| 1. |
- Arnerup Christiansson, Jenny, et al.
(författare)
-
The primary module in Norway spruce defence signalling against H. annosum s.l. seems to be jasmonate-mediated signalling without antagonism of salicylate-mediated signalling
- 2013
-
Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 237, s. 1037-1045
-
Tidskriftsartikel (refereegranskat)abstract
- A key tree species for the forest industry in Europe is Norway spruce [Picea abies (L.) Karst.]. One of its major diseases is stem and butt rot caused by Heterobasidion parviporum (Fr.) Niemelä & Korhonen, which causes extensive revenue losses every year. In this study, we investigated the parallel induction of Norway spruce genes presumably associated with salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways previously observed in response to H. parviporum. Relative gene expression levels in bark samples of genes involved in the salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways after wounding and inoculation with either the saprotrophic biocontrol fungus Phlebiopsis gigantea or with H. parviporum were analysed with quantitative PCR at the site of the wound and at two distal locations from the wound/inoculation site to evaluate their roles in the induced defence response to H. parviporum in Norway spruce. Treatment of Norway spruce seedlings with methylsalicylate, methyljasmonate and inhibitors of the jasmonic acid/ethylene signalling pathway, as well as the Phenylalanine ammonia lyase inhibitor 2-aminoindan-2-phosphonic acid were conducted to determine the responsiveness of genes characteristic of the different pathways to different hormonal stimuli. The data suggest that jasmonic acid-mediated signalling plays a central role in the induction of the genes analysed in this study irrespective of their responsiveness to salicylic acid. This may suggest that jasmonic acid-mediated signalling is the prioritized module in the Norway spruce defence signalling network against H. parviporum and that there seems to be no immediate antagonism between the modules in this interaction.
|
|
| 2. |
- Arnerup, Jenny, et al.
(författare)
-
The pathogenic white-rot fungus Heterobasidion parviporum triggers non-specific defence responses in the bark of Norway spruce
- 2011
-
Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 31:11, s. 1262-1272
-
Tidskriftsartikel (refereegranskat)abstract
- Norway spruce [Picea abies (L.) Karst.] is one of the economically most important conifer species in Europe. The major pathogen on Norway spruce is Heterobasidion parviporum (Fr.) Niemelä & Korhonen. To achieve a better understanding of Norway spruce's defence mechanisms, transcriptional responses in bark to H. parviporum infection were compared with the response to wounding using cDNA-amplified fragment length polymorphism. The majority of the recovered transcript-derived fragments (TDFs) showed a similar expression pattern for infection and wounding treatment, although inoculated samples showed an enhanced reaction. Genes related to systemic acquired resistance, e.g., PR1, accumulated after H. parviporum infection. Simultaneously, several transcripts involved in various aspects of jasmonic acid (JA)- and ethylene (ET)-mediated signalling accumulated. Genes involved in the ubiquitin/proteasome system were also regulated. Expression patterns have been confirmed by quantitative polymerase chain reaction. The expression patterns of the isolated TDFs suggest that infection with H. parviporum in Norway spruce induces a broad defence, with many similarities to non-specific defence responses in angiosperms. The parallel induction of salicylic acid- and JA/ET-mediated pathways implies spatially separated responses in different cell layers, with and without hyphal contact. A set of TDFs were analysed in an independent experiment with unrelated material treated with wounding or with inoculation with H. parviporum or Phlebiopsis gigantea, verifying the original observations and underlining the non-specific defence responses. In addition, our data suggest that rerouting of carbon in secondary metabolism is an integral part of Norway spruce induced defence. We report the sequences of three 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase genes (PaDAHP1, PaDAHP2 and PaDAHP3) and their relative expression in response to wounding and infection with H. parviporum and P. gigantea. The results clearly indicate differential regulation of the three DAHPs in the induced defence responses in Norway spruce. This study gives insights into the central mechanisms in the induced defences in Norway spruce.
|
|
| 3. |
- Arnerup, Jenny, et al.
(författare)
-
Variation in growth of Heterobasidion parviporum in a full-sib family of Picea abies
- 2010
-
Ingår i: Scandinavian Journal of Forest Research. - : Taylor & Francis. - 0282-7581 .- 1651-1891. ; 25:2, s. 106-110
-
Tidskriftsartikel (refereegranskat)abstract
- Heterobasidion parviporum (Fr.) Niemelä & Korhonen and Heterobasidion annosum (Fr.) Bref. sensu lato are some of the major forest pathogens in the northern hemisphere causing root and butt rot to conifers. The relative susceptibility to H. parviporum was investigated in a full-sib family of Norway spruce [Picea abies (L.) Karst.] by inoculating a set of 252 cloned progenies from a controlled cross. Four ramets of each progeny were used and the 2-year-old rooted cuttings were incubated for 6 weeks under greenhouse conditions. The condition of the cuttings was assessed visually and all the plants were in excellent vigour with no mortality recorded during the experiment. To score the relative susceptibility, lesion length in the inner bark and fungal growth in the sapwood were measured. Among the progenies, significant differences were found for fungal growth in the sapwood (p<0.0005). There was no significant difference for lesion length; however, there was a significant positive correlation between fungal growth and lesion length. The broad-sense heritability was 0.11 for fungal growth. This shows that the genetic component for susceptibility to H. parviporum can be detected even within a full-sib family of Norway spruce and that there is a potential for mapping quantitative trait loci for this trait in Norway spruce.
|
|
| 4. |
- Brodde, Laura, et al.
(författare)
-
A Reliable and Simple Method for the Production of Viable Pycnidiospores of the Pine Pathogen Diplodia sapinea and a Spore-Based Infection Assay on Scots Pine
- 2023
-
Ingår i: Plant Disease. - 0191-2917 .- 1943-7692. ; 107, s. 3370-3377
-
Tidskriftsartikel (refereegranskat)abstract
- Diplodia sapinea is a globally distributed opportunistic fungal pathogen of conifers that causes severe production losses in forestry. The fungus frequently colonizes pine trees as an endophyte without causing visible symptoms but can become pathogenic when the host plant is weakened by stress, such as drought or heat. Forest damage might therefore further increase due to the effects of climate change. The future development of control strategies depends on a better understanding of the fungus' biology, which requires experimental methods for its investigation in the laboratory. An efficient, standardized protocol for the production and storage of highly viable pycnidiospores was developed, and a spore-based infection method was devised. We compared infection rates of dormant and actively growing, wounded, or nonwounded Scots pine seedlings inoculated with in vitro-produced spores and mycelium from agar-plugs. Spores were a much more efficient inoculum for causing disease symptoms on wounded plants than the conventional agar plug. The application of spores on nonwounded plants lead to high rates of asymptomatic infection, suggesting endophytic fungal development. These methods enable standardized spore infection and virulence assays and promote D. sapinea as a model organism for studying the switch from endophytic to pathogenic life styles of forest pathogens.
|
|
| 5. |
- Brodde, Laura, et al.
(författare)
-
Diplodia sapinea as a contributing factor in the crown dieback of Scots pine (Pinus sylvestris) after a severe drought
- 2023
-
Ingår i: Forest Ecology and Management. - 0378-1127 .- 1872-7042. ; 549
-
Tidskriftsartikel (refereegranskat)abstract
- The frequency and impact of drought on global ecosystems have increased within the last century, while drought has affected tree health in many regions. Diplodia sapinea is a widespread, opportunistic pathogen infecting most conifers, causing Diplodia tip blight, thriving on hosts impacted by stress such as drought, heat, or mechanical wounding. In summer of 2018, a large-scale drought was recorded all over Europe. In late summer, pine trees all over Gotland showed crown dieback, where necrotic twigs and needles were found, especially in the upper part of the crowns. Symptoms were consistent with a potential outbreak of D. sapinea. Effects of the combination of drought and Diplodia tip blight on mortality or recovery of Scots pine in Nordic conditions are unknown. This study confirmed the presence and potential contribution of D. sapinea in the observed damages of Scots pine. Shoot blight and drought led to crown defoliation which was observed one year post-drought, while trees showed a clear recovery of newly grown shoots within the second year. Severely affected pines (>70% of the upper third of the crown with shoot blight) showed increased mortality. Recovery of the surviving trees was independent of previous dieback levels. Diplodia sapinea was most abundant in twigs with shoot blight of the symptomatic trees compared to healthy-looking twigs from the same trees and asymptomatic trees in affected and healthy pine stands. Sampling on affected and healthy sites showed possible endophytic infections with low abundance within healthy-looking twigs. Spore deposition of D. sapinea was monitored on healthy and affected sites for two consecutive years after crown damages occurred to confirm the presence of the opportunistic pathogen in the affected region. Spore deposition was observed during all seasons and correlated with high precipitation during sampling. Our observations provide insights into the emergence of Diplodia tip blight in the Northern countries and underline the potential impact of D. sapinea on tree health in the course of a changing climate.
|
|
| 6. |
- Capador‐Barreto, Hernán D., et al.
(författare)
-
Killing two enemies with one stone? : Genomics of resistance to two sympatric pathogens in Norway spruce
- 2021
-
Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 30:18, s. 4433-4447
-
Tidskriftsartikel (refereegranskat)abstract
- Trees must cope with the attack of multiple pathogens, often simultaneously during their long lifespan. Ironically, the genetic and molecular mechanisms controlling this process are poorly understood. The objective of this study was to compare the genetic component of resistance in Norway spruce to Heterobasidion annosum s.s. and its sympatric congener Heterobasidion parviporum. Heterobasidion root- and stem-rot is a major disease of Norway spruce caused by members of the Heterobasidion annosum species complex. Resistance to both pathogens was measured using artificial inoculations in half-sib families of Norway spruce trees originating from central to northern Europe. The genetic component of resistance was analysed using 63,760 genome-wide exome-capture sequenced SNPs and multitrait genome-wide associations. No correlation was found for resistance to the two pathogens; however, associations were found between genomic variants and resistance traits with synergic or antagonist pleiotropic effects to both pathogens. Additionally, a latitudinal cline in resistance in the bark to H. annosum s.s. was found; trees from southern latitudes, with a later bud-set and thicker stem diameter, allowed longer lesions, but this was not the case for H. parviporum. In summary, this study detects genomic variants with pleiotropic effects which explain multiple disease resistance from a genic level and could be useful for selection of resistant trees to both pathogens. Furthermore, it highlights the need for additional research to understand the evolution of resistance traits to multiple pathogens in trees.
|
|
| 7. |
- Chaudhary, Rajiv, et al.
(författare)
-
Combining transcriptomics and genetic linkage based information to identify candidate genes associated with Heterobasidion-resistance in Norway spruce
- 2020
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- The Heterobasidion annosum s.l species complex comprises the most damaging forest pathogens to Norway spruce. We revisited previously identified Quantitative Trait Loci (QTLs) related to Heterobasidion-resistance in Norway spruce to identify candidate genes associated with these QTLs. We identified 329 candidate genes associated with the resistance QTLs using a gene-based composite map for Pinaceae. To evaluate the transcriptional responses of these candidate genes to H. parviporum, we inoculated Norway spruce plants and sequenced the transcriptome of the interaction at 3 and 7 days post inoculation. Out of 298 expressed candidate genes 124 were differentially expressed between inoculation and wounding control treatment. Interestingly, PaNAC04 and two of its paralogs in the subgroup III-3 of the NAC family transcription factors were found to be associated with one of the QTLs and was also highly induced in response to H. parviporum. These genes are possibly involved in the regulation of biosynthesis of flavonoid compounds. Furthermore, several of the differentially expressed candidate genes were associated with the phenylpropanoid pathway including a phenylalanine ammonia-lyase, a cinnamoyl-CoA reductase, a caffeoyl-CoA O-methyltransferase and a PgMYB11-like transcription factor gene. Combining transcriptome and genetic linkage analyses can help identifying candidate genes for functional studies and molecular breeding in non-model species.
|
|
| 8. |
- Chaudhary, Rajiv, et al.
(författare)
-
Marker-Trait Associations for Tolerance to Ash Dieback in Common Ash (Fraxinus excelsior L.)
- 2020
-
Ingår i: Forests. - : MDPI. - 1999-4907. ; 11:10
-
Tidskriftsartikel (refereegranskat)abstract
- Common ash (Fraxinus excelsior L.) is a tree species of significant ecological and economic importance that has suffered a devastating decline since the 1990s in Europe. Native ash species are being threatened by the alien invasive fungus Hymenoscyphus fraxineus, which causes ash dieback. The main goal of the study was to develop markers for traits related to tolerance to ash dieback and to investigate whether genotypes selected for tolerance were genetically different from susceptible wild populations. We phenotyped 326 ash trees from Sweden for disease severity and genotyped them using 63 amplicon-derived single-nucleotide polymorphism (SNP) markers derived from genes in 40 scaffolds spanning 8 MB in total, which represents approximately 1% of the ash genome. We used a mixed linear model to test for an association between genotypic variation at these loci and disease severity of ash. In total, two SNPs were found to have significant associations. One non-synonymous SNP associated with the disease severity of ash was found in a gene predicted to encode a subtilisin-related peptidase S8/S53 domain. A second marginally significant marker was associated with an LRR gene. Our results demonstrate an inexpensive time-effective method for generating genomic data that could have potential for use in future tree breeding programs and provide information for marker-assisted selection. Our study also showed a low differentiation between genotypes selected for disease tolerance and the wild population of ash representing a range of susceptibilities to ash dieback, indicating opportunities for further selection without significantly losing genetic diversity in the ash population.
|
|
| 9. |
- Chen, Zhi‑Qiang, et al.
(författare)
-
Early selection for resistance to Heterobasidion parviporum in Norway spruce is not likely to adversely affect growth and wood quality traits in late-age performance
- 2018
-
Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 137:4, s. 517-525
-
Tidskriftsartikel (refereegranskat)abstract
- Infections with Heterobasidion parviporum devalue the Norway spruce timber as the decayed wood does not meet the necessary quality requirements for sawing. To evaluate the incorporation of disease resistance in the Norway spruce breeding strategy, an inoculation experiment with H. parviporum on 2-year-old progenies of 466 open-pollinated families was conducted under greenhouse (nursery) conditions. Lesion length in the phloem (LL), fungal growth in sapwood (FG) and growth (D) were measured on an average of 10 seedlings for each family. The genetic variation and genetic correlations between both LL, FG and growth in the nursery trial and wood quality traits measured previously from 21-year old trees in two progeny trials, including solid-wood quality traits (wood density, and modulus of elasticity) and fiber properties traits (radial fiber width, tangential fiber width, fiber wall thickness, fiber coarseness, microfibril angle and fiber length). For both LL and FG, large coefficients of phenotypic variation (> 26%) and genetic variation (> 46%) were detected. Heritabilities of LL and FG were 0.33 and 0.42, respectively. We found no significant correlations between wood quality traits and growth in the field progeny trials with neither LL nor FG in the nursery trial. Our data suggest that the genetic gains may reach 41 and 52% from mass selection by LL and FG, respectively. Early selection for resistance to H. parviporum based on assessments of fungal spread in the sapwood in nursery material, FG, will not adversely affect growth and wood quality traits in late-age performance.
|
|
| 10. |
- Cleary, Michelle, et al.
(författare)
-
Genotypes of Fraxinus excelsior with different susceptibility to the ash dieback pathogen Hymenoscyphus pseudoalbidus and their response to the phytotoxin viridiol - A metabolomic and microscopic study
- 2014
-
Ingår i: Phytochemistry. - : Elsevier BV. - 0031-9422 .- 1873-3700. ; 102, s. 115-125
-
Tidskriftsartikel (refereegranskat)abstract
- Eight European ash (Fraxinus excelsior) genotypes with different known susceptibility to Hymenoscyphus pseudoalbidus were tested against the phytotoxin viridiol and their response described at the microscopic and metabolomic level. All ash genotypes were sensitive to the toxin and necrosis was detectable after 24 h. Among the three viridiol concentrations used in the experiment, the lowest concentration (14.7 mu M) yielded markedly lower mean damage scores compared to those resulting from seedlings tested at higher dosages. The highest damage scores were associated with the susceptible ash clones S-101, S-106 and S-125, but also with resistant clone R-104. Three resistant clones (R-131, R-121, and R-118) had lower mean damage scores compared to susceptible clones. Wilting of leaves was more common 48 h after treatment and more pronounced on seedlings with high damage scores. The resulting lesions generally lacked browning of tissue and displayed only surface disruption of cells in direct contact with the toxin. A delay in symptom development was evident on all five resistant clones tested with the two higher concentrations of viridiol. LC-HRMS and MS/MS analyses of ash seedling extracts suggest several secoiridoid compounds as well as compounds related to abscisic acid (ABA) to be produced in response to viridiol. ABA-cysteine and xanthoxin were found at significantly higher concentrations in susceptible clones compared to resistant clones after treatment with viridiol, suggesting a primary role of ABA in response to stress. The results observed in this study suggest that genetic resistance to H. pseudoalbidus among ash genotypes may be explained, in part, by the varied response to phytotoxins produced by the fungus. (C) 2014 Elsevier Ltd. All rights reserved.
|
|
