The antagonistic strain Bacillus subtilis UMAF6639 also confers protection to melon plants against cucurbit powdery mildew by activation of jasmonate- and salicylic acid-dependent defence responses.

Laura García-Gutiérrez,Jaime Cubero,Alejandro Pérez-García,Houda Zeriouh,Antonio De Vicente,Diego Romero

doi:10.1111/1751-7915.12028

Abstract

Biological control of plant diseases has gained acceptance in recent years. Bacillus subtilis UMAF6639 is an antagonistic strain specifically selected for the efficient control of the cucurbit powdery mildew fungus Podosphaera fusca, which is a major threat to cucurbits worldwide. The antagonistic activity relies on the production of the antifungal compounds iturin and fengycin. In a previous study, we found that UMAF6639 was able to induce systemic resistance (ISR) in melon and provide additional protection against powdery mildew. In the present work, we further investigated in detail this second mechanism of biocontrol by UMAF6639. First, we examined the signalling pathways elicited by UMAF6639 in melon plants, as well as the defence mechanisms activated in response to P. fusca. Second, we analysed the role of the lipopeptides produced by UMAF6639 as potential determinants for ISR activation. Our results demonstrated that UMAF6639 confers protection against cucurbit powdery mildew by activation of jasmonate- and salicylic acid-dependent defence responses, which include the production of reactive oxygen species and cell wall reinforcement. We also showed that surfactin lipopeptide is a major determinant for stimulation of the immune response. These results reinforce the biotechnological potential of UMAF6639 as a biological control agent.

Highlights

Biological control, i.e. the use of natural enemies to combat pests or plant diseases, has gained acceptance in recent years
Bacillus subtilis UMAF6639 is an antagonistic strain selected for the efficient control of the cucurbit powdery mildew fungus Podosphaera fusca, which is a major threat to cucurbits worldwide
We found that UMAF6639 was able to induce systemic resistance (ISR) in melon and provide additional protection against powdery mildew

Summary

Introduction

Biological control, i.e. the use of natural enemies to combat pests or plant diseases, has gained acceptance in recent years. Among the different microbial species examined for that purpose, some aerobic spore-forming bacteria possess several advantages that make them good candidates for biological control agents. They produce several different types of insecticidal and antimicrobial compounds. Bacillus species are able to produce spores that allow them to resist adverse environmental conditions and permit easy formulation and storage of commercial products (Schallmey et al, 2004; Francis et al, 2010). Bacillus-based biopesticides are widely used in conventional agriculture and represent the most important class of microbial products commercially available for phytosanitary use. Implementation of Bacillus-based biofungicides is still a pending issue (Pérez-García et al, 2011)

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