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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

Test for the ability of the candidate endophytes to reduce DON mycotoxin accumulation in maize grain during storage. DON measurements after storage of maize grain from: (A) greenhouse trial 1 (summer 2012), and (B) greenhouse trial 2 (summer 2013). For both trials, n = 3 pools of seeds. The black asterisk indicates that the treatment means were significantly different from the Fusarium only treatment at p ≤ 0.05. The green asterisk indicates that the treatment means were significantly different from the prothioconazole fungicide (Proline) treatment at p ≤ 0.05.
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Figure 9: Test for the ability of the candidate endophytes to reduce DON mycotoxin accumulation in maize grain during storage. DON measurements after storage of maize grain from: (A) greenhouse trial 1 (summer 2012), and (B) greenhouse trial 2 (summer 2013). For both trials, n = 3 pools of seeds. The black asterisk indicates that the treatment means were significantly different from the Fusarium only treatment at p ≤ 0.05. The green asterisk indicates that the treatment means were significantly different from the prothioconazole fungicide (Proline) treatment at p ≤ 0.05.

Mentions: In order to quantify DON levels in maize seeds, ELISA-based testing was conducted. Immediately after harvest, only traces of DON were detected in plants treated with Fusarium only (approximately 0.1 ppm) while all other treatments did not show any detectable levels of DON (data not shown). Seeds were stored at room temperature inside closed envelopes for one year, then the samples were analyzed again for DON content. Consistently in both trials, all four endophyte treatments caused dramatic reductions in DON accumulation during storage, with DON levels declining from approximately 3.5 ppm to 0.1–1.0 ppm (Figure 9, Table 3). The majority of the endophyte treatments resulted in a DON content of only 0.1 ppm, equivalent to a 97% reduction compared to the Fusarium-only control.


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)

Test for the ability of the candidate endophytes to reduce DON mycotoxin accumulation in maize grain during storage. DON measurements after storage of maize grain from: (A) greenhouse trial 1 (summer 2012), and (B) greenhouse trial 2 (summer 2013). For both trials, n = 3 pools of seeds. The black asterisk indicates that the treatment means were significantly different from the Fusarium only treatment at p ≤ 0.05. The green asterisk indicates that the treatment means were significantly different from the prothioconazole fungicide (Proline) treatment at p ≤ 0.05.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 9: Test for the ability of the candidate endophytes to reduce DON mycotoxin accumulation in maize grain during storage. DON measurements after storage of maize grain from: (A) greenhouse trial 1 (summer 2012), and (B) greenhouse trial 2 (summer 2013). For both trials, n = 3 pools of seeds. The black asterisk indicates that the treatment means were significantly different from the Fusarium only treatment at p ≤ 0.05. The green asterisk indicates that the treatment means were significantly different from the prothioconazole fungicide (Proline) treatment at p ≤ 0.05.
Mentions: In order to quantify DON levels in maize seeds, ELISA-based testing was conducted. Immediately after harvest, only traces of DON were detected in plants treated with Fusarium only (approximately 0.1 ppm) while all other treatments did not show any detectable levels of DON (data not shown). Seeds were stored at room temperature inside closed envelopes for one year, then the samples were analyzed again for DON content. Consistently in both trials, all four endophyte treatments caused dramatic reductions in DON accumulation during storage, with DON levels declining from approximately 3.5 ppm to 0.1–1.0 ppm (Figure 9, Table 3). The majority of the endophyte treatments resulted in a DON content of only 0.1 ppm, equivalent to a 97% reduction compared to the Fusarium-only control.

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