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

Lucas R Petigrosso,Ignacio Damiano,M Mercedes Echeverría,Mabel N Colabelli,Pedro E Gundel,Osvaldo R Vignolio

doi:10.25260/ea.19.29.1.0.764

Abstract

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 vertical-transmission 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.https://doi.org/10.25260/EA.19.29.1.0.764

Highlights

We found that the two fungicides applied at the base of tillers had contrasting effects on the endophyte vertical transmission to the seeds
We are here showing for a first time that a fungicide applied on endophyte-infected mother plants, prevented the fungus to be found in the produced seeds
We cannot ensure that the mother plants were completely clean of fungal endophyte since it is hardly impossible to scrutinize the individual as a whole

Summary

Introduction

J. Darbyshire, Schedonorus phoenix (Scop.) Holub], commonly known as tall fescue, is likely the most important perennial forage grass in temperate zones of the world (Gibson and Newman 2001; Lattanzi et al 2007; Scheneiter et al 2015). Darbyshire, Schedonorus phoenix (Scop.) Holub], commonly known as tall fescue, is likely the most important perennial forage grass in temperate zones of the world (Gibson and Newman 2001; Lattanzi et al 2007; Scheneiter et al 2015) It is a high-quality forage species with production in winter, two characteristics that make it crucial in forage production chains, it can present anti-quality factors such as fungal alkaloids.

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