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- Kälin, Carol
(författare)
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Aphanomyces root rot in pea : genomic insights into pathogen diversity and disease resistance
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cultivation of vining pea (Pisum sativum) faces significant challenges due to root rot, primarily caused by Aphanomyces euteiches, a soil-borne oomycete pathogen. Pea cultivars resistant to aphanomyces root rot (ARR) are currently lacking and common mitigation methods include crop rotation and avoidance of highly infested fields. The thesis work integrates population genetic, transcriptomic, and comparative genomic analyses to enhance our understanding of aphanomyces root rot in pea, providing valuable knowledge for future breeding and disease management efforts. Genetic diversity analyses of A. euteiches in Europe revealed three distinct groups on a north to south gradient: a north-eastern (NE), central European (CE) and southern (S) group. Shared multilocus genotypes between geographically distant regions indicate genetic movement between countries. The S group differed in virulence and oospore size compared to NE and CE and displayed signs of genetic isolation, all of them indications to view group S as a separate Aphanomyces species. The use of partial resistance in the pea genotype PI180693 was assessed in crosses with the susceptible, commercial cultivar Linnea in controlled and field conditions. The new breeding lines displayed enhanced disease resistance to ARR compared to the susceptible parent. The results further highlighted the difficulties of predicting breeding line performance in the field based on trials in controlled conditions and of breaking the linkage between ARR resistance and unfavourable breeding traits in classical breeding. Characterization of the transcriptomic immune response in Linnea and PI180693 to A. euteiches infection showed to be time- and genotype-dependent, involving differential regulation of transcription factors and genes associated with hormone signalling. Cross-referencing with genes located in resistance quantitative trait loci led to the identification of 39 candidate disease resistance genes, including a putative immune receptor with NLR structure that was polymorphic between the pea genotypes.
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| 2. |
- Kälin, Carol, et al.
(författare)
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Evaluation of pea genotype PI180693 partial resistance towards aphanomyces root rot in commercial pea breeding
- 2023
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The cultivation of vining pea (Pisum sativum) faces a major constraint with root rot diseases, caused by a complex of soil-borne pathogens including the oomycetes Aphanomyces euteiches and Phytophtora pisi. Disease resistant commercial varieties are lacking but the landrace PI180693 is used as a source of partial resistance in ongoing pea breeding programs. In this study, the level of resistance and their interaction with A. euteiches virulence levels of six new back-crossed pea breeding lines, deriving from the cross between the susceptible commercial cultivar Linnea and PI180693, were evaluated for their resistance towards aphanomyces root rot in growth chamber and green house tests. Resistance towards mixed infections by A. euteiches and P. pisi and commercial production traits were evaluated in field trials. In growth chamber trials, pathogen virulence levels had a significant effect on plant resistance, as resistance was more consistent against A. euteiches strains exhibiting high or intermediate virulence compared with lowly virulent strains. In fact, line Z1701-1 showed to be significantly more resistant than both parents when inoculated with a lowly virulent strain. In two separate field trials in 2020, all six breeding lines performed equally well as the resistant parent PI180693 at sites only containing A. euteiches, as there were no differences in disease index. In mixed infections, PI180693 exhibited significantly lower disease index scores than Linnea. However, breeding lines displayed higher disease index scores compared with PI180693, indicating higher susceptibility towards P. pisi. Data on seedling emergence from the same field trials suggested that PI180693 was particularly sensitive towards seed decay/damping off disease caused by P. pisi. Furthermore, the breeding lines performed equally well as Linnea in traits important for green pea production, again emphasizing the commercial potential. In summary, we show that the resistance from PI180693 interacts with virulence levels of the pathogen A. euteiches and is less effective towards root rot caused by P. pisi. Our results show the potential use of combining PI180693 partial resistance against aphanomyces root rot with commercially favorable breeding traits in commercial breeding programs.
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| 3. |
- Kälin, Carol, et al.
(författare)
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Genetic diversity of the pea root pathogen Aphanomyces euteiches in Europe
- 2022
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Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 71, s. 1570-1578
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Tidskriftsartikel (refereegranskat)abstract
- The oomycete pathogen Aphanomyces euteiches causes root rot in various legume species. In this study we focused on A. euteiches causing root rot in pea (Pisum sativum), thereby being responsible for severe yield losses in pea production. We aimed to understand the genetic diversity of A. euteiches in Europe, covering a north-to-south gradient spanning from Sweden, Norway and Finland to the UK, France and Italy. A collection of 85 European A. euteiches strains was obtained, all isolated from infected pea roots from commercial vining pea cultivation fields. The strains were genotyped using 22 simple-sequence repeat markers. Multilocus genotypes were compiled and the genetic diversity between individual strains and population structure between countries was analysed. The population comprising strains from Italy was genetically different and did not share ancestry with any other population. Also, strains originating from Finland and the eastern parts of Sweden were found to be significantly different from the other populations, while strains from the rest of Europe were more closely related. A subset of 10 A. euteiches strains from four countries was further phenotyped on two susceptible pea genotypes, as well as on one genotype with partial resistance towards A. euteiches. All strains were pathogenic on all pea genotypes, but with varying levels of disease severity. No correlation between the genetic relatedness of strains and virulence levels was found. In summary, our study identified three genetically distinct groups of A. euteiches in Europe along a north-to-south gradient, indicating local pathogen differentiation.
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| 4. |
- Kälin, Carol, et al.
(författare)
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Transcriptomic analysis identifies candidate genes for Aphanomyces root rot disease resistance in pea
- 2024
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Ingår i: BMC Plant Biology. - 1471-2229. ; 24
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundAphanomyces euteiches is a soil-borne oomycete that causes root rot in pea and other legume species. Symptoms of Aphanomyces root rot (ARR) include root discoloration and wilting, leading to significant yield losses in pea production. Resistance to ARR is known to be polygenic but the roles of single genes in the pea immune response are still poorly understood. This study uses transcriptomics to elucidate the immune response of two pea genotypes varying in their levels of resistance to A. euteiches.ResultsIn this study, we inoculated roots of the pea (P. sativum L.) genotypes 'Linnea' (susceptible) and 'PI180693' (resistant) with two different A. euteiches strains varying in levels of virulence. The roots were harvested at 6 h post-inoculation (hpi), 20 hpi and 48 hpi, followed by differential gene expression analysis. Our results showed a time- and genotype-dependent immune response towards A. euteiches infection, involving several WRKY and MYB-like transcription factors, along with genes associated with jasmonic acid (JA) and abscisic acid (ABA) signaling. By cross-referencing with genes segregating with partial resistance to ARR, we identified 39 candidate disease resistance genes at the later stage of infection. Among the genes solely upregulated in the resistant genotype 'PI180693', Psat7g091800.1 was polymorphic between the pea genotypes and encoded a Leucine-rich repeat receptor-like kinase reminiscent of the Arabidopsis thaliana FLAGELLIN-SENSITIVE 2 receptor.ConclusionsThis study provides new insights into the gene expression dynamics controlling the immune response of resistant and susceptible pea genotypes to A. euteiches infection. We present a set of 39 candidate disease resistance genes for ARR in pea, including the putative immune receptor Psat7g091800.1, for future functional validation.
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