A meta-analysis reveals that the protective role of silicon in grasses against fungal pathogens depends on infection mechanism

Pathogen infection drives plant community structure and constrains global agricultural productivity. Silicon (Si) improves resistance to abiotic and herbivory stress, particularly in grasses, but relatively little attention has addressed Si-mediated resistance to pathogens, nor has it tested how this varies according to the type of plant and pathogen and is altered by environmental factors. We performed a meta-analysis to quantitatively assess the benefits of Si fertilisation for improving disease resistance against fungal pathogens in grasses. Overall, Si fertilisation decreased disease severity by 43% and increased biomass of infected plants by 35%. The underlying mechanisms were investigated by analysing the impacts of Si against diverse fungal infection strategies. The disease suppressive effect of Si was greater for pathogens producing appressoria, a structure involved in cell wall penetration and effector release, but lower against pathogens entering through stomata. Furthermore, Si was more effective against pathogens that produce haustoria or infection hyphae, which are involved in nutrient acquisition. These findings advance knowledge of plant-pathogen interactions by identifying key pathogen traits determining Si effectiveness against pathogen attack in grasses. Our results support using Si fertiliser for cereal crops to reduce fungal damage and suggest Si should be considered in studies of grass evolutionary history and community structure.