Dataset Information

Comparison of bacterial community structures in the rhizoplane of tomato plants grown in soils suppressive and conducive towards bacterial wilt.

ABSTRACT: It has been reported that the growth of Ralstonia solanacearum is suppressed at the rhizoplane of tomato plants and that tomato bacterial wilt is suppressed in plants grown in a soil (Mutsumi) in Japan. To evaluate the biological factors contributing to the suppressiveness of the soil in three treated Mutsumi soils (chloroform fumigated soil; autoclaved soil mixed with intact Mutsumi soil; and autoclaved soil mixed with intact, wilt-conducive Yamadai soil) infested with R. solanacearum, we bioassayed soil samples for tomato bacterial wilt. Chloroform fumigation increased the extent of wilt disease. More of the tomato plant samples wilted when mixed with Yamadai soil than when mixed with Mutsumi soil. Consequently, the results indicate that the naturally existing population of microorganisms in Mutsumi soil was significantly able to reduce the severity of bacterial wilt of tomato plants. To characterize the types of bacteria present at the rhizoplane, we isolated rhizoplane bacteria and classified them into 22 groups by comparing their 16S restriction fragment length polymorphism patterns. In Yamadai soil a single group of bacteria was extremely predominant (73.1%), whereas in Mutsumi soil the distribution of the bacterial groups was much more even. The 16S rDNA sequence analysis of strains of dominant groups suggested that gram-negative bacteria close to the beta-proteobacteria were most common at the rhizoplane of the tomato plants. During in vitro assays, rhizoplane bacteria in Mutsumi soil grew more vigorously on pectin, one of the main root exudates of tomato, compared with those in Yamadai soil. Our results imply that it is difficult for the pathogen to dominate in a diversified rhizobacterial community that thrives on pectin.

SUBMITTER: Shiomi Y

PROVIDER: S-EPMC99732 | biostudies-literature | 1999 Sep

REPOSITORIES: biostudies-literature

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Comparison of bacterial community structures in the rhizoplane of tomato plants grown in soils suppressive and conducive towards bacterial wilt.

Shiomi Y Y Nishiyama M M Onizuka T T Marumoto T T

Applied and environmental microbiology 19990901 9

It has been reported that the growth of Ralstonia solanacearum is suppressed at the rhizoplane of tomato plants and that tomato bacterial wilt is suppressed in plants grown in a soil (Mutsumi) in Japan. To evaluate the biological factors contributing to the suppressiveness of the soil in three treated Mutsumi soils (chloroform fumigated soil; autoclaved soil mixed with intact Mutsumi soil; and autoclaved soil mixed with intact, wilt-conducive Yamadai soil) infested with R. solanacearum, we bioas ...[more]

PMID: 10473407

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Project description:Disease-suppressive soils are soils in which specific soil-borne plant pathogens cause only limited disease although the pathogen and susceptible host plants are both present. Suppressiveness is in most cases of microbial origin. We conducted a comparative metabarcoding analysis of the taxonomic diversity of fungal and bacterial communities from suppressive and non-suppressive (conducive) soils as regards Fusarium wilts sampled from the Châteaurenard region (France). Bioassays based on Fusarium wilt of flax confirmed that disease incidence was significantly lower in the suppressive soil than in the conducive soil. Furthermore, we succeeded in partly transferring Fusarium wilt-suppressiveness to the conducive soil by mixing 10% (w/w) of the suppressive soil into the conducive soil. Fungal diversity differed significantly between the suppressive and conducive soils. Among dominant fungal operational taxonomic units (OTUs) affiliated to known genera, 17 OTUs were detected exclusively in the suppressive soil. These OTUs were assigned to the Acremonium, Chaetomium, Cladosporium, Clonostachys, Fusarium, Ceratobasidium, Mortierella, Penicillium, Scytalidium, and Verticillium genera. Additionally, the relative abundance of specific members of the bacterial community was significantly higher in the suppressive and mixed soils than in the conducive soil. OTUs found more abundant in Fusarium wilt-suppressive soils were affiliated to the bacterial genera Adhaeribacter, Massilia, Microvirga, Rhizobium, Rhizobacter, Arthrobacter, Amycolatopsis, Rubrobacter, Paenibacillus, Stenotrophomonas, and Geobacter. Several of the fungal and bacterial genera detected exclusively or more abundantly in the Fusarium wilt-suppressive soil included genera known for their activity against F. oxysporum. Overall, this study supports the potential role of known fungal and bacterial genera in Fusarium wilt suppressive soils from Châteaurenard and pinpoints new bacterial and fungal genera for their putative role in Fusarium wilt suppressiveness.

Project description:BACKGROUND AND AIMS: Recent studies have shown that certain composts may trigger indirect defence mechanisms by sensitizing the plant to create an increased state of resistance, similar to systemic acquired resistance. In this study, the capacity of a disease-suppressive compost to alter the expression pattern of certain pathogenesis-related (PR) genes in the root system of tomato plants (Solanum lycopersicum) provided the opportunity to study their cellular expression pattern and to investigate putative roles of these genes in the mechanisms of plant defence. METHODS: Employing the reverse transcription-polymerase chain reaction (RT-PCR) and in situ RNA:RNA hybridization techniques, the accumulation and distribution of the transcripts of the differentially expressed PR genes were examined in plants grown on compost and compared with those of control plants grown on peat. KEY RESULTS: Elevated levels of expression of the pathogenesis-related genes PR-1, PR-5 and P69/PR-7 were detected in the roots of tomato plants grown on the compost. A clearly distinguished spatial induction pattern was observed for these PR genes: PR-1 transcripts were almost exclusively detected in the pericycle cells surrounding the root stele of the main and lateral roots; PR-5 transcripts were present in the phloem of the root and stem tissues; and the accumulation and distribution of PR-7 transcripts was detected in discrete groups of cells that appeared sporadically in both the parenchyma and vascular system of the root, suggesting that the gene is not expressed in a tissue-specific manner. In addition, a novel cDNA clone was isolated (P69G), which probably encodes a new tomato P69 isoform. CONCLUSIONS: This study provides evidence that a suppressive compost is able to elicit consistent and increased expression of certain PR genes in the roots of tomato plants, even in the absence of any pathogen. The in situ localization studies reveal expression patterns which are in accordance with the presence of protein or with the putative roles of the respective encoded proteins. The expression of the PR genes may be triggered by the microflora of the compost or could be associated with abiotic factors of the compost.

Dataset Information

Comparison of bacterial community structures in the rhizoplane of tomato plants grown in soils suppressive and conducive towards bacterial wilt.

Publications

Comparison of bacterial community structures in the rhizoplane of tomato plants grown in soils suppressive and conducive towards bacterial wilt.

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