Transcriptomic Analysis Using RNA Sequencing of Hard Fescue (Festuca brevipila) Treated with Triazolic Fungicide.

Fungal endophytes have been shown to enhance abiotic and biotic stress tolerance in turfgrass species. This symbiotic relationship has been studied intensively in cool-season turfgrasses including perennial ryegrass (Lolium perenne) and the fine fescues (Festuca spp.). Researchers studying the effect of endophytes on plant response to various stresses often make comparisons between endophyte-free and endophyte-infected plant genotypes. One way the endophyte-free plant is created is by removing the Epichloe endophyte with fungicide applications. Propiconazole is a systemic triazole fungicide used for endophyte removal in turfgrasses. This demethylation inhibiting (DMI) fungicide binds and inhibits the 14-α demethylase enzyme (Cytochrome P450 family 51, Cyp51), inhibiting ergosterol synthesis in fungi. The inhibition of the 14-α demethylase helps to stop fungal growth by suppressing cell membrane formation. Cytochrome P450 genes are, however, highly conserved across plants, animals, and fungi, and it is not clear if the application of propiconazole fungicide affects the future disease resistance of plants. In this study, we sprayed endophyte-free hard fescue (Festuca trachyplla) plants with propiconazole. A total of five applications of propiconazole were applied at 1.27mL/m² with one-week intervals. Plant material was sampled prior to and after the second fungicide application, and this tissue was used for RNA sequencing. After three months of recovery, plants were then inoculated with the pink snow mold pathogen (Microdochium nivale) to examine how fungicide applications affect plant disease resistance in endophyte-free plants. Following the second fungicide application, we observed the suppression of the Cytochrome P450 Cyp51, and increased production of dehydrin proteins in fungicide-treated plants. In addition, we also observed that fungicide application increased expression of a MYB-like transcription factor. Snow mold inoculation experiments have further provided us with increased knowledge on how this fungicide affects plant disease resistance.