Silicon nonspecifically affects aggressiveness in Fusarium head blight pathogens

Silicon (Si) has been largely regarded to have no selection pressure on plant pathogens because it regulates plant defense system to reduce pathogen infection and development and does not directly affect pathogen itself; however, its effect seems to be specific in some pathogen-host plant interactions. In Fusarium head blight (FHB), associated with devastating agronomic effects on total yield and grain quality, which infects higher Si-absorbers and –accumulators wheat and barley plants; its effect on aggressiveness is unknown. To clarify the nature of reduction of FHB symptoms upon Si treatment at the earliest and latest development stages, we analyzed Si effect on nine aggressiveness components obtained under several experimental conditions. We used 16 fungal isolates of varying aggressiveness and eight bread wheat, durum wheat and barley cultivars with contrast susceptibility to disease. The positive effect of Si on enhancing host resistance against Fusarium infection in the young and adult host parts showed that the nine components evaluated in this study were negatively impacted by Si. Definitely, Si at 1.7 mM reduced equally FHB symptoms from the highest and least pathogenic isolates of the four tested Fusarium species regardless of botanical background for the used plant materials. This indicates for the first time that Si nonspecifically affects aggressiveness in FHB pathogens. Our results reveal that Si could be a valuable tool in integrated pathogen management by suppressing pathogen development on wheat and barley when affected by Fusarium. Most importantly, no hazard exists to emergence of Si-resistant pathogen populations upon Si applications on diverse FHB populations.