Abstract
Fusarium head blight (FHB), or scab, is one of the most devastating fungal diseases affecting small-grain cereals and maize, causing severe yield losses and contamination of grain with mycotoxins such as deoxynivalenol (DON) worldwide. Fusarium graminearum (teleomorph Gibberella zeae) and Fusarium culmorum are the most prevalent Fusarium species in wheat production in Central and Northern Europe. Breeding for increased resistance to FHB in wheat is considered the most effective strategy for large scale disease management and mycotoxin reduction. Height reducing Rht genes are extensively used in wheat breeding programmes worldwide in order to improve lodging resistance and yield potential, with Rht-D1b being the most important Rht allele in Northern Europe. However, their individual effects on FHB resistance are yet unclear. Due to the incremental approach to increase host resistance the question arises whether the Fusarium pathogen has the capability to adapt by increased aggressiveness and/or increased mycotoxin production. Therefore, the objectives of the present study were to investigate the effects on FHB resistance of Rht-D1b and additional Rht alleles, the segregation variance for FHB resistance and identification of FHB resistance QTL in subsequent mapping analyses in three crossing populations segregating for the semi-dwarfing Rht-D1b allele and two sets of isogenic wheat lines. Regarding the pathogen, the study aims to determine the segregation variance in two F. graminearum crosses of highly aggressive parental isolates and to examine the stability of host FHB resistance, pathogen aggressiveness and the complex host-pathogen-environment interactions in a factorial field trial. All experiments were conducted on the basis of multienvironmental field trials including artificial inoculation of spores. The presence of Rht-D1b resulted in 7-18% reduction in plant height, but considerably increased FHB severity by 22-53% within progenies from three tested European elite winter wheat crosses. In the following QTL mapping analyses the QTL with the strongest additive effects was located at the Rht-D1 locus on chromosome arm 4DS and accordingly coincided with a major QTL for plant height in all three wheat populations. On total, a high number of 8 to 14 minor QTL for FHB reaction that were found in the three populations which emphasised the quantitative inheritance of FHB resistance in European winter wheat. The detected QTL mostly showed significant QTL-by-environment interactions and often coincided with QTL for plant height. By means of isogenic lines in the genetic background of the variety Mercia, Rht-D1b and Rht-B1d significantly increased mean FHB severity by 52 and 35%, respectively, compared to the wild-type (rht). Among the Maris Huntsman data set, the Rht alleles increased mean FHB severity by 22 up to 83%, but only the very short lines carrying Rht-B1c or Rht-B1b+Rht-D1b showed significance. The analyses of 120 progenies of the crosses from each of the highly aggressive parental F. graminearum isolates revealed significant genetic variation for aggressiveness, DON and fungal mycelium production following sexual recombination. This variation resulted in stable transgressive segregants towards increased aggressiveness in one of the two progeny. The factorial field trial, including eleven F. graminearum and F. culmorum isolates varying in aggressiveness and seven European elite winter wheat varieties, varying in their FHB resistance level, displayed no significant wheat variety × isolate interaction. Nevertheless, isolates possessing increased aggressiveness significantly increased FHB severity and DON production at a progressive rate on varieties with reduced FHB resistance. In conclusion, the analysed Rht alleles led to differently pronounced negative effects on FHB resistance that strongly depended on the genetic background. However, significant genetic variation for FHB resistance exists for selection and, thus, to largely counteract these effects by accumulating major and minor FHB resistance QTL. Significant genetic variation for aggressiveness among F. graminearum and the capability to increase its level of aggressiveness beyond yet known levels simply by sexual recombination may lead to long term erosion of FHB resistance. The rate at which increased aggressiveness develops will depend on the selection intensity and whether it is of constant, episodic or balanced nature. Consequently, the selection pressure imposed on the pathogen should be minimized by creating and maintaining a broad genetic base of FHB resistance that relies on more than one genetically unrelated resistance source by combining phenotypic and marker-assisted selection to achieve a sustainably improved FHB resistance in wheat breeding.
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Claims 15
Claim · model-written summary
Rht-D1b reduced plant height by 7–18% in three European elite winter wheat crosses.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- presence of Rht-D1be0
- Gene
- Rht-D1be0
- Outcome
- plant heighte0
- Direction
- reductione0
- Value
- 7-18%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of Rht-D1b resulted in 7-18% reduction in plant height, but considerably increased FHB severity by 22-53% within progenies from three tested European elite winter wheat crosses.”
Claim · model-written summary
Rht-D1b increased FHB severity by 22–53% in progeny of three European elite winter wheat crosses.
- Taxon
- wheatTriticum aestivume0
- Treatment
- presence of Rht-D1be0
- Gene
- Rht-D1be0
- Outcome
- FHB severitye0
- Direction
- increasede0
- Value
- 22-53%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The presence of Rht-D1b resulted in 7-18% reduction in plant height, but considerably increased FHB severity by 22-53% within progenies from three tested European elite winter wheat crosses.”
Claim · model-written summary
The strongest additive FHB reaction QTL mapped to Rht-D1 on chromosome arm 4DS and coincided with a major plant height QTL in all three populations.
- Taxon
- wheatTriticum aestivume0
- Gene
- Rht-D1 locuse0
- Outcome
- QTL with the strongest additive effectse0
- Setting
- chromosome arm 4DSe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the QTL with the strongest additive effects was located at the Rht-D1 locus on chromosome arm 4DS and accordingly coincided with a major QTL for plant height in all three wheat populations.”
Claim · model-written summary
Each of the three wheat populations had 8 to 14 minor QTL for FHB reaction.
- Taxon
- wheatTriticum aestivume1
- Outcome
- minor QTL for FHB reactione0
- Value
- 8 to 14e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a high number of 8 to 14 minor QTL for FHB reaction that were found in the three populations”
e1“wheat populations”
Claim · model-written summary
Detected FHB QTL mostly had significant interactions with environment.
- Taxon
- wheatTriticum aestivume1
- Gene
- QTLe0
- Outcome
- QTL-by-environment interactionse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The detected QTL mostly showed significant QTL-by-environment interactions and often coincided with QTL for plant height.”
e1“wheat populations”
Claim · model-written summary
Detected FHB QTL often coincided with plant height QTL.
- Taxon
- wheatTriticum aestivume1
- Gene
- QTLe0
- Outcome
- coincided with QTL for plant heighte0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The detected QTL mostly showed significant QTL-by-environment interactions and often coincided with QTL for plant height.”
e1“wheat populations”
Claim · model-written summary
In Mercia isogenic lines, Rht-D1b increased mean FHB severity by 52% relative to wild type.
- Taxon
- wheatTriticum aestivume1
- Material
- Merciae0
- Treatment
- Rht-D1be0
- Gene
- Rht-D1be0
- Outcome
- mean FHB severitye0
- Direction
- increasede0
- Value
- 52e0
- Comparator
- wild-type (rht)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“By means of isogenic lines in the genetic background of the variety Mercia, Rht-D1b and Rht-B1d significantly increased mean FHB severity by 52 and 35%, respectively, compared to the wild-type (rht).”
e1“wheat populations”
Claim · model-written summary
In Mercia isogenic lines, Rht-B1d increased mean FHB severity by 35% relative to wild type.
- Taxon
- wheatTriticum aestivume1
- Material
- Merciae0
- Treatment
- Rht-B1de0
- Gene
- Rht-B1de0
- Outcome
- mean FHB severitye0
- Direction
- increasede0
- Value
- 35%e0
- Comparator
- wild-type (rht)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“By means of isogenic lines in the genetic background of the variety Mercia, Rht-D1b and Rht-B1d significantly increased mean FHB severity by 52 and 35%, respectively, compared to the wild-type (rht).”
e1“wheat populations”
Claim · model-written summary
In Maris Huntsman lines, Rht alleles increased mean FHB severity by 22 to 83%, with significance only for very short lines carrying Rht-B1c or Rht-B1b+Rht-D1b.
- Taxon
- wheatTriticum aestivume1
- Material
- Maris Huntsmane0
- Treatment
- Rht allelese0
- Gene
- Rht allelese0
- Outcome
- mean FHB severitye0
- Direction
- increasede0
- Value
- 22 up to 83%e0
- Qualifier
- only the very short lines carrying Rht-B1c or Rht-B1b+Rht-D1b showed significancee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the Maris Huntsman data set, the Rht alleles increased mean FHB severity by 22 up to 83%, but only the very short lines carrying Rht-B1c or Rht-B1b+Rht-D1b showed significance.”
e1“wheat populations”
Claim · model-written summary
Sexual recombination in F. graminearum crosses yielded significant genetic variation for aggressiveness, DON and fungal mycelium production.
- Taxon
- F. graminearum
_on_Corn_(Zea_mays)_at_Waimea%2C_Hawaii.jpg?width=60)
Fusarium graminearume0 - Outcome
- genetic variation for aggressiveness, DON and fungal mycelium productione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_on_Corn_(Zea_mays)_at_Waimea%2C_Hawaii.jpg?width=500)
Verbatim
e0“The analyses of 120 progenies of the crosses from each of the highly aggressive parental F. graminearum isolates revealed significant genetic variation for aggressiveness, DON and fungal mycelium production following sexual recombination.”
Claim · model-written summary
One of the two F. graminearum progenies had stable transgressive segregants with increased aggressiveness.
- Taxon
- F. graminearumFusarium graminearume1
- Outcome
- stable transgressive segregants towards increased aggressivenesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This variation resulted in stable transgressive segregants towards increased aggressiveness in one of the two progeny.”
e1“highly aggressive parental F. graminearum isolates”
Claim · model-written summary
The field trial showed no significant wheat variety by Fusarium isolate interaction.
- Taxon
- wheatTriticum aestivume0
- Material
- European elite winter wheat varietiese0
- Interactor
- F. graminearum and F. culmorum
.jpg?width=60)
Fusarium culmorumFusarium graminearume0pathogen - Outcome
- wheat variety × isolate interactione0
- Direction
- no significante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“The factorial field trial, including eleven F. graminearum and F. culmorum isolates varying in aggressiveness and seven European elite winter wheat varieties, varying in their FHB resistance level, displayed no significant wheat variety × isolate interaction.”
Claim · model-written summary
More aggressive isolates increased FHB severity on wheat varieties with reduced FHB resistance.
- Taxon
- wheatTriticum aestivume1
- Material
- varieties with reduced FHB resistancee0
- Interactor
- isolatese0pathogen
- Outcome
- FHB severitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“isolates possessing increased aggressiveness significantly increased FHB severity and DON production at a progressive rate on varieties with reduced FHB resistance.”
e1“seven European elite winter wheat varieties”
Claim · model-written summary
More aggressive isolates increased DON production on wheat varieties with reduced FHB resistance.
- Taxon
- wheatTriticum aestivume1
- Material
- varieties with reduced FHB resistancee0
- Interactor
- isolatese0pathogen
- Outcome
- DON productione0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“isolates possessing increased aggressiveness significantly increased FHB severity and DON production at a progressive rate on varieties with reduced FHB resistance.”
e1“seven European elite winter wheat varieties”
Claim · model-written summary
The authors recommend maintaining a broad genetic base of FHB resistance using more than one unrelated resistance source and phenotypic plus marker-assisted selection.
- Taxon
- wheatTriticum aestivume0
- Outcome
- creating and maintaining a broad genetic base of FHB resistancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the selection pressure imposed on the pathogen should be minimized by creating and maintaining a broad genetic base of FHB resistance that relies on more than one genetically unrelated resistance source by combining phenotypic and marker-assisted selection to achieve a sustainably improved FHB resistance in wheat breeding.”