Unlocking the potential of rhizobacteria in Moroccan vineyard soils: Biocontrol of grapevine trunk diseases and plant growth promotion

Abstract

Rhizospheric bacteria isolated from the root system of Vitis vinifera plants in Morocco were evaluated for their activities against fungi associated with grapevine trunk diseases namely Diplodia mutila, Neoscytalidium dimidiatum, Trichothecium roseum, and Neopestalotiopsis vitis. Those pathogens cause grapevine decline and impede growth and are known as the greatest threat to production worldwide. Among a collection of 196 rhizobacteria, twenty-four isolates exhibited potential antifungal activity against all the tested fungal pathogens. Based on the partial 16S rDNA genes, different genera were identified namely Bacillus, Pseudomonas, Achromobacter, Ensifer, and Brucella. In particular, Bacillus halotolerans (JFM-64 and JMS-14), Pseudomonas koreensis (JRSK-45), and Ensifer adhaerens (JRSK-84) were found to be the most effective strains. Furthermore, the potential of bacterial isolates to promote plant growth was assessed. The funding revealed that of twenty-four antagonist rhizobacteria, seventeen displayed protease and chitinase production, while fifteen, thirteen, and twelve bacteria demonstrated the production of amylase, cellulase, and pectinase respectively. Furthermore, thirteen bacterial isolates produced hydrocyanic acid (HCN), sixteen isolates harbor the ability to solubilize tricalcium phosphate and seventeen were able to produce siderophores and indole acetic acid (IAA). The results of the current study showed that the most effective bacterial isolates could exhibit traits other than Plant Growth-Promoting Rhizobacteria (PGPR). Our results showed that the bacterization of B. napus seedlings with the selected bacteria improved plant growth when compared to untreated controls. Autoclaved grape wood assays were used to further confirm the in vitro results. The growth of Diplodia mutila, Neopestalotiopsis vitis, Neoscytalidium dimidiatum, and Trichothecium roseum was effectively reduced by rhizobacterial isolate Pseudomonas koreensis (JRSK-45) by 97.31, 97.14, 94.17, and 91.91%, respectively. This study highlights the potential of specific rhizobacteria as a promising approach to controlling fungal trunk pathogens associated with grapevine decline.