Substrate and Plant Genotype Strongly Influence the Growth and Gene Expression Response to Trichoderma afroharzianum T22 in Sugar Beet.

John Schmidt,Bradley R Dotson,Ludwig Schmiderer,Adriaan Van Tour,Allan G Rasmusson,Susanne Widell,Banushree Kumar,Kenneth M Fredlund,Salla Marttila

doi:10.3390/plants9081005

Abstract

Many strains of Trichoderma fungi have beneficial effects on plant growth and pathogen control, but little is known about the importance of plant genotype, nor the underlying mechanisms. We aimed to determine the effect of sugar beet genotypic variation on Trichoderma biostimulation. The effect of Trichoderma afroharzianum T22 on sugar beet inbred genotypes were investigated in soil and on sterile agar medium regarding plant growth, and by quantitative reverse transcriptase-linked polymerase chain reaction (qRT-PCR) analysis for gene expression. In soil, T22 application induced up to 30% increase or decrease in biomass, depending on plant genotype. In contrast, T22 treatment of sterile-grown seedlings resulted in a general decrease in fresh weight and root length across all sugar beet genotypes. Root colonization of T22 did not vary between the sugar beet genotypes. Sand- and sterile-grown roots were investigated by qRT-PCR for expression of marker genes for pathogen response pathways. Genotype-dependent effects of T22 on, especially, the jasmonic acid/ethylene expression marker PR3 were observed, and the effects were further dependent on the growth system used. Thus, both growth substrate and sugar beet genotype strongly affect the outcome of inoculation with T. afroharzianum T22.

Highlights

Trichoderma spp. are filamentous fungi that are commonly found in soil, rhizosphere, and foliar environments, and some species have been found to grow endophytically [1,2]
We report a pronounced effect of the sugar beet genome on the outcome of the interaction, including both stimulation and inhibition of plant growth, and that absolute changes depended on the plant growth systems used
One line, designated F, displayed a negative effect by T22 treatment on total and shoot dry weight weight (DW), and deviated significantly from three genotypes (D, G, and I), which were positively affected by T22

Summary

Introduction

Trichoderma spp. are filamentous fungi that are commonly found in soil, rhizosphere, and foliar environments, and some species have been found to grow endophytically [1,2]. Strains of several species are beneficial to plants. They are used for both growth promotion and as biocontrol agents against a broad variety of diseases in crops, including cereals, oil seeds, and even trees [3,4,5,6]. Plants 2020, 9, 1005 pathogen defense systems, and directly stimulating plant growth and nutrient uptake [5,9]. Most of these interactions will demand active participation of both the plant and the Trichoderma. Sterile-grown plant cells have been shown susceptible to permeabilization by the model peptaibol alamethicin [11] from Trichoderma viride

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