Elucidation of mechanisms of host plant resistance to wheat stem sawfly (Cephus cinctus Norton) in relation to antibiosis and the early stem solidness phenotype

Abstract

In the North American Great Plains, wheat stem sawfly (WSS), Cephus cinctus Norton is a serious pest of cultivated cereals including common bread wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var durum). The solid stem phenotype is usually the basis of an effective management strategy in preventing infestation and yield loss in areas which experience pressure from large and damaging WSS populations. However solid stem expression can be negatively influenced by environmental effects and fully solid stems decrease the effectiveness of biological control of WSS by endemic parasitoids, highlighting a need for new sources of resistance outside of the solid stem phenotype. Here, we use 'omics technologies to comprehensively examine potential mechanisms of resistance including antibiotic resistance in oat, as well as small molecules, transcripts, photosynthetic parameters and volatile organic compounds in spring and durum wheat which help to explain decreased levels of infestation and lower incidence of stem cutting observed with the early solid stem phenotype. Genes and metabolites related to cellular organization, lignin composition and stem tissue structure appear to be involved in the resistance observed in oat and are also related to the early stem solidness phenotype in spring and durum wheat. Additionally, metabolic differences in abundance of lipids and carbohydrates were observed between oat and wheat as well as in spring and durum wheat near isogenic lines. Collectively, this research provides insight into the impacts that plant metabolites and gene expression may have on plant resistance to WSS.