Pseudomonas species isolated via high-throughput screening significantly protect cotton plants against verticillium wilt

Abstract

Verticillium wilt (VW) caused by Verticillium dahliae is a devastating soil-borne disease that causes severe yield losses in cotton and other major crops worldwide. Here we conducted a high-throughput screening of isolates recovered from 886 plant rhizosphere samples taken from the three main cotton-producing areas of China. Fifteen isolates distributed in different genera of bacteria that showed inhibitory activity against V. dahliae were screened out. Of these, two Pseudomonas strains, P. protegens XY2F4 and P. donghuensis 22G5, showed significant inhibitory action against V. dahliae. Additional comparative genomic analyses and phenotypical assays confirmed that P. protegens XY2F4 and P. donghuensis 22G5 were the strains most efficient at protecting cotton plants against VW due to specific biological control products they produced. Importantly, we identified a significant efficacy of the natural tropolone compound 7-hydroxytropolone (7-HT) against VW. By phenotypical assay using the wild-type 22G5 and its mutant strain in 7-HT production, we revealed that the 7-HT produced by P. donghuensis is the major substance protecting cotton against VW. This study reveals that Pseudomonas specifically has gene clusters that allow the production of effective antipathogenic metabolites that can now be used as new agents in the biocontrol of VW.

Necessity requires no decision: carbon source-dependent pattern of antimicrobial activity and gene expression in Pseudomonas donghuensis P482

“…While glucose was the single carbon source in the growth medium, the antibacterial activity of the mutants with inactivated genes required for 7-HT biosynthesis (KN4705, KN4706, KN4709) was reduced to about 50 % of the P482 wt activity. This is consistent with the fact that 7-HT is reported as one of the compounds responsible for antimicrobial activity in all P. donghuensis strains described so far [10], [16], [19]. Yet, when the carbon source was changed to glycerol, the activity of these mutants was not impaired in comparison to the P482 wt activity.…”

“…insecticidal, antimicrobial, antiviral and antitumor [65]- [67]. 7-HT is considered to be the major antimicrobial of P. donghuensis strains, being responsible both for antibacterial and antifungal properties of all P. donghuensis strains described so far [10], [16], [19], [20].…”

“…Like many other fluorescent pseudomonads [12], P482 produces a pyoverdine siderophore and hydrogen cyanide, however, it lacks for the genes essential for the synthesis of the compounds such as [10]: phenazines, 2,4-DAPG, pyrrolnitrin, pyoluteorin or (cyclic)-lipopeptides, important for the antimicrobial activity of other Pseudomonas [13]. P482 is one of only four strains of P. donghuensis species described so far [10], [14]- [16], therefore knowledge concerning its biology, genetics and ecology is still limited.…”

Verticillium dahliae Inoculation and in vitro Propagation Modify the Xylem Microbiome and Disease Reaction to Verticillium Wilt in a Wild Olive Genotype

“…These bacterial taxa have also been identified in olive xylem in other works in which olive trees of different ages, belonging to different cultivars or growing under different environments, were evaluated ( Müller et al, 2015 ; Fausto et al, 2018 ; Sofo et al, 2019 ; Anguita-Maeso et al, 2020 ; Giampetruzzi et al, 2020 ), which strengthens the hypothesis that those genera may represent keystone olive xylem bacteria. More interestingly, some of these genera have already been reported or used as plant growth-promoting bacteria ( Otieno et al, 2015 ; Subramanian et al, 2015 ) or proposed as biological control agents against V. dahliae ( Berg et al, 2006 ; Aranda et al, 2011 ; Gómez-Lama Cabanás et al, 2018 ; Tao et al, 2020 ). Interestingly, the ratio Cutibacterium/Pseudomonas seemed to be an important factor associated to the plant propagation procedure.…”

Bacillus circulans GN03 Alters the Microbiota, Promotes Cotton Seedling Growth and Disease Resistance, and Increases the Expression of Phytohormone Synthesis and Disease Resistance-Related Genes

“…Accordingly, beneficial PGPB with inhibitory action against V. dahliae are a promising biocontrol agent for the control of cotton Verticillium wilt. To date, some researchers have isolated multiple strains with biocontrol activities against V. dahliae from Bacillus, Enterobacter, Paenibacillus, Pseudomonas, Serratia, and Streptomyces genera (Erdogan and Benlioglu, 2010;Zhang et al, 2018;Cheng et al, 2020;Hasan et al, 2020;Sherzad and Canming, 2020;Tao et al, 2020;Zhang et al, 2020).…”