Eradication of the fungus Epichlo? coenophiala from Schedonorus arundinaceus (tall fescue) seeds by interrupting the vertical transmission process

摘要

Tall fescue is usually infected by a fungal endophyte, responsible of livestock intoxication due to fungal alkaloids. An endophyte fungus grows in the apoplast of aboveground tissues and is vertically transmitted through the seeds. Disinfecting plants or clones not only is useful as a way of eliminating a dangerous microorganism from cultivars, but also for experimental purposes. However, not all fungicides are effective, and if they are, a waiting period must be respected in order to avoid confounding effects of the endophyte and the treatment. We subjected plants (ramets from four genotypes) to different doses of two fungicides, Almagor? (Triazole + Imidazole) and Amistar? (Methoxy-acrylate), and evaluated the endophyte persistence. Fungicides were pipette-poured on pseudostems' bases of each plant. Endophytic status was diagnosed in tillers that received the fungicide and in the new tillers produced by the plants and seeds. While Amistar? had no detectable effect, Almagor? was 100% effective at all doses. The latter interrupted the verticaltransmission processes (5400 evaluated seeds were endophyte-free). Phytotoxic effects were not observed in seeds. Proportion of normal and abnormal seedlings depended only on plant genotype. Almagor? was effective in stopping the fungus from growing into reproductive buds when apical meristems were down on the bases. Use of Almagor? is promising on old pastures dominated by toxic tall fescue, with the purpose of enriching the soil seed-bank with endophyte-free seeds.