Abstract
Farmers rely heavily on the use of strobilurin fungicides to manage sheath blight (ShB) caused by Rhizoctonia solani AG1-IA, the most important disease in rice in the southern United States. Greenhouse and field studies were conducted to evaluate the potential use of plant growth–promoting rhizobacteria (PGPRs) in combination with a reduced rate of azoxystrobin application as a strategy to improve the current fungicide-reliant management. Of the nine antagonistic PGPR strains screened in the greenhouse, Bacillus subtilis strain MBI600 provided the most significant and consistent suppression of ShB. Efficacy of strain MBI600 was further evaluated at the concentrations of 0, 10 3 , 10 6 , 10 9 , and 10 11 CFU/ml alone or in combinations with 0, 17, 33, 50, 67, 83, and 100% of the recommended application rate (0.16 kg a.i./ha) of azoxystrobin. Strain MBI600 applied at 10 6 ,10 9 , and 10 11 CFU/ml alone was effective in reducing ShB severity. Combinations of this strain at these rates with ≥33% of the recommended application rate of azoxystrobin further reduced ShB severity. A dose–response model defining the relationships between strain MBI600, azoxystrobin, and ShB severity was established. Estimates of the effective concentrations (EC 50 and EC 90 ) of strain MBI600 when applied in combination with 50% of the recommended application rate of azoxystrobin were 10 4 and 10 9 CFU/ml, respectively. A field trial was conducted over 4 years to verify the efficacy of their combinations. Strain MBI600 alone, when applied at 10 9 CFU/ml at the boot stage, reduced ShB severity but did not significantly increase grain yields each year. Combination of strain MBI600 with azoxystrobin at half of the recommended application rate improved efficacy of strain MBI600, reducing ShB severity to a level comparable to that of azoxystrobin applied at the full rate in all 4 years. The combined treatment also increased grain yield by 14 to 19%, comparable to the fungicide applied at the full rate in 3 of 4 years. Combined use of PGPR strain MBI600 with a reduced rate of azoxystrobin application can be a viable management option for control of ShB while allowing producers to use less fungicide on rice.
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Claims 11
Claim · model-written summary
Bacillus subtilis strain MBI600 gave the strongest and most consistent greenhouse sheath blight suppression among nine strains.
- Taxon
- rice
Oryza sativat0 - Treatment
- Bacillus subtilis strain MBI600e0
- Interactor
- Bacillus subtilis strain MBI600
Bacillus subtilise0biocontrol_agent - Outcome
- suppression of ShBe0
- Direction
- most significant and consistente0
- Comparator
- nine antagonistic PGPR strainse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Of the nine antagonistic PGPR strains screened in the greenhouse, Bacillus subtilis strain MBI600 provided the most significant and consistent suppression of ShB.”
t0“Rice”
Claim · model-written summary
MBI600 alone at three tested concentrations reduced sheath blight severity.
- Taxon
- riceOryza sativat0
- Treatment
- Strain MBI600 applied at 10 6 ,10 9 , and 10 11 CFU/ml alonee0
- Interactor
- Strain MBI600e0biocontrol_agent
- Outcome
- ShB severitye0
- Direction
- reducinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Strain MBI600 applied at 10 6 ,10 9 , and 10 11 CFU/ml alone was effective in reducing ShB severity.”
t0“Rice”
Claim · model-written summary
MBI600 at those concentrations combined with at least 33% azoxystrobin further reduced sheath blight severity.
- Taxon
- riceOryza sativat0
- Treatment
- ≥33% of the recommended application rate of azoxystrobine0
- Interactor
- Rhizoctonia solani AG1-IARhizoctonia solani AG-1 IAe1pathogen
- Outcome
- ShB severitye0
- Direction
- further reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Combinations of this strain at these rates with ≥33% of the recommended application rate of azoxystrobin further reduced ShB severity.”
t0“Rice”
e1“Rhizoctonia solani AG1-IA”
Claim · model-written summary
A dose-response model relating MBI600, azoxystrobin and sheath blight severity was established.
- Taxon
- riceOryza sativat0
- Outcome
- relationships between strain MBI600, azoxystrobin, and ShB severitye0
Not reportedComparatorValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A dose–response model defining the relationships between strain MBI600, azoxystrobin, and ShB severity was established.”
t0“Rice”
Claim · model-written summary
With half-rate azoxystrobin, the estimated MBI600 EC50 was 10 4 CFU/ml.
- Taxon
- riceOryza sativat0
- Treatment
- 50% of the recommended application rate of azoxystrobine0
- Interactor
- strain MBI600e0biocontrol_agent
- Outcome
- EC 50e0
- Value
- 10 4e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Estimates of the effective concentrations (EC 50 and EC 90 ) of strain MBI600 when applied in combination with 50% of the recommended application rate of azoxystrobin were 10 4 and 10 9 CFU/ml, respectively.”
t0“Rice”
Claim · model-written summary
With half-rate azoxystrobin, the estimated MBI600 EC90 was 10 9 CFU/ml.
- Taxon
- riceOryza sativat0
- Treatment
- 50% of the recommended application rate of azoxystrobine0
- Interactor
- strain MBI600e0biocontrol_agent
- Outcome
- EC 90e0
- Value
- 10 9 CFU/mle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Estimates of the effective concentrations (EC 50 and EC 90 ) of strain MBI600 when applied in combination with 50% of the recommended application rate of azoxystrobin were 10 4 and 10 9 CFU/ml, respectively.”
t0“Rice”
Claim · model-written summary
Field-applied MBI600 alone reduced sheath blight severity.
- Taxon
- riceOryza sativat0
- Organ / stage
- boot stagee0
- Treatment
- Strain MBI600 alone, when applied at 10 9 CFU/mle0
- Interactor
- Strain MBI600e0biocontrol_agent
- Outcome
- ShB severitye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Strain MBI600 alone, when applied at 10 9 CFU/ml at the boot stage, reduced ShB severity but did not significantly increase grain yields each year.”
t0“Rice”
Claim · model-written summary
Field-applied MBI600 alone did not significantly increase grain yield each year.
- Taxon
- riceOryza sativat0
- Treatment
- Strain MBI600 alone, when applied at 10 9 CFU/mle0
- Interactor
- Strain MBI600e0biocontrol_agent
- Outcome
- grain yieldse0
- Direction
- did not significantly increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Strain MBI600 alone, when applied at 10 9 CFU/ml at the boot stage, reduced ShB severity but did not significantly increase grain yields each year.”
t0“Rice”
Claim · model-written summary
Combining MBI600 with half-rate azoxystrobin reduced sheath blight severity to the full-rate fungicide level in all four years.
- Taxon
- riceOryza sativat0
- Treatment
- Combination of strain MBI600 with azoxystrobin at half of the recommended application ratee0
- Interactor
- strain MBI600e0biocontrol_agent
- Outcome
- ShB severitye0
- Direction
- reducinge0
- Comparator
- azoxystrobin applied at the full ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Combination of strain MBI600 with azoxystrobin at half of the recommended application rate improved efficacy of strain MBI600, reducing ShB severity to a level comparable to that of azoxystrobin applied at the full rate in all 4 years.”
t0“Rice”
Claim · model-written summary
The combined treatment increased rice grain yield by 14 to 19%, comparable with full-rate fungicide in three of four years.
- Taxon
- riceOryza sativat0
- Treatment
- The combined treatmente0
- Outcome
- grain yielde0
- Direction
- increasede0
- Value
- 14 to 19%e0
- Qualifier
- in 3 of 4 yearse0
- Comparator
- the fungicide applied at the full ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The combined treatment also increased grain yield by 14 to 19%, comparable to the fungicide applied at the full rate in 3 of 4 years.”
t0“Rice”
Claim · model-written summary
The authors identify MBI600 with reduced azoxystrobin as a viable rice sheath blight management option.
- Taxon
- riceOryza sativae0
- Treatment
- Combined use of PGPR strain MBI600 with a reduced rate of azoxystrobin applicatione0
- Outcome
- viable management option for control of ShBe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Combined use of PGPR strain MBI600 with a reduced rate of azoxystrobin application can be a viable management option for control of ShB while allowing producers to use less fungicide on rice.”
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