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1.
Biol Pharm Bull ; 46(12): 1692-1698, 2023.
Article in English | MEDLINE | ID: mdl-38044092

ABSTRACT

Ephedra herb, a dried terrestrial stem of Ephedra sinica, is used in traditional Japanese medicine (Kampo) and Chinese medicine to treat the common cold, headaches, bronchial asthma, and nasal inflammation. E. sinica predominantly contains two ephedrine alkaloids-(-)-ephedrine and (+)-pseudoephedrine-which are crucial for its medicinal effects. This study aimed to reveal the influence of genetic and environmental factors on ephedrine alkaloids content using statistical genetic analyses. To evaluate the influence of genetic factors on ephedrine alkaloids content, 25 clonal lines were cultivated in Ibaraki and the broad-sense heritability of the traits was estimated. The heritabilities of (-)-ephedrine, (+)-pseudoephedrine, and "total alkaloids" (TA) content were 0.871, 0.969, and 0.865, respectively. The heritabilities of ephedrine alkaloids content were high. To evaluate the influence of environmental factors on ephedrine alkaloids content, four clonal lines which have different genotypes were cultivated in three locations (Ibaraki, Shizuoka, and Yamanashi prefectures). The effects of genotype (G), location (L), and genotype by environment (G × E) interactions on ephedrine alkaloids content were found to be significant (p < 0.05) by two-way ANOVA, and, in particular, the genotypic effects were found to be the largest. Our results indicate that the ephedrine alkaloids content in E. sinica is under relatively strong genetic control and remains stable under various environments. These findings suggest that E. sinica with a higher and stable ephedrine alkaloids content could be cultivated in different locations through selective breeding.


Subject(s)
Alkaloids , Drugs, Chinese Herbal , Ephedra sinica , Ephedrine , Ephedra sinica/genetics , Pseudoephedrine
2.
Palliat Med Rep ; 2(1): 324-327, 2021.
Article in English | MEDLINE | ID: mdl-34927158

ABSTRACT

We describe the case of a 37-year-old woman with autism spectrum disorder (ASD) who lived with a mother with end-stage breast cancer and a visually impaired father. She was the main caregiver for her mother, who was receiving home-based palliative care. The caregiver needed training on communication and task management so that she could manage the communication with home care staff and perform more house chores. It was also necessary to share information with home care staff about ASD and how to treat her with understanding and respect. Although most support for people with ASD focuses on schools and workplaces, to offer successful end-of-life care at home, medical and home staff need to understand and communicate well with people with ASD and provide multiple types of support. Research, guidebooks, and visuals about main caregivers who have ASD and improving the inclusivity among staff members are necessary for providing successful home care and meeting caregivers' and patients' needs and expectations.

3.
Biol Pharm Bull ; 44(11): 1781-1789, 2021.
Article in English | MEDLINE | ID: mdl-34719654

ABSTRACT

Dried terrestrial stems of Ephedra sinica are known as 'Ephedra herb.' The pharmacological effects are mainly related to two major ingredients, (-)-ephedrine and (+)-pseudoephedrine (total alkaloids which are defined in Japanese Pharmacopoeia, TA). In this study, in order to aid in cultivation and breeding, the stability of TA content and stem dry weight of 46 E. sinica genets was evaluated from the first year of transplantation to the sixth year. TA content and composition ratio of these genets were stable after the second year, and dry weight was stable after the fourth year. These traits showed high inter-genet variability but low annual variability for each genet. Additionally, rank correlation coefficients of each trait among the genets were high. There was no significant correlation between these traits. Furthermore, to assess the reproducibility of these traits in clones, we evaluated TA content and dry weight of three clonal lines with high TA contents. TA content and composition ratio of the clonal lines were also stable after the second year of transplantation, and dry weight of the clonal lines was also stable after the fourth year. Moreover, TA content and composition ratio in each clonal line were comparable with those of each original genet after the second year. These results suggested that ephedrine alkaloids content and dry weight of E. sinica plants are stable, and that these traits are highly reproducible in clones. Therefore, selection breeding of E. sinica using vegetative propagation can be effective for high and stable quality of Ephedra herb.


Subject(s)
Alkaloids/analysis , Ephedra sinica/chemistry , Plant Stems/chemistry , Ephedrine/analysis , Pseudoephedrine/analysis , Reproducibility of Results
4.
Transgenic Res ; 30(4): 551-584, 2021 08.
Article in English | MEDLINE | ID: mdl-33970411

ABSTRACT

Genome editing in agriculture and food is leading to new, improved crops and other products. Depending on the regulatory approach taken in each country or region, commercialization of these crops and products may or may not require approval from the respective regulatory authorities. This paper describes the regulatory landscape governing genome edited agriculture and food products in a selection of countries and regions.


Subject(s)
Biotechnology/legislation & jurisprudence , Crops, Agricultural/genetics , Food, Genetically Modified/standards , Gene Editing , Genome, Plant , Government Regulation , Plants, Genetically Modified/genetics , Global Health , Humans
5.
Biol Pharm Bull ; 44(2): 287-291, 2021.
Article in English | MEDLINE | ID: mdl-33518684

ABSTRACT

Dried terrestrial stems of Ephedra sinica are called 'Ephedra herb,' whose pharmacological effects are due mainly to two major ingredients, (-)-ephedrine and (+)-pseudoephedrine (total alkaloids which are defined in Japanese Pharmacopoeia (TA)). Ephedra herb is an important crude drug in Japan. However, E. sinica is widely distributed in arid areas of northeastern China and Mongolia. Recently, E. sinica has started to be cultivated in Japan. This study aimed to assess the validity of selection breeding on TA content of E. sinica in several locations in Japan. In this experiment, we grew approximately 350 seedlings and divided them randomly into seven groups. Nearly fifty plants were cultivated at each of seven locations. In Ibaraki, Yamanashi, and Shizuoka, average TA content of whole samples satisfied the criteria for Ephedra herb defined in Japanese Pharmacopoeia (7.0 mg/g of dry weight (DW)). Plants with high and intermediate TA content at four locations were selected and transplanted to Ibaraki. There were significant differences in TA content between selected plants with high and intermediate TA content before and after transplanting (p < 0.05). TA content of high-TA plants was significantly higher than that of control plants cultivated continuously at Ibaraki (p < 0.05). These results suggest that the selection on content of ephedrine alkaloids in E. sinica under various locations in Japan is valid, and high- TA E. sinica plants can be selected at various locations.


Subject(s)
Ephedra sinica/genetics , Ephedrine/isolation & purification , Plant Breeding/methods , Selection, Genetic , Ephedra sinica/growth & development , Ephedra sinica/metabolism , Ephedrine/metabolism , Geography , Japan , Plant Stems/metabolism
6.
PLoS One ; 15(9): e0238128, 2020.
Article in English | MEDLINE | ID: mdl-32946484

ABSTRACT

Genome-editing technology has become increasingly known in recent years, and the 2018 news of genome-edited twins in China had a particularly significant impact on public awareness. In the present study we investigate the effect of Japanese media coverage on public opinions of this technology. To identify the effects we employ a questionnaire survey method on a pre-registered sample from online research company Macromill. Our repeated survey from 2016 through 2019 reveal a generally supportive attitude toward the medical application of genome-editing methods. To see this we employed a multinomial logit analysis examining the determinants of negative and positive impressions of the technology. Results show that although editing for medical purposes remained mostly acceptable, its use in fertilizing human eggs was increasingly rejected, especially in 2019, the most recent sample year. The suggestion is that while genome-editing applications in general medical fields are publicly accepted, its use in human functionality enhancement is heavily increasingly resisted. News of the twin babies in China did raise public awareness of the methods but also damaged their reputation. It therefore is important for genome researchers to hold such concerns in mind, keeping the public informed of changing technology fundamentals. As a related question we inquire into the public acceptability of genome editing for animal and plant breeding, such as in agriculture and fisheries, as well. We find the Japanese public views the medical and breeding applications of this technology to be unconnected with each other, despite that awareness of both has risen significantly in recent years.


Subject(s)
Attitude , Gene Editing , Twins , China , Gene Editing/ethics , Humans , Mass Media/statistics & numerical data , Surveys and Questionnaires
8.
Breed Sci ; 70(1): 3-12, 2020 Mar.
Article in English | MEDLINE | ID: mdl-32351299

ABSTRACT

In this review, the current status and prospects of common buckwheat (Fagopyrum esculentum Moench.) breeding in Japan are summarized. The varieties that have been registered in Japan so far are introduced with details regarding their breeding source populations and breeding methods. Because the main breeding method used for common buckwheat is mass selection, the merits and demerits of this method are explored from the perspective of heritability. Although there are many breeding objectives in common buckwheat, high yield and yield stability are discussed here. Regarding the potential of common buckwheat breeding in the future, the prospects of effective exploitation of self-fertility and selection based on genomic information are examined.

9.
Breed Sci ; 70(1): 101-111, 2020 Mar.
Article in English | MEDLINE | ID: mdl-32351309

ABSTRACT

Ecotype breeding is a key technology in common buckwheat (Fagopyrum esculentum Moench) for the breeding of highly adaptive cultivars and their introduction to other cultivation areas. However, the details of the relationship between photoperiod sensitivity and ecotype remain unclear. Here, we evaluated photoperiod sensitivity in 15 landraces from different parts of Japan, and analyzed quantitative trait loci (QTLs) for photoperiod sensitivity using two F2 segregating populations derived from the crosses between self-compatible lines ('Kyukei SC2' or 'Buckwheat Norin PL1', early days-to-flowering) and allogamous plants (intermediate or late days-to-flowering). We clarified that (1) photoperiod sensitivity and differences in ecotype are closely related; (2) photoperiod sensitivity is controlled by several QTLs common among population of different ecotypes; and (3) orthologues of GIGANTEA and EARLY FLOWERING 3 will be useful markers in future detailed elucidation of the photoperiod sensitivity mechanism in common buckwheat. This study provides the basis for genomics-assisted breeding for local adaptation and ecotype breeding in common buckwheat.

10.
Hereditas ; 157(1): 7, 2020 Mar 11.
Article in English | MEDLINE | ID: mdl-32160928

ABSTRACT

BACKGROUND: Atractylodes lancea De Candolle is a medicinal plant distributed in East Asia. Its rhizome has been used as an important crude drug in traditional Chinese and Japanese medicines for the treatment of numerous diseases and disorders. In recent years, the demand for mass production of the crude drug with a stable quality has increased. Its major active compounds are sesquiterpenoids, such as ß-eudesmol and hinesol that have closely related chemical structures with each other. As the criteria for evaluating the quality of A. lancea, the ß-eudesmol/hinesol content ratio is considered important. In A. lancea, the ratio could be considered to be influenced by genetic factors, geographical environment factors and these interactions. Few studies of a detail genetic analyses for ß-eudesmol/hinesol content ratio have been reported. Therefore, we evaluated the heritability and genotype-environment interaction on the ß-eudesmol/hinesol content ratio in A. lancea using clonal lines propagated with division of rhizome. RESULTS: The heritability of the ß-eudesmol/hinesol content ratio in A. lancea was evaluated through the cultivation of clonal lines of A. lancea in both different years (2016, 2017) and locations (Hokkaido, Ibaraki). Correlations between ß-eudesmol and hinesol contents were identified in all clonal lines, with high correlation coefficients (r = 0.73-0.99). The broad-sense heritability of the ß-eudesmol/hinesol content ratio was revealed to be high at 0.92. The effects of cultivation year were smaller than that of genotype, and few genotype-environment interactions were observed. In addition, the influence of cultivation location was also smaller than that of genotype, and the correlation between the two cultivation locations on the ß-eudesmol/hinesol content ratio was high. The results suggested that the ß-eudesmol/hinesol content ratio in A. lancea is highly dependent on genetic factors. CONCLUSION: We demonstrate that the heritability of ß-eudesmol/hinesol content ratio is high and that the effects of genetic factors were stronger than that of environmental factors such as cultivation location and year. Our findings suggested that selective breeding and clonal propagation are effective strategies for the production of A. lancea with stable qualities for use in the production of crude drugs.


Subject(s)
Atractylodes/metabolism , Sesquiterpenes, Eudesmane/metabolism , Sesquiterpenes/metabolism , Spiro Compounds/metabolism , Atractylodes/genetics , Plants, Medicinal/metabolism
11.
Sci Rep ; 10(1): 4914, 2020 03 18.
Article in English | MEDLINE | ID: mdl-32188926

ABSTRACT

Although the advent of several new breeding techniques (NBTs) is revolutionizing agricultural production processes, technical information necessary for their regulation is yet to be provided. Here, we show that high-throughput DNA sequencing is effective for the detection of unintended remaining foreign DNA segments in genome-edited rice. A simple k-mer detection method is presented and validated through a series of computer simulations and real data analyses. The data show that a short foreign DNA segment of 20 nucleotides can be detected and the probability that the segment is overlooked is 10-3 or less if the average sequencing depth is 30 or more, while the number of false hits is less than 1 on average. This method was applied to real sequencing data, and the presence and absence of an external DNA segment were successfully proven. Additionally, our in-depth analyses also identified some weaknesses in current DNA sequencing technologies. Hence, for a rigorous safety assessment, the combination of k-mer detection and another method, such as Southern blot assay, is recommended. The results presented in this study will lay the foundation for the regulation of NBT products, where foreign DNA is utilized during their generation.


Subject(s)
Agriculture , DNA Contamination , Gene Editing , High-Throughput Nucleotide Sequencing , Plants, Genetically Modified , Breeding , Computational Biology/methods , Plants, Genetically Modified/chemistry , Plants, Genetically Modified/classification , Reproducibility of Results
12.
PLoS One ; 15(1): e0227990, 2020.
Article in English | MEDLINE | ID: mdl-31945118

ABSTRACT

Rapeseed (Brassica napus L.) is one of the most economically important oilseed crops worldwide. In Japan, it has been cultivated for more than a century and has formed many feral populations. The aim of this study was to elucidate the genetic diversity of feral rapeseeds by genotyping 537 individuals (among which 130 were determined to be genetically modified) sampled from various regions in Japan. Analysis of 30 microsatellite markers amplified 334 alleles and indicated moderate genetic diversity and high inbreeding (expected heterozygosity, 0.50; observed heterozygosity, 0.16; inbreeding coefficient within individuals, 0.68) within the feral populations. The Mantel test showed only an insignificant weak positive correlation between geographic distance and genetic distance. Analysis of molecular variance showed a greater genetic diversity among individuals than between populations. These results are in accordance with population structure assessed by using principal coordinate analysis and the program STRUCTURE, which showed that the 537 individuals could be assigned to 8 genetic clusters with very large genetic differences among individuals within the same geographic population, and that among feral individuals, many are closely related to rapeseed accessions in the NARO Genebank but some have unknown origins. These unique feral rapeseeds are likely to be affected by strong selection pressure. The results for genetically modified individuals also suggest that they have two different sources and have a considerable degree of diversity, which might be explained by hybridization with nearby individuals and separation of hybrid cultivars. The information obtained in this study could help improve the management of feral rapeseed plants in Japan.


Subject(s)
Brassica napus , Crops, Agricultural , Plants, Genetically Modified , Biodiversity , Brassica napus/classification , Brassica napus/genetics , Crops, Agricultural/classification , Crops, Agricultural/genetics , Genetic Variation , Japan , Phylogeny , Plants, Genetically Modified/genetics
13.
Transgenic Res ; 29(2): 229-242, 2020 04.
Article in English | MEDLINE | ID: mdl-31997144

ABSTRACT

To date, there have been 160 regulatory approvals for environmental safety in Japan for the major genetically modified (GM) crops, including corn, soybean, canola and cotton. Confined field trials (CFTs) have been conducted in Japan for all single events, which contain various traits. The accumulated information from these previously conducted CFTs, as well as the agronomic field study data from other countries, provides a rich source of information to establish "familiarity" with the crops. This familiarity can be defined as the knowledge gained through experience over time, and used to inform the environmental risk assessments (ERA) of new GM crops in Japan. In this paper, we compiled agronomic data from the CFTs performed in Japan for 11 GM soybean events which obtained food, feed and environmental safety approvals from regulatory agencies in Japan. These CFTs were conducted by multiple developers according to Japan regulations to support the ERA of these GM soybean, covering standard measurement endpoints evaluated across developers in Japan. With this dataset, we demonstrate how familiarity gained from the CFTs of GM soybeans in Japan can be used to inform on the ERA of new GM soybean events. By leveraging this concept of familiarity, we discuss potential enhancements to the ERA process for GM soybean events in Japan.


Subject(s)
Crops, Agricultural/genetics , Environmental Exposure/prevention & control , Food, Genetically Modified/standards , Glycine max/genetics , Plants, Genetically Modified/adverse effects , Risk Assessment/methods , Consumer Product Safety , Crops, Agricultural/growth & development , Humans , Japan , Glycine max/growth & development
14.
Article in English | MEDLINE | ID: mdl-31867318

ABSTRACT

The Japanese government recognizes the substantial values of genome-edited agricultural organisms and has defined in which cases these are covered by the existing regulatory framework to handle this technology. Genome-editing technologies could revolutionize and accelerate plant breeding owing to the simplicity of the methods and precision of genome modifications. These technologies have spread rapidly and widely, and various genome-edited crops have been developed recently. The regulatory status of genome-edited end products is a subject of controversy worldwide. In February 2019, the Japanese government defined genome-edited end products derived by modifications of SDN-1 type (directed mutation without using a DNA sequence template) as not representing "living modified organisms" according to the Japanese Cartagena Act. Here, we describe the classification and regulatory status of genome-edited end products in this decision. We hope that reporting the progress in Japan toward the implementation of this regulatory approach will provide insight for scientific and regulatory communities worldwide.

15.
PLoS One ; 14(5): e0217522, 2019.
Article in English | MEDLINE | ID: mdl-31136627

ABSTRACT

Rhizomes of Atractylodes lancea are used in traditional Japanese medicine (Kampo) and Chinese medicine to treat numerous diseases and disorders because they contain many pharmacologically active compounds. The major active compounds in A. lancea are essential oil compounds such as ß-eudesmol, hinesol, atractylon, and atractylodin. The contents of the compounds in A. lancea exhibit high variability depending on their habitat. We cultivated clonal lines of A. lancea in different years (2016, 2017) and different locations (Hokkaido, Ibaraki) to investigate the influence of genetic and environmental factors on the contents of major compounds, namely, ß-eudesmol, hinesol, atractylon, and atractylodin. Broad sense heritability of ß-eudesmol, hinesol, atractylon, and atractylodin contents were 0.84, 0.77, 0.86, and 0.87, respectively. The effects of interannual variability on the contents of the compounds were lower than those of genotype. In addition, the cultivated environmental factors were assessed by different locations, and the correlations between Hokkaido and Ibaraki grown plants based on ß-eudesmol, hinesol, atractylon, and atractylodin contents were 0.94, 0.94, 1.00, and 0.83, respectively. The results suggest that the contents of ß-eudesmol, hinesol, atractylon, and atractylodin in A. lancea are largely influenced by genetic factors, and clonal propagation could be an effective strategy for obtaining populations with high contents of essential oil compounds. Furthermore, the contents of ß-eudesmol, hinesol, atractylon, and atractylodin in A. lancea exhibited few correlations with rhizome yields. A. lancea cultivars with not only high contents of essential oil compounds but also high rhizome yield could be developed through selective breeding.


Subject(s)
Atractylodes/growth & development , Atractylodes/genetics , Oils, Volatile/metabolism , Plant Breeding
16.
Breed Sci ; 69(4): 640-650, 2019 Dec.
Article in English | MEDLINE | ID: mdl-31988628

ABSTRACT

Leafy amaranths, which are consumed as traditional food in Asia and Africa, are now considered among the most promising vegetables. In Vietnam, leafy amaranths, particularly Amaranthus tricolor L., are important summer vegetables due to their excellent nutritional values and high tolerance to biotic and abiotic stresses. However, this species has not been subjected to systematic breeding. Here we describe species identification and evaluation of the genetic diversity of Vietnamese amaranth collection by using matK and simple sequence repeats (SSR) markers. Our phylogenetic analysis based on the matK marker classified the species of 68% of the accessions, of which 120 belonged to A. tricolor. We developed 21 SSR markers, which amplified a total of 153 alleles in 294 A. tricolor accessions originating from Vietnam and overseas, with a mean allelic richness of 7.29 per marker, observed heterozygosity of 0.14, expected heterozygosity of 0.38, and polymorphic information content of 0.35. The STRUCTURE and FST analysis indicated a positive relationship between geographic distance and genetic differentiation among most of the overseas groups and the Vietnamese collection, but not among geographic groups within the Vietnamese collection. Vietnamese amaranths could be divided into two major types, one common in East Asia and the other one unique to Vietnam.

17.
Breed Sci ; 69(4): 672-679, 2019 Dec.
Article in English | MEDLINE | ID: mdl-31988632

ABSTRACT

A total of 47 rice accessions collected from Kenya were investigated the genetic variations and classified into two cluster groups, A and B, by polymorphism data of 65 simple sequence repeat (SSR) markers. Clusters A and B corresponded to Japonica and Indica Groups, respectively. The number of Japonica Group accessions was limited in comparison with those of the Indica Group. Based on their patterns of reaction to standard differential blast isolates (SDBIs), these accessions and 57 control cultivars including differential varieties and several accessions harboring partial resistance genes were classified again into three cluster groups: Ia (high resistance), Ib (intermediate resistance) and II (susceptible). The rice accessions from Kenya were classified only into groups Ia and Ib. The accessions from Kenya were finally classified into three categories, A-Ia, B-Ia and B-Ib, based on the two classifications of polymorphism of SSR markers and resistance. The Indica Group accessions had wider genetic variation for blast resistance than did the Japonica Group accessions. The three leading cultivars (Basmati 217, Basmati 370 and ITA 310) categorized into Cluster group Ia were susceptible to some SDBIs from Kenya. The genetic variation for blast resistance in Kenya was demonstrated as the first report using SDBIs.

18.
Front Plant Sci ; 9: 276, 2018.
Article in English | MEDLINE | ID: mdl-29619035

ABSTRACT

To evaluate the potential of genomic selection (GS), a selection experiment with GS and phenotypic selection (PS) was performed in an allogamous crop, common buckwheat (Fagopyrum esculentum Moench). To indirectly select for seed yield per unit area, which cannot be measured on a single-plant basis, a selection index was constructed from seven agro-morphological traits measurable on a single plant basis. Over 3 years, we performed two GS and one PS cycles per year for improvement in the selection index. In GS, a prediction model was updated every year on the basis of genotypes of 14,598-50,000 markers and phenotypes. Plants grown from seeds derived from a series of generations of GS and PS populations were evaluated for the traits in the selection index and other yield-related traits. GS resulted in a 20.9% increase and PS in a 15.0% increase in the selection index in comparison with the initial population. Although the level of linkage disequilibrium in the breeding population was low, the target trait was improved with GS. Traits with higher weights in the selection index were improved more than those with lower weights, especially when prediction accuracy was high. No trait changed in an unintended direction in either GS or PS. The accuracy of genomic prediction models built in the first cycle decreased in the later cycles because the genetic bottleneck through the selection cycles changed linkage disequilibrium patterns in the breeding population. The present study emphasizes the importance of updating models in GS and demonstrates the potential of GS in mass selection of allogamous crop species, and provided a pilot example of successful application of GS to plant breeding.

19.
Breed Sci ; 67(4): 348-356, 2017 Sep.
Article in English | MEDLINE | ID: mdl-29085244

ABSTRACT

Environmental risk assessment is required for genetically modified (GM) crops before their import into Japan. Annual roadside monitoring along transportation routes from ports to processing facilities for GM soybean (Glycine max (L.) Merr.) have been requested as a condition of import only approval because of lack of information on the likelihood of persistence of imported GM soybean for food, feed and processing and the potential for transfer of transgenes into wild soybean (Glycine soja Seib. et Zucc.) through gene flow under the Japanese environment. The survey of soybean seeds, plants and wild soybean populations were conducted along transportation routes from unloading ports to processing facilities that provided data to help quantify actual exposure. The survey indicated that the opportunities for co-existence and subsequent crossing between wild soybean populations and imported soybean are highly unlikely. Together the survey results and the comprehensive literature review demonstrated low exposure of imported GM soybean used for food, feed and processing in Japan. This evaluation of exposure level is not specific to particular GM soybean event but can apply to any GM soybean traits used for food, feed and processing if their weediness or invasiveness are the same as those of the conventional soybean.

20.
Breed Sci ; 67(3): 239-247, 2017 Jun.
Article in English | MEDLINE | ID: mdl-28744177

ABSTRACT

Diversity analysis of rapeseed accessions preserved in the Japanese Genebank can provide valuable information for breeding programs. In this study, 582 accessions were genotyped with 30 SSR markers covering all 19 rapeseed chromosomes. These markers amplified 311 alleles (10.37 alleles per marker; range, 3-39). The genetic diversity of Japanese accessions was lower than that of overseas accessions. Analysis of molecular variance indicated significant genetic differentiation between Japanese and overseas accessions. Small but significant differences were found among geographical groups in Japan, and genetic differentiation tended to increase with geographical distance. STRUCTURE analysis indicated the presence of two main genetic clusters in the NARO rapeseed collection. With the membership probabilities threshold, 227 accessions mostly originating from overseas were assigned to one subgroup, and 276 accessions mostly originating from Japan were assigned to the other subgroup. The remaining 79 accessions are assigned to admixed group. The core collection constructed comprises 96 accessions of diverse origin. It represents the whole collection well and thus it may be useful for rapeseed genetic research and breeding programs. The core collection improves the efficiency of management, evaluation, and utilization of genetic resources.

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