The efficacy of acibenzolar-S-methyl (ASM) in inducing resistance against Fusarium graminearum sensu stricto in wheat (Triticum aestivum L.)

Four ASM (acibenzolar-S-methyl) concentrations were applied on wheat plants at different growth stages prior to inoculation with 1x105 conidia/ml of Fusarium graminearum. Thereafter, disease severity was monitored and recorded over time. All ASM concentrations reduced disease severity compared to the control. The best treatment, providing the lowest Area Under the Disease Progress Curve (AUDPC) units, high average Hundred Seed Weight (HSW) and reduced average Percentage Seed Infection (PSI), was 0.075 g/L ASM applied at anthesis. A weak but significant positive correlation was observed between AUDPC and PSI (r = 0.33; p = 0.0001). However, a moderate and weak negative correlation was observed between AUDPC and HSW (r = - 0.41; p < 0.0001) and HSW and PSI (r = - 0.18; p = 0.04) respectively. Higher ASM concentrations were more effective when applied at anthesis and lower concentrations at late boot. Moreover, repeated applications (applied at both late boot and anthesis) did not improve disease reduction. A disease reduction and deoxynivalenol (DON) reduction of up to 28.97% (0.075 g/L ASM applied at anthesis) and 18.79% (0.0375 g/L ASM applied at anthesis) was observed. However, DON and zearalenone (ZEA) reduction did not always correspond with disease severity reduction of tested treatments. This accentuates the importance of the development of integrated control strategies for the improved and effective management of Fusarium head blight (FHB) in wheat.