second author: Institut für Pflanzenkrankheiten und Pflanzenschutz, Universität Hannover, Herrenhäuser Str. 2, 30419 Germany; and third author: Departamento de Protección de Cultivos, IAS-CSIC, and Escuela Técnica Superior de Ingenieros Agrónomos y de Montes, Universidad de Córdoba, Apartado 3048, 14080 Spain
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Accepted for publication 1 August 2000.
Development of 108 epidemics of Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris were studied on cvs. P-2245 and PV-61 in field microplots artificially infested with races 0 and 5 of F. oxysporum f. sp. ciceris in 1986 to 1989. Disease progression data were fitted to the Richards model using nonlinear regression. The shape parameter was influenced primarily by date of sowing and, to a lesser extent, by chick-pea cultivars and races of F. oxysporum f. sp. ciceris. Fusarium wilt reduced chickpea yield by decreasing both seed yield and seed weight. These effects were related to sowing date, chickpea cultivar, and virulence of the prevalent F. oxysporum f. sp. ciceris race. Regression models were developed to relate chickpea yield to Fusarium wilt disease intensity with the following independent variables: time to initial symptoms (tis), time to inflection point (tip) of the disease intensity index (DII) progress curve, final DII (DIIfinal), standardized area under DII progress curve (SAUDPC), and the Richards weighted mean absolute rate of disease progression (rho). Irrespective of the chickpea cultivar × pathogen race combination, the absolute and relative seed yields decreased primarily by delayed sowing. The relative seed yield increased with the delay in tis and tip and decreased with increasing DIIfinal, SAUDPC, and rho. A response surface as developed in which seed yield loss decreased in a linear relationship with the delay in tis and increased exponentially with the increase of rho.
crop loss models,
© 2000 The American Phytopathological Society