Effect of infection timing and chemotype of Fusarium asiaticum on fusarium head blight and mycotoxin accumulation in rice.

To confirm the most susceptible stage of Fusarium infection and evaluate the pathogenicity of different chemotypes of Fusarium isolates are essential for managing Fusarium head blight (FHB). Extensive research has been conducted on wheat and barley, while there has been limited studies in rice. A 2-year greenhouse experiment was conducted to reveal the effects of infection timing and chemotype of Fusarium asiaticum on FHB severity and mycotoxin accumulation in four rice varieties. The results showed that all the rice varieties could be infected at 0, 3, 6, 9, and 12 days after anthesis (daa) by R3 (the 3-acetyldeoxynivalenol chemotype) and R5 (the nivalenol chemotype). The area under the disease progress curve (AUDPC), total trichothecenes, and fungal biomass caused by R3 were obviously lower than that caused by R5 across all varieties. Moreover, susceptible varieties exhibited higher values for these parameters than resistant varieties following inoculation with R3 or R5. Notably, the most seriously symptoms, highest total trichothecenes accumulation, and greatest fungal biomass were observed when inoculation at 3 daa, which was significantly higher than that at other inoculation timing (P < 0.05), and tended to be 3 daa > 6 daa > 0 daa > 9 daa > 12 daa. In addition, a significantly positive correlation (P < 0.01) was observed between AUDPC and total trichothecenes, AUDPC and fungal biomass, and total trichothecenes and fungal biomass, respectively.