Genetic Similarity Matrices Research Articles

A comparison between similarity matrices for principal component analysis to assess population stratification in sequenced genetic data sets.

Genetic similarity matrices are commonly used to assess population substructure (PS) in genetic studies. Through simulation studies and by the application to whole-genome sequencing (WGS) data, we evaluate the performance of three genetic similarity matrices: the unweighted and weighted Jaccard similarity matrices and the genetic relationship matrix. We describe different scenarios that can create numerical pitfalls and lead to incorrect conclusions in some instances. We consider scenarios in which PS is assessed based on loci that are located across the genome ('globally') and based on loci from a specific genomic region ('locally'). We also compare scenarios in which PS is evaluated based on loci from different minor allele frequency bins: common (>5%), low-frequency (5-0.5%) and rare (<0.5%) single-nucleotide variations (SNVs). Overall, we observe that all approaches provide the best clustering performance when computed based on rare SNVs. The performance of the similarity matrices is very similar for common and low-frequency variants, but for rare variants, the unweighted Jaccard matrix provides preferable clustering features. Based on visual inspection and in terms of standard clustering metrics, its clusters are the densest and the best separated in the principal component analysis of variants with rare SNVs compared with the other methods and different allele frequency cutoffs. In an application, we assessed the role of rare variants on local and global PS, using WGS data from multiethnic Alzheimer's disease data sets and European or East Asian populations from the 1000 Genome Project.

AFLP MARKER IN GENETIC DIVERSITYASSESSMENT OF FIG (Ficus carica L.) POPULATIONS IN KURDISTAN REGION – IRAQ.

In this study, the genetic relatedness of 12 cultivars of fig from different populations in Kurdistan region- Iraq were analyzed using eleven AFLP primers pairs combinations by using the technology of molecular analysis the DNA. Genetic similarity matrices were produced for the AFLP data to calculate genetic distances among their cultivars. Genetic similarity coefficient ranged from 0.1261 to 0.3905. The lowest genetic similarity was observed between Kola and Gala Zard (0.1261). The Hejeera Rash and Shela cultivars were most similar ones with a coefficient of 0.3905. Clustering based on AFLP data for the 12 fig cultivars was identified at the 0.32 similarity level. In the developed dendogram two main groups were found, the first one combined Ketek and Shela together, while the second group contained two sub group Shingaly and Benatty combined together, while in the other sub group cluster three other sub-group were identified. The results of this study may help in the formulation of appropriate strategies for conservation and cultivar improvement in figs, for which limited knowledge of the genetic diversity is available.

Estimating Genetic Similarity Matrices Using Phylogenies.

Genetic similarity is a measure of the genetic relatedness among individuals. The standard method for computing these matrices involves the inner product of observed genetic variants. Such an approach is inaccurate or impossible if genotypes are not available, or not densely sampled, or of poor quality (e.g., genetic analysis of extinct species). We provide a new method for computing genetic similarities among individuals using phylogenetic trees. Our method can supplement (or stand in for) computations based on genotypes. We provide simulations suggesting that the genetic similarity matrices computed from trees are consistent with those computed from genotypes. With our methods, quantitative analysis on genetic traits and analysis of heritability and coheritability can be conducted directly using genetic similarity matrices and so in the absence of genotype data, or under uncertainty in the phylogenetic tree. We use simulation studies to demonstrate the advantages of our method, and we provide applications to data.

Ficus Species Genetic Diversity Based on Internal Transcribed Spacer (ITS) Region Analysis

Ficus species (Moraceae) is a globally distributed species and considered one of the largest and most diverse genera of woody plants with growing genetic, environmental, economic, nutritional, and medicinal importance. This study was conducted to detect the genetic and evolutionary relationships among eight species of the genus Ficus (Ficus microcarpa var nitida, F. retusa, F. benjamina Vivian, F. benjamina Starlight, F. cyathistipula, F. elastica Decora and F. binnendijkii, and F. religiosa), by ITS1 and ITS4 primer, the DNA genetic analysis was performed. The eight Ficus species traits ITS phylogenetic analyses indicated that all species were separated into two main clusters containing four groups with identity ranging from 94-100%. The eight Ficus species relationships were estimated by a neighbor-joining (NJ) cluster analysis of genetic similarity matrices. The highest similarity was found between F. benjamina Vivian (Acc.no. MW301203), F. binnendijkii (Acc.no. MW301207), and between Ficus microcarpa var nitida (Acc.no. MW301202) and F. retusa (Acc.no. MW301205), gave the lower similarity index based on the analysis of the morphological features, and the lowest similarity was between F. religiosa (Acc.no. MW301209) and F. cyathistipula (Acc.no. MW301206).

Kinship Solutions for Partially Observed Multiphenotype Data

Current work for multivariate analysis of phenotypes in genome-wide association studies often requires that genetic similarity matrices be inverted or decomposed. This can be a computational bottleneck when many phenotypes are presented, each with a different missingness pattern. A usual method in this case is to perform decompositions on subsets of the kinship matrix for each phenotype, with each subset corresponding to the set of observed samples for that phenotype. We provide a new method for decomposing these kinship matrices that can reduce the computational complexity by an order of magnitude by propagating low-rank modifications along a tree spanning the phenotypes. We demonstrate that our method provides speed improvements of around 40% under reasonable conditions.

Genome-wide associations and detection of potential candidate genes for direct genetic and maternal genetic effects influencing dairy cattle body weight at different ages

BackgroundBody weight (BW) at different ages are of increasing importance in dairy cattle breeding schemes, because of their strong correlation with energy efficiency traits, and their impact on cow health, longevity and farm economy. In total, 15,921 dairy cattle from 56 large-scale test-herds with BW records were genotyped for 45,613 single nucleotide polymorphisms (SNPs). This dataset was used for genome-wide association studies (GWAS), in order to localize potential candidate genes for direct and maternal genetic effects on BW recorded at birth (BW0), at 2 to 3 months of age (BW23), and at 13 to 14 months of age (BW1314).ResultsThe first 20 principal components (PC) of the genomic relationship matrix ({mathbf{G}}) grouped the genotyped cattle into three clusters. In the statistical models used for GWAS, correction for population structure was done by including polygenic effects with various genetic similarity matrices, such as the pedigree-based relationship matrix ({mathbf{A}}), the {mathbf{G}}-matrix, the reduced {mathbf{G}}-matrix LOCO (i.e. exclusion of the chromosome on which the candidate SNP is located), and LOCO plus chromosome-wide PC. Inflation factors for direct genetic effects using {mathbf{A}} and LOCO were larger than 1.17. For {mathbf{G}} and LOCO plus chromosome-wide PC, inflation factors were very close to 1.0. According to Bonferroni correction, ten, two and seven significant SNPs were detected for the direct genetic effect on BW0, BW23, and BW1314, respectively. Seventy-six candidate genes contributed to direct genetic effects on BW with four involved in growth and developmental processes: FGF6, FGF23, TNNT3, and OMD. For maternal genetic effects on BW0, only three significant SNPs (according to Bonferroni correction), and four potential candidate genes, were identified. The most significant SNP on chromosome 19 explained only 0.14% of the maternal de-regressed proof variance for BW0.ConclusionsFor correction of population structure in GWAS, we suggest a statistical model that considers LOCO plus chromosome-wide PC. Regarding direct genetic effects, several SNPs had a significant effect on BW at different ages, and only two SNPs on chromosome 5 had a significant effect on all three BW traits. Thus, different potential candidate genes regulate BW at different ages. Maternal genetic effects followed an infinitesimal model.

Prediction of slaughter age in pigs and assessment of the predictive value of phenotypic and genetic information using random forest

The weight of a pig and the rate of its growth are key elements in pig production. In particular, predicting future growth is extremely useful, since it can help in determining feed costs, pen space requirements, and the age at which a pig reaches a desired slaughter weight. However, making these predictions is challenging, due to the natural variation in how individual pigs grow, and the different causes of this variation. In this paper, we used machine learning, namely random forest (RF) regression, for predicting the age at which the slaughter weight of 120 kg is reached. Additionally, we used the variable importance score from RF to quantify the importance of different types of input data for that prediction. Data of 32,979 purebred Large White pigs were provided by Topigs Norsvin, consisting of phenotypic data, estimated breeding values (EBVs), along with pedigree and pedigree-genetic relationships. Moreover, we presented a 2-step data reduction procedure, based on random projections (RPs) and principal component analysis (PCA), to extract features from the pedigree and genetic similarity matrices for use as inputs in the prediction models. Our results showed that relevant phenotypic features were the most effective in predicting the output (age at 120 kg), explaining approximately 62% of its variance (i.e., R2 = 0.62). Estimated breeding value, pedigree, or pedigree-genetic features interchangeably explain 2% of additional variance when added to the phenotypic features, while explaining, respectively, 38%, 39%, and 34% of the variance when used separately.

Molecular Characterization and Genetic Relationships of Some Stress Tolerant Grape Rootstock Genotypes as Revealed by ISSR and SSR Markers

Grapevine rootstocks are a complex group of plants; most of them are interspecific hybrids evolved using parent genotypes having inherent tolerance to biotic and abiotic stresses. Fifteen species and interspecific hybrids of grape rootstocks along with three Vitis vinifera cultivars from IARI germplasm unit were analyzed with ten ISSR and seven SSR primers combinations. These ISSR produced 69 scorable bands with band size ranged from 200 to 1500 bp, PIC from 0.66 to 0.86 and primer heterozygosity ranged from 0.71 to 0.88. While, SSR primers detected a total of 24 alleles across 15 genotypes with PIC from 0.43 to 0.78 and primer heterozygosity from 0.49 to 0.81.The genetic similarity among the 15 grape genotypes using ISSR and SSR ranged from 0.27 to 1.00 in ISSR and 0.05 to 1.00 in SSR analysis. The genetic similarity matrices using ISSR analysis ranged from 27.0 to 85.0% and SSR 5.0 to 83.0%, respectively. The Vitis species Dogridge and Salt Creek had the highest similarity coefficient of 85% with ISSR analysis, while the interspecific hybrids 1103 Paulsen and 110 Richtier had the maximum similarity coefficient of 83% as identified by SSR analysis. The two marker systems formed two main clusters which were almost similar to that of PCA values. The principal coordinate analysis further helped in depicting the variability among species and hybrids of grape genotypes in three dimensional modes. In case of ISSRs, the first three coordinates accounted 51.92% for the existing variability, while with SSRs the variability accounted is 59.69%. The results revealed that ISSR and SSR markers could be exploited for genetic diversity analysis among the highly heterozygous grape rootstock species and interspecific hybrids.Plant Tissue Cult. &amp; Biotech. 28(1): 77-90, 2018 (June)

Analysis of the genetic diversity of super sweet corn inbred lines using SSR and SSAP markers.

In this study, we compared the efficiency of simple sequence repeat (SSR) and sequence specific amplified polymorphism (SSAP) markers for analyzing genetic diversity, genetic relationships, and population structure of 87 super sweet corn inbred lines from different origins. SSR markers showed higher average gene diversity and Shannon's information index than SSAP markers. To assess genetic relationships and characterize inbred lines using SSR and SSAP markers, genetic similarity (GS) matrices were constructed. The dendrogram using SSR marker data showed a complex pattern with nine clusters and a GS of 53.0%. For SSAP markers, three clusters were observed with a GS of 50.8%. Results of combined marker data showed six clusters with 53.5% GS. To analyze the genetic population structure of SSR and SSAP marker data, the 87 inbred lines were divided into groups I, II, and admixed based on the membership probability threshold of 0.8. Using combined marker data, the population structure was K = 3 and was divided into groups I, II, III, and admixed. This study represents a comparative analysis of SSR and SSAP marker data for the study of genetic diversity and genetic relationships in super sweet corn inbred lines. Our results would be useful for maize-breeding programs in Korea.

English

Six Egyptian pomegranate (Punica granatum L.) cultivars were characterized by fruit characteristics (physical and chemical) and two molecular markers; Inter simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP). Genetic diversity of the pomegranate genotypes was evaluated. Physical fruit traits were determined (weight, volume and diameter), calyx [diameter, length (mm) and Carpels number], fruit firmness (Newton), peel as (weight and thickness), arils weight (g), volume of juice (ml), seeds [fresh and dry weight (g)], and color parameter of (fruit skin, internal peel, arils, juice and seeds). The chemical traits such as soluble solids contents (SSC), vitamin C content, anthocyanin content, pH, and titratable acidity (TA) were assessed and wide variations were observed in each of these traits among the studied cultivars. The genetic variability and relationships among six Egyptian pomegranate cultivars were tested using ISSR and AFLP analyses. The level of polymorphism across cultivars was 53 and 90.7% as revealed by ISSR and AFLP, respectively. ISSR and AFLP revealed different genetic similarities among the six pomegranate cultivars. Each analysis differs not only in its underlying principle, but also in their in-formativeness with regard to the type and amount of polymorphism detected. Genetic similarity matrices estimated from ISSR and AFLP data, showed similarity coefficients to range from 0.77 to 0.94 and 0.33 to 0.73, respectively. ISSR and AFLP characterized the six pomegranate cultivars by a large number of unique markers being 23 and 46 unique markers, respectively. The fruit weight ranged between 479.4 to 185 g of ʻNab El Gamalʼ and ʻAssuityʼ, the firmness was 79.98 of ʻNab El Gamalʼ and 71.84 Newton of ʻManfaloutyʼ cv. The fruit peel thickness varied from 0.6 mm ʻArabyʼ, ʻHegazyʼ and ʻWardiʼ to 0.3 mm ʻAssuityʼ. The arils weight ranged from 87.5 to 275 g of ʻAssuityʼ and ʻNab El Gamalʼ cvs. The percentage net of arils weight/ fruit weight was the highest (59.34% of ʻManfaloutyʼ cv). The juice volume ranged from 62.41 to 71.81 ml/100 g arils for ʻ Wardiʼ and ʻNab El Gamalʼ cvs. The SSC content ranged between 16.01 ʻHegazyʼ and 12.55% ʻAssuityʼ. V.C. content ranged from 3.21 to 14 mg. vitamin/100 ml juice of ʻNab El Gamalʼ and ʻAssuityʼ. The anthocyanin content ranged from 1.47 to 10.03 for ʻArabyʼ and ʻHegazyʼ. The pH values varied from 3.3 (Wardi) to 2.9 (Araby). The Egyptain cultivars of pomegranate have a wide variation in the morphological and chemical characteristics for many uses of fresh fruit and of industry purpose. &nbsp; Key words: Morphological and chemical fruits characterization, pomegranate, inter simple sequence repeat (ISSR), DNA markers, amplified fragment length polymorphism (AFLP).

Genetic Relationships Among Chinese Maize OPVs Based on SSR Markers

Bulk-SSR method was used to analyze the genetic diversity of 44 open-pollinated varieties collected from Henan, Shandong, Shanxi, and Jilin provinces and Guangxi Zhuang Autonomous Region, China using 70 pairs of SSR primers. The purposes of this study were to (1) compare the genetic diversity among 44 Chinese maize open-pollinated varieties; (2) estimate the minimum number of alleles for construction of a stable dendrogram; and (3) trace the genetic relationships among local germplasm from different regions of China. In total, these 70 SSR primers yielded 292 alleles in 176 samples (4×44) analyzed. The number of alleles per locus was 4.17 on average and ranged from 2 to 8. The highest number of alleles per open-pollinated variety (55.25) was detected in Shanxi germplasm, which indicated that open-pollinated varieties from Shanxi possessed the largest genetic diversity among those from the five locations. The correlation coefficients between different genetic similarity matrices suggested that 200 alleles were sufficient for analysis of the genetic diversity of these 44 open-pollinated varieties. The cluster analysis showed that 44 open-pollinated varieties collected from three growing regions in China were accurately classified into three groups that were highly consistent with their geographic origins, and there is no correlation between GS and geographic distance in this study.

Genotyping and identification of six date palm (Phoenix dactylifera L.) cultivars&lt;br&gt;of the Gaza Strip by random amplification of polymorphic DNA

Date palm (Phoenix dactylifera L.) is one of the major fruit crops in the Gaza Strip. The main cultivars are Hayani, Bentaisha, Barhi, Zahedi, Ameri and Halawy. Because of the difficulty associated with morphological identification of date palm cultivars, development of cultivar specific genetic markers have been extensively studied. The purpose of this study was to optimize and apply a reliable molecular marker protocol for genotyping and identification of these cultivars. Random amplification of polymorphic DNA (RAPD) was used to study the genetic diversity among the six cultivars using 42 primers. Genetic similarity matrices were constructed for the six cultivars using the Nei and Li formula and clustered with the UPGMA to determine the relationships between the six cultivars. Nine primers were informative and reproducible, and gave a number of polymorphic bands (on average, 7.2 bands per primer). The overall level of polymorphism was 49%. Genetic similarity among the six cultivars ranged from 76.3 to 93.5%. Some primers gave reproducible cultivar-specific bands that may be reliable to identify that cultivar. Our study introduces for the first time a molecular marker approach, capable of distinguishing and studying the genetic diversity among the six date palm cultivars in the Gaza Strip.

R-ISSR – for Fingerprinting, Mapping and Identification of New Genomic Loci in Rye (Secale cerealeL.)

The results of the research confirming the possibility of applying various combinations of RAPD and ISSR primers in one multiplex PCR and the generation of a new type of R-ISSR products for the rye genome were presented in this work. The following was applied in the research: five rye genotypes including two inbred lines (153/79-1 and Otl-3), hybrid F1 and two bulks (tolerant and susceptible) formed from recombinant inbred lines - RILs (F9) varying in the response to abiotic stress caused by nutrient deficiencies at the seedling stage. While evaluating the possibility of applying R-ISSR to the assessment of the rye variability, five of its genotypes were amplified separately with the RAPD and ISSR primers in each PCR reaction. These primers were combined in R-ISSR amplifications. The products of RAPD, ISSR and R-ISSR amplification were separated in 1.5% agarose gel. 32 R-ISSR combinations were examined, combining 20 and 8 selected RAPD and ISSR primers, respectively. 658 loci were amplified, including 230 RAPD, 180 ISSR and 271 R-ISSR, including 157 new loci. Over 91 loci were found, with an identical electrophoretic mobility for three methods. It was shown that R-ISSR products with electrophoretic mobility on agarose gels, identical to the co-migrating RAPD or ISSR, are not products of RAPD or ISSR, but they possess sequences of heteroamplicons - R-ISSR. The occurrence of sequences of primers used to R-ISSR was demonstrated while sequencing seven selected products of the above type. The ISSR primers with a low Tm were proven to generate repeatable fingerprints in the thermal profile of the reaction specific for RAPD and combined with the RAPD primer - repeatable R-ISSR profiles. A similar range of variability as described in RAPD or ISSR was observed in the R-ISSR profiles. The correlation coefficient between genetic similarity matrices for five rye genotypes, calculated with the Mantel test, amounted to rABC = 0.870.

Genetic variance between some Egyptian Date Palm cultivars using PCR-based markers with emphasis on the prevalence of Al wijam disease

Date Palm is one of the most important crops in Egypt. At present, Egypt ranked second in world date production. The objectives of this study are the identification the genetic variance between some local varieties of Date Palm, in line with the establishment of a molecular diagnostic method to study the aetiology and the prevalence of Al Wijam disease. Date palm plantations have been suffering from number of pests and diseases infestation, mainly due to Dubas Bug, Red Palm Weevil, Lesser Date moth, and Al Wijam disease. Genomic DNAs were extracted from 18 Date Palm cultivars collected from Date Palm Research Institute, ARC using three different extraction methods. Nine common cultivars (Zaghlool, Hayani, Oraibi, Samani, Sultan, Bent-Aisha, Amrey, Aglani, and Barhee) and nine Siwi cultivars (Siwi, Fryhee, Taktakt, Quaipe, Karama Ghazally, Helw Ghanem, Gorm Agazal, and Oshbeigel,) were used in this study. In order to determine the genetic polymorphism and discriminate between each of these cultivars, RAPD and ISSR analysis were conducted on the isolated DNA samples from each cultivar. DNA fingerprints of the studied cultivars were conducted using 10 RAPD and eight ISSR primers. Dendrograms representing genetic relationships as well as genetic similarity matrices were performed for the studied cultivars using the UPGMA (Unweighted Pair Group Method with Arithmetic Average). Furthermore, 40 date palm trees representing the studied cultivars were collected from El-Marazik, El-Badrasheen, El-Wahat, and Demiate Governorates to study the prevalence of Al-Wijam disease using the DNA hybridisation technique. Symptoms including retardation in terminal bud growth, whole crown of leaves (rosetting symptoms), and yellow longitudinal lines on the midribs were observed. Non-radioactive Dig-labeled probes specific for 16s rDNA region of virus like agents were used to detect the infected trees.

Understanding natural epigenetic variation

Understanding natural epigenetic variation

Disparity between Multilocus Enzyme Electrophoresis, Microsatellite Markers and Pulsed-Field Gel Electrophoresis in epidemiological tracking of Candida albicans

Various molecular systems are available for epidemiological, genetic, evolutionary, taxonomic and systematic studies of innumerable fungal infections, especially those caused by the opportunistic pathogen C. albicans. A total of 75 independent oral isolates were selected in order to compare Multilocus Enzyme Electrophoresis (MLEE), Electrophoretic Karyotyping (EK) and Microsatellite Markers (Simple Sequence Repeats - SSRs), in their abilities to differentiate and group C. albicans isolates (discriminatory power), and also, to evaluate the concordance and similarity of the groups of strains determined by cluster analysis for each fingerprinting method. Isoenzyme typing was performed using eleven enzyme systems: Adh, Sdh, M1p, Mdh, Idh, Gdh, G6pdh, Asd, Cat, Po, and Lap (data previously published). The EK method consisted of chromosomal DNA separation by pulsed-field gel electrophoresis using a CHEF system. The microsatellite markers were investigated by PCR using three polymorphic loci: EF3, CDC3, and HIS3. Dendrograms were generated by the SAHN method and UPGMA algorithm based on similarity matrices (SSM). The discriminatory power of the three methods was over 95%, however a paired analysis among them showed a parity of 19.7-22.4% in the identification of strains. Weak correlation was also observed among the genetic similarity matrices (SSMMLEE×SSMEK×SSMSSRs). Clustering analyses showed a mean of 9±12.4 isolates per cluster (3.8±8 isolates/taxon) for MLEE, 6.2±4.9 isolates per cluster (4±4.5 isolates/taxon) for SSRs, and 4.1±2.3 isolates per cluster (2.6±2.3 isolates/taxon) for EK. A total of 45 (13%), 39 (11.2%), 5 (1.4%) and 3 (0.9%) clusters pairs from 347 showed similarity (SJ) of 0.1-10%, 10.1-20%, 20.1-30% and 30.1-40%, respectively. Clinical and molecular epidemiological correlation involving the opportunistic pathogen C. albicans may be attributed dependently of each method of genotyping (i.e., MLEE, EK, and SSRs) supplemented with similarity and grouping analysis. Therefore, the use of genotyping systems that give results which offer minimum disparity, or the combination of the results of these systems, can provide greater security and consistency in the determination of strains and their genetic relationships.

Estimation of genetic distance and its predictability of F1 hybrid performance in barley

Heterotic performance of hybrids is dependent upon the amount of genetic variability among parents and combining ability of alleles at the loci associated with target traits. This study was carried out to determine if (1) pedigree-based genetic distance could explain molecular levels of genetic diversity, and (2) molecular marker-based genetic distance could predict the degree of hybrid performance in barley. The average value of Random Amplified Polymorphic DNA (RAPD)-based genetic similarity for all 58 genotypes was 0.641. Twenty-two hulless barley and eight malt barley varieties showed low levels of genetic diversity with higher similarity values than the average of all or of the hulled barley variety pool. Coefficients of parentage (COPs) computed for 1,653 pairs of 58 Korean barley varieties ranged from 0 to 0.984 with a mean of 0.048. Correlation between the genealogical and RAPD-based genetic similarity matrices was 0.256 (P < 0.01). Correlation values for the related and for all (related + unrelated) genotype pairs were almost similar to each other, indicating that the unrelated genotypes share a large portion of genomes alike in state, not identical by descent. RAPD-based genetic similarity estimates among parents were poorly correlated with their hybrid performance such as 1,000-grain weight (r = 0.34), biomass yield (r = −0.12), and grain yield (r = −0.04) for 11 genotype pairs of hulled barley. However, correlations between heterozygosity at marker loci and hybrid performance for biomass and grain yield slightly increased when two F1 hybrids were excluded in the analysis due to their low yield.

Features of SNP and SSR diversity in a set of ICARDA barley germplasm collection

Detection and utilization of genetic variation available in the germplasm collection for crop improvement have been the prime activities of breeders. Here a set of ICARDA barley germplasm collection comprising of 185 cultivated (Hordeum vulgare L.) and 38 wild (H. spontaneum L.) genotypes originated from 30 countries of four continents was genotyped with 68 single nucleotide polymorphism (SNP) and 45 microsatellite or simple sequence repeat (SSR) markers derived from genes (expressed sequence tags, ESTs). As two SNP markers provided 2 and 3 datapoints, a total of 71 SNPs were surveyed that yielded a total of 143 alleles. The number of SSR alleles per locus ranged from 3 to 22 with an average of 7.9 per marker. Average PIC (polymorphism information content) value for SSR and SNP markers were recorded as 0.63 and 0.38, respectively. Heterogeneity was recorded at both SNP and SSR loci in an average of 5.72 and 12.42% accessions, respectively. Genetic similarity matrices for SSR and SNP allelic data were highly correlated (r = 0.75, P < 0.005) and therefore allelic data for both markers were combined and analyzed for understanding the genetic relationships among the germplasm surveyed. Majority of clusters/subclusters were found to contain genotypes from the same geographic origins. While comparing the genetic diversity, the accessions coming from Middle East Asia and North East Asia showed more diversity as compared to that of other geographic regions. Majority of countries representing Africa, Middle East Asia, North East Asia and Arabian Peninsula included the genotypes that contained rare alleles. As expected, spontaneum accessions, as compared to vulgare accessions, showed a higher number of total alleles, higher number of alleles per locus, higher effective number of alleles and higher allelic richness and a higher number of rare alleles were observed. In summary, the examined ICARDA germplasm set showed ample natural genetic variation that can be harnessed for future breeding of barley as climate change and sustainability have become important throughout all growing areas of the world, drought/heat tolerance being the most important ones.

Comparison of RAPD, ISSR and SSR markers in assessing genetic diversity among rye (Secale cereale L.) inbred lines

Comparison of RAPD, ISSR and SSR markers in assessing genetic diversity among rye (Secale cereale L.) inbred lines Forty eight inbred lines of winter rye, of various origin and pedigree, were analysed using 19 RAPD (random amplified polymorphic DNA) primers, 8 ISSR (inter-simple sequence repeats) primers and 13 SSR (simple sequence repeats) primer pairs. On the basis of particular marker types, there were created three separate dendrograms and one combined similarity tree, prepared on account of the whole data. Correlation coefficients for individual technique based on genetic similarity matrices were not significant. By comparing the GS data obtained on the basis of singular methods with collective matrix, it was observed that the highest correlation rate was for ISSR method (r=0.68). The utility of each marker technique was compared by using marker index MI. Diversity detecting index (DDT) was suggested in the paper, which may prove helpful in planning and comparing researches on phenetic relationships.

Molecular diversity in the primary and secondary gene pools of genus Oryza

The objective of the present investigation was to assess the genetic relationships among the species of Oryza that belong to the primary gene pool (sativa complex) and the secondary gene pool (officinalis complex) using three marker systems such as RAPDs, ISSRs and SSRs. A total of 432 clear and reproducible bands were amplified from 18 RAPD primers; 113 bands were detected from 8 ISSR primers and 78 alleles were found to be amplified across the Oryza species from 13 SSR primer pairs. All the three dendrograms constructed, using UPGMA from the genetic similarity matrices based on the three marker data sets, were similar in their groupings. In all the three trees, two accessions of Oryza sativa formed an exclusive group indicating its genomic differentiation from its wild ancestors through the process of domestication. Distinctness between the wild species of the sativa and officinalis complexes was evident in all the trees derived from different markers. The groupings obtained among the species of the sativa complex were in perfect concordance with the species relationships established through classical crossability and cytogenetic analysis. This study has brought out some information on the species relationship between the diploid and tetraploid genomes of the officinalis complex possessing BB, CC and DD genomes. The higher level of similarity observed between the species possessing C and D genomes supports the view of many earlier authors that these two genomes might have originated from a single hybridization event. The results of this study also show that the diploid species possessing C genomes such as Oryza officinalis, Oryza rhizomatis and Oryza eichingeri are distinct from their allotetraploid counterparts possessing BBCC and CCDD genomes indicating a wider genomic differentiation in their evolutionary process.