The Activation of Genes of Wheat and Barley by Fungal Phytopathogens

Abstract

The induction of six infection-related mRNAs (IRmRNAs) was studied in barley and wheat following infection by different pathogens. Barley was inoculated with the compatible pathogens, chlorostriate mosaic virus, barley stripe virus, Pseudomonas syringae, Pyrenophora teres, Bipolaris sorokiniana, Erysiphe graminis f. sp. hordei and the incompatible pathogens E. graminis f. sp. tritici, Puccinia graminis f. sp. tritici and Py. tritici-repentis. Wheat was inoculated with the compatible pathogens B. sorokiniana, Pu. Graminis f. sp. tritici and E. graminis f. sp. tritici and the incompatible pathogen E. graminis f. sp. hordei. Induction of the IRmRNAs was observed after inoculation with fungi but not by bacterial or viral infection. The results demonstrated that necrotrophic fungi will induce the mRNAs at very early stages of infection. The IRmRNAs are thus not specifically related to obligate parasites. A comparison of the extent and speed of mRNA induction following infection of both wheat and barley by closely related fungal species suggested a role for IRmRNAs 2, 5 and 6 in non-host resistance reactions. These studies indicate that cereals may resist fungal pathogens by the early activation of a series of defence genes.