Isolation and Screening of Extracellular PGPR from the Rhizosphere of Tomato Plants after Long-Term Reduced Tillage and Cover Crops.

Maria Chiara Guerrieri,Edoardo Puglisi,Andrea Fiorini,Marco Trevisan,Elisabetta Fanfoni

doi:10.3390/plants9050668

Maria Chiara Guerrieri, Edoardo Puglisi + Show 3 more

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https://doi.org/10.3390/plants9050668

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Abstract

Plant growth promoting rhizobacteria provide an innovative solution to address challenges in sustainable agro-ecosystems, improving plant growth as well as acting as agents of biocontrol. In this study autochthonous bacteria were isolated from the rhizosphere of processing tomato plants (Solanum lycopersicum L.) cultivated with conservation agriculture practices (i.e., reduced tillage and cover crops), and evaluated for both growth-promoting activities (PGPAs), and antagonistic potential against the phytopathogenic pest Sclerotinia sclerotiorum. Considering the several activities of PGPR, we decided to structure the screening with a hierarchic approach, starting from testing the capability of fixing nitrogen. The obtained bacteria were processed through the molecular typing technique rep-PCR (Repetitive Extragenic Palindromic) in order to discriminate microbial strains with the same profiles, and identified via 16S rDNA sequencing. Thirty-eight selected isolates were screened in vitro for different activities related to plant nutrition and plant growth regulation as well as for antifungal traits. Isolated bacteria were found to exhibit different efficiencies in indoleacetic acid production and siderophore production, phosphate solubilization and biocontrol activity against the widespread soil-borne plant pathogen S. sclerotiorum. All the 38 bacterial isolates showed at least one property tested. With a view to detect the suitable candidates to be developed as biofertilizers, the selected isolates were ranked by their potential ability to function as PGPR. Thus, consortium of native PGPR bacteria inoculants may represent a suitable solution to address the challenges in sustainable agriculture, to ensure crop yield and quality, lowering the application of chemicals input.

Highlights

Plants can no longer be seen as standalone entities; it has been ascertained the role of plant microbiota in promoting plants fitness thanks to an intimacy of interactions between the plant and a wide diversity of microorganisms both inside and outside plant tissues, in the endosphere and rhizosphere respectively [1]
We focused on the identification of potential plant growth promoting rhizobacteria (PGPR) isolates by using selective or semi-selective culture media, by characterizing their specify metabolic features, by screening them with rep-PCR and by determining the identities of selected bacteria using 16S rRNA gene sequencing
According to the protocol proposed by Ambrosini and Passaglia [43], from each vial only one bacteria isolate is obtained

Summary

Introduction

Plants can no longer be seen as standalone entities; it has been ascertained the role of plant microbiota in promoting plants fitness thanks to an intimacy of interactions between the plant and a wide diversity of microorganisms both inside and outside plant tissues, in the endosphere and rhizosphere respectively [1]. This is especially the case for soils where conservation agriculture practices (i.e., reduced tillage, cover crops) are performed [2,3], due to enhanced soil fertility conditions [4]. PGPR are involved in amelioration of abiotic stress such as dryness and salinity stress [14], in revitalization of soil quality and plants growth [15] and enhancement phytoremediation of heavy metals [16]

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