Mycorrhization Mitigates Disease Caused by "Candidatus Liberibacter solanacearum" in Tomato.

Eric-Olivier Tiénébo,Elizabeth A. Pierson,Leland S. Pierson,Julien G. Levy,Kyle Harrison,Cecilia Tamborindeguy,Kouabenan Abo,Yao Casimir Brou

doi:10.3390/plants8110507

Abstract

Disease caused by the bacterial pathogen “Candidatus Liberibacter solanacearum” (Lso) represents a serious threat to solanaceous crop production. Insecticide applications to control the psyllid vector, Bactericera cockerelli Šulc (Hemiptera: Triozidae) has led to the emergence of resistance in psyllids populations. Efforts to select natural resistant cultivars have been marginally successful and have been complicated by the presence of distinct Lso haplotypes (LsoA, LsoB) differing in symptoms severity on potato and tomato. A potentially promising management tool is to boost host resistance to the pathogen and/or the insect vector by promoting mycorrhization. Here we tested the hypothesis that mycorrhizal fungi can mitigate the effect of Lso infection on tomato plants. The presence of mycorrhizal fungi substantially delayed and reduced the incidence of Lso-induced symptoms on tomato as compared to non-mycorrhized plants. However, PCR with specific Lso primers revealed that mycorrhization did not prevent Lso transmission or translocation to newly formed leaves. Mycorrhization significantly reduced oviposition by psyllids harboring LsoA and survival of nymphs from these eggs. However, mycorrhization had no effect on oviposition by psyllids harboring LsoB or the survival of nymphs from parents harboring LsoB. These findings indicate the use of mycorrhizal fungi is a promising strategy for the mitigation of disease caused by both LsoA and LsoB and warrants additional field testing.

Highlights

Diseases caused by “Candidatus Liberibacter solanacearum” (Lso) have had significant economic impacts on potato and tomato production in North and Central America and New Zealand [1,2].Lso is a rod-shaped, Gram-negative bacterial species belonging to the α-proteobacteria class and the Rhizobiaceae family [3]
We investigate whether mycorrhization alters insect fertility or fitness that may be linked to a mycorrhizal induced resistance (MIR) effect
Disease incidence based on symptoms at 6 WAI was 100% for non-mycorrhized plants treated with Lso-infected psyllids compared to 42% for mycorrhized plants treated with Lso-infected psyllids (Table 2)

Summary

Introduction

Diseases caused by “Candidatus Liberibacter solanacearum” (Lso) have had significant economic impacts on potato and tomato production in North and Central America and New Zealand [1,2]. Lso is a rod-shaped, Gram-negative bacterial species belonging to the α-proteobacteria class and the Rhizobiaceae family [3]. “Ca. Liberibacter” species are generally regarded as important emerging plant pathogens worldwide, and all of them rely on psyllid vectors for transmission [2]. Lso is related closely to “Ca. Liberibacter” species responsible for Huanglongbing (HLB), known as citrus greening disease. These include: “Ca. L. asiaticus” (CLas), “Ca. L. africanus,” and “Ca. L. americanus.”.

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Results

Conclusion