Different effects of phytohormones on Fusarium head blight and Fusarium root rot resistance in Brachypodium distachyon

J F Haidoulis,P Nicholson

doi:10.1080/17429145.2020.1820592

J F Haidoulis, P Nicholson

Open Access

https://doi.org/10.1080/17429145.2020.1820592

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Abstract

ABSTRACT Fusarium graminearum is a devastating pathogen of small grain cereals causing both Fusarium head blight (FHB) and Fusarium root rot (FRR). Exogenous application of phytohormones has been shown to affect FHB resistance. In contrast to FHB, FRR remains poorly characterised and it is unknown whether phytohormones play similar roles in FHB and FRR. In this present study, B. distachyon floral tissues at mid-anthesis and root tissues from seedlings were exogenously treated with several phytohormones before inoculation with F. graminearum. The canonical defence-associated phytohormones had differing effects on FHB and FRR. Salicylic acid (SA) significantly increased susceptibility to FRR but not to FHB while jasmonic acid (JA) and ethylene increased resistance to FRR but increased susceptibility to FHB. Additionally, the growth-associated phytohormones auxin and cytokinin significantly increased resistance and susceptibility, respectively, to both diseases. This study is the first to compare phytohormone effects between FHB and FRR in the same host. Highlight The tissue-dependent effects of defence phytohormones and tissue-independent effects of development phytohormones on F. graminearum-induced Fusarium head blight and Fusarium root rot diseases in the model cereal Brachypodium distachyon. Abbreviations: ACC, 1-aminocyclopropane-1-carboxylic acid; BABA, 3-aminobutanoic acid; dpi, days post inoculation; FHB, Fusarium head blight; FRR, Fusarium root rot; IAA indole-3-acetic acid; JA, jasmonic acid; NAA, 1-naphthaleneacetic acid; PDA, potato dextrose agar; RNL, root necrosis length; SA, salicylic acid

Highlights

Fusarium graminearum is one of the most important plant pathogens in the world (Dean et al, 2012), affecting small grain cereals such as bread wheat (T. aestivum), barley (H. vulgare), and rye (S. cereale)
The difference in root necrosis length (RNL) over time for all three compounds remained similar with the regression lines remaining parallel rather than diverging over time
The differential RNL symptoms resulting from pre-application of 3-aminobutanoic acid (BABA) increased over time with application leading to near doubling of necrosis at 4 dpi and 6 dpi relative to the control (p < .001)

Summary

Introduction

Fusarium graminearum is one of the most important plant pathogens in the world (Dean et al, 2012), affecting small grain cereals such as bread wheat (T. aestivum), barley (H. vulgare), and rye (S. cereale). F. graminearum can infect almost the entire plant (Miedaner, 1997) causing a range of diseases. The most well-known and economically important disease is Fusarium head blight (FHB). Other diseases include Fusarium crown rot, Fusarium root rot (FRR), and seedling blight. Plant pathogens often adopt specific trophic lifestyles. Biotrophs obtain nutrients from living tissue, necrotrophs from dead tissue, and hemibiotrophic pathogens adopt an early biotrophic phase that is followed by a necrotrophic phase sometime later in infection (Glazebrook, 2005, Zeilinger et al, 2016).

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