Role of cereal secondary metabolites involved in mediating the outcome of plant-pathogen interactions

Abstract

Cereal crops such as wheat, rice and barley underpin the staple diet for human consumption globally. A multitude of threats to stable and secure yields of these crops exist including from losses caused by pathogens, particularly fungal. Plants have evolved complex mechanisms to resist pathogens including programmed cell death responses, the release of pathogenicity-related proteins and oxidative bursts. Another such mechanism is the synthesis and release of secondary metabolites toxic to potential pathogens. Several classes of these compounds have been identified and their anti-fungal properties demonstrated. However the lack of suitable analytical techniques has hampered the progress of identifying and exploiting more of these novel metabolites. In this review, we summarise the role of the secondary metabolites in cereal crop diseases and briefly touch on the analytical techniques that hold the key to unlocking their potential in reducing yield losses.

Figure 1.

Simplified diagram illustrating the biosynthetic pathways of the discussed plant secondary metabolites involved in pathogen defence. Cyanogenic glucosides, flavonoids and benzoxazanoids are all synthesised from the aromatic amino acids derived from shikimate. Saponins and terpenoids are synthesised via the melavonate or non-melavonate pathway in plants, which occur in the cytoplasm and plastids of plants respectively.