Isolation, screening and identification of antagonistic downy mildew endophytic bacteria from cucumber

Sun, Zhan‐Bin; Yuan, Xing-Fang; Zhang, Hui; Wu, Lei-Fei; Chen, Liang; Feng, Yongjun

doi:10.1007/s10658-013-0293-5

Cited by 28 publications

(15 citation statements)

References 21 publications

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“…Adapting a previous protocol ( Sun et al, 2013 ), the leaves from the 2nd to 5th node of cucumber plants were detached and 0.5 inch-diameter leaf-disks were created by using a paper puncher. Fifteen leaf-disks were used for each endophytic bacterium (3 Petri dishes, 5 disks per dish) by soaking them in a bacterial suspension of LB broth amended with filter sterilized 0.01% Tween 20 and adjusted to OD 600 ∼0.3–0.5 for 1 min with gentle shaking.…”

Section: Methodsmentioning

confidence: 99%

“…Adapting a previous protocol ( Sun et al, 2013 ), whole cucumber leaves from the 2nd – 5th node were selected, and each leaf was placed on a damp filter paper wetted with the same nutrient solution used in leaf disk bioassay and placed in a 150 mm diameter Petri dish. The petiole of each leaf was wrapped in an autoclaved, wetted (with cucumber nutrient solution) cotton puff.…”

Section: Methodsmentioning

confidence: 99%

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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: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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

2018

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“…The samples were then washed several times with sterilized distilled water, the final wash was spread plated onto nutrient agar plate (g/L; peptone 5, beef extract 2, yeast extract 3, sodium chloride 5 and agar 18, pH 7.0) and cultivated at 28°C for 3 days as a sterility check. Samples were discarded if the growth was detected in the sterility check samples after 3 days ( Tiwari et al, 2010 ; Sun et al, 2013 ).…”

Section: Methodsmentioning

confidence: 99%

An Endophytic Bacterial Strain Isolated from Eucommia ulmoides Inhibits Southern Corn Leaf Blight

Ding

Chen

et al. 2017

Front. Microbiol.

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Bacillus subtilis DZSY21 isolated from the leaves of Eucommia ulmoides oliv. was labeled by antibiotic marker and found to effectively colonize the leaves of maize plant. Agar diffusion assays and biocontrol effect experiments showed that strain DZSY21 and its lipopeptides had antagonistic activity against Bipolaris maydis, as well as high biocontrol effects on southern corn leaf blight caused by B. maydis. Using MALDI-TOF-MS analysis, we detected the presence of antimicrobial surfactin A, surfactin B, and fengycin in the strain DZSY21. Signaling pathways mediated by DZSY21 were analyzed by testing the expression of key plant genes involved in regulation of salicylic acid (SA) or JA/ET pathways, the defense-related genes PR1 and LOX were concurrently expressed in the leaves of DZSY21-treated plants; this corresponded to slight increase in the expression level of PDF1.2 and decreases in ERF gene transcription levels. The results indicated an induced systemic response that is dependent on the SA and jasmonic acid (JA) pathways. Thus, we hypothesized that the strain DZSY21 inhibits B. maydis by producing antifungal lipopeptides and activating an induced systemic response through SA- and JA-dependent signaling pathways. This work describes a mechanism behind reduced disease severity in plants inoculated with the endophytic bacteria DZSY21.

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“…In the absence of targeted plant disease-control approaches, soil-borne pathogens continue to cause significant crop losses worldwide in both conventional and organic field production systems (Khabbaz and Abbasi 2014). Development of biological control measures using antagonistic bacteria is one of the most attractive alternatives to chemical fungicides, which has many limitations including environmental concerns, food quality issues, and tolerance to antifungal agents after long-term applications (Sun et al 2013). A trend exists in terms of utilizing micro-organisms isolated from rhizosphere soil as biological agents, which may be better adapted to colonize the rhizosphere of crop plants and show better disease control than organisms isolated from the other sources, such as seawater, compost, and silt (Cook 2003;Kamilova et al 2010).…”

Section: Discussionmentioning

confidence: 99%

Isolation and characterization of antagonistic bacteria with the potential for biocontrol of soil-borne wheat diseases

Wang

et al. 2018

J Appl Microbiol

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Isolation, screening and identification of antagonistic downy mildew endophytic bacteria from cucumber

Cited by 28 publications

References 21 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

An Endophytic Bacterial Strain Isolated from Eucommia ulmoides Inhibits Southern Corn Leaf Blight

Isolation and characterization of antagonistic bacteria with the potential for biocontrol of soil-borne wheat diseases

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