A Microbial Fermentation Mixture Primes for Resistance Against Powdery Mildew in Wheat.

Mark Gaffney,Tony Twamley,Angela Feechan

doi:10.3389/fpls.2019.01241

Mark Gaffney, Tony Twamley + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2019.01241

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Abstract

Since many fungal pathogens develop resistance to fungicides, novel and low-cost alternative methods to improve plant health and fitness need to be developed. An approach to improve productivity in crops is to stimulate the plant’s own defence mechanisms via priming. Therefore, we investigated if a fermentation-based elicitor could prime plant defences against powdery mildew in wheat by inducing the expression of endogenous defence-related genes. Wheat seedlings were spray-treated with a fermentation-based elicitor 8 days prior to inoculation with powdery mildew. Disease assays showed a significantly reduced number of powdery mildew pustules were formed on wheat treated with the mixed elicitor. In vitro sensitivity assays tested the ability of powdery mildew conidia to germinate on agar amended with the fermentation-based product and concluded that fungal germination and differentiation were also inhibited. Tissue samples were taken at time points pertaining to different developmental stages of powdery mildew infection. Significantly higher expression of PR genes (PR1, PR4, PR5, and PR9) was observed in the microbial fermentation mixture-treated plants compared with untreated plants. These genes are often associated with the elicitation of plant defence responses to specific biotrophic pathogens, such as powdery mildew, suggesting an elicitor-mediated response in the wheat plants tested. The product components were assessed, and the components were found to act synergistically in the microbial fermentation mixture. Therefore, this fermentation-based elicitor provides an effective method for powdery mildew control.

Highlights

It is conservatively estimated that fungal pathogens alone are responsible for losses of 15% to 20% of wheat production annually (Figueroa et al, 2018), costing billions of dollars to the global economy (Dean et al, 2012)
Microbial Ferment Mix Primes fungicides as part of an integrated pest management (IPM) system is of increasing importance with regards to the EU Framework Directive 2009/128/EC on the sustainable use of pesticides
The first recognized study to verify this hypothesis came in the late 1970s, when applications of salicylic acid (SA) were reported to promote resistance against tobacco mosaic virus (TMV) while inducing the expression of pathogenesis-related (PR) genes (White, 1979)

Summary

Introduction

It is conservatively estimated that fungal pathogens alone are responsible for losses of 15% to 20% of wheat production annually (Figueroa et al, 2018), costing billions of dollars to the global economy (Dean et al, 2012). Tritici, the causal agent of wheat powdery mildew, increases with the intensity of production (Oerke, 2006). Yield losses caused by powdery mildew in wheat can range from 13% to 20% in winter and spring wheat, respectively (Griffey et al, 1993; Conner et al, 2003; Lackermann et al, 2011). Preparing uninfected systemic tissues for a subsequent enhanced defence response to plant pathogens, is called systemic-acquired resistance (SAR) or “priming” (Bektas and Eulgem, 2015; Schwachtje et al, 2018)

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