Simulation studies on risk analysis of rice leaf blast epidemics associated with global climate change in several Asian countries

The combination model (coupling of CERERS-RICE and BLASTSIM) was used to study the effects of global climate change on rice leaf blast epidemics in several Asian countries by simulations. Historical daily weather data were collected from fifty-three locations in five Asian countries. Two weather generators, WGEN and WMAK, from the Decision Support System for Agrotechnology Transfer (DSSAT) were utilized to produce estimated daily weather data for each location. Effects of global climate change in terms of temperature change and enhanced UV-B (ultraviolet-B) on blast epidemics were simulated. Thirty years of daily weather data produced by one of the two generators for each of fifty-three locations in five Asian rice-growing countries were used for driving the combination model to simulate blast epidemics under each condition of global climate change. Maximum blast severity, the distribution of area under disease progress curve (AUDPC) and estimated yield losses caused by leaf blast resulting from 30 years of simulation were analysed statistically. In most locations, temperature changes had significant effects on disease development. However, these effects varied between different agroecological zones. In cool subtropical zones such as Japan and northern China, elevation of ambient temperature resulted in a higher risk of blast epidemics. Situations in the humid tropics and warm humid subtropics were opposite to those in cool areas. A lower temperature resulted in greater risk of blast epidemics. Higher AUDPC did not always cause more yield losses. The same AUDPCs did not cause the same yield losses during different growing seasons under different weather conditions. The yield loss caused by enhanced UV-B was normally at 9-10%, independent of temperature change, and the deviation was much smaller than that caused by blast. Enhanced UV-B would cause much more severe blast when the temperature changes to cooler than normal, especially in tropical countries.