Isolation and selection of plant growth-promoting rhizobacteria as inducers of systemic resistance in melon

García-Gutiérrez, Laura; Romero, Diego; Zeriouh, Houda; Cazorla, Francisco M.; Torés, J. A.; Vicente, Antonio de; Pérez-Garcı́a, Alejandro

doi:10.1007/s11104-012-1173-z

Cited by 52 publications

(18 citation statements)

References 47 publications

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“…With regard to the role of Bacillus in managing cucurbit powdery mildew, in a previous study, four Bacillus strains isolated from the healthy phyllosphere and rhizosphere of cucurbits infected with powdery mildew demonstrated antagonism against the fungus Podosphaera fusca on detached melon leaves and seedlings; the suppressive efficacy was up to 80% ( Romero et al, 2004 ). In another study, Bacillus subtilis strain UMAF6639 demonstrated reduction of powdery mildew disease severity in infected melon leaves ( García-Gutiérrez et al, 2012 ). The antagonism involved three major mechanisms including induction of host systemic resistance ( García-Gutiérrez et al, 2012 ), stimulation of plant signaling pathways mediated by jasmonate and salicylic acid, and finally induction of host defense mediated by a surfactin lipopeptide.…”

Section: Discussionmentioning

confidence: 97%

Bacterial Seed Endophytes of Domesticated Cucurbits Antagonize Fungal and Oomycete Pathogens Including Powdery Mildew

2018

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The cucurbit vegetables, including cucumbers, melons and pumpkins, have been cultivated for thousands of years without fungicides. However, their seed germination stage is prone to be infected by soil-borne fungal and oomycete pathogens. Endophytes are symbionts that reside inside plant tissues including seeds. Seed endophytes are founders of the juvenile plant microbiome and can promote host defense at seed germination and later stages. We previously isolated 169 bacterial endophytes associated with seeds of diverse cultivated cucurbits. We hypothesized that these endophytes can antagonize major fungal and oomycete pathogens. Here we tested the endophytes for in vitro antagonism (dual culture assays) against important soil-borne pathogens (Rhizoctonia solani, Fusarium graminearum, Phytophthora capsici, Pythium aphanidermatum). The endophytes were also assayed in planta (leaf disk and detached leaf bioassays) for antagonism against a foliar pathogen of global importance, Podosphaera fuliginea, the causative agent of cucurbit powdery mildew. The endophytes were further tested in vitro for secretion of volatile organic compounds (VOCs) known to induce plant defense. Extracellular ribonuclease activity was also tested, as a subset of pathogenesis-related (PR) proteins of plant hosts implicated in suppression of fungal pathogens, displays ribonuclease activity. An unexpected majority of the endophytes (70%, 118/169) exhibited antagonism to the five phytopathogens, of which 68% (50/73) of in vitro antagonists belong to the genera Bacillus and Paenibacillus. All Lactococcus and Pantoea endophytes exhibited anti-oomycete activity. However, amongst the most effective inoculants against Podosphaera fuliginea were Pediococcus and Pantoea endophytes. Interestingly, 67% (113/169) of endophytes emitted host defense inducing VOCs (acetoin/diacetyl) and 62% (104/169) secreted extracellular ribonucleases in vitro, respectively. These results show that seeds of cultivated cucurbits package microbes with significant disease-suppression potential. As seeds can act as vectors for genetic transmission of endophytes across host generations, it is interesting to hypothesize whether humans, when selecting seeds of healthy hosts, may have inadvertently selected for disease-suppressing seed endophytes. As the majority of pathogen-suppressing endophytes belong to Bacillus and Paenibacillus, and since Bacilli are widely used as commercial biocontrol agents of vegetables, we propose that these agents are mimicking the ecological niche established by their endophytic cousins.

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Section: Discussionmentioning

confidence: 97%

Bacterial Seed Endophytes of Domesticated Cucurbits Antagonize Fungal and Oomycete Pathogens Including Powdery Mildew

2018

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“…For Bacillus spp., as far as we are aware, no antagonistic effects on control of bacteria, fungi, and viruses have been reported. García-Gutiérrez et al(2012) tested suppression of both fungal and bacterial pathogens by P. fluorescens in combination with Bacillus ; combinations were equally effective as single introductions of P. fluorescens. The improved control of Fusarium disease by a combination of P. fluorescens and Bacillus was associated with the induction of the defense-related enzymes peroxidase and polyphenol oxidase (Akila et al, 2011; Sundaramoorthy et al, 2012).…”

Section: Pseudomonas Combined With Other Pseudomonas Strains or With mentioning

confidence: 99%

Getting the ecology into interactions between plants and the plant growth-promoting bacterium Pseudomonas fluorescens

Hol¹,

Bezemer²,

Biere³

2013

Front. Plant Sci.

119

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Plant growth-promoting rhizobacteria (PGPR) are increasingly appreciated for their contributions to primary productivity through promotion of growth and triggering of induced systemic resistance in plants. Here we focus on the beneficial effects of one particular species of PGPR (Pseudomonas fluorescens) on plants through induced plant defense. This model organism has provided much understanding of the underlying molecular mechanisms of PGPR-induced plant defense. However, this knowledge can only be appreciated at full value once we know to what extent these mechanisms also occur under more realistic, species-diverse conditions as are occurring in the plant rhizosphere. To provide the necessary ecological context, we review the literature to compare the effect of P. fluorescens on induced plant defense when it is present as a single species or in combination with other soil dwelling species. Specifically, we discuss combinations with other plant mutualists (bacterial or fungal), plant pathogens (bacterial or fungal), bacterivores (nematode or protozoa), and decomposers. Synergistic interactions between P. fluorescens and other plant mutualists are much more commonly reported than antagonistic interactions. Recent developments have enabled screenings of P. fluorescens genomes for defense traits and this could help with selection of strains with likely positive interactions on biocontrol. However, studies that examine the effects of multiple herbivores, pathogens, or herbivores and pathogens together on the effectiveness of PGPR to induce plant defenses are underrepresented and we are not aware of any study that has examined interactions between P. fluorescens and bacterivores or decomposers. As co-occurring soil organisms can enhance but also reduce the effectiveness of PGPR, a better understanding of the biotic factors modulating P. fluorescens–plant interactions will improve the effectiveness of introducing P. fluorescens to enhance plant production and defense.

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“…PGPR is a collective term used to describe a group of beneficial bacteria capable of colonizing the rhizosphere leading to the stimulation of plant growth and/or the protection of plants from soil-borne phytopathogens 1 . Plant growth promoting mechanisms include the production of antimicrobial compounds such as lipopeptides and polyketides which are bioactive against phytopathogens 2 3 ; the secretion of phytohormones such as indole acetic acid and gibberellic acid, which stimulate plant growth 4 5 , induction systemic resistance against pathogens 6 and the production of bioactive volatile organic compounds 7 8 . However, in order for plants to acquire the beneficial effects from PGPR, as previously mentioned, it is crucial for PGPR to colonize the plant root system 9 10 .…”

mentioning

confidence: 99%

Organic acids from root exudates of banana help root colonization of PGPR strain Bacillus amyloliquefaciens NJN-6

Yuan

Zhang

Huang

et al. 2015

Sci Rep

199

113

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The successful colonization of plant growth promoting rhizobacteria (PGPR) in the rhizosphere is an initial and compulsory step in the protection of plants from soil-borne pathogens. Therefore, it is necessary to evaluate the role of root exudates in the colonization of PGPR. Banana root exudates were analyzed by high pressure liquid chromatography (HPLC) which revealed exudates contained several organic acids (OAs) including oxalic, malic and fumaric acid. The chemotactic response and biofilm formation of Bacillus amyloliquefaciens NJN-6 were investigated in response to OA’s found in banana root exudates. Furthermore, the transcriptional levels of genes involved in biofilm formation, yqxM and epsD, were evaluated in response to OAs via quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Results suggested that root exudates containing the OAs both induced the chemotaxis and biofilm formation in NJN-6. In fact, the strongest chemotactic and biofilm response was found when 50 μM of OAs were applied. More specifically, malic acid showed the greatest chemotactic response whereas fumaric acid significantly induced biofilm formation by a 20.7–27.3% increase and therefore biofilm formation genes expression. The results showed banana root exudates, in particular the OAs released, play a crucial role in attracting and initiating PGPR colonization on the host roots.

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Isolation and selection of plant growth-promoting rhizobacteria as inducers of systemic resistance in melon

Cited by 52 publications

References 47 publications

Bacterial Seed Endophytes of Domesticated Cucurbits Antagonize Fungal and Oomycete Pathogens Including Powdery Mildew

Bacterial Seed Endophytes of Domesticated Cucurbits Antagonize Fungal and Oomycete Pathogens Including Powdery Mildew

Getting the ecology into interactions between plants and the plant growth-promoting bacterium Pseudomonas fluorescens

Organic acids from root exudates of banana help root colonization of PGPR strain Bacillus amyloliquefaciens NJN-6

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