Abstract
The emergence of new fungal pathogens through hybridization represents a serious challenge for agriculture. Hybridization between the wheat mildew (Blumeria graminis f. sp. tritici) and rye mildew (B. graminis f. sp. secalis) pathogens has led to the emergence of a new mildew form (B. graminis f. sp. triticale) growing on triticale, a man-made amphiploid crop derived from crossing rye and wheat, which was originally resistant to the powdery mildew disease. The identification of the genetic basis of host adaptation in triticale mildew has been hampered by the lack of a reference genome. Here, we report the 141.4-Mb reference assembly of triticale mildew isolate THUN-12 derived from long-read sequencing and genetic map-based scaffolding. All 11 triticale mildew chromosomes were assembled from telomere-to-telomere and revealed that 19.7% of the hybrid genome was inherited from the rye mildew parental lineage. We identified lineage-specific regions in the hybrid, inherited from the rye or wheat mildew parental lineages, that harbor numerous bona fide candidate effectors. We propose that the combination of lineage-specific effectors in the hybrid genome is crucial for host adaptation, allowing the fungus to simultaneously circumvent the immune systems contributed by wheat and rye in the triticale crop. In line with this, we demonstrate the functional transfer of the SvrPm3 effector from wheat to triticale mildew, a virulence effector that specifically suppresses resistance of the wheat Pm3 allelic series. This transfer is the likely underlying cause for the observed poor effectiveness of several Pm3 alleles against triticale mildew and exemplifies the negative implications of pathogen hybridizations on resistance breeding. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
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Claims 7
Claim · model-written summary
A 141.4-Mb reference assembly was produced for triticale mildew isolate THUN-12.
- Taxon
- triticale
×Triticosecalee0 - Interactor
- triticale mildewe0pathogen
- Outcome
- reference assemblye0
- Value
- 141.4-Mbe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“141.4-Mb reference assembly of triticale mildew isolate THUN-12”
Claim · model-written summary
All 11 triticale mildew chromosomes were assembled telomere to telomere.
- Taxon
- triticale×Triticosecalee0
- Outcome
- chromosomes were assembled from telomere-to-telomeree0
- Value
- 11e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All 11 triticale mildew chromosomes were assembled from telomere-to-telomere”
Claim · model-written summary
The hybrid mildew genome inherited 19.7% from rye mildew.
- Taxon
- triticale×Triticosecalee1
- Interactor
- rye mildewe0pathogen
- Outcome
- hybrid genome was inherited from the rye mildew parental lineagee0
- Value
- 19.7%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“19.7% of the hybrid genome was inherited from the rye mildew parental lineage”
e1“growing on triticale”
Claim · model-written summary
Hybrid lineage-specific regions inherited from rye or wheat mildew harbored numerous candidate effectors.
- Taxon
- triticale×Triticosecalee1
- Outcome
- lineage-specific regions in the hybrid, inherited from the rye or wheat mildew parental lineages, that harbor numerous bona fide candidate effectorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lineage-specific regions in the hybrid, inherited from the rye or wheat mildew parental lineages, that harbor numerous bona fide candidate effectors”
e1“growing on triticale”
Claim · model-written summary
The authors propose that combined lineage-specific effectors enable host adaptation by circumventing wheat and rye immunity in triticale.
- Taxon
- triticale×Triticosecalee0
- Outcome
- host adaptatione0
- Qualifier
- combination of lineage-specific effectorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“combination of lineage-specific effectors in the hybrid genome is crucial for host adaptation, allowing the fungus to simultaneously circumvent the immune systems contributed by wheat and rye in the triticale crop”
Claim · model-written summary
SvrPm3 transferred functionally from wheat to triticale mildew and suppresses resistance of wheat Pm3 alleles.
- Taxon
- wheat
Triticum aestivume0 - Interactor
- triticale mildewe0pathogen
- Gene
- SvrPm3e0
- Outcome
- suppresses resistance of the wheat Pm3 allelic seriese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“functional transfer of the SvrPm3 effector from wheat to triticale mildew, a virulence effector that specifically suppresses resistance of the wheat Pm3 allelic series”
Claim · model-written summary
Several Pm3 alleles had poor effectiveness against triticale mildew.
- Taxon
- wheatTriticum aestivume1
- Interactor
- triticale mildewe0pathogen
- Gene
- Pm3e0
- Outcome
- poor effectiveness of several Pm3 allelese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“observed poor effectiveness of several Pm3 alleles against triticale mildew”
e1“wheat Pm3 allelic series”