Comparing models for temporal progress of zonate leaf spot (Gloeocercospora sorghi) disease in sorghum (Sorghum bicolor)

Abstract

Field studies were conducted during 2004–06 rainy (kharif) seasons to analyze the temporal progress of zonate leaf spot (Gloecercospora sorghi. Bain & Edgerton) . Two growth models (Gompertz & logistic) were used to fit empirically derived disease progress curves. The Gompertz transformation effectively linearized the disease progress for all the 3 seasons. A close agreement was observed between the predicted and observed disease level in case of Gompertz model which accounted for > 90% of disease severity (P < 0.01) along with low root mean square error (0.053 to 0.061) as compared to logistic model (R*2 > 80%, RMSE* =0.063 to 0.105) over the years. The Gompertz model was found to be best fit over the years for describing zonate leaf spot disease progression in a natural inoculum population of G. sorghi on sorghum (Sorghum bicolor L.).