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The oomycete Phytophthora infestans, the cause of late blight, is one of the most important potato pathogens. During infection, it secretes effector proteins that manipulate host cell function, thus contributing to pathogenicity. This study examines sequence differentiation of two P. infestans effectors from 91 isolates collected in Poland and Norway and five reference isolates. A gene encoding the Avr-vnt1 effector, recognized by the potato Rpi-phu1 resistance gene product, is conserved. In contrast, the second effector, AvrSmira1 recognized by Rpi-Smira1, is highly diverse. Both effectors contain positively selected amino acids. A majority of the polymorphisms and all selected sites are located in the effector C-terminal region, which is responsible for their function inside host cells. Hence it is concluded that they are associated with a response to diversified target protein or recognition avoidance. Diversification of the AvrSmira1 effector sequences, which existed prior to the large-scale cultivation of plants containing the Rpi-Smira1 gene, may reduce the predicted durability of resistance provided by this gene. Although no isolates virulent to plants with the Rpi-phu1 gene were found, the corresponding Avr-vnt1 effector has undergone selection, providing evidence for an ongoing ‘arms race’ between the host and pathogen. Both genes remain valuable components for resistance gene pyramiding.

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The apple fruit moth Argyresthia conjugella (Lepidoptera, Yponomeutidae) is a seed predator of rowan (Sorbus aucuparia) and is distributed in Europe and Asia. In Fennoscandia (Finland, Norway and Sweden), rowan fruit production is low every 2–4 years, and apple (Malus domestica) functions as an alternative host, resulting in economic loss in apple crops in inter-mast years. We have used Illumina MiSeq sequencing to identify a set of 19 novel tetra-nucleotide short tandem repeats (STRs) in Argyresthia conjugella. Such motifs are recommended for genetic monitoring, which may help to determine the eco-evolutionary processes acting on this pest insect. The 19 STRs were optimized and amplified into five multiplex PCR reactions. We tested individuals collected from Norway and Sweden (n = 64), and detected very high genetic variation (average 13.6 alleles, He = 0.75) compared to most other Lepidoptera species studied so far. Spatial genetic differentiation was low and gene flow was high in the test populations, although two non-spatial clusters could be detected. We conclude that this set of genetic markers may be a useful resource for population genetic monitoring of this economical important insect species.

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Undersøkelse av antibiotikaresistensmarkørgenet neomycin fosfotransferase II (nptII) i prøver fra 12 ville arter fra Norge I et prosjekt fra Miljødirektoratet har vi testa for tilstedeværelse av nptII genet i 219 prøver fra 12 ulike ville arter fra hele Norge. Utvalget av prøver inkluderte planter (løvetann, rødkløver og markjordbær), insekter (skogmaur, rognebærmøll og liten høstmåler), snegl (brunsnegl), fisk (ørret og rognkjeks) og pattedyr (rødrev, brunbjørn og isbjørn). Vi brukte to ulike sanntids-PCR (Real-Time-PCR) tester for å undersøke fo tilstedeværelsen av kopier av nptII-genet i de 219 prøvene. Vi fant at nesten alle prøvene var negative (99%), mens kun tre enkeltprøver (løvetann, rødkløver og skogmaur) viste et svært lavt nivå av nptII (3-4 kopier). De positive prøvene kan være naturlige varianter eller kontaminering fra forskningslaboratorier. Vi konkluderer med at der er behov for utvida undersøkelser innenen for dette fagfeltet.

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Knowledge about the reproduction strategies of invasive species is fundamental for effective control. The invasive Fallopia taxa (Japanese knotweed s.l.) reproduce mainly clonally in Europe, and preventing spread of vegetative fragments is the most important control measure. However, high levels of genetic variation within the hybrid F. × bohemica indicate that hybridization and seed dispersal could be important. In Norway in northern Europe, it is assumed that these taxa do not reproduce sexually due to low temperatures in the autumn when the plants are flowering. The main objective of this study was to examine the genetic variation of invasive Fallopia taxa in selected areas in Norway in order to evaluate whether the taxa may reproduce by seeds in their most northerly distribution range in Europe. Fallopia stands from different localities in Norway were analyzed with respect to prevalence of taxa, and genetic variation within and between taxa was studied using amplified fragment length polymorphism (AFLP). Taxonomic identification based on morphology corresponded with identification based on simple sequence repeats (SSR) and DNA ploidy levels (8× F. japonica, 6× F. × bohemica and 4× F. sachalinensis). No genetic variation within F. japonica was detected. All F. × bohemica samples belonged to a single AFLP genotype, but one sample had a different SSR genotype. Two SSR genotypes of F. sachalinensis were also detected. Extremely low genetic variation within the invasive Fallopia taxa indicates that these taxa do not reproduce sexually in the region, suggesting that control efforts can be focused on preventing clonal spread. Climate warming may increase sexual reproduction of invasive Fallopia taxa in northern regions. The hermaphrodite F. × bohemica is a potential pollen source for the male-sterile parental species. Targeted eradication of the hybrid can therefore reduce the risk of increased sexual reproduction under future warmer climate.

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Important losses in strawberry production are often caused by the oomycete Phytophthora cactorum, the causal agent of crown rot. However, very limited studies at molecular levels exist of the mechanisms related to strawberry resistance against this pathogen. To begin to rectify this situation, a PCR-based approach (NBS profiling) was used to isolate strawberry resistance gene analogs (RGAs) with altered expression in response to P. cactorum during a time course (2, 4, 6, 24, 48, 96 and 192 h post-infection). Twenty-three distinct RGA fragments of the NB-LRR type were identified from a resistance genotype (Bukammen) of the wild species Fragaria vesca. The gene transcriptional profiles after infection showed that the response of most RGAs was quicker and stronger in the resistance genotype (Bukammen) than in the susceptible one (FDP821) during the early infection stage. The transcriptional patterns of one RGA (RGA109) were further monitored and compared during the P. cactorum infection of two pairs of resistant and susceptible genotype combinations (Bukammen/FDP821 and FDR1218/1603). The 5′ end sequence was cloned, and its putative protein was characteristic of NBS-LRR R protein. Our results yielded a first insight into the strawberry RGAs responding to P. cactorum infection at molecular level.

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The apple fruit moth (Argyresthia conjugella (A. conjugella)) in Norway was first identified as a pest in apple production in 1899. We here report the first genetic analysis of A. conjugella using molecular markers. Amplified fragment length polymorphism (AFLP) analysis was applied to 95 individuals from six different locations in the two most important apple-growing regions of Norway. Five AFLP primer combinations gave 410 clear polymorphic bands that distinguished all the individuals. Further genetic analysis using the Dice coefficient, Principal Coordinate analysis (PCO) and Bayesian analyses suggested clustering of the individuals into two main groups showing substantial genetic distance. Analysis of molecular variance (AMOVA) revealed greater variation among populations (77.94%) than within populations (22.06%) and significant and high FST values were determined between the two major regions (Distance = 230 km, FST = 0.780). AFLP analysis revealed low to moderate genetic diversity in our population sample from Norway (Average: 0.31 expected heterozygosity). The positive significant correlation between the geographic and the molecular data (r2 = 0.6700) indicate that genetic differences between the two major regions may be due to geographical barriers such as high mountain plateaus (Hardangervidda) in addition to isolation by distance (IBD).

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Amplified fragment length polymorphism (AFLP) was used to study the genetic variation among 80 F. verticillioides isolates from kernels of Ethiopian maize, collected from 20 different maize growing areas in four geographic regions. A total of 213 polymorphic fragments were obtained using six EcoRI/MseI primer combinations. Analysis of the data based on all 213 polymorphic AFLP fragments revealed high level of genetic variation in the F. verticillioides entities in Ethiopia. About 58% of the fragments generated were polymorphic. The genetic similarity among F. verticillioides isolates varied from 46% to 94% with a mean Dice similarity of 73%. Unweighted Pair Group Method with Arithmetic Average (UPGMA) analysis revealed two main groups and four subgroups. The principal coordinate analysis (PCO) also displayed two main groups that agreed with the results of UPGMA analysis, and there was no clear pattern of clustering of isolates according to geographic origin. Analysis of molecular variance: (AMOVA) showed that only 1.5% of the total genetic variation was between geographic regions, while 98.5% was among isolates from the same geographic regions of Ethiopia. Eighty distinct haplotypes were recognized among the 80 isolates analyzed. Hence, breeding efforts should concentrate on quantitative resistance that is effective against all genotypes of the pathogen.

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According to the Norwegian Diversity Act, practitioners of restoration in Norway are instructed to use seed mixtures of local provenance. However, there are no guidelines for how local seed should be selected. In this study, we use genetic variation in a set of alpine species (Agrostis mertensii, Avenella flexuosa, Carex bigelowii, Festuca ovina, Poa alpina and Scorzoneroides autumnalis) to define seed transfer zones to reduce confusion about the definition of ‘local seeds’. The species selected for the study are common in all parts of Norway and suitable for commercial seed production. The sampling covered the entire alpine region (7–20 populations per species, 3–15 individuals per population). We characterised genetic diversity using amplified fragment length polymorphisms. We identified different spatial genetic diversity structures in the species, most likely related to differences in reproductive strategies, phylogeographic factors and geographic distribution. Based on results from all species, we suggest four general seed transfer zones for alpine Norway. This is likely more conservative than needed for all species, given that no species show more than two genetic groups. Even so, the approach is practical as four seed mixtures will serve the need for restoration of vegetation in alpine regions in Norway.

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Initial sources of inoculum of Phytophthora infestans were investigated in ten potato fields with early outbreaks of potato late blight. Infected plant samples and isolates from these fields were examined with respect to mating type prevalence, fungicide resistance and genotypes based on microsatellites A high proportion (91 %) of the isolates recovered were of mating type A1. However, both mating types were found in 3 of 9 fields with more than one isolate recovered, and sometimes both mating types were found on the same plant. Most of the isolates recovered from fields treated with metalaxyl-M prior to sampling had reduced sensitivity or were resistant to metalaxyl-M, and most of the isolates recovered form fields without metalaxyl treatment were sensitive. The isolates recovered from fields treated with propamocarb prior to sampling had a higher frequency of reduced sensitivity to propamocarb than isolates from fields without propamocarb treatment. We found that most plants contained more than one P. infestans SSR-genotype. Clustering analysis of the infected samples revealed that most samples clustered together according to fields. By combining information from P. infestans isolates and DNA extracts from the leaf lesions we found examples of both mating type A1 and A2 having the same multilocus genotype. This result indicates that both of these genotypes have a common ancestor, hence the inoculum originates from oospores. Although this a minor study of only 10 fields with a limited amount of isolates and plant samples, the results indicate oospores in the soil is an inoculum source. Hence the forecasting model to predict outbreaks of potato late blight should be modified to include this.       

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Initial sources of inoculum of Phytophthora infestans were investigated in ten potato fields with early outbreaks of potato late blight. Infected plant samples and isolates from these fields were examined with respect to mating type prevalence, fungicide resistance and genotypes based on microsatellites A high proportion (91 %) of the isolates recovered were of mating type A1. However, both mating types were found in 3 of 9 fields with more than one isolate recovered, and sometimes both mating types were found on the same plant. Most of the isolates recovered from fields treated with metalaxyl-M prior to sampling had reduced sensitivity or were resistant to metalaxyl-M, and most of the isolates recovered form fields without metalaxyl treatment were sensitive. The isolates recovered from fields treated with propamocarb prior to sampling had a higher frequency of reduced sensitivity to propamocarb than isolates from fields without propamocarb treatment. We found that most plants contained more than one P. infestans SSR-genotype. Clustering analysis of the infected samples revealed that most samples clustered together according to fields. By combining information from P. infestans isolates and DNA extracts from the leaf lesions we found examples of both mating type A1 and A2 having the same multilocus genotype. This result indicates that both of these genotypes have a common ancestor, hence the inoculum originates from oospores. Although this a minor study of only 10 fields with a limited amount of isolates and plant samples, the results indicate oospores in the soil is an inoculum source. Hence the forecasting model to predict outbreaks of potato late blight should be modified to include this.

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Plasmopara halstedii is a diploid oomycete plant pathogen causing downy mildew on sunflower (Helianthus annuus). Due to changes in cultural systems and the introduction of new exotic cultivars, the pathogen developed many races and have now become a serious problem affecting sunflower growing fields in Europe. The yield losses in sunflower crop caused by P. halstedii can be up to 85 %.

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Background to the research and aims. Sunflower downy mildew exhibit mixed asexual and sexual reproduction. Rare events of recombination can have a drastic effect on the reshuffling of genetic material and result in the emergence of new virulence combinations. Overview of the methods. In this study, we have used a molecular epidemiology approach to identify population sources, investigate the mating system and track pathogen movement at the field scale. Using a hierarchical sampling design, we have collected 250 P. halstedii isolates from 20 geo-referenced sites in an infected sunflower field located in Southern France. These samples were genetically characterized using 12 single nucleotide polymorphisms markers (SNP) and one microsatellite locus(Giresse et al. 2007) and, for a subset of 60 samples, the virulence profile was determined. Key results. Characterization of virulence profiles revealed the presence of 8 races within the field (100, 300, 304, 307, 703, 704, 707, 714), race 304 being predominant among the samples tested. Race were randomly distributed within the field. Among the 250 isolates that were genotyped, there were 109 different multilocus genotypes (MLG), of which four were highly represented. The significant deficit in heterozygotes observed confirmed that P. halstedii is a highly selfing species (Delmotte et al. 2008). Bayesian clustering analyses revealed that isolates belonged to two genetically differentiated groups (FST> 0.2) that were correlated with race. A low level of genetic differentiation (FST = 0.06) was observed among the 20 sites that were constituted of a mixture of samples from the two groups. Theestimation of gene flow using hierarchical FST and spatial autocorrelation analysis bring evidence a lack of spatial genetic structure that likely result from field plowing. Finally, the estimation of gene flow atvarious scales using hierarchical FST and spatial autocorrelation analysis bring evidence for race emergence through genetic recombination between differentiated genetic genotypes. Main conclusions. This study brings evidence for an absence of spatial genetic structure of P. halstedii population, that could result from field plowing. It also reveals that genetically and phenotypically (virulence) differentiated isolates of P. hasltedii do coexist at a very fine spatial scale. The coexistence of genetically and phenotypically differentiated isolates of P. hasltedii may allow the emergence of new races through recombination. Nature of the contribution to current knowledge. This study has allowed to identify and delineate pathogen populations at the field scale. By bringing new insights in to the evolutionary mechanisms responsible for the emergence of races, these results will help identifying management units for sunflower protection strategies. Keywords. Plasmopara halstedii, race, pathotype, virulence evolution, population genetics

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Rotstokkråte i jordbær ble første gang rapportert i Norge i 1992 og siden er den blitt funnet på mer enn 100 steder over hele landet. Sykdommen forårsakes av Phytophthora cactorum og karakteriseres ved at unge blader visner raskt og hele planten visner i løpet av noen dager. I løpet av en sesong kan opptil 40 % av plantene dø. P. cactorum smitter plantene gjennom rothårene ved hjelp av svermesporer (zoosporer). Sykdommen starter oftest i fuktige områder av et felt siden sporene trenger vann for å bevege seg. Når en først har fått smitten i jorda er det vanskelig å bli kvitt den siden P. cactorum danner hvilesporer som kan overleve i flere år. Ulike jordbærsorter har ulik grad av mottakelighet for sykdommen. De mest brukte kommersielle sortene er dessverre mottakelige for sykdommen. Resistensegenskaper kan styres av ett eller flere gener og man kan derfor foredle fram resistente sorter. Tradisjonell foredling er tidkrevende og overføringa av resistens til en mottakelig sort vil kreve gjentatte tilbakekrysninger slik at man ikke mister alle de positive egenskapene til denne sorten. Ved å utvikle genetiske kart med markører for resistens kan man teste planter raskere og slik komme raskere fram til en resistent sort. Kunnskap om hvor mange resistensgener som er involvert i kampen mot skadegjøreren, når disse blir slått på og hvilke proteiner disse lager er også viktig. Når en skadegjører angriper en plante lager den bl.a. proteiner som bryter ned plantecelleveggen og svekker plantens immunforsvar. Planten på sin side lager resistensproteiner som gjenkjenner proteinene laget av skadegjøreren. Denne gjenkjennelsen setter i gang en forsvarsrespons hos planten. Resistensproteinene kodes for av resistensgener (R-gener). De fleste kjente R-genene inneholder en kort bestemt nukleotidsekvens. Dette fellestrekket gjør jakten på resistensgener enklere. I jakten på resistensgener i jordbær har vi valgt å arbeide med markjordbær (Fragaria vesca) istedenfor kommersielle jordbær (Fragaria x ananassa Duch.). Markjordbær er diploid og egner seg derfor godt for molekylærbiologiske studier. For å isolere R-gener og studere hvordan de ble uttrykt ble en mottakelig kultivar og en resistent kultivar smittet med zoosporer. Vevsprøver ble høstet i en tidsserie fra tid 0 (kontroll før smitting) til maksimum 8 dager etter smitting. Resultatet så langt viser at vi har isolert fragmenter fra mange ulike resistensgener og at disse blir uttrykt gjennom hele tidsrommet fra smitting til 8 dager etterpå.

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Roseroot, Rhodiola rosea, is a perennial herbaceous plant of the family Crassulaceae. The rhizomes of 95 roseroot clones in the Norwegian germplasm collection were analysed and quantified for their content of the bioactive compounds rosavin, salidroside, rosin, cinnamyl alcohol and tyrosol using HPLC analysis. All five bioactive compounds were detected in all 95 roseroot clones but in highly variable quantities. The ranges observed for the different compounds were for rosavin 2.90-85.95mgg-1, salidroside 0.03-12.85mgg-1, rosin 0.08-4.75mgg-1, tyrosol 0.04-2.15mgg-1 and cinnamyl alcohol 0.02-1.18mgg-1. The frequency distribution of the chemical content of each clone did not reflect a certain geographic region of origin or the gender of the plant. Significant correlations were found for the contents of several of these bioactive compounds in individual roseroot clones. A low, but not significant correlation was found between AFLP markers previously used to study the genetic diversity of the roseroot clones and their production of the chemical compounds. The maximum level of rosavin, rosin and salidroside observed were higher than for any roseroot plant previously reported in literature, and the roseroot clones characterized in this study might therefore prove to be of high pharmacological value.

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Artikkelen forteller om Colletotrichum acutatum i norsk jordbærproduksjon, om vertplanter for soppen, om genetiske analyser av soppisolater fra ulike vertplanter og smitteforsøk i jordbær og kirsebær.

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In Tanzania sweet potato ranks as the third most important crop after cassava and potato. We studied the phenotypic diversity of morphological plant and root descriptor traits in accessions of the sweet potato germplasm collection of Sokoine University of Agriculture, Morogoro and Sugarcane Research Institute, Kibaha, Tanzania, using phenotypic characters. A total number of 105 sweet potato accessions of different geographic origins were studied in field trials of The Sugarcane Research Institute at Kibaha Tanzania, and data were recorded for 27 phenotypic characters. Estimates of pair-wise phenotypic similarities using the Manhattan coefficient varied from 0.023 to 0.814, with a mean of 0.285. Cluster analysis was conducted using the unweighted pair group method with arithmetic mean (UPGMA) and Principal Coordinate Analysis (PCO). The clustering of phenotypic data resulted in a dendrogram which was discordant with geographic origin and AFLP data. The analysis of variance (ANOVA) revealed highly significant variation among the accessions for 21 out of the 27 characters studied. Phenotypic analyses revealed a wider range of variability than AFLP analyses. Comparison of molecular and phenotypic data using the Mantel test showed a very low correlation (r2 = 0.0007). Molecular and phenotypic classifications are discordant, and both are necessary to classify the germplasm correctly and to clarify genetic relationships among sweet potato accessions.

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Phytophthora cactorum causes crown rot in strawberry (Fragaria x ananassa Dutch.), which is characterized by wilting and eventually collapse of the plant. An efficient control measure is the use of resistant cultivars, however most commercial cultivars are susceptible to the disease. The aim of our work is to generate basic knowledge about P. cactorum resistance as well as to develop genetic markers that can be used as tools for development of resistant cultivars. The genetic complexity of the octoploid cultivated strawberry, has led to development of the diploid wild strawberry (F. vesca) as a model system for Fragaria. We have identified suitable parents after screening accessions of diploid Fragaria sp. for resistance [1], and generated a mapping population which we are currently characterizing. In order to study the plant-pathogen interaction in detail we have identified and characterized resistance genes from diploid strawberry and effector genes from P. cactorum using different transcriptional analysis techniques; nucleotide-binding site (NBS)-profiling for resistance genes, and suppression subtractive hybridization (SSH) as well as a designed effector-specific differential display (ESDD) for genes involved in pathogenicity.   This work is supported by The Research Council of Norway.   [1] Eikemo H, Brurberg MB, Davik J (2010). Resistance to Phytophthora cactorum in diploid Fragaria species. HortScience. 45:193-197.  

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Abstract Germplasm characterization is an important component contributing to the effective management of plant genetic resources. The goal of this thesis was to study the genetic diversity of two models of vegetatively propagated plant species; roseroot (Rhodiola rosea L.) and sweet potato (Ipomoea batatas (L.) Lam), based on germplasm collections. Roseroot was recently collected from natural habitats and then vegetatively propagated at the germplasm centre while sweet potato already has a long tradition as a vegetatively propagated food species. I. Roseroot (Rhodiola rosea) Roseroot, R. rosea, also commonly known as golden root or arctic root, is a perennial herbaceous plant of the Crassulaceae family. R. rosea has its origin from the cold, humid regions of the northern hemisphere and grows mostly in the mountains near the snow border. R. rosea is widely distributed in Norway. As part of an effort to identify commercially valuable genotypes characterization of a germplasm collection from Norway was initiated. Amplified Fragment Length Polymorphism (AFLP) analysis was used to estimate genetic diversity within the Norwegian R. rosea germplasm collection. AFLP analysis of 97 R. rosea clones using five primer combinations gave a total of 109 polymorphic bands. A large molecular marker variation was found among roseroot clones in Norway with an average percentage of polymorphic bands (PPB) of 82.3%. Analysis of molecular variance (AMOVA) revealed a significantly greater variation within regions (92.03%) than among regions (7.97%) demonstrating that there was no close genetic similarity among clones originating from the same county. A low level of genetic differentiation (FST = 0.043) was observed, indicating a high level of gene flow, which had a strong influence on the genetic structure in Norway. Our results indicate high gene flow among R. rosea clones that might be a result of seed dispersal rather than cross-pollination. Ninety five clones of the Norwegian roseroot germplasm collection were analysed and quantified for their content of the bioactive compounds rosavin, salidroside, rosin, cinnamyl alcohol and tyrosol using High Performance Liquid Chromatography (HPLC) analysis. All bioactive compounds were detected in all clones but in highly variable quantities. The frequency distribution of the chemical content of each clone was not correlated with geographic region of origin or gender of the plant. Significant correlations between the content of these bioactive compounds were observed within individual roseroot clones.  Low and nonsignificant correlations were found between AFLP markers used to study genetic diversity of the roseroot clones and their content of chemical compounds. The maximum content of rosavin, rosin and salidroside observed were substantially higher than previously reported for roseroot plants, and the roseroot clones characterized in this study might therefore be of high pharmacological value. The large quantitative and qualitative variation of the chemical compounds observed in this study and the large genetic diversity observed in this germplasm constitute a firm basis for improving traits such as chemical composition in a breeding program for roseroot. This is the first report that combines the analysis of genetic diversity with information of the chemical composition of roseroot. Further studies of the roseroot populations from Norway as well as from other countries should be performed throughout the following years to identify clones with optimal chemical compositions and to maintain high genetic diversity of this species. II. Sweet potato (Ipomoea batatas (L.) Lam) Sweet potato has its origin in South America and is the 7th most important crop in the world. A Tanzanian sweet potato germplasm collection was characterized using molecular markers and morphological traits. The AFLP method was used to study the genetic diversity and relationships of sweet potato accessions in the germplasm collection from Tanzania. AFLP analysis of 97 sweet potato accessions using ten primer combinations gave a total of 202 clear polymorphic bands. The Unweighted Pair Group Method with Arithmetic Mean (UPGMA) analysis divided the accessions into two main clusters. Principal Coordinate analysis (PCO) confirmed the pattern of the cluster analysis. AMOVA revealed larger variation within regions (96.19%) than among regions (3.81%), a relatively low genetic diversity among germplasm accessions, and low genetic distances between regions. A maximally diverse subset (MDS) of 13 accessions capturing 97% of the molecular marker diversity was identified. The limited genetic diversity detected among these diverse sweet potato accessions using AFLP analysis did not reflect the wide range of variation observed in the field for morphological traits. This lack of correspondence between phenotypic and molecular variation might be due to phenotypic plasticity expressed under heterogeneous environmental conditions. Since analyses of phenotypic and molecular variation show little correspondence, both types of data are needed in order to characterize sweet potato germplasm thoroughly. AFLP markers were found to be efficient molecular markers for studying genetic diversity of clonal germplasm collections. Seedling recruitment seems to be the key factor that determines the genetic diversity of clonal plant species and sexual reproduction provides high genetic variation and promotes seed dispersal. Considering the high number of genotypes and high genetic variability of roseroot detected in this study, it might be assumed that roseroot exhibit a combination of sexual reproduction and vegetative propagation. In contrast, the low number of genotypes (13) in sweet potato, which has a long tradition as a vegetatively propagated food species, shows the absence of sexual reproduction. These results indicate a huge demand for improvements of sweet potato genetic diversity in the future. This knowledge will contribute to a better quality control of clonal plant materials based on both phenotypic and genetic information, and will facilitate the selection of superior genotypes with important components for utilization, cultivation, and conservation.

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Søtpotet er den femte viktigste kulturen i utviklingsland. Amplified lenght polymorphism (AFLP) metoden ble brukt for å studere genetisk diversitet i søtpotetsamlingen til Sokoine University of Agriculture, Morogoro, Tanzania. Analyser av 97 accessioner gav 202 klare polymorfe bånd og indikerte relativt liten genetisk diverstitet. We oppdaget duplikater i samlingen. AFLP viste seg å være et effektivt vertøy for å karakterisere genetisk diversitet i søtpotet.

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Sweet potato (Ipomoea batatas L.) is the fifth most important crop in the developing countries after rice, wheat, maize and cassava. The amplified fragment length polymorphism (AFLP) method was used to study the genetic diversity and relationships of sweet potato accessions in the germplasm collection of Sokoine University of Agriculture, Morogoro and Sugarcane Research Institute, Kibaha, Tanzania. AFLP analysis of 97 sweet potato accessions using ten primer combinations gave a total of 202 clear polymorphic bands. Each one of the 97 sweet potato accessions could be distinguished based on these primer combinations. Estimates of genetic similarities were obtained by the Dice coefficient, and a final dendrogram was constructed with the un-weight pair-group method using arithmetic average. AFLP-based genetic similarity varied from 0.388 to 0.941, with a mean of 0.709. Cluster analysis using genetic similarity divided the accessions into two main groups suggesting that there are genetic relationships among the accessions. Principal Coordinate analysis confirmed the pattern of the cluster analysis. Analysis of molecular variance revealed greater variation within regions (96.19%) than among regions (3.81%). The results from the AFLP analysis revealed a relatively low genetic diversity among the germplasm accessions and the genetic distances between regions were low. A maximally diverse subset of 13 accessions capturing 97% of the molecular markers diversity was identified. We were able to detect duplicates accessions in the germplasm collection using the highly polymorphic markers obtained by AFLP, which were found to be an efficient tool to characterize the genetic diversity and relationships of sweet potato accessions in the germplasm collection in Tanzania.

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The ascigerous stage (formation of perithecia with viable ascospores) of Colletotrichum acutatum was recently reported to occur on fruits of highbush blueberry (Vaccinium corymbosum) in Norway. When 113 isolates of C. acutatum from various plant species were cultured on strawberry leaf agar, nine developed perithecia with viable ascospores. Four isolates originated from apple (Malus domestica) and one each from sweet cherry (Prunus avium), raspberry (Rubus idaeus), highbush blueberry (Vaccinium corymbosum), hollyberry cotoneaster (Cotoneaster bullatus), and northern dock (Rumex longifolius). Except from blueberry, we never detected the ascigerous stage on decaying fruits or any other parts of the above mentioned plant species. On potato dextrose agar, colour of the underside of the cultures forming perithecia varied from light grey-green to dark grey-green or dark brown-green. Colour of the upperside varied greatly, being dark grey-green, grey-brown, grey, and beige-pink, and only two of the isolates were beige-pink (the raspberry and blueberry isolates). Amplified fragment length polymorphism (AFLP) analysis of the isolates using six primer combinations resulted in 103 clear polymorphic bands. A dendrogram was constructed, and based on cluster analysis using genetic similarity, the isolates could be divided into several clusters. Eight of nine perithecia-forming isolates grouped together in the dendrogram, indicating genetical difference from other isolates. This was also supported by Principal Coordinate (PCO) analysis.

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Rhodiola rosea is widely distributed in Norway, but so far limited knowledge exists on the level of genetic diversity. To initiate a selective breeding program, Amplified Fragment Length Polymorphism (AFLP) analysis was used to estimate genetic diversity within the Norwegian R. rosea germplasm collection. AFLP analysis of 97 R. rosea clones using five primer combinations gave a total of 109 polymorphic bands. We detected high percentage of polymorphic bands (PPB) with a mean of 82.3% among the clones of R. rosea. Each of the 97 R. rosea clones could be unambiguously identified based on these primer combinations. Estimates of genetic similarities were obtained by the Dice coefficient, and a final dendrogram was constructed with the Unweighted Pair Group Method with Arithmetic mean (UPGMA). Genetic similarity based on the AFLP data ranged from 0.440 to 0.950 with a mean of 0.631. This genetic analysis showed that there was no close genetic similarity among clones related to their original growing county. No gender-specific markers were found in the R. rosea clones. Analysis of molecular variance (AMOVA) revealed a significantly greater variation within regions (92.03%) than among regions (7.97%). A low level of genetic differentiation (F-ST=0.043) was observed, indicating a high level of gene flow, which had a strong influence on the genetic structure at different counties. Our results indicate high gene flow among R rosea clones that might be a result of seed dispersal rather than cross-pollination. Further world-wide studies are required to compare the level of genetic diversity and more studies in R. rosea detailing the consequences of different patterns of gene flow (pollen spread and dispersal of seeds and clonal plants) will be useful for characterization of roseroot. (C) 2008 Elsevier Ltd. All rights reserved.

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Det første og viktigste trinn i bekjempelse av planteskadegjørere er en korrekt identifisering av organismen som forårsaker skade. Testmetoder som er basert på deteksjon av arvestoff (DNA) til en organisme har vist seg å være svært nyttige i diagnostikken. Vi har etablert en DNA-basert test for identifisering av potetcystenematoder.

Sammendrag

Det første og viktigste trinn i bekjempelse av planteskadegjørere er en korrekt identifisering av organismen som forårsaker skade. Testmetoder som er basert på deteksjon av arvestoff (DNA) til en organisme har vist seg å være svært nyttige i diagnostikken. Vi har etablert en DNA-basert test for identifisering av potetcystenematoder.

Sammendrag

Studies of genetic variation of the late blight pathogen among isolates collected in 2003  in the Nordic countries were presented

Sammendrag

Phytophthora infestans was isolated from potato leaves collected from 200 fields located in different parts of Finland, Denmark, Sweden and Norway in 2003. Sampling was carried out relatively late in the epidemic. The SSR analysis was carried out in Norway. Nine SSR markers were tested; Pi4B, Pi4G, PiG11, Pi02, Pi04, Pi16, Pi26, Pi33 and D13. Based on only 7 SSR markers 190 genotypes were found. Six genotypes occurred twice and one genotype occurred six times. The high genetic variation indicates sexual reproduction in the Nordic late blight population

Sammendrag

The pine wood nematode, Bursaphelenchus xylophilus, which is indigenous to North America, was introduced to Asia in the early 1900 and now causes severe damage to susceptible pine species in Japan, China, Korea and Taiwan. B. xylophilus was included in the A1 list of quarantine organisms by EPPO (European Plant Protection Organization) in 1985. B. xylophilus was reported for the first time in Europe in Portugal in 1999. There are more than 50 described species within the genus Bursaphelenchus worldwide, that are associated with coniferous and deciduous trees and spread by insect vectors. Within this genus is a group of morphologically very similar species; B. xylophilus, B. mucronatus, B. fraudulentus, B. kolymensis, B. conicaudatus and B. luxuriosae. This group of species is often referred to as the "B. xylophilus group". Due to the morphological similarity of the species, identification of Bursaphelenchus species in the B. xylophilus group is difficult. The common method of molecular identification for separating species within the B. xylophilus group is the use of ITS-RFLP (Hoyer et al. 1998). We have developed a multiplex polymerase chain reaction (PCR) method with specific primers, and the primers amplified product were 740, 340 and 300 bp for B. xylophilus, B. fraudulentus and B. mucronatus respectively. No cross reactions on the three studied species were observed. In contrast to the previously described PCR-RFLP method, this new method allows detection not only on pure isolates, but also on crude nematode suspensions from wood samples, and it could be very useful for quarantine purposes. References Hoyer U, Burgermeister W, Braasch H 1998 Identification of Bursaphelenchus species (Nematoda, Aphelenchoididae) on the basis of amplified ribosomal DNA (ITS-RFLP). Nachrichtenbl. Deut. Pflanzenschutzd. 50:273-27. Mota M M, Braasch H, Bravo M A, Penas A C, Burgermeister W, Metge K, and Sousa E 1999. First report of Bursaphelenchus xylophilus in Portugal and in Europe. Nematology 1:727-734. Smith, I. M. 1985. Pests and disease problems in European forests. FAO Plant Prot. Bull. 33:159-164. Yi C, Park J, and Chang K 1989. Occurrence of pinewood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, and its vector, Monochamus alternatus Hope, in Korea. Pages 183-193 in: Proc. IUFRO Reg. Workshop For. Insect Pests and Tree Dis. in NE Asia. For. Prod. Res. Inst., Tsukuba, Japan.

Sammendrag

Studier av tørråtepopulasjonen i Norge fra 2003 bekrefter tidligere års undersøkelser at den er svært variabel både i genotype og fenotype. Andelen av metalaksyl-resistente individer har gått tilbake. Det er påvist en relativt stor andel isolater som tolererer å vokse på 100 ppm propamokarb, men det er ikke konstatert resistensproblemer i felt. Krysningstype A2 er ikike påvist blant 110 isolater fra Nord-Norge i 2004, noe som antyder at kjønna formering av tørråtesoppen er sjelden eller fraværende i denne landsdelen. Problemene med tørråte i Sør-Norge var mindre i 2004 enn i de foregående årene. Feltforsøk med ulike strategier i 2004 viste at en kunne bekjempe tørråte med godt resultat både med dynamiske fungiciddoser ved faste intervall og ved sprøyting etter ulike varslingsmodeller. Det var imidlertid vanskelig å påvise sikre forskjeller mellom de ulike strategiene.