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| 2. |
- 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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| 3. |
- Elsafy, Mohammed, et al.
(författare)
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Elucidating the genetic diversity of farmer cultivars of female date palms (Phoenix dactylifera L.) from Sudan by microsatellite markers
- 2016
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Ingår i: Genetic Resources and Crop Evolution. - : Springer Science and Business Media LLC. - 0925-9864 .- 1573-5109. ; 63, s. 975-986
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Tidskriftsartikel (refereegranskat)abstract
- Genetic diversity in female date palms for a total of 89 tree samples, representing 18 cultivar groups, was investigated using 10 loci of microsatellite (SSR) primers. The microsatellites examined showed high polymorphism, a total of 126 for the 10 microsatellite loci, giving an average of 12.6. Low F-ST values were observed among different fruit classification groups of Sudanese date palms (soft, semi-soft and dry) suggesting that the observed high genetic variability is maintained locally within cultivars. Across all genetic parameters, in comparison among the cultivar groups, the Jaw group was consistently highly variable followed by Korsha, Gondela and Barakawi, respectively. Multivariate analysis of the 89 date palms showed some strong relationships with some mixed grouping, showing a tendency of relate fruit classification and related genotypes. Dry dates almost grouped together while the soft and semi-soft were mixed and somewhat related to genotypes. The effect of genotype was highly supported by the relationship of 14 cultivar groups, in which similar cultivars were associated regardless of the state to which they belong. Further detailed analyses of female date palm populations from different geographic locations represented by a minimum of five plants per cultivar is necessary to provide the basis for understanding of the date palm genomes, revealing the true extent of gene flow between farmer cultivars.
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| 4. |
- 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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| 5. |
- Ghasemkhani, Marjan, et al.
(författare)
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Real-time PCR for detection and quantification, and histological characterization of Neonectria ditissima in apple trees
- 2016
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Ingår i: Trees - Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 30, s. 1111-1125
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Tidskriftsartikel (refereegranskat)abstract
- Neonectria ditissima, the causal pathogen of fruit tree canker, is a sordariomycete fungus that affects apple orchards, especially in north-western Europe. To prevent serious disease epidemics, an accurate, rapid, and sensitive method for detection of N. ditissima is needed for pathogen identification. A quantitative real-time PCR (qPCR) assay was developed for both detection and quantification of this pathogen in infected apple cultivars. Several primer sets were designed from regions of the β-tubulin gene. One primer set passed several validation tests, and the melting curve confirmed species-specific amplification of the correct product. In addition, the N. ditissima biomass could be detected at variable amounts in samples from the infection sites of six different cultivars, with ‘Aroma' having the lowest amount of N. ditissima biomass and ‘Elise' the highest. To complement the qPCR results, tissue from detached shoots and 1-year-old trees of ‘Cox's Orange Pippin' (susceptible) and ‘Santana' (partially resistant) was used in a histopathology study. In both detached shoots and trees, fungal hyphae were found in cells of all tissues. No qualitative differences in the anatomy of the infected samples were observed between the cultivars. In the detached shoot experiment, both cultivars were affected but differences in the rate of disease progression suggest that the partially resistant cultivar could resist the fungus longer. The qPCR assay developed in our study produced reproducible results and can be used for detection of N. ditissima in infected trees.
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| 6. |
- Gustavsson, Larisa, et al.
(författare)
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Approaches for evaluation of resistance to European canker (Neonectria ditissima) in apple
- 2016
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Ingår i: Acta Horticulturae. - 0567-7572 .- 2406-6168. ; 1127, s. 75-81
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- European canker is caused by the fungus Neonectria ditissima (Neonectria galligena, formerly Nectria galligena). The disease causes significant losses to apple production in Sweden and many other countries with a temperate wet climate. Application of fungicides and good horticultural practices do not prevent canker damage in nurseries and orchards. Disease outbreaks damage and even completely destroy trees. To date, complete resistance to N. ditissima is not known in apple, but cultivars differ considerably in their level of partial resistance. To be able to conduct breeding for resistance to European canker, reliable plant tests are urgently needed. Differences in resistance to N. ditissima (colonization rate; CR) in apple cultivars were evaluated by wound inoculations with a standardized number of conidia on cut shoots from mature trees placed in a climate chamber and on potted trees in an unheated greenhouse. Infection percentage (Inf%) was assessed by 'natural' inoculations in leaf scars under high infection pressure in the field. All the experiments were carried out over 2 years. Lengths of lesions were measured at regular time intervals on five occasions for shoots and seven occasions for trees. Considerable differences in CR and Inf% were found among the cultivars. The relative levels of resistance obtained are consistent with previous reports for most cultivars. Assessment of CR (area under curve) and Inf% thus proved to be useful tools for evaluation of resistance to European canker. Also, some potentially new sources of resistance were identified.
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| 7. |
- 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. |
- Mujaju, Claid, et al.
(författare)
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Genetic diversity among and within watermelon (Citrullus lanatus) landraces in Southern Africa
- 2011
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Ingår i: Journal of Horticultural Science and Biotechnology. - : Informa UK Limited. - 1462-0316 .- 2380-4084. ; 86, s. 353-358
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Tidskriftsartikel (refereegranskat)abstract
- Genetic diversity in watermelon (Citrullus lanatus) was estimated among 213 seedlings from 22 accessions collected in Botswana, Namibia, South Africa, Zambia, and Zimbabwe. The accessions consisted of two types of watermelon landraces: sweet watermelon (C. lanatus var. lanatus) and cow-melon (C. lanatus var. citroides), also known as citron melon. In addition, three commercial varieties of C. lanatus var. lanatus from the USA were included for comparison. Ten simple sequence repeat (SSR; microsatellite) loci detected a total of 153 alleles. The polymorphic information content (PIC) ranged from 0.833 - 0.963, suggesting sufficient discriminatory power. Both a cluster analysis and a principal co-ordinate analysis produced two major clusters, one with the 13 cow-melon accessions and the other with the 12 sweet watermelon accessions. Within the sweet watermelon cluster, the three US cultivars grouped together with the Botswana accessions. Some of the other accessions also grouped according to their country of origin, but others did not. Within-accession diversity parameters showed that those sweet watermelon accessions found in traditional agrosystems were just as genetically variable as the cow-melon accessions.
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| 9. |
- Nybom, Hilde, et al.
(författare)
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Problem med fruktsättningen på dina äppleträd? : DNA-analyser visar vilka äpplesorter som kan pollinera varandra
- 2012
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Ingår i: LTJ-fakultetens faktablad.
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Annan publikation (populärvet., debatt m.m.)abstract
- Äppleträd dignande av vacker och välsmakande frukt…. ja, detta ser nog alla framför sig när de planterar nyinköpta äppleträd. Men det finns många fallgropar. Förutom alla de vanliga problemen med olämplig jord, torka, vårfrost, otrevliga insektsangrepp och ännu otrevligare svampsjukdomar, så finns det ytterligare ett besvärande faktum. Nämligen att blommorna måste pollineras! Och detta pollen måste komma från en annan äpplesort – annars kan inte pollenslangen växa ner genom blommans pistill och utföra en befruktning (Nybom m.fl. 2007a).
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| 10. |
- Torutaeva, Elnura, et al.
(författare)
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Evaluation of microsatellite-based genetic diversity, protein and mineral content in chickpea accessions grown in Kyrgyzstan
- 2014
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Ingår i: Hereditas. - : Springer Science and Business Media LLC. - 0018-0661 .- 1601-5223. ; 151, s. 81-90
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Tidskriftsartikel (refereegranskat)abstract
- The genetic diversity of 23 chickpea accessions representing Kyrgyz landraces and cultivars, ICARDA breeding lines, Spanish and Turkish cultivars was characterized using nine microsatellite (SSR) markers which generated a total of 122 alleles. The number of alleles (Na) per locus varied from 9 to 20. The observed heterozygosity (Ho) ranged between 0.05 and 0.43 (average 0.13) whereas both the expected heterozygosity (He) and polymorphic information content (PIC) ranged from 0.71 to 0.90 (average 0.83). Analysis of molecular variance (AMOVA) showed that 62% of the total genetic variation was found within accessions while the remaining 38% was found among accessions. Principal coordinate analysis (PCoA) indicated the presence of two groups. The two Kyrgyz cultivars were found apart from these groups. Cluster analysis generally confirmed the results of PCoA and also separated the Kyrgyz cultivars from the subcluster formed by Kyrgyz landraces and the subclusters formed by breeding lines from ICARDA along with landraces from Turkey and Spain. In addition, protein content and mineral concentration were determined. Protein content and mineral concentrations for Ca, S, Mg, P, K, Fe, Mn, Cu and Zn varied significantly among accessions. The results show that Kyrgyz germplasm provides a source of diversity for improvement of chickpea.
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