Beneficial Microorganisms to Control the Gray Mold of Grapevine: From Screening to Mechanisms.

Zakaria Amarouchi,Cédric Jacquard,Majida Hafidi,Essaid Ait Barka,Lisa Sanchez,Nathalie Vaillant-Gaveau,Qassim Esmaeel

doi:10.3390/microorganisms9071386

Abstract

In many vineyards around the world, Botrytis cinerea (B. cinerea) causes one of the most serious diseases of aerial grapevine (Vitis vinifera L.) organs. The control of the disease relies mainly on the use of chemical products whose use is increasingly challenged. To develop new sustainable methods to better resist B. cinerea, beneficial bacteria were isolated from vineyard soil. Once screened based on their antimicrobial effect through an in vivo test, two bacterial strains, S3 and S6, were able to restrict the development of the pathogen and significantly reduced the Botrytis-related necrosis. The photosynthesis analysis showed that the antagonistic strains also prevent grapevines from considerable irreversible PSII photo-inhibition four days after infection with B. cinerea. The 16S rRNA gene sequences of S3 exhibited 100% similarity to Bacillus velezensis, whereas S6 had 98.5% similarity to Enterobacter cloacae. On the other hand, the in silico analysis of the whole genome of isolated strains has revealed the presence of “biocontrol-related” genes supporting their plant growth and biocontrol activities. The study concludes that those bacteria could be potentially useful as a suitable biocontrol agent in harvested grapevine.

Highlights

All isolates were screened for their ability to inhibit the mycelial growth of B. cinerea by direct confrontation tests in potato dextrose agar (PDA) medium plates
They were nominated S3 and S6 which were the most active against fungal culture, by showing the strong percentage of inhibition I (%) (Figure 1A). These isolates were tested for their ability to protect grapevines against gray mold (GM) in planta
When plantlets were previously bacterized with S3 or S6 infected with the B. cinerea, the symptoms of gray mold were reduced compared to control, confirming the beneficial effect of these strains as reported in in vitro confrontation test

Summary

Introduction

Pathogens cause a devastating impact on crops varying from economic hardship to poisoning of food supplies (such as ergotism) and horrendous famines such as the Irish potato famine that lasted from 1845 to 1852. After their assaults, pathogens might trigger substantial changes to the host physiology, which can occur directly by secreting toxins and lytic enzymes or indirectly through inducing host responses stimulated by the pathogen. The decline in photosynthesis, infections can trigger other physiological changes such as limited water use efficiency, which in turn, excessive water restriction may further induce a lower rate of photosynthesis (as reviewd in [2])

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Discussion

Conclusion