Relationship between disease severity (Xt) and area under disease progress curve (AUDPC) of sheath blight with rice yield

Abstract Sheath blight ( Rhizoctonia solani Kühn) is the important rice diseases in Indonesia. The disease develops from the tillering stage to the panicle ripening of rice plant and disease severity can be measured at each growth stage. Therefore, this research aims to study the relationship between disease severity (Xt) and area under disease progress curve (AUDPC) of sheath blight with rice yield. The rice varieties tested were Ciherang and Sintanur, both of which have different plant types. The variation of disease severity was obtained by applying fungicide to rice plants with different spraying frequencies. Disease severity at the final growth stage (Xt) describes the level of damage shown by the rice plant at that stage, but disease severity at each growth stage can cause health problems and can affect rice yields. AUDPC can describe disease pressure throughout plants growth. Both Xt and AUDPC can be used to predict rice yield loss. The effect of disease development on rice yields shows a strong correlation level, (reaching R 2 =0.72% to 0.94%). The relationship between Xt and AUDPC to rice yield was linier with negative regression coefficient. In the AUDPC-yield relationship, the regression coefficient was obtained from −0.25 to −0.31, while in the Xt-yield relationship, it was obtained from −0.05 to −0.10. The correlation in the AUDPC-yield relationship is more significant in reducing yield than the Xt-yield relationship when the disease developed more severely in rice plants.