Trichoderma asperellum efficiently protects Quercus robur leaves against Erysiphe alphitoides

Tomasz Oszako,Anna Linkiewicz,Tadeusz Malewski,Justyna Anna Nowakowska,Natalia Stocka,Tom Hsiang,Marcin Stocki,Lassaâd Belbahri,Daria Berezovska,Dmitry Voitka

doi:10.1007/s10658-020-02162-y

Abstract

The protective effects of Trichoderma asperellum IZR D-11 as a biocontrol agent against the powdery mildew Erysiphe alphitoides infecting leaves of Quercus robur were evaluated for the first time. A strain of Trichoderma had earlier been isolated in Belarus, and was identified in this study as T. asperellum by sequencing of three genomic markers: internal transcribed spacer, translation elongation factor 1 alpha and RNA polymerase II subunit 2, with over 99.2% identity to corresponding genomic sequences in GenBank. When applied once in the first year just after onset of powdery mildew disease, T asperellum IZR D-11 reduced disease progression and continued to reduce powdery mildew levels during the following three years. Photosynthetic activity as represented by chlorophyll fluorescence measured in oak seedlings was increased in treated plants, and greater assimilate production was also found. The use of this antagonistic fungus increased the total water content in oak leaves suggesting that T. asperellum IZR D-11 can serve as a preventive measure to reduce energy losses in the process of water transpiration. GC-MS analysis detected 49 volatile compounds in the headspace of pure cultures of T. asperellum. Sesquiterpenes represented mainly by daucene, dauca-4(11),8-diene and isodaucene were the largest group of compounds emitted. We speculate that these volatiles from T. asperellum IZR D-11 may be involved in induced resistance in the plant, but further research is needed. The above results suggest that T. asperellum strain IZR D-11 has potential as a biocontrol agent of oak powdery mildew in forest nurseries.

Highlights

Common oak Quercus robur L. and sessile oak Q. petraea (Matt.) Liebl. are major oaks species in central and eastern European forests
Our findings revealed that the use of antagonistic fungus positively affected the total content of water in oak leaves, and biological control agents (BCA) can serve as a preventive measure to reduce energy losses in the process of water transpiration in infected plants
In volatile emissions of T. asperellum, we identified compounds previously detected in other Trichoderma species but not previous reported for T. asperellum including sesquiterpenes such as β-farnesene found in T. atroviride (Stoppacher et al 2010) and T. asperelloides (GalHemed et al 2011), β-bisabolene found in T. atroviride

Summary

Introduction

Common oak Quercus robur L. and sessile oak Q. petraea (Matt.) Liebl. are major oaks species in central and eastern European forests. Are major oaks species in central and eastern European forests. Since the early 1900’s, records of powdery mildews affecting European oaks have been mentioned since they are important fungal diseases (Mougou et al 2008). In Europe, powdery mildew infections of common oak are caused by Erysiphe alphitoides (Braun and Cook 2012) Microsphaera alphitoides Griffon & Maubl.), which is the most prevalent and damaging foliar fungal species in oak stands, and along with primary insect attacks, they cause periodic dips in oak health (Topalidou and Shaw 2016). Common oak is one of the most susceptible species to E. alphitoides (Desprez-Loustau et al 2011), and this pathogen is often mentioned as an inciting factor in European oak decline (Keča et al 2016). Powdery mildew has damaging effects on young seedlings, in nurseries, plantations, and can even damage mature trees under conditions favorable to disease (Marçais and DesprezLoustau 2014)

Objectives

Methods

Findings

Discussion

Conclusion