Genetic structure and differentiation in hop (Humulus lupulus L.) as inferred from microsatellites

A set of 67 wild and cultivated hop accessions, representative of hop diversity, was genotyped with 29 SSR markers in order to investigate the population structure and genetic diversity among hop genotypes. A total of 314 alleles was detected, with an average of 10.8 alleles per locus and an average PIC content of 0.607. Model-based clustering placed the accessions into five germplasm groups. A distance-based tree showed good agreement with five germplasm groups, and additionally assigned accessions omitted from model-based analysis into two additional germplasm groups. The 67 hop accessions were thus subdivided in seven germplasm groups, with three corresponding to major breeding groups and four to wild hops. This finding is in accordance with two biogeographically separated hop germplasms (European and North American origin) and with the known history of the accessions. North American hop germplasm was partitioned into native and cultivated germplasm groups. European germplasm was divided into two groups of hop cultivars representing distinguishable European germplasms and three new groups of native hops, which were differentiated for the first time by this analysis. Admixture analysis showed shares of various ancestries in hop cultivars, mostly congruent with pedigree data, and the introgression of various ancestries in some native hops. The above results have so far given the most detailed insight to date into the population structure of hop diversity, which is important for its effective use in hop breeding.     

Genetic relationships in cultivars of hop, Humulus lupulus L., determined by RAPD analysis

Random amplified polymorphic DNA (RAPD) was used to evaluate the genetic variability and relationship of 65 hop cultivars from all the major hop-growing regions in the world. Twenty-eight selected random primers used in the RAPD reaction generated an average of 38.6%) polymorphic fragments, which was sufficient to produce 47 different RAPD profiles among the cultivars examined. The level of genetic variability was much higher than previously reported. Genetic similarity was estimated and UPGMA cluster analysis was performed using the RAPD data. Cluster analysis separated the cultivars into genetically related RAPD groups which were compared with pedigree data and grouping of the hop cultivars by essential oil type. The RAPD groups, strongly supported by pedigree data, gave more precise information on the level and distribution of genetic variability within hop cultivars than characterization by essential oils. Cultivars were divided into American and European groups, supporting the distinction between two geo-graphically distinct hop germplasms. Five genetically distinct groups revealed differences within the European germplasm, reflecting past hop breeding practices which have been adopted in different regions. The use of RAPD markers for hop germplasm characterization and genetic diversity study is discussed.     

Genetic diversity and relationships among pea cultivars revealed by RAPDs and AFLPs

In order to obtain an overview of the genetic diversity present within the set of pea cultivars released in Germany, 21 cultivars were analysed at the DNA level by random amplified polymorphic DNAs (RAPDs) and amplified fragment length polymorphisms (AFLPs), as well as for agronomic traits. Yield of grain cultivars ranged from 2.95 to 3.87 t/ha. Based on the screening of 60 RAPD primers and 32 Eco RI + 3/Mse I+3 AFLP primer combinations, 20 RAPD primers and 11 Eco RI + 3/MseI+ 3 primer combinations generating polymorphic and distinct fragments were chosen for estimation of genetic diversity. Twenty RAPD primers amplified a total of 314 scorable bands ranging from about 262 bp to 1996 bp. Of these, 175 fragments (55.7%) were polymorphic. Based on these data, genetic similarity (GS) was estimated between 0.80 (‘Lisa’ vs.‘Grapis’) and 0.94 (‘Bohatyr’ vs. ‘Sponsor’; mean GS = 0.88). Eleven AFLP primer combinations led to the amplification of 949 scorable fragments ranging from 43 to 805 bp and of these, 462 (48.7%) were polymorphic. Genetic similarity based on AFLPs was calculated between 0.85 (‘Lisa’ vs.‘Laser’) and 0.94 (‘Bohatyr’ vs. ‘Sponsor’, mean GS = 0.90). Correlation of genetic similarity estimated on RAPDs and AFLPs was estimated at r = 0.79** using Spearman's rank correlation coefficient and at r = 0.84 by the Mantel test, respectively. UPGMA cluster analysis carried out on these data separately for RAPDs and AFLPs and on the combined data reflected, to some extent, pedigree relationships and cophenetic correlations (r = 0.89 for RAPDs, r = 0.88 for AFLPs, and r = 0.93 RAPDs + AFLPs) indicate a good fit of respective clusters to genetic similarity data. The correlation of cluster analyses to pedigree information and the impact on parental genotype selection is discussed.     

Genetic diversity of Cannabis sativa germplasm based on RAPD markers

Random amplified polymorphic DN A (RAPD) markers were generated from 13 cultivars and accessions of Cannabis sativa L. Approximately 200 fragments generated by 10 primers of arbitrary sequence were used to assess the level of DNA variation. Statistical analysis was performed using the Dice coefficient of similarity and principal coordinate analysis. The grouping of the accessions according to the cluster analysis was in good agreement with their origin and lines with common ancestors were grouped together. Principal coordinates 1 and 2 revealed a clear separation of Italian and Hungarian germplasm and a third group, including a mixture of genotypes coming from different places; the third coordinate separated the Korean group which is probably the most divergent germplasm. Variability within the two cultivars ‘Carmagnola’ and ‘Fibranova1’ was also shown, suggesting good possibilities for long–term selection work. RAPD markers provide a powerful tool for the investigation of genetic variation in cultivars/accessions of hemp.     

Genetic relationships of sesame germplasm collection as revealed by inter-simple sequence repeats

Inter‐simple sequence repeats (ISSR) polymorphism was used to determine genetic relationships among 75 Sesamum indicum L. accessions of Korean and exotic sesame. Fourteen reliable ISSR primers were selected for the assessment of genetic diversity, yielding 79 amplification products. Of these polymerase chain reaction products, 33% revealed polymorphism among the 75 accessions. Genetic distances ranged from 0 to 0.255, with a mean genetic distance of 0.0687. The 75 accessions were divided into seven groups on the basis of unweighted pair‐group method with arithmetic averages (UPGMA) cluster analysis. The largest group consisted of 25 Korean cultivars, eight Korean breeding lines and 17 world‐wide accessions. The other groups included 25 accessions, several of which contained useful traits. The dendrogram did not indicate any clear division among sesame accessions based on their geographical origin. However, all Korean sesame cultivars except ‘Namsankkae’ were clustered in the same group, indicating a narrow gene pool. Some of the Korean breeding lines were spread along the dendrogram, showing enlargement of genetic diversity. The genetic diversity data uncovered in this study can be used in future breeding programmes.     

谷子核心种质表型遗传多样性分析及综合评价

通过遗传种质的多样性评估可以指导深入研究资源和育种中优异互补亲本的选择进而提高优异基因的交流累加和新品种培育的效率。本研究选用了来自世界各地的份谷子核心种质通过个表型性状的综合鉴定评估遗传多样性和筛选优异种质资源结果表明我国谷子资源的表型遗传多样性丰富单穗粒重、穗长、穗粗、株高、茎节数和生育期均表现了丰富的变异谷子育成品种遗传多样性相比农家品种下降明显育种的遗传增益主要体现在株高和穗长的适度减低,以及茎粗、茎节数、穗粗、单穗粒重、单穗重及生育期的适度增加系统聚类分析将谷子资源分成类第类以来源为东北欧国家的品种为主第类以北美和非洲的品种为主第类以东亚、南亚的品种为主我国种质可划分为春播型、春夏兼播型和南方型类型采用主成分分析法和逐步回归分析法综合评判表明叶鞘色、刚毛长度、粒色、米色、株高、穗长、茎粗和单穗粒重个性状可作为谷子表型鉴定的主要指标。     

Genetic diversity in cornsalad (Valerianella locusta) and related species as determined by AFLP markers

Fifteen amplified fragment length polymorphism (AFLP) EcoRI/MseI‐based primer combinations with five selective bases (Eco RI‐ANN, MseI‐CN) were used to estimate genetic diversity among 45 line varieties of cultivated cornsalad and 19 genebank accessions classified into nine different species related to cornsalad. Polymorphic fragments were scored for calculation of Jaccard's coefficient of genetic similarity (GS). The average GS estimate in elite germplasm (GS = 0.90) was substantially higher than in exotic germplasm (GS = 0.47). UPGMA‐cluster analysis revealed genetic relationships among recently bred varieties, old varieties and genebank accessions. Analysis of molecular variance indicated almost threefold variability within sets compared with between sets due to a high level of polymorphism among wild species. Sources for increasing genetic diversity in elite germplasm of cornsalad were suggested and a duplicate among the genebank accessions was detected. AFLPs could be considered a powerful tool for genetic diversity estimation in cornsalad germplasm and are recommended for systematic fingerprinting of remaining cornsalad species.     

Male and female genetic linkage map of hops, Humulus lupulus

A male and female linkage map of hop has been constructed using 224 DNA polymorphisms (106 amplified fragment length polymorphisms (AFLPs), three random amplified polymorphic DNAs (RAPDs), one RAPD‐sequence‐tagged‐site (STS), and three microsatellite (STSs) segregating in an F₁ population of the English cultivar ‘Wye Target’‐the German male breeding line ‘85/54/15’. Linkage between these loci was estimated using JOINMAP Version 2.0. The final map for the female parent consisted of 110 loci assigned to eight linkage groups covering a distance of 346.7 cM. For the male map, 57 loci could be mapped on nine linkage groups spanning over 227.4 cM. One of these male linkage groups (Gr09‐M) presumably represents the Y chromosome, since all markers assigned (10 AFLPs, three RAPDs and one STS) were closely linked to the male sex (M). Because of their sex‐specific segregation, 10 doubly heterozygous AFLPs spanning a distance of 18.7 cM could be identified as markers describing the X chromosome, which is part of the male and female map. Three STMSs, which had already proved useful in hop genotyping, could be integrated as codominant locus‐specific markers and thus allowed to produce reliable allelic bridges between the female and male counterparts.     

黑龙江省大豆遗传结构及遗传多样性分析

利用22个表型性状和60个微卫星(simple sequence repeat, SSR)位点对黑龙江省140份代表性种质(78份地方品种和62份育成品种)进行分析, 根据UPGMA (unweighted pair group method with arithmetic mean)和Model-base对SSR数据进行遗传结构划分。结果表明, 参试品种可分为2大类群, 第II类群的各项多样性指标均高于第I类群, 2个类群遗传距离为0.2427;PCO结果显示这2个类群分布在不同区域, 这与地理来源和育成年代密切有关。依据品种类型分为育成品种和地方品种两组, 后者的各项多样性指标均高于前者, 两组间的遗传距离为0.1131。依据表型数据的PCO分析表明, 分布区域与品种类型有关, 与SSR结构分类的结果吻合度低, 两组品种主要在3个主成分的6个表型性状上有所不同。它们不是2个相对独立的遗传群体, 根据分子标记和表型分类各有特点;建议在种质遗传多样性研究中将分子数据和表型数据结合起来。     

Field variation in a tetraploid progeny derived by selfing a Solanum commersonii (+) S. tuberosum somatic hybrid: A multivariate analysis

A phenotypic diversity index (PDI) was calculated using 10 agronomiccharacteristics recorded in 90 accessions of 2-row spring barleys and 29accessions of 6-row spring barleys grown in the Nordic Region. The PDIranged from 0.0308 to 0.6245 in 2-row barley accessions and from0.0314 to 0.7016 in 6-row barley accessions. The average PDIs were0.2178 and 0.2438 in 2-row and 6-row barley germplasm, which confirmsthat some older cultivars were parents of newer cultivars. The lowest PDIwas between accessions with the same name, which suggest that irrespectiveof their market source, they were the same cultivars. The largest PDI rangesin 2-row barley cultivars within the same country or release decade werecorrelated to the number of accessions in the respective cluster, whichsuggests that phenotypic diversity in this germplasm depends on the numberof cultivars included in the cluster. However, this association was not alwaysobserved in 6-row barley cultivars. The most distinct 2-row cultivars wereArla and Akka from Sweden, whereas Sigur and Tampa from Iceland werethe most distinct 6-row cultivars as determined by both PDI and averagelinkage cluster analysis. This analysis also confirm that the 2-row barleyaccessions Jenny, Triumph, and Vega, which were obtained from twodistinct market sources, and the 6-row barley accessions under the nameAgneta (but from three market sources) were the same. The analysis ofvariance of the PDI indicates that 6-row germplasm may be clusteredaccording to their geographical origin or decade of release, but this was notobserved in 2-row barley germplasm. This research demonstrates theadvantage of PDI to assess variation among breeding pools.     

Genetic diversity evaluation of a loquat (<Emphasis Type="Italic">Eriobotrya japonica</Emphasis> (Thunb) Lindl) germplasm collection by SSRs and <Emphasis Type="Italic">S</Emphasis>-allele fragments

Loquat (Eriobotrya japonica (Thunb.) Lindl.) is a minor Rosaceae fruit of growing interest as an alternative to the main fruit crops. In this context, the selection of new cultivars to satisfy the market demand will request the suitable characterization of the available germplasm. In this work, genetic relationships among 83 loquat accessions from different countries belonging to the European loquat germplasm collection, held at the Instituto Valenciano de Investigaciones Agrarias (IVIA) in Moncada (Spain) were evaluated using microsatellites and S-allele fragments. A total of nine single sequence repeats (SSRs) from Malus and Eriobotrya genera revealed 53 informative alleles and the S-RNases consensus primers detected 11 self-incompatibility putative alleles. The combined data allow to distinguish unambiguously 80 out of the 83 accessions studied. Unweighted pair-group method (UPGMA) cluster and principal coordinates analysis (PCoA), based on Dice’s genetic distance, generally grouped genotypes according to their geographic origins and pedigrees. Discrepancies and similarities of the results obtained with other variability analysis, based on pomological traits or molecular markers, on the same loquat collection are discussed.     

以SRAP和EST-SSR标记分析芝麻种质资源的遗传多样性

利用SRAP和EST-SSR分子标记对192份国内外芝麻种质资源进行遗传多样性分析。结果表明,2种标记都能很好地揭示品种间遗传关系;在31对SRAP引物组合扩增的270个等位基因中多态性占62.08%,平均每对引物可以检测5.45个;25对SSR引物扩增的136个等位基因中56.28%呈多态性,平均每对检测引物产生3.04个。UPGMA聚类结果显示,在相似性系数为0.70时,192份材料可被分为3个类群;阈值为0.75时类群Ⅰ又可分为6组,表明芝麻品种遗传多样性比较丰富。我国南部地区芝麻品种遗传多样性(多样性指数H_i=2.572)较中部(H_i=2.117)和北部地区 (H_i=2.114)丰富。分析结果将有助于更好地保护和利用芝麻种质资源,并为育种工作提供依据。     

Phenotypic variation and the relationships among mustard (Brassica juncea L.) germplasm from Pakistan

An investigation was conducted to determine the extent of diversity and relationships among the Brassica juncea germplasm from Pakistan using morphological characters. A total of 52 accessions, including the collected germplasm as well as commercial cultivars/improved lines, were studied under field conditions at Tsukuba, Japan during 1995 and 1996. All the accessions were characterized for 35 agro-morphological characters from seedling emergence to crop maturity. Morphological data were analyzed by numerical taxonomic techniques using two complementary procedures: cluster and principal component analyses. Phenograms based on Euclidean distance placed the accessions into six groups during both years. Landrace groups were primarily associated with morphological differences among the accessions and secondarily with the breeding objectives and horticultural uses. The mustard germplasm collected from Pakistan showed a comparatively low level of phenotypic variation amongst themselves and were genetically similar to the oilseed cultivars. However, the oilseed forms and vegetable cultivars were genetically distinct. This study revealed that the evaluated germplasm appears to have a narrow genetic base which undergoes a high level of genetic erosion. This is perhaps due to the use of the same ancestors in the selection of new lines for similar horticultural traits, replacement by major crops and changes in agricultural land uses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular analysis of the barley cv. 'Valticky' and its X-ray-derived semidwarf-mutant 'Diamant'

The outstanding semidwarf spring barley cultivar ‘Diamant’ was derived from the cv.‘Valticky’ by X‐ray mutagenesis. More than 120 European spring barley varieties trace back to ‘Diamant’. This variety and nine German spring barley cultivars having ‘Diamant’ in their pedigree, as well as four cultivars not related to ‘Diamant’, were analysed by amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs) in order to identify genomic regions associated with traits derived from ‘Diamant’. The total number of SSRs tested was 122, of which 88 were polymorphic taking all varieties into account, with 51 for ‘Valticky’ and ‘Diamant’, i.e. 42.8%. A varying level of polymorphism was detected on individual chromosomes (11.1–78.6%). In addition, AFLP revealed a high level of polymorphism. Out of the total number of 1591 bands, 670 were polymorphic for all varieties studied with 182 for ‘Valticky’ and ‘Diamant’, i.e. 11.4%. Based on SSR and AFLP data UPGMA cluster analysis was carried out, but no grouping according to the relatedness with ‘Diamant’ or ‘Valticky’, respectively, was found. It is concluded from these results that the mutagenic effect leading to the development of ‘Diamant’ out of ‘Valticky’ affected many genetic loci and is thus larger than expected.     

云南茶树资源遗传多样性与亲缘关系的ISSR分析

以8个种群134份云南茶树资源为材料,应用ISSR标记方法,进行了遗传多样性与亲缘关系分析。结果表明,18个多态性ISSR引物对全部试验材料进行PCR扩增,共获得475条稳定的谱带,其中多态性谱带470条(占98.9%),遗传多样性丰富;应用Nei-Li相似系数法估算了134个材料间的相似系数为0.445~0.819,平均为0.512,说明茶树资源间的遗传基础较宽;对134份茶树资源的分子系统聚类分析(UPGMA)将资源分为3大组,聚类结果与地理距离没有明显的相关性;主成分分析(PCA)表明主成分分析的结果与系统聚类基本一致,但是主成分分析更加直观清晰地显示各个材料间的亲缘关系;大厂茶等8个种群间的遗传相似系数于0.850~0.987间,平均为0.92,表明不同种群间的遗传差异较小。     

Genetic diversity in apricot, Prunus armeniaca, aimed at improving resistance to plum pox virus

Plum Pox Virus, a non-persistent virus transmitted by aphids, causes serious damage to stone fruits. The apricot tree is very sensitive and in order to breed apricot cultivars resistant to Plum Pox Virus and establish breeding strategies, genetic diversity based on 10 enzymatic systems, six of which were polymorphic, has been studied. The plant material studied, 94 accessions, included the most important apricot cultivars grown in PPV-affected areas. Genetic diversity is high and showed important differences between the three geographical groups studied (North African, European and North American). The North American group was very diverse and allozymes can be used to identify three subgroups. Some North American PPV-resistant cultivars were very distant from the rest of the cultivars, mainly due to the presence of rare alleles found in an Asian apricot related species. These results support the hypothesis that Asian-related species might be the origin of PPV resistance within the North American cultivars. Three North American cultivars have been considered as putative donors of PPV resistance to the European cultivars because of their agronomic behaviour, chilling requirements and distance from European cultivars. However, to increase the genetic variability of the European group and thereby to favour recombination, the study of Asian apricot resources is also recommended.     

部分烟草种质遗传多样性与亲缘关系的ISSR标记分析

烟草遗传资源多样性与亲缘关系研究，是烟草遗传育种与起源演化研究的重要基础，本文首次应用ISSR标记，对烟草属（Nicotiana）4个种30份材料的遗传多样性进行分析。从70个ISSR引物中共筛选出16个多态性明显、条带清晰、反应稳定的引物，对30个样品DNA共扩增出309条谱带，平均每个引物扩增出19.31条带，多态性条带比率（PPB）达93.20%。种间遗传相似系数在0.26~0.96之间，表现出丰富的遗传多态性。系统聚类结果显示，N. glutinosa、N. suaveolens、N. gossei 3个野生种间存在较大的遗传差异，遗传相似系数在0.29~0.52之间；27份栽培品种种内遗传相似性相对较高，在0.54~0.96之间，显示出栽培种内的遗传基础相对比较狭窄，但其中白肋21、台烟7号与其他供试材料有较大的遗传差异。ISSR聚类分析表明，当L1取值为D = 0.475时，可将3个野生种与27份烟草栽培品种明显区分开，反映出种间的遗传差异；当L2取值为D = 0.776时，可将30份材料分为2个大类、3个小类和6个独立的个类，较好地揭示了烟草属种间或栽培种品种类型间的遗传多样性与亲缘关系，可为烟草遗传育种和遗传连锁图谱构建的杂交亲本选择提供科学依据。本研究还表明ISSR标记比RAPD标记具有更高的稳定性，在植物遗传多样性的分子标记或克隆研究中，可优先使用ISSR标记。     

Genetic diversity in cultivated Osteospermum as revealed by random amplified polymorphic DNA analysis

A collection of 28 Osteospermum clones and cultivated varieties of different origin were evaluated by random amplified polymorphic DNA (RAPD) analysis. All the clones were identified by 12 decamers selected from a set of 30. This is the first characterization by molecular markers of the genetic material of Osteospermum. The level of genetic diversity among genotypes was assayed and all the accessions tested were then classified into six groups by UPGMA cluster analysis; the clustering of genotypes using the RAPD data proved to be in accordance with their breeding group origin. RAPD analysis can therefore be a useful tool for evaluating genetic variability in other Osteospermum germplasm collections for breeding purposes and for protecting intellectual property rights of improved varieties.     

Efficiency of SNP and SSR-based analysis of genetic diversity,population structure,and relationships among cowpea (<Emphasis Type="Italic">Vigna unguiculata</Emphasis> (L.) Walp.) germplasm from East Africa and IITA inbred lines

The extent of genetic diversity and relatedness of cowpea germplasm from East Africa are poorly understood. A set of 13 microsatellites (SSR) and 151 single nucleotide polymorphisms (SNPs) markers were applied to assess the levels of genetic diversity in a sample of 95 accessions of local cowpea germplasm and inbred lines of Vigna unguiculata. The average genetic diversity (D), as quantified by the expected heterozygosity, was higher for SSR loci (0.52) than for SNPs (0.34). The polymorphic information content was 0.48 for SSR and 0.28 for SNP while the fixation index was 0.095 for SSR and 0.15 for SNPs showing moderate differentiation and high gene flow among cowpea accessions from East African countries. The results of data analysis of both SSR and SNP markers showed similar clustering patterns suggesting a substantial degree of association between origin and genotype. Principal coordinate analysis (PCoA) with SSR and SNP markers showed that accessions were grouped into two and three broad groups across the first two axes, respectively. Our study found that SNP markers were more effective than SSR in determining the genetic relationship among East African local cowpea accessions and IITA inbred lines. Based on this analysis, five local cowpea accessions Tvu-13490, Tvu-6378, Tvu-13448, Tvu-16073, and 2305675 were identified to be tightly clustered sharing several common alleles with the drought tolerant variety Danila when analyzed with SSR and SNP markers. The findings will assist and contribute to future genetic diversity studies aimed at the genetic improvement of local Eastern Africa cowpea accessions for improved overall agronomic performance in general and breeding for drought tolerant in particular.     

Genetic diversity of Brassica napus L. Germplasm from China and Europe assessed by some agronomically important characters

Summary The genetic diversity and relationships among 63 rapeseed accessions, including 34 Chinese, 22 Czech, 2 Swedish, 2 German, one French and 2 Canadian accessions, were evaluated by nine agronomically important characters in the field at Yangling, Shaanxi, China. Significant differences between Chinese and European group in plant height, setting position of the first primary branch, number of siliques of the terminal raceme, thousand seed weight and seed yield per plant were detected. There were significant variations in nine agronomic characters among the tested rapeseed accessions. Ward’s minimum variance cluster analysis based on Mahalanobis distances on the raw data of nine agronomic characters clearly separated the European accessions from the Chinese ones. However, the Chinese accessions with erucic acid free and/or low glucosinolates could not be separated from those Chinese accessions with both high erucic acid and glucosinolates. In general, cluster analysis of the 63 accessions based on the selected agronomic characters was consistent with known pedigree information and geographic origin, as well as the previous RAPD results of these accessions. The European rapeseed could be important germplasm resources for enriching the genetic background of Chinese rapeseed, and vice versa.