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| 2. |
- Andreasen, Katarina, et al.
(författare)
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Genetic identity of putative Linnaean plants : Successful DNA amplification of Linnaeus's crab apple Malus baccata
- 2014
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Ingår i: Taxon. - : Wiley. - 0040-0262 .- 1996-8175. ; 63:2, s. 408-416
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Advancements in molecular techniques enable us to extract DNA from historic herbarium specimens and facilitate genetic comparisons between herbarium material and living plant collections. These recent advances offer an exciting opportunity for identifying extant Linnaean plants by genetic comparisons of Linnaeus's own herbarium specimens with potentially remnant plants from his cultivations. DNA from the lectotype of Malus baccata (L.) Borkh. in the Linnaean Herbarium was successfully extracted and amplified for five of twelve loci of microsatellites. Results of genetic comparisons with M. baccata trees from Linnaeus's Hammarby, Sweden, show that the trees at Hammarby are closely related to each other, but not to the lectotype, which is closer to material from Russia. This suggests that Linnaeus received M. baccata from more than one source. Although not close to the lectotype and not represented by a specimen in the Linnaean Herbarium, the extant M. baccata at Hammarby may still represent Linnaean plants, that were grown by Linnaeus himself, or the descendants to such plants. Future studies on the almost 50 living, potential Linnaean plants may reveal an invaluable biological, scientific and cultural heritage from the era that saw the rise of systematic biology.
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| 3. |
- Ghasemkhani, Marjan, et al.
(författare)
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Cut-off shoots method for estimation of partial resistance in apple cultivars to fruit tree canker caused by Neonectria ditissima
- 2015
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 65, s. 412-421
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Tidskriftsartikel (refereegranskat)abstract
- Fruit tree canker, caused by the fungus Neonectria ditissima, is an economically devastating disease in apple orchards, especially in north-western Europe. Complete resistance has not yet been reported in apple, but variation in levels of partial resistance has been described and could be valuable in plant breeding programmes. A screening method based on spore inoculation of manually inflicted leaf scars on cut shoots was evaluated for reliability and repeatability in discrimination of 11 apple cultivars during two years - 2012 and 2013 - in two different facilities - biotron and standard greenhouse - and different time periods (February-May). The resulting cankers were counted (infection percentage), first appearance noted (incubation period) and lesion size measured at regular intervals during a period of 25-29 days for comparison of resistance levels. Results of two-way analysis of variance and correlation analyses showed that the area under the disease progress curve yielded the most robust data. This parameter was then applied for screening 30 apple cultivars using the same cut-shoot method. 'Elise' showed very high susceptibility, while the ornamental 'Prairifire' showed the highest level of partial resistance. Results suggested that cut shoots can be used to assess levels of resistance among cultivars, but great care must be taken to provide stable experimental conditions.
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| 4. |
- Ghasemkhani, Marjan, et al.
(författare)
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Screening for Partial Resistance to Fruit Tree Canker in Apple Cultivars
- 2015
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Ingår i: Acta Horticulturae. - 0567-7572 .- 2406-6168. ; 1099, s. 687-690
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Konferensbidrag (refereegranskat)abstract
- Fruit tree canker in apple, caused by the fungus Neonectria ditissima, is considered as a serious economic problem in apple orchards, especially in northwestern Europe. This fungus produces cankers on the wood of branches and trunks, and severe attacks can result in the loss of limbs or whole trees. The fungus produces conidia and ascospores, both of which are dispersed and cause infection during prolonged periods of rainy weather. Apple cultivars show variable levels of partial resistance to the fungus, whereas complete resistance has not yet been reported. Therefore, apple genotypes with high levels of genetically determined resistance should be identified for use in apple breeding. In this study, ten apple cultivars were screened for resistance to N. ditissima. For each cultivar, both potted trees and cut-off shoots in glass bottles were inoculated in a greenhouse. The resulting lesions were measured and disease progression curves were calculated; AUC (area under curve) was used for comparisons of infection severity. Significant differences between cultivars were observed in both experiments. The cultivar 'Rodluvan' showed the highest degree of resistance in both experiments, while the most susceptible were 'Jonathan'(cut shoots) and 'Akero' (potted trees).
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| 5. |
- Gustavsson, Larisa, et al.
(författare)
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Genetic diversity in Swedish and Finnish heirloom apple cultivars revealed with SSR markers
- 2013
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Ingår i: Scientia Horticulturae. - : Elsevier BV. - 0304-4238 .- 1879-1018. ; 162, s. 43-48
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Tidskriftsartikel (refereegranskat)abstract
- A set of 85 heirloom apple cultivars aimed for long-term preservation in two germplasm collections in Sweden and Finland was evaluated with 8 SSR primer pairs to evaluate genetic diversity and genetic relatedness. An additional set of 16 European cultivars was included for comparison. The eight SSR primer pairs amplified 9 loci and 105 alleles. Genetic analyses performed by MDS indicated some differentiation between Swedish and Finnish cultivars, with European cultivars intermixed with the Swedish. The existence of three groups was, however, indicated by a Bayesian model-based clustering. One of the groups was clearly dominated by Swedish cultivars and another by Finnish. The third group included almost equal proportions of representatives from all three areas. The obtained results confirmed the genetic distinctness of Finnish apple cultivars, which can be explained by climate adaptation and admixture with a Russian gene pool. (C) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Gustavsson, Larisa, et al.
(författare)
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Screening of Apple Cultivars for Resistance to European Canker, Neonectria ditissima
- 2013
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Ingår i: Acta Horticulturae. - 0567-7572 .- 2406-6168. ; 976, s. 529-536
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Konferensbidrag (refereegranskat)abstract
- European canker, caused by the fungus Neonectria ditissima, is a severe problem in apple production both in Sweden and in many other northern European countries. Even when applying fungicides and good horticultural practices, canker damage occurs almost yearly in nurseries and orchards. Some years, devastating outbreaks destroy numerous trees. To date, complete resistance to N. ditissima is not known in apple. For further research and plant breeding, heritable variation in quantitative resistance should be investigated by phenotyping large sets of cultivars. In the present project, 55 apple cultivars were screened for resistance to N. ditissima. One-year-old shoots from mature trees were inoculated in the greenhouse with a standardized volume and concentration of conidia suspension using different inoculation methods. Two-year-old trees of five cultivars were inoculated in the field. Length of the occurring cankers was measured at regular intervals throughout a period of up to three months. The investigated cultivars showed considerable differences in colonization rate. In cultivars known to be highly resistant, i.e., 'Santana', lesions progressed much slower compared to susceptible cultivars like 'Cox's Orange Pippin' and 'James Grieve'. Since the inoculation-based phenotyping is demanding in labour and time (duration), especially when the test is performed on grafted trees, qPCR-based assessment of fungal biomass at early stages of infection was explored as an alternative or complementary approach for phenotyping.
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| 9. |
- Loots, Sonja, et al.
(författare)
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Distribution, habitat profile and genetic variability of Namibian succulent Lithops ruschiorum
- 2019
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Ingår i: Bothalia - African Biodiversity and Conservation. - : South African National Biodiversity Institute. - 0006-8241 .- 2311-9284. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- Background: The species-rich flora of southern Africa comprises a high number of endemics, including succulents such as the flowering stones in the genus Lithops, but conservation status for these species is not well underpinned because detailed field data and assessments of genetic diversity are lacking.Objectives: We wanted to assess plant abundance and identify factors that may affect survival in Lithops ruschiorum through carefully conducted field surveys, and to determine amount and partitioning of genetic variation by amplified fragment length polymorphism (AFLP) analysis.Method: Field surveys were carried out in nine populations in Namibia. The most meticulously studied population was divided into 51 sites, while another 43 sites were recognised in the remaining eight populations. At each site, occupied area and number of plants were recorded as well as altitude, aspect, slope, soil texture and substrate. Amplified fragment length polymorphism markers were employed to study 52 individuals from seven populations. Results: In total, 8465 individuals were recorded. Plant density and/or plant number was associated with aspect, slope, soil texture, substrate and geographic distance from the coast. Analysis of molecular variation showed that 95% of the variability occurs within populations. Genetic and geographic distances among populations were correlated suggesting an isolation-by-distance pattern.Conclusion: Results are concordant with a strong impact of fog-based precipitation on plant density in the coastal populations, whereas rain probably is more important at one population which is situated further inland. Within-population genetic variation was medium high as usually reported for perennial, outcrossing species, but the low population differentiation implies considerable gene flow and/or population fragmentation.
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| 10. |
- Loots, Sonja, et al.
(författare)
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Genetic variation among and within Lithops species in Namibia
- 2019
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Ingår i: Plant Systematics and Evolution. - : Springer Science and Business Media LLC. - 0378-2697 .- 1615-6110 .- 2199-6881.
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Tidskriftsartikel (refereegranskat)abstract
- The dwarf succulent genus Lithops is endemic to Southern Africa and of considerable conservation concern. Species delimitation is often problematic and based mainly on leaf morphology, which is strongly associated with habitat. Relationships between taxa and populations in Namibia were studied with amplified fragment length polymorphisms using 44 wild Lithops populations representing 15 species and 23 taxa. Four primer pairs produced 92 polymorphic bands in the 223 samples. Expected heterozygosity (H-e) within taxa ranged from 0.086 to 0.450. Genetic and geographic distances were correlated according to a Mantel test. Analysis of molecular variance showed only 23% variation among the 15 investigated species. Genetic differentiation and structuring were investigated with a principal coordinate analysis, a neighbour-joining and a Bayesian phylogeny, a Bayesian clustering analysis and a discriminant analysis of principal components. In all five analyses, L. optica and L. herrei, which differ only in flower colour, clustered closely together and are here combined under L. optica. The morphologically similar species L. amicorum and L. karasmontana clustered together. Lithops amicorum is therefore reduced to subspecific level: L. karasmontana subsp. amicorum, comb. nov. Subspecific taxa overlapped to a large extent except in L. karasmontana where 13% of the variability resided among subspecies, whereas the nominal subspecies differed from subsp. bella and subsp. eberlanzii; the latter two could not be separated and are here combined under L. karasmontana subsp. bella.
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