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Bacterial endophytes from wild maize suppress Fusarium graminearum in modern maize and inhibit mycotoxin accumulation.

Mousa WK, Shearer CR, Limay-Rios V, Zhou T, Raizada MN - Front Plant Sci (2015)

Bottom Line: The teosinte endophytes also suppressed DON mycotoxin during storage to below acceptable safety threshold levels.Our results suggest that the wild relatives of modern crops may serve as a valuable reservoir for endophytes in the ongoing fight against serious threats to modern agriculture.We discuss the possible impact of crop evolution and domestication on endophytes in the context of plant defense.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Agriculture, University of Guelph Guelph, ON, Canada ; Department of Pharmacognosy, Mansoura University Mansoura, Egypt.

ABSTRACT
Wild maize (teosinte) has been reported to be less susceptible to pests than their modern maize (corn) relatives. Endophytes, defined as microbes that inhabit plants without causing disease, are known for their ability to antagonize plant pests and pathogens. We hypothesized that the wild relatives of modern maize may host endophytes that combat pathogens. Fusarium graminearum is the fungus that causes Gibberella Ear Rot (GER) in modern maize and produces the mycotoxin, deoxynivalenol (DON). In this study, 215 bacterial endophytes, previously isolated from diverse maize genotypes including wild teosintes, traditional landraces and modern varieties, were tested for their ability to antagonize F. graminearum in vitro. Candidate endophytes were then tested for their ability to suppress GER in modern maize in independent greenhouse trials. The results revealed that three candidate endophytes derived from wild teosintes were most potent in suppressing F. graminearum in vitro and GER in a modern maize hybrid. These wild teosinte endophytes could suppress a broad spectrum of fungal pathogens of modern crops in vitro. The teosinte endophytes also suppressed DON mycotoxin during storage to below acceptable safety threshold levels. A fourth, less robust anti-fungal strain was isolated from a modern maize hybrid. Three of the anti-fungal endophytes were predicted to be Paenibacillus polymyxa, along with one strain of Citrobacter. Microscopy studies suggested a fungicidal mode of action by all four strains. Molecular and biochemical studies showed that the P. polymyxa strains produced the previously characterized anti-Fusarium compound, fusaricidin. Our results suggest that the wild relatives of modern crops may serve as a valuable reservoir for endophytes in the ongoing fight against serious threats to modern agriculture. We discuss the possible impact of crop evolution and domestication on endophytes in the context of plant defense.

No MeSH data available.


Related in: MedlinePlus

The effects of the candidate endophytes on F. graminearum in vitro using the vitality stain, Evans blue. Shown are representative microscope slide pictures (n = 3) of the interactions of F. graminearum with: (A) the commercial biological control agent, Bacillus subtilis (100 mg/10 ml) compared to (B) the buffer control; (C) Strain 1D6 compared to (D) the buffer control; (E) strain 3H9 compared to (F) the buffer control; (G) Strain 4G12 compared to (H) the buffer control; (I) Strain 4G4 compared to (J) the buffer control.
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Figure 5: The effects of the candidate endophytes on F. graminearum in vitro using the vitality stain, Evans blue. Shown are representative microscope slide pictures (n = 3) of the interactions of F. graminearum with: (A) the commercial biological control agent, Bacillus subtilis (100 mg/10 ml) compared to (B) the buffer control; (C) Strain 1D6 compared to (D) the buffer control; (E) strain 3H9 compared to (F) the buffer control; (G) Strain 4G12 compared to (H) the buffer control; (I) Strain 4G4 compared to (J) the buffer control.

Mentions: To better understand the anti-fungal mode of action of the candidate endophytes, the in vitro interactions between F. graminearum and each endophyte were visualized following their co-incubation on a microscope slide and subsequent staining with the vitality stains, neutral red and Evans blue. All the four endophytes caused apparent dramatic breakage of F. graminearum hyphae when compared to the control zone on the other side of the microscope slide (that was exposed to only LB media) (Figure 4). Upon staining with Evans blue (which stains dead cells in blue), fungal hyphae in contact with the commercial biological control or each of the four endophytes stained blue (Figures 5A,C,E,G,I) compared to the buffer controls (Figures 5B,D,F,H,J), suggesting that hyphae in contact with each bacterial endophyte died. Combined, these results suggest that all four endophytes have fungicidal activity.


Bacterial endophytes from wild maize suppress Fusarium graminearum in modern maize and inhibit mycotoxin accumulation.

Mousa WK, Shearer CR, Limay-Rios V, Zhou T, Raizada MN - Front Plant Sci (2015)

The effects of the candidate endophytes on F. graminearum in vitro using the vitality stain, Evans blue. Shown are representative microscope slide pictures (n = 3) of the interactions of F. graminearum with: (A) the commercial biological control agent, Bacillus subtilis (100 mg/10 ml) compared to (B) the buffer control; (C) Strain 1D6 compared to (D) the buffer control; (E) strain 3H9 compared to (F) the buffer control; (G) Strain 4G12 compared to (H) the buffer control; (I) Strain 4G4 compared to (J) the buffer control.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4593954&req=5

Figure 5: The effects of the candidate endophytes on F. graminearum in vitro using the vitality stain, Evans blue. Shown are representative microscope slide pictures (n = 3) of the interactions of F. graminearum with: (A) the commercial biological control agent, Bacillus subtilis (100 mg/10 ml) compared to (B) the buffer control; (C) Strain 1D6 compared to (D) the buffer control; (E) strain 3H9 compared to (F) the buffer control; (G) Strain 4G12 compared to (H) the buffer control; (I) Strain 4G4 compared to (J) the buffer control.
Mentions: To better understand the anti-fungal mode of action of the candidate endophytes, the in vitro interactions between F. graminearum and each endophyte were visualized following their co-incubation on a microscope slide and subsequent staining with the vitality stains, neutral red and Evans blue. All the four endophytes caused apparent dramatic breakage of F. graminearum hyphae when compared to the control zone on the other side of the microscope slide (that was exposed to only LB media) (Figure 4). Upon staining with Evans blue (which stains dead cells in blue), fungal hyphae in contact with the commercial biological control or each of the four endophytes stained blue (Figures 5A,C,E,G,I) compared to the buffer controls (Figures 5B,D,F,H,J), suggesting that hyphae in contact with each bacterial endophyte died. Combined, these results suggest that all four endophytes have fungicidal activity.

Bottom Line: The teosinte endophytes also suppressed DON mycotoxin during storage to below acceptable safety threshold levels.Our results suggest that the wild relatives of modern crops may serve as a valuable reservoir for endophytes in the ongoing fight against serious threats to modern agriculture.We discuss the possible impact of crop evolution and domestication on endophytes in the context of plant defense.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Agriculture, University of Guelph Guelph, ON, Canada ; Department of Pharmacognosy, Mansoura University Mansoura, Egypt.

ABSTRACT
Wild maize (teosinte) has been reported to be less susceptible to pests than their modern maize (corn) relatives. Endophytes, defined as microbes that inhabit plants without causing disease, are known for their ability to antagonize plant pests and pathogens. We hypothesized that the wild relatives of modern maize may host endophytes that combat pathogens. Fusarium graminearum is the fungus that causes Gibberella Ear Rot (GER) in modern maize and produces the mycotoxin, deoxynivalenol (DON). In this study, 215 bacterial endophytes, previously isolated from diverse maize genotypes including wild teosintes, traditional landraces and modern varieties, were tested for their ability to antagonize F. graminearum in vitro. Candidate endophytes were then tested for their ability to suppress GER in modern maize in independent greenhouse trials. The results revealed that three candidate endophytes derived from wild teosintes were most potent in suppressing F. graminearum in vitro and GER in a modern maize hybrid. These wild teosinte endophytes could suppress a broad spectrum of fungal pathogens of modern crops in vitro. The teosinte endophytes also suppressed DON mycotoxin during storage to below acceptable safety threshold levels. A fourth, less robust anti-fungal strain was isolated from a modern maize hybrid. Three of the anti-fungal endophytes were predicted to be Paenibacillus polymyxa, along with one strain of Citrobacter. Microscopy studies suggested a fungicidal mode of action by all four strains. Molecular and biochemical studies showed that the P. polymyxa strains produced the previously characterized anti-Fusarium compound, fusaricidin. Our results suggest that the wild relatives of modern crops may serve as a valuable reservoir for endophytes in the ongoing fight against serious threats to modern agriculture. We discuss the possible impact of crop evolution and domestication on endophytes in the context of plant defense.

No MeSH data available.


Related in: MedlinePlus