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Tomato pith necrosis (TPN) is a highly destructive disease caused by species of the Pseudomonas genus and other bacteria, resulting in a significant reduction in tomato yield. Members of the genus Bacillus are beneficial microorganisms extensively studied in the rhizosphere. However, in most cases, the potential of Bacillus members in controlling TPN and their impact on the rhizosphere microbial composition remain rarely studied. In this study, Bacillus velezensis ZN-S10 significantly inhibited the growth of Pseudomonas viridiflava ZJUP0398-2, and ZN-S10 controlled TPN with control efficacies of 60.31%. P. viridiflava ZJUP0398-2 significantly altered the richness and diversity of the tomato rhizobacterial community, but pre-inoculation with ZN-S10 mitigated these changes. The correlation analysis revealed that ZN-S10 maybe inhibits the growth of nitrogen-fixing bacteria and recruits beneficial bacterial communities associated with disease resistance, thereby suppressing the occurrence of diseases. In summary, the comparative analysis of the rhizosphere microbiome was conducted to explore the impact of ZN-S10 on the composition of rhizosphere microorganisms in the presence of pathogenic bacteria, aiming to provide insights for further research and the development of scientific and eco-friendly control strategies for this disease. [ABSTRACT FROM AUTHOR]

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Tomato pith necrosis (TPN) is a highly destructive disease caused by species of the Pseudomonas genus and other bacteria, resulting in a significant reduction in tomato yield. Members of the genus Bacillus are beneficial microorganisms extensively studied in the rhizosphere. However, in most cases, the potential of Bacillus members in controlling TPN and their impact on the rhizosphere microbial composition remain rarely studied. In this study, Bacillus velezensis ZN-S10 significantly inhibited the growth of Pseudomonas viridiflava ZJUP0398-2, and ZN-S10 controlled TPN with control efficacies of 60.31%. P. viridiflava ZJUP0398-2 significantly altered the richness and diversity of the tomato rhizobacterial community, but pre-inoculation with ZN-S10 mitigated these changes. The correlation analysis revealed that ZN-S10 maybe inhibits the growth of nitrogen-fixing bacteria and recruits beneficial bacterial communities associated with disease resistance, thereby suppressing the occurrence of diseases. In summary, the comparative analysis of the rhizosphere microbiome was conducted to explore the impact of ZN-S10 on the composition of rhizosphere microorganisms in the presence of pathogenic bacteria, aiming to provide insights for further research and the development of scientific and eco-friendly control strategies for this disease.

Pseudomonas species causing pith necrosis on tomato were collected from 2005 to 2012 in different regions of the Republic of Macedonia and identified as Pseudomonas mediterranea and P. viridiflava. Other Pseudomonas spp. were also recovered, but they are still under identification. The obtained bacterial isolates were compared with reference strains on the basis of phenotypic characteristics, pathogenicity, sensitivity to antibiotics, BIOLOG tests, DNA fingerprinting by multiplex PCR using two specific primers [type I (PC5/1 and PC 5/2) and type II (PC1/1 and PC 1/2)], and 16S rRNA-RFLP analysis. Unique DNA bands from 10 representative strains isolated from symptomatic tomato plants disclosed the presence of P. mediterranea by amplification of their genomic DNA. All strains produced one specific band (600 bp) compared with the representative samples IPVCT9.1 (P. mediterranea). Also, we used another representative sample IPVCT10.3 (P. corrugata), to check if we already have P. corrugata or no, in our samples. In order to investigate the bacterial populations causing tomato pith necrosis in Macedonia, a total of 150 isolates were collected and compared with reference strains. This is the first report on Pseudomonas population causing pith necrosis of tomato in the Republic of Macedonia. [ABSTRACT FROM AUTHOR]

Pseudomonas corrugata is a phytopathogenic bacterium, causal agent of tomato pith necrosis, yet it is an ubiquitous bacterium that is part of the microbial community in the soil and in the rhizosphere of different plant species. Although it is a very heterogeneous species, all the strains tested were able to produce short chain acyl homoserine lactone (AHL) quorum sensing signal molecules. The main AHL produced was N-hexanoyl-l-homoserine lactone (C6-AHL). An AHL quorum sensing system, designated PcoI/PcoR, was identified and characterized. The role of the quorum sensing system in the expression of a variety of traits was evaluated. Inactivation of pcoI abolished the production of AHLs. The pcoR mutant, but not the pcoI mutant, was impaired in swarming, unable to cause a hypersensitivity response on tobacco and resulted in a reduced tomato pith necrosis phenotype. The pcoI mutant showed a reduced antimicrobial activity against various fungi and bacteria when assayed on King's B medium. These results demonstrate that the AHL quorum sensing in Ps. corrugata regulates traits that contribute to virulence, antimicrobial activity and fitness. This is the first report of genes of Ps. corrugata involved in the disease development and biological control activity. [ABSTRACT FROM AUTHOR]

Pseudomonas species causing pith necrosis symptoms on tomato and pepper collected in different areas of Argentina were identified as Pseudomonas corrugata , P. viridiflava and Pseudomonas spp. Their diversity was analysed and compared with reference strains on the basis of their phenotypic characteristics, copper and antibiotic sensitivity tests, serology, pathogenicity, DNA fingerprinting and restriction fragment length polymorphism (RFLP) analysis of a 16S rRNA gene fragment. All P. corrugata strains tested were copper-resistant while P. viridiflava strains were more variable. Numerical analysis of phenotypic data showed that all P. corrugata strains formed a single phenon that clustered at a level of about 93%, while all the P. viridiflava strains clustered in a separated phenon at a level of 94%. Genomic analysis by repetitive (rep)-PCR and 16S rRNA-RFLP fingerprinting and serological analysis showed that the two species contained considerable genetic diversity. Inoculations of tomato and pepper plants with strains from both hosts caused similar pith necrosis symptoms. Strains of both P. corrugata and P. viridiflava were grouped according to their geographical origin and not according to the original host. This is the first report of Pseudomonas viridiflava causing pith necrosis on pepper. [ABSTRACT FROM AUTHOR]