| 1. |
- Andersson, Björn, et al.
(författare)
-
Spatio-temporal distribution of DMI and SDHI fungicide resistance of Zymoseptoria tritici throughout Europe based on frequencies of key target-site alterations
- 2021
-
Ingår i: Pest Management Science. - : Wiley. - 1526-498X .- 1526-4998. ; 77, s. 5576-5588
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND Over the past decade, demethylation inhibitor (DMI) and succinate dehydrogenase inhibitor (SDHI) fungicides have been extensively used to control to septoria tritici blotch, caused by Zymoseptoria tritici on wheat. This has led to the development and selection of alterations in the target-site enzymes (CYP51 and SDH, respectively). RESULTS Taking advantage of newly and previously developed qPCR assays, the frequency of key alterations associated with DMI (CYP51-S524T) and SDHI (SDHC-T79N/I, C-N86S and C-H152R) resistance was assessed in Z. tritici-infected wheat leaf samples collected from commercial crops (n = 140) across 14 European countries prior to fungicide application in the spring of 2019. This revealed the presence of a West to East gradient in the frequencies of the most common key alterations conferring azole (S524T) and SDHI resistance (T79N and N86S), with the highest frequencies measured in Ireland and Great Britain. These observations were corroborated by sequencing (CYP51 and SDH subunits) and sensitivity phenotyping (prothioconazole-desthio and fluxapyroxad) of Z. tritici isolates collected from a selection of field samples. Additional sampling made at the end of the 2019 season confirmed the continued increase in frequency of the targeted alterations. Investigations on historical leaf DNA samples originating from different European countries revealed that the frequency of all key alterations (except C-T79I) has been gradually increasing over the past decade. CONCLUSION Whilst these alterations are quickly becoming dominant in Ireland and Great Britain, scope still exists to delay their selection throughout the wider European population, emphasizing the need for the implementation of fungicide antiresistance measures.
|
|
| 2. |
- Berlin, Anna, et al.
(författare)
-
Disease development and genotypic diversity of Puccinia graminis f. sp avenae in Swedish oat fields
- 2013
-
Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 62, s. 32-40
-
Tidskriftsartikel (refereegranskat)abstract
- The disease development and population structure of Puccinia graminis f. sp. avenae, which causes stem rust on oats, were studied to investigate if sexual reproduction plays an important role in the epidemiology of the disease. The genetic population structure of P. graminis f. sp. avenae in Sweden was investigated by sampling 10 oat fields in July and August 2008 and seven fields during the same period in 2009. Nine single-pustule isolates were first used to test simple sequence repeat (SSR) markers developed for P. graminis f. sp. tritici. Eleven of the 68 tested SSR markers were useful for genotyping P. graminis f. sp. avenae. For the main study, DNA from single uredinia was extracted and the SSR markers were used to genotype 472 samples. Both allelic and genotypic diversity were high in all fields, indicating that P. graminis f. sp. avenae undergoes regular sexual reproduction in Sweden. No significant relationship between genetic and geographic distances was found. Disease development was studied on two farms during 2008 and 2009. The apparent infection rates ranged between 0.17 and 0.55, indicating the potential for rapid disease development within fields. The incidence of oat stem rust has increased recently in Sweden. One possible explanation is a resurgence of its alternate host, barberry (Berberis spp.), after the repeal of the barberry eradication law in 1994. Barberry is present in several grain-producing areas in Sweden, which supports the conclusion that P. graminis f. sp. avenae undergoes regular sexual reproduction there.
|
|
| 3. |
|
|
| 4. |
- Berlin, Anna, et al.
(författare)
-
Genetic variation in Puccinia graminis collected from oats, rye, and barberry
- 2012
-
Ingår i: Phytopathology. - 0031-949X .- 1943-7684. ; 102, s. 1006-1012
-
Tidskriftsartikel (refereegranskat)abstract
- Puccinia graminis, the causal agent of stem rust, was collected from its alternate host barberry (Berberis spp.) and two different uredinial hosts, oats (Avena sativa) and rye (Secale cereale). The samples were analyzed using 11 polymorphic simple sequence repeat (SSR) markers. There were large differences between fungal populations on oats (P. graminis f. sp. avenae) and rye (P. graminis f. sp. secalis), and the genetic variation within the different formae speciales was also high. It was possible to distinguish between the two formae speciales on barberry. Additional genotypic groups not present in the field samples from oats and rye were also identified on barberry. Our results confirm the importance of barberry in maintaining the populations of P. graminis in Sweden and the importance of the sexual stage for the survival of the pathogen.
|
|
| 5. |
|
|
| 6. |
- Berlin, Anna, et al.
(författare)
-
Population structure of Puccinia graminis f.sp. avenae in Sweden
- 2009
-
Konferensbidrag (refereegranskat)abstract
- Stem rust, caused by Puccinia graminis, is a serious disease of cereal crops and in the past this pathogen has caused severe epidemics worldwide. Incidence of oat stem rust in Sweden has increased recently. One possible explanation could be an increase in the occurrence of barberry (Berberis spp.), on which P. graminis sexual cycle can be completed, due to the repeal of the barberry eradication law in 1994. The epidemiology of P. graminis is not well known in Sweden. In this project, the population biology and epidemiology of P. graminis f. sp. avenae are investigated. Multiple samples of P. graminis f. sp. avenae were collected from 33 different oat fields during the summer of 2008. Single pustule isolates were obtained from the field collections and increased in a greenhouse. DNA from these isolates was extracted from urediniospores and infected leaf tissue and was used to screen Simple Sequence Repeat (SSR) markers developed for P. graminis f.sp. tritici. Some of the markers successfully produced amplicons indicating that they will be useful for genotyping isolates of P. graminis f. sp. avenae. Allele sizes for P. graminis f. sp. avenae were different than those from a U.S. reference isolate of P. graminis f.sp. tritici. A selected set of North American isolates of P. graminis f.sp. avenae are also included in the study. The results from this study will indicate if the oat stem rust pathogen in Sweden is a sexual population and the role of barberry in the epidemiology of P. graminis f. sp. avenae
|
|
| 7. |
|
|
| 8. |
- Berlin, Anna, et al.
(författare)
-
Rusts on Berberis spp. in Sweden
- 2012
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The barberry eradication law in Sweden was repealed in 1994, and incidence of barberry ( Berberis spp.) has increased as a consequence. To investigate the importance of barberry in survival and reproduction of cereal rust pathogens, aecia were collected during 2008-2010. Uredinia of P. graminis were collected from oats ( Avena sativa ) and rye ( Secale cereale ). The samples were analyzed using 11 polymorphic SSR markers. In addition, ITS (Internal transcript spacer region) and EF-1 α (Elongation factor-1 α ) were sequenced in samples collected from barberry, and the identit ies of the species were determined by comparing the sequences to BLAST databases. Cross-section al morpholog ies of a selection of samples of aecia and aeciospores were also examined. SSR marker results revealed large differences between the fungal populations on oats ( P. graminis f. sp. avenae ) and rye ( P. graminis f. sp. secalis ), and genetic variation within the different formae speciales was also high. It was possible to distinguish between the two formae speciales on barberry by SSR markers, ITS sequences and morphological characteristics. Additional genotypic groups of P. graminis not present in samples from either oats or rye were identified on barberry with the SSR markers. Our results confirm the importance of barberry for survival and maintenance of P. graminis populations in Sweden. A not yet identified species showing similar sequences to P. striiformis and P. poa-nemoralis was found on barberry.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
- Bila, Joao, et al.
(författare)
-
First report of 'Candidatus Phytoplasma palmicola' detection in the planthopper Diostrombus mkurangai in Mozambique
- 2017
-
Ingår i: Bulletin of insectology. - 1721-8861. ; 70, s. 45-48
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of putative insect species vectors of the coconut lethal yellowing disease (CLYD) in Mozambique is crucial to develop an effective disease management plan. Hemiptera specimens from the families Derbidae and Pentatomidae were collected in the Inhambane and Zambezia provinces of the coastal region of Mozambique in 2014, covering the two main growing seasons. Sequence analyses of the 16S rRNA gene were used for phytoplasma clustering. Polymerase chain reaction (PCR) amplification was performed employing three different primer sets specific for phytoplasma. BLAST sequence comparison and phylogenetic analysis of the 16S rDNA PCR products revealed that collected specimens of Derbidae Diostrombus mkurangai Wilson were carrying the CLYD phytoplasma. Virtual RFLP analyses of the obtained sequences confirmed this assigning the detected phytoplasmas to the 16SrXX-A subgroup, confirming that they are 'Candidatus Phytoplasma palmicola'-related strains. This is the first detection of a 'Candidatus Phytoplasma palmicola'-related strain in D. mkurangai.
|
|
| 12. |
- Bila, Joao, et al.
(författare)
-
High diversity, expanding populations and purifying selection in phytoplasmas causing coconut lethal yellowing in Mozambique
- 2015
-
Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 64, s. 597-604
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the putative phytoplasma species causing coconut lethal yellowing disease in Mozambique and Tanzania were characterized. The 16S rRNA and secA genes were sequenced. Phylogenetic analysis revealed that Mozambican coconut phytoplasmas belong to three different types: Candidatus Phytoplasma palmicola' 16SrXXII-A, a second strain that was previously isolated in Tanzania and Kenya (16SrIV-C), and a third strain that was different from all known lethal yellowing phytoplasma species. The third strain potentially represents a novel species and is closely related to pine phytoplasma. Co-infection with Ca. Phytoplasma pini'-related and Ca. Phytoplasma palmicola' 16SrXXII-A strains was observed. Furthermore, sequence variation in Ca. Phytoplasma palmicola' at the population level was consistent with purifying selection and population expansion.
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
- Capador-Barreto, Hernán Dario, et al.
(författare)
-
Development of microsatellite markers for Thekopsora areolata, the causal agent of cherry spruce rust
- 2018
-
Ingår i: Forest Pathology. - : Wiley. - 1437-4781 .- 1439-0329. ; 48
-
Tidskriftsartikel (refereegranskat)abstract
- Cherry spruce rust is a fungal disease of Norway spruce cones caused by Thekopsora areolata and responsible for significant losses in seed production in Sweden and Finland. Here, we report the first set of nine microsatellites, which will allow an effective genetic fingerprinting of T.areolata. The markers were isolated using the FIASCO method and were characterized using DNA from 49 single aecia sampled from spruce cones in three different seed orchards in Sweden. Eight of the nine markers were shown to be polymorphic among the aecia. The markers were unlinked and are therefore suitable for future population genetic studies.
|
|
| 16. |
- Capador-Barreto, Hernán Dario, et al.
(författare)
-
Genetic evidence for sexual reproduction and multiple infections of Norway spruce cones by the rust fungus Thekopsora areolata
- 2020
-
Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 10, s. 7389-7403
-
Tidskriftsartikel (refereegranskat)abstract
- Rust fungi are obligate parasites, of plants, with complex and in many cases poorly known life cycles which may include host alteration and up to five spore types with haploid, diploid, and dikaryotic nuclear stages. This study supports thatThekopasora areolata, the causal agent of cherry-spruce rust in Norway spruce, is a macrocyclic heteroecious fungus with all five spore stages which uses two host plantsPrunus padusandPicea abiesto complete its life cycle. High genotypic diversity without population structure was found, which suggests predominantly sexual reproduction, random mating and a high gene flow within and between the populations in Fennoscandia. There was no evidence for an autoecious life cycle resulting from aeciospore infection of pistillate cones that would explain the previously reported rust epidemics without the alternate host. However, within cones and scales identical multilocus genotypes were repeatedly sampled which can be explained by vegetative growth of the fertilized mycelia or repeated mating of mycelium by spermatia of the same genotype. The high genotypic diversity within cones and haplotype inference show that each pistillate cone is infected by several basidiospores. This study provides genetic evidence for high gene flow, sexual reproduction, and multiple infections of Norway spruce cone by the rust fungusT. areolatawhich expands the general understanding of the biology of rust fungi.
|
|
| 17. |
|
|
| 18. |
- Martin, Thomas, et al.
(författare)
-
Identification of a Differentially Expressed TIR-NBS-LRR Gene in a Major QTL Associated to Leaf Rust Resistance in Salix
- 2016
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- An earlier identified major quantitative trait locus for resistance towards the willow leaf rust fungus Melampsora larici-epitea in a Salix viminalis x (S. viminalis x S. schwerinii) population was used to identify potential resistance genes to the rust pathogen. Screening a genomic bacterial artificial chromosome library with markers from the peak position of the QTL region revealed one gene with TIR-NBS-LRR (Toll Interleukin1 Receptor-Nucleotide Binding Site-Leucine-Rich Repeat) domain structure indicative of a resistance gene. The resistance gene analog was denoted RGA1 and further analysis revealed a number of non-synonymous single nucleotide polymorphisms in the LRR domain between the resistant and susceptible Salix genotypes. Gene expression levels under controlled conditions showed a significantly lower constitutive expression of RGA1 in the susceptible genotype. In addition, the susceptible genotype showed a significantly reduced expression level of the RGA1 gene at 24 hours post inoculation with M. larici-epitea. This indicates that the pathogen may actively suppress RGA1 gene expression allowing a compatible plant-pathogen interaction and causing infection.
|
|
| 19. |
- Persson, Torgny, et al.
(författare)
-
The inheritance of resistance to Scots pine blister rust in Pinus sylvestris
- 2024
-
Ingår i: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 568
-
Tidskriftsartikel (refereegranskat)abstract
- Scots pine blister rust is a rust fungal pathogen that has become more noticeable in recent years and has increased in recorded incidence in Northern Scandinavia. This has prompted an initiation of resistance breeding to the fungus in the Northern Swedish pine breeding program. To accomplish this, it is necessary to evaluate the breeding potential for increased resistance and putative impact on other breeding objective traits that may have genetic correlations to resistance. To assess the potential of the trait to be included in the breeding program we examined half sibling families in four trials of which two had high incidence of Scots pine blister rust in a range of 25.4–42.1 %. We assessed vitality and height in one year and rust lesion frequency at two later time points. We found that rust resistance had a narrow sense heritability of 0.36–0.41, while vitality reached 0.17 and height 0.25. We found a high genetic correlation between sites in rust resistance and no genetic correlation between rust resistance and either vitality or height. This means that breeding for increased resistance in Scots pine can be done effectively without risking a negative impact on established breeding objective traits and that resistance is stable across environments.
|
|
| 20. |
- Ronnberg-Wastljung, Ann-Christin, et al.
(författare)
-
Resistance to Melampsora larici-epitea leaf rust in Salix : analyses of quantitative trait loci
- 2008
-
Ingår i: Journal of Applied Genetics. - 1234-1983 .- 2190-3883. ; 49:4, s. 321-331
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative resistance of Salix to Melampsora larici--epitea leaf rust was studied in 2 Salix mapping populations. One population was a backcross between a S, schwerinii x S. viminalis hybrid and S. viminalis, and the other was all F-2 population between S. viminalis and S. dasyclados. A leaf disc bioassay was used to study the components of quantitative resistance (latent period, uredinia number, and uredinia size) to 3 isolates of the leaf rust. The analysis of quantitative trait loci (QTLs) revealed 9 genomic regions in the backcross population and 7 genomic regions in the F-2 population that were important for rust resistance, with QTLs explaining 8-26% of the phenotypic variation. An important genomic region was identified for the backcross population in linkage group 2, where QTLs were identified for all resistance components for 2 of the rust isolates. Four of the QTLs had overlapping mapping intervals, demonstrating a common genetic background for latent period, uredinia diameter, and uredinia number. QTLs specific to some rust isolates and to some resistance components were also found, indicating a combination of common and specific mechanisms involved in the various resistance components. Breeding implications in relation to these findings are discussed.
|
|
| 21. |
- Samils, Berit, et al.
(författare)
-
A review of biology, epidemiology and management of Cronartium pini with emphasis on Northern Europe
- 2022
-
Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 37, s. 153-171
-
Forskningsöversikt (refereegranskat)abstract
- Severe outbreaks of Scots pine blister rust, caused by Cronartium pini (Willd.) Jorst., have occurred in several regions in Europe and Asia for at least hundred years. The rust fungus has a complex biology and epidemiology with two different life-cycle forms and five different spore stages. This review summarizes research on: taxonomy and host species, geographical distribution and historic epidemics, life-cycle forms and spore stages, population structure, infection and lesion development, susceptibility of pine provenances, impact of environmental conditions, climate change effects and management. The focus is on conditions in Northern Europe.
|
|
| 22. |
- Samils, Berit
(författare)
-
Alternate host ranges of Cronartium flaccidum and Cronartium ribicola in northern Europe
- 2012
-
Ingår i: Botany. - 1916-2790 .- 1916-2804. ; 90, s. 694-703
-
Tidskriftsartikel (refereegranskat)abstract
- Attached and detached leaves of 60 potential host species were inoculated in the greenhouse and laboratory with aeciospores of Cronartium ribicola J.C. Fisch. from six Finnish locations and of Cronartium flaccidum (Alb. & Schw.) Wint. from 20 locations in Finland and Sweden in 2011. Candidate hosts represented 16 plant families: Solanaceae, Verbenaceae, Asclepiadaceae, Grossulariaceae, Paeoniaceae, Balsaminaceae, Gentianaceae, Scrophulariaceae, Loasaceae, Tropaeolaceae, Acanthaceae, Myricaceae, Phrymaceae, Plantaginaceae, Orobanchaceae, and Apocynaceae. Inoculations of C. flaccidum produced uredinia after 2 weeks and (or) telia after 4 weeks of incubation on 25 hosts. Inoculation trials identified several new hosts for C. flaccidum in Fennoscandia, namely Impatiens balsamina, Swertia fedtschenkoana, Loasa tricolor, Myrica gale, Verbena canadensis, Saxifraga spp., Paeonia obovata, and Veronica daurica. Myricaceae and Saxifragaceae represent new host families for these rusts. Cronartium ribicola formed uredinia or telia on 10 species: Ribes spp. (7 species/cultivars), Pedicularis palustris subsp. palustris, Bartsia alpina, and Loasa triphylla. Results suggest wider alternate host ranges for both C. flaccidum and C. ribicola than previously recognized. Spores were virulent regardless of their source location, suggesting a lack of host-specificity among Fennoscandian populations of Cronartium.
|
|
| 23. |
- Samils, Berit, et al.
(författare)
-
Development of a PacBio Long-Read Sequencing Assay for High Throughput Detection of Fungicide Resistance in Zymoseptoria tritici
- 2021
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media S.A.. - 1664-302X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Fungicide resistance has become a challenging problem in management of Septoria tritici blotch (STB), caused by Zymoseptoria tritici, the most destructive disease of winter wheat throughout western and northern Europe. To ensure the continued effectiveness of those fungicides currently used, it is essential to monitor the development and spread of such resistance in field populations of the pathogen. Since resistance to the key families of fungicides used for STB control (demethyalation inhibitors or azoles, succinate dehydrogenase inhibitors or SDHIs and Quinone outside Inhibitors or QoIs) is conferred through target-site mutations, the potential exists to monitor resistance through the molecular detection of alterations in the target site genes. As more efficient fungicides were developed and applied, the pathogen has continuously adapted through accumulating multiple target-site alterations. In order to accurately monitor these changes in field populations, it is therefore becoming increasingly important to completely sequence the targeted genes. Here we report the development of a PacBio assay that facilitates the multiplex amplification and long-read sequencing of the target gene(s) for the azole (CYP51), SDHI (Sdh B, C, and D), and QoI (cytochrome b) fungicides. The assay was developed and optimised using three Irish Z. tritici collections established in spring 2017, which capture the range of fungicide resistance present in modern European populations of Z. tritici. The sequences obtained through the PacBio assay were validated using traditional Sanger sequencing and in vitro sensitivity screenings. To further exploit the long-read and high throughput potential of PacBio sequencing, an additional nine housekeeping genes (act, BTUB, cal, cyp, EF1, GAPDH, hsp80-1, PKC, TFC1) were sequenced and used to provide comprehensive Z. tritici strain genotyping.
|
|
| 24. |
- Samils, Berit, et al.
(författare)
-
Multiplex qPCR assay for simultaneous quantification of CYP51-S524T and SdhC-H152R substitutions in European populations ofZymoseptoria tritici
- 2020
-
Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 69, s. 1666-1677
-
Tidskriftsartikel (refereegranskat)abstract
- Demethylation inhibitor (DMI) and succinate dehydrogenase inhibitor (SDHI) fungicides are currently relied upon for the control of septoria tritici blotch (STB) in European wheat fields. However, multiple mutations have occurred over time in the genes encoding the targeted proteins that have led to a practical loss of fungicide efficacies. Among the different amino acid substitutions inZymoseptoria triticiassociated with resistance to these fungicides, S524T in CYP51 (DMI target) and H152R in SdhC (SDHI target) are regarded as conferring the highest resistance factors to DMI and SDHI, respectively. To facilitate further studies on the monitoring and selection of these substitutions inZ.triticipopulations, a multiplex allele-specific quantitative PCR (qPCR) assay allowing for estimation of both allele frequencies in bulk DNA matrices was developed. The assay was then used on complex DNA samples originating from a spore trap network set up in Belgium, Denmark, Sweden, and Ireland in 2017 and 2018, as well as on leaf samples with symptoms. The S524T allele was present in all field samples and its proportion was significantly higher in Ireland than in Belgium, whereas the proportion of H152R was only sporadically present in both countries. The frequency of S524T varied greatly in the airborne inoculum of all four countries; however, the H152R allele was never detected in the airborne inoculum. The method developed in this study can be readily adopted by other laboratories and used for multiple applications including resistance monitoring in field populations ofZ.tritici.
|
|
| 25. |
- Samils, Berit, et al.
(författare)
-
New genetic markers for identifying Cronartium flaccidum and Peridermium pini and examining genetic variation within and between lesions of Scots pine blister rust in Sweden
- 2011
-
Ingår i: Fungal Biology. - : Elsevier BV. - 1878-6146. ; 115, s. 1303-1311
-
Tidskriftsartikel (refereegranskat)abstract
- Microsatellite markers were developed as an identification tool and for analysis of the genetic variation in the pathogens Cronartium flaccidum and Peridermium pini, causing Scots pine blister rust in Pinus spp. Six reference aeciospore samples from Finland were used to examine genetic differences between the two pathogens. Genetic variation within and between 27 lesions on Scots pines from seven locations in Sweden was also investigated. Aeciospores were collected from single aecia within the lesions. Reference samples from P. pini were homozygous for all seven microsatellite loci investigated, while the three C. flaccidum samples contained heterozygous loci. These results confirm previous studies, where homozygous aeciospores were indicated to be characteristic for P. pini. The majority of aeciospores had two nuclei in both heterozygotic and homozygotic samples. Five of the Swedish lesions contained only homozygotic aecia, while the aecia in the remaining 22 lesions were heterozygotic. All lesions with homozygotic aecia contained only one single multilocus genotype, while many of the lesions with heterozygotic aecia contained several genotypes. The latter indicates the occurrence of multiple matings within a lesion between the resident spermogonia and alien fertilizing spermatia. (C) 2011. British Mycological Society. Published by Elsevier Ltd. All rights reserved.
|
|
| 26. |
- Samils, Berit, et al.
(författare)
-
QTL mapping of resistance to leaf rust in Salix
- 2011
-
Ingår i: Tree Genetics and Genomes. - : Springer Science and Business Media LLC. - 1614-2942 .- 1614-2950. ; 7, s. 1219-1235
-
Tidskriftsartikel (refereegranskat)abstract
- Genetic mapping of quantitative trait loci (QTL) for resistance to Melampsora leaf rust was performed in two willow families: the progeny from a backcross between Salix viminalis and a hybrid S. viminalis x Salix schwerinii (population S(1)), and the F(1) progeny of a cross between two S. viminalis (population S(3)). Disease levels were scored in the field for three consecutive years. In the laboratory, five different rust strains were sprayed onto leaf disks and the following resistance components were scored: latent period, diameter and number of uredinia, and flecking. One major QTL and 14 smaller were identified in the S(1) host population. One rust strain, that represents a Melampsora form with limited incidence on S. viminalis, showed lower aggressiveness to the S(1) host population together with a different pattern in QTLs. In the S(3) host population, we detected 13 QTLs for rust resistance, of which two were located to the same genomic regions as those found for the S(1) population. We showed that the strongest QTL co-segregated with a gene homologous to a known Toll/interleukin receptor-nucleotide binding site-leucine-rich repeat resistance gene in poplar. The importance of the identified QTLs is discussed in relation to breeding for durable resistance.
|
|
| 27. |
- Samils, Berit, et al.
(författare)
-
Relationship and genetic structure among autoecious and heteroecious populations of Cronartium pini in northern Fennoscandia
- 2021
-
Ingår i: Fungal Ecology. - : Elsevier BV. - 1754-5048 .- 1878-0083. ; 50
-
Tidskriftsartikel (refereegranskat)abstract
- Epidemics of Scots pine blister rust, caused by Cronartium pini, have become an increasing problem in northern Finland and Sweden. The biology of the rust fungus is complex, with two different life cycle forms that cannot be morphologically distinguished, and it is unclear to what extent the two forms contribute to the epidemics. Genetic structure of fourteen populations of C. pini were investigated in Fennoscandia. Distinction between the two life cycle forms, a heteroecious and an autoecious one, was made by determining zygosity using microsatellite markers, and AFLP markers were developed to analyse population genetic relationships. The results showed that the two life cycle forms are clearly differentiated and occur in separate populations. Within the life cycle forms, geographic differentiation was evident, probably due to restricted gene flow as well as connection with different alternating hosts. The host-alternating form dominated in the epidemic regions in northern Fennoscandia. Implications for silvicultural practices are discussed. (C) 2021 The Authors. Published by Elsevier Ltd.
|
|
| 28. |
|
|
| 29. |
- Zhang, Ke, et al.
(författare)
-
Alternate host screening of Thekopsora areolata in Scandinavia: a new record on Prunus grayana
- 2021
-
Ingår i: Botany. - : Canadian Science Publishing. - 1916-2790 .- 1916-2804. ; 99, s. 589-600
-
Tidskriftsartikel (refereegranskat)abstract
- The cherry spruce rust caused by Thekopsora areolata (Fr.) Magnus results in significant losses in spruce seed production in the forest industry. The pathogen is present in Asia and Europe but absent from North America where it has been considered as a potential threat and listed as a quarantine organism by the United States Department of Agriculture. A comprehensive list and in-depth information regarding the alternate hosts of this pathogen are important for conducting epidemiological studies and for optimal disease control. Prunus padus L. is the main alternate host reported for T. areolata. In this study, we investigated the susceptibility of domestic and exotic Prunus spp. and other potential alternate host-plant species native to Scandinavia to T. areolata infection through a field survey and aeciospore inoculation experiments in the greenhouse and laboratory. No new susceptible species were found. In Sweden, a new record of Prunus grayana Maxim. with low susceptibility to T. areolata was found. In addition, we updated the list of currently confirmed alternate hosts of T. areolata according to field observations and inoculation results. Prunus padus and Prunus serotina Ehrh., as well as their hybrids and subspecies of Prunus padus, are highly susceptible, while Prunus depressa Pursh, Prunus grayana, Prunus spinosa L., and Prunus tenella Batsch are considered slightly susceptible.
|
|
| 30. |
- Zhang, Ke, et al.
(författare)
-
Temporal and spatial dispersal of Thekopsora areolata basidiospores, aeciospores, and urediniospores
- 2022
-
Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 71, s. 668-683
-
Tidskriftsartikel (refereegranskat)abstract
- Cherry spruce rust causes huge yield losses in Norway spruce seed production in Fennoscandia. The causal agent, Thekopsora areolata, has three types of spores that disperse during spring: basidiospores are produced on basidia that grow out from teliospores in overwintered bird cherry leaf litter to infect new pistillate spruce cones, aeciospores are released from old diseased spruce cones to infect bird cherry leaves, and urediniospores are produced from new bird cherry leaves for reinfection. No study has examined the dispersal of T. areolata spores, including the basidiospores that cause primary infection in spruce cones. In this study, teliospores of T. areolata were germinated in the laboratory and the morphology of basidiospores was described. T. areolata spores were sampled in Ultuna, Sweden and Joutsa, Finland with 21 spore traps at each site. Peaks in aeciospores were observed from 11 to 25 May and from 2 to 8 June at the Finnish site, and from 4 to 18 May at the Swedish site. Urediniospores were first observed 2-3 weeks after the peaks in aeciospores and they were mainly distributed within 10 m from the bird cherry trees. Peaks of 1-2 weeks in basidiospore detection coincided with multiple rain events. The basidiospore peak overlapped with the spruce pollen peak in Finland but not in Sweden. The quantities of basidiospores from different spore traps within 100 m from the spore source had no gradient. Information on spatial and temporal spore release is important for making decisions on disease management strategies.
|
|
