Soybean Nodule-Associated Non-Rhizobial Bacteria Inhibit Plant Pathogens and Induce Growth Promotion in Tomato

Serkan Tokgöz; Dilip K. Lakshman; Mahmoud H. Ghozlan; Hasan Pinar; Daniel P. Roberts; Amitava Mitra

doi:10.3390/plants9111494

Plants (Nov 2020)

Soybean Nodule-Associated Non-Rhizobial Bacteria Inhibit Plant Pathogens and Induce Growth Promotion in Tomato

Serkan Tokgöz,
Dilip K. Lakshman,
Mahmoud H. Ghozlan,
Hasan Pinar,
Daniel P. Roberts,
Amitava Mitra

Affiliations

Serkan Tokgöz: Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
Dilip K. Lakshman: Sustainable Agricultural Systems Laboratory, USDA-ARS, Beltsville, MD 20705, USA
Mahmoud H. Ghozlan: Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
Hasan Pinar: Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
Daniel P. Roberts: Sustainable Agricultural Systems Laboratory, USDA-ARS, Beltsville, MD 20705, USA
Amitava Mitra: Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE 68588, USA

DOI: https://doi.org/10.3390/plants9111494
Journal volume & issue: Vol. 9, no. 11
p. 1494

Abstract

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The root nodules are a unique environment formed on legume roots through a highly specific symbiotic relationship between leguminous plants and nodule-inducing bacteria. Previously, Rhizobia were presumed to be the only group of bacteria residing within nodules. However, recent studies discovered diverse groups of bacteria within the legume nodules. In this report soybean nodule-associated bacteria were studied in an effort to identify beneficial bacteria for plant disease control and growth promotion. Analysis of surface-sterilized single nodules showed bacterial diversity of the nodule microbiome. Five hundred non-rhizobial colonies from 10 nodules, 50 colonies per nodule, were tested individually against the tomato wilt causing bacterial pathogen Clavibacter michiganensis subsp. michiganensis (Cmm) for inhibition of pathogen growth. From the initial screening, 54 isolates were selected based on significant growth inhibition of Cmm. These isolates were further tested in vitro on another bacterial pathogen Pseudomonas syringae pv. tomato (Pst) and two fungal pathogens Rhizoctonia solani and Sclerotinia sclerotiorum. Bacterial metabolites were extracted from 15 selected isolates with ethanol and tested against pathogen Cmm and Pst. These isolates were identified by using MALDI-TOF mass spectrometry and 16S rRNA gene sequencing. Pseudomonas spp. were the dominant soybean nodule-associated non-rhizobial bacterial group. Several isolates imparted significant protection against pathogens and/or plant growth promotion on tomato seedlings. The most promising nodule-associated bacterial isolate that suppressed both Cmm and Pst in vitro and Pst in tomato seedlings was identified as a Proteus species. Isolation and identification of beneficial nodule-associated bacteria established the foundation for further exploration of potential nodule-associated bacteria for plant protection and growth promotion.

Published in Plants

ISSN: 2223-7747 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Science: Botany
Website: http://www.mdpi.com/journal/plants

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