HMCES Maintains Genome Integrity by Shielding Abasic Sites in Single-Strand DNA.

Abasic sites are one of the most common DNA lesions. All known abasic site repair mechanisms operate only when the damage is in double-stranded DNA. Here, we report the discovery of 5-hydroxymethylcytosine (5hmC) binding, ESC-specific (HMCES) as a sensor of abasic sites in single-stranded DNA. HMCES acts at replication forks, binds PCNA and single-stranded DNA, and generates a DNA-protein crosslink to shield abasic sites from error-prone processing. This unusual HMCES DNA-protein crosslink intermediate is resolved by proteasome-mediated degradation. Acting as a suicide enzyme, HMCES prevents translesion DNA synthesis and the action of endonucleases that would otherwise generate mutations and double-strand breaks. HMCES is evolutionarily conserved in all domains of life, and its biochemical properties are shared with its E. coli ortholog. Thus, HMCES is an ancient DNA lesion recognition protein that preserves genome integrity by promoting error-free repair of abasic sites in single-stranded DNA.

Genetic diversity and structure of the coffee leaf rust fungus Hemileia vastatrix across different coffee management systems in Ethiopia.

Although coffee leaf rust (CLR), caused by Hemileia vastatrix, poses an increasing threat to coffee production in Ethiopia, little is known regarding its genetic diversity and structure and how these are affected by coffee management. Here, we used genetic fingerprinting based on sequence-related amplified polymorphism (SRAP) markers to genotype H. vastatrix samples from different coffee shrubs, across 40 sites, covering four coffee production systems (forest coffee, semi plantation coffee, home garden coffee, and plantation coffee) and different altitudes in Ethiopia. In total, 96 H. vastatrix samples were successfully genotyped with three primer combinations, producing a total of 79 scorable bands. We found 35.44% of amplified bands to be polymorphic, and the polymorphic information content (PIC) was 0.45, suggesting high genetic diversity among our CLR isolates. We also found significant isolation-by-distance across the samples investigated and detected significant differences in fungal genetic composition among plantation coffee and home garden coffee and a marginally significant difference among plantation coffee and forest coffee. Furthermore, we found a significant effect of altitude on CLR genetic composition in the forest coffee and plantation systems. Our results suggest that both spore dispersal and different selection pressures in the different coffee management systems are likely responsible for the observed high genetic diversity and genetic structure of CLR isolates in Ethiopia. When selecting Ethiopian coffee genotypes for crop improvement, it is important that these genotypes carry some resistance against CLR. Because our study shows large variation in genetic composition across relatively short geographical distances, a broad selection of rust isolates must be used for coffee resistance screening.

The SOS response-associated peptidase (SRAP) domain of YedK catalyzes ring opening of abasic sites and reversal of its DNA-protein cross-link.

Apurinic/apyrimidinic (AP, or abasic) sites in DNA are one of the most common forms of DNA damage. AP sites are reactive and form cross-links to both proteins and DNA, are prone to strand breakage, and inhibit DNA replication and transcription. The replication-associated AP site repair protein HMCES protects cells from strand breaks, inhibits mutagenic translesion synthesis, and participates in repair of interstrand DNA cross-links derived from AP sites by forming a stable thiazolidine DNA-protein cross-link (DPC) to AP sites in single-stranded DNA (ssDNA). Despite the importance of HMCES to genome maintenance and the evolutionary conservation of its catalytic SRAP (SOS Response Associated Peptidase) domain, the enzymatic mechanisms of DPC formation and resolution are unknown. Using the bacterial homolog YedK, we show that the SRAP domain catalyzes conversion of the AP site to its reactive, ring-opened aldehyde form, and we provide structural evidence for the Schiff base intermediate that forms prior to the more stable thiazolidine. We also report two new activities, whereby SRAP reacts with polyunsaturated aldehydes at DNA 3'-ends generated by bifunctional DNA glycosylases and catalyzes direct reversal of the DPC to regenerate the AP site, the latter of which we observe in both YedK and HMCES-SRAP proteins. Taken together, this work provides insights into possible mechanisms by which HMCES DPCs are resolved in cells.

Inheritance and molecular mapping of solitary/cluster fruit-bearing habit in Luffa.

Fruiting behaviour and sex form are important goals for Luffa breeders and this study aimed to shed light upon inheritance patterns for both these traits. The hermaphrodite form of Luffa acutangula (known as Satputia) is an underutilized vegetable with a unique clustered fruiting habit. Its desirable traits, such as plant architecture, earliness, as well as contrasting traits like unique clustered fruiting, bisexual flower, and crossability with Luffa acutangula (monoecious ridge gourd with solitary fruits), make it a potential source for trait improvement and mapping of desirable traits in Luffa. In the present study, we have elucidated the inheritance pattern of fruiting behaviour in Luffa using F2 mapping population generated from a cross between Pusa Nutan (Luffa acutangula, monoecious, solitary fruiting) × DSat-116 (Luffa acutangula, hermaphrodite, cluster fruiting). In F2 generation, the observed distribution of plant phenotypes fitted in the expected ratio of 3:1 (solitary vs cluster) for fruit-bearing habit. This is the first report of monogenic recessive control for cluster fruit-bearing habit in Luffa. Herein, we designate for the first time the gene symbol cl for cluster fruit bearing in Luffa. Linkage analysis revealed that SRAP marker ME10 EM4-280 was linked to the fruiting trait at the distance of 4.6 cM from the Cl locus. In addition, the inheritance pattern of hermaphrodite sex form in Luffa was also studied in the F2 population of Pusa Nutan × DSat-116 that segregated into 9:3:3:1 ratio (monoecious:andromonoecious:gynoecious:hermaphrodite), suggesting a digenic recessive control of hermaphrodite sex form in Luffa, which was further confirmed by the test cross. The inheritance and identification of molecular marker for cluster fruiting trait provides a basis for breeding in Luffa species.

Development of a novel SRAP-SCAR marker for rapid identification of lager and ale types in brewer's yeast.

BACKGROUND: Beer is a globally consumed and universally popular beverage. According to the fermentation conditions of brewer's yeast, ale yeast and lager yeast are the two major varieties. Normal phenotypic and genotypic approaches are insufficient and time-consuming for identifying these two forms of yeast. Therefore, a method for the rapid and cost-effective identification of lager and ale-type brewer's yeasts is necessary. METHODS AND RESULTS: In this study, we analysed the genetic diversity of 23 industrial brewer's yeasts from around the world using sequence-related amplified polymorphism (SRAP) markers and produced stable sequence characteristic amplification region (SCAR) markers. The specific DNA fragments identified by the SRAP marker were sequenced and primers were constructed; the resultant SCAR marker (757 bp) was then confirmed against the indicated brewer's yeast type. CONCLUSION: The development of SRAP-SCAR marker is more economical, simple, and fast compared to morphological markers.

SRAP markers as an alternative tool for Alternaria classification.

Alternaria is one of the main fungal contaminants of cereal grains worldwide with the potential to produce mycotoxins hazardous to human and animal health. Many studies have been carried out to characterize Alternaria sp.-grp. using traditional morphology or polyphasic approach, but a good correlation between morphological sp.-grp., molecular, and chemotaxonomic groups has not always been achieved. For this reason, this study aimed to investigate the usefulness of a cheaper alternative tool, SRAP markers, in identifying Alternaria sp.-grps. obtained from Argentinean barley grains and to compare it with preliminary characterization using morphological traits, phylogeny, and metabolite profiles. Fifty-three Alternaria isolates from barley grains of the main producing regions of Argentina were analyzed with four combinations of SRAP markers. The UPGMA dendrogram, based on the Simple Matching similarity coefficient, revealed three distinct groups. SRAP markers allowed the separation of Alternaria from Infectoriae sections in agreement with the results of a polyphasic approach previously made. Besides, isolates of A. arborescens sp.-grp. were clustered in a separate group from isolates of A. tenuissima and A. alternata sp.-grp., which were grouped in the same cluster. SRAP markers are a recommended tool for classifying Alternaria isolates because of its simplicity, reliability, and cost-effectiveness compared to other molecular markers.

The Glycoprotein 340's Scavenger Receptor Cysteine-Rich Domain Promotes Adhesion of Staphylococcus aureus and Pseudomonas aeruginosa to Contact Lens Polymers.

Contact lenses are biomaterials worn on the eye to correct refractive errors. Bacterial adhesion and colonization of these lenses results in adverse events, such as microbial keratitis. The adsorption of tear proteins to contact lens materials enhances bacterial adhesion. Glycoprotein 340 (Gp340), a tear component, is known to promote microbial colonization in the oral cavity; however, it has not been investigated in any contact lens-related adverse event. Therefore, this study examined the adsorption of Gp340 and its recombinantly expressed scavenger receptor cysteine-rich (iSRCR1Gp340) domain on two common contact lens materials, etafilcon A and lotrafilcon B, and the concomitant effects on the adherence of clinical isolates of microbial keratitis causative agents, Pseudomonas aeruginosa (PA6206; PA6294), and Staphylococcus aureus (SA38; USA300). Across all strains and materials, iSRCR1Gp340 enhanced adherence of bacteria in a dose-dependent manner. However, iSRCR1Gp340 did not modulate the lysozyme's or lactoferrin's effects on bacterial adhesion to the contact lens. The Gp340 binding serine-rich surface protein (SraP) significantly enhanced the binding of USA300 to iSRCR1Gp340-coated lenses. In addition, iSRCR1Gp340-coated surfaces had significantly diminished biofilms with the SraP mutant (ΔSraP), and there was a further reduction in biofilms with the sortase A mutant (ΔSrtA), indicating the likely involvement of additional surface proteins. Finally, the binding affinities between iSRCR1Gp340 and SraP were determined using surface plasmon resonance (SPR), where the complete SraP binding region displayed nanomolar affinity, whereas its smaller fragments adhered with micromolar affinities. This study concludes that Gp340 and its SRCR domains play an important role in bacterial adhesion to the contact lens.

Development of molecular markers linked to QTL/genes controlling Zn efficiency.

BACKGROUND: Zinc (Zn) deficiency is a widespread problem in reducing the yield and quality of crop plants worldwide. It is important to utilize molecular markers linked to Zn efficiency to develop high Zn efficient cultivars in pepper (Capsicum annuum L.). METHODS AND RESULTS: In present study, genetic map was constructed using a F2 populations derived from C. annuum L. (Alata 21A) × C. frutescens L. (PI 281420) cross. The quantitative trait locus (QTLs) for Zn efficiency were mapped using F2:3 population. A genetic map with 929.6 cM in length and 12 linkage groups were obtained using 62 markers (31 sequence-related amplified polymorphism (SRAP), 19 simple sequence repeat (SSR) and 11 random amplified polymorphic DNA (RAPD) markers). The 41 linked QTLs related with nine (9) Zn efficiency characters were mapped on linkage groups. Results suggest that selecting plants for tolerance to Zn deficiency are expected to be rather responsive among segregating populations for breeding and developing Zn efficient genotypes in pepper. CONCLUSIONS: The molecular markers are expected to aid selection and expedite breeding peppers resistant to Zn deficiency in soils low for available Zn contents.

Determination of the effective radiation dose for mutation breeding in purple carrot (Daucus carota L.) and possible variations formed.

BACKGROUND: Plant breeding allows altering the genetic structure of plants to meet human needs. The use of radiation technology for inducing mutations and -thereby- new phenotypic variants has become increasingly common as a tool for developing new crops. The aim of this study was to determine the effective gamma irradiation dose for inducing mutations in purple carrot. METHODS AND RESULTS: Increasing gamma radiation doses [0, 50, 100, 200, 300, 400, 500, and 600 Gy] were applied to purple carrot seeds. The irradiated seeds were sown in pots and the emergence and survival rates of the seedlings were analyzed. Considering plant emergence (%) as a response variable, the LD50 dose was 387.5 Gy. Analysis of root length, root width (shoulder diameter) and plant height in control (0 Gy) and irradiated plants (50-600 Gy) revealed an inverse association between these morphological traits and radiation dose. SRAP and ISSR markers were used to identify DNA polymorphisms in irradiated and control plants. The range of amplicons per primer set revealed by ISSR and SRAP markers was 4-10 and 2-13, respectively. In the ISSR analysis of the irradiated carrots (for the 8 doses used), we obtained range values for the average Nei's gene diversity, Shannon's information index, and polymorphism information content (PIC) of 0.13-0.25, 0.20-0.35, and 1.39-1.67, respectively, whereas in the SRAP analysis, the range values for these parameters were 0.15-0.25, 0.23-0.37, and 0.43-0.58, respectively. Cluster analysis revealed three main groups; (a) non-irradiated (control) plants, (b) plants from the 600 Gy dose, and (c) a third group with two subgroups: one with individuals from the lowest irradiation doses (50-200 Gy) and a second group with individuals from the highest irradiation doses (300-500 Gy). CONCLUSIONS: This is the first report on determining effective mutagen doses and genetic characterization of induced mutagenesis via gamma irradiation in purple carrot. ISSR and SRAP markers were successful in detecting variations among different levels of mutagen doses.

Genetic diversity and verbascoside content in natural populations of Pyrostegia venusta (Ker Gawl.) Miers.

BACKGROUND: Pyrostegia venusta (Ker Gawl.) Miers occurs in threatened biodiversity hotspots of Cerrado and Atlantic forest biomes in Brazil and is used in traditional medicine to treat various respiratory and skin diseases. METHODS AND RESULTS: This study (i) examined the genetic diversity and structure of six natural populations of P. venusta from different Brazilian regions using sequence-related amplified polymorphism (SRAP) markers; and (ii) compared the intra- and inter-populational levels of the bioactive component verbascoside using high-performance liquid chromatography. The population from Nova Mutum, Mato Grosso, presented the highest genetic variability (Nei index H = 0.2759; Shannon index I = 0.4170; 85.14% polymorphic loci), whereas the population from Araxá, Minas Gerais, presented the lowest genetic variability (H = 0.1811; I = 0.2820; 70.27% polymorphic loci). The intra-populational variability (79%) was significantly higher (p = 0.001) than the inter-populational variability (21%). The populations were clustered into two groups but their genetic differentiation was not associated with geographical origin (Mantel test, r = 0.328; p > 0.05). The verbascoside content significantly differed (p > 0.05) among the six populations and between the individuals from each population. The highest verbascoside levels (> 200 µg/mg extract) were detected in populations from Araxá and Serrana, while the lowest verbacoside levels were detected in populations from Paranaíta and Sinop. CONCLUSIONS: This is the first report on the use of SRAP markers to analyze genetic variability in the family Bignoniaceae. Our findings shall help to better understand the genetic and chemical diversity of P. venusta populations, as well as provide useful information to select the most appropriate individuals to prepare phytomedicines.

Development of SCAR Markers to Identify Medicinal Cultivars of Paeonia lactiflora.

Paeoniae Radix, the dried root of Paeonia lactiflora, is one of the most important ingredients in Kampo medicine. It is known that Paeoniae Radix is derived from various P. lactiflora cultivars, including medicinal and horticultural cultivars, and that cultivar identification by DNA analysis has been unsuccessful. We attempted to develop sequence characterized amplified region (SCAR) markers as useful DNA markers for the identification and herbal medicine authentication of two cultivars developed in Japan, 'Bonten' and 'Kitasaisho,' which are two superior medicinal strains of P. lactiflora. Sequence-related amplified polymorphism (SRAP) analysis was conducted on fourteen P. lactiflora cultivars, and polymorphic fragments specific to 'Bonten' or 'Kitasaisho' were detected. Then, SCAR markers for 'Bonten' and 'Kitasaisho' were developed from the sequence information of these polymorphic fragments. Thirty cultivars of P. lactiflora and five herbal medicine samples were used to validate the specificity of the developed SCAR markers. As a result, we confirmed that our SCAR markers can identify 'Bonten' or 'Kitasaisho' from the plant samples and the herbal medicine samples. Thus, we have successfully designed two highly specific DNA markers and established an easy, rapid, and cost-efficient method to identify specific cultivars of P. lactiflora. Our SCAR markers are expected to contribute to the maintenance of P. lactiflora cultivars such as 'Bonten' as superior medicinal strains, the development of more elite cultivars in the future, and the deterrence of outflow of original cultivars to foreign countries.

Analysis of differential gene expression by SRAP-cDNA in mantle tissue of Meretrix petechialis with different external shell color.

Gene expression of two shell colors in Meretrix petechialis were analyzed by sequence related amplified polymorphism-cDNA to screen the associated molecular markers. The two shell color genomes of M. petechialis were amplified using combinations of 30 primers; 11 pairs of primers showed differential fragments, and by recovery, cloning and sequencing, 18 different differential sequences were obtained. The sequencing results were analyzed by BlastX. Only one fragment shared high homology with memory-related protein-2 and TonB-dependent receptor was found that related to shell color. Sequence characterized amplified region primers were designed according to the difference sequences, and PCR amplification was performed in both 'yellow' and 'red' M. petechialis. Four pairs of differential primers were obtained. Using the population to verify the four markers (Me1-Em2, Me2-Em3, Me4-The Em11 and Me4-Em12), it was found that Me1-Em2 and Me2-Em3 were positive in the 'yellow' and Me4-The Em11 and Me4-Em12 were positive in the 'red' M. petechialis populations. All four markers can, therefore, be used as M. petechialis shell color related markers. This provides a theoretical basis for studying shell color regulation in M. petechialis, which may help to reveal the underlying molecular mechanisms more comprehensively.

Genetic Diversity Assessment of a Chinese Medicinal Endemic Species, Aspidopterys obcordata var. obcordata, by Combined Molecular Marker Methods (ISSR & SRAP).

Aspidopterys obcordata var. obcordata, a medicinal plant endemic to China, is a narrowly distributed species and wild resources are extremely limited. To evaluate the genetic variability and degree of genetic divergence of A. obcordata var. obcordata, and to make rational scientific decisions on its harvest and germplasm conservation, we collected 122 samples from across nearly all of its distribution area and studied genetic diversity using inter-simple sequence repeats (ISSRs), sequence-related amplified polymorphisms (SRAPs), and a method combining the two techniques. The results revealed the high genetic diversity of A. obcordata var. obcordata, mainly due to its intra-population diversity, and the top two populations with the highest levels of intra-population diversity were ML and DH, individuals of which can serve as excellent germplasm candidates during the processing of germplasm screening and conservation. In general, the combining method was prior to the ISSR analyses and SRAP analyses results, except for a slight difference in the genetic structure of individual populations. Therefore, we suggest that a combination analysis of the two marker methods is ideal for evaluating the genetic diversity and genetic relationships of A. obcordata var. obcordata.

Genetic analysis of anther culture response and identification of QTLs associated with response traits in wheat (Triticum aestivum L.).

Anther culture is the most effective tool for doubled haploid production of wheat. This investigation was conducted to estimate genetic parameters of anther culture response in wheat and identification of putative Quantitative trait loci (QTLs) associated with response traits. Two varieties of wheat, namely ICR-DH (P1) and Sle 1 × 15 (P2) and their F1 and F2 progenies were used in the present investigation to estimate genetic parameters of anther culture response. Two molecular marker systems, SRAP and SSR markers were used to detect the polymorphism between two anther donor parents. Single marker analysis (SMA) and Composite interval mapping (CIM) were used to localize the putative QTL associated with four anther culture response in wheat using 100 plants of F2 population derived from F1 cross 'ICR-DH' × 'Sel 1 × 15'. Analyses of variance indicated significant differences between four populations (P1, P2, F1 and F2) for callus induction (CAL), number of green plants per 100 anther (GR), number of albino plant per 100 anther (AR) and total regenerated plants per 100 anther (TR). The additive effects were more important than dominance effects in controlling these traits. The two molecular marker systems were sufficient in detecting polymorphism between two parents. Thirty two putative QTLs were detected on eight linkage groups. Our study indicated that the additive effects of genes and detection of new QTLs permit marker-assisted selection of genotypes with high green plantlet regeneration efficiency in anther culture, and therefore favor efficient use of anther culture in wheat breeding programs.

Evaluation of the genetic diversity of wild Salvadora persica 'Arak' from Saudi Arabia.

Assessment of genetic diversity is crucial for efficient selection genotypes in plant breeding and improvement programs. Studies of genetic diversity of S. persica are rare relative to the large species diversity in Saudi Arabia, despite its valuable importance as one of the most popular medicinal plants. We investigate the genetic variability and genetic differentiation among and within wild Salvadora persica populations distributed in four regions of Saudi Arabia. Twelve sequence-related amplified polymorphism (SRAP) primers combination generated 326 alleles, with an average of 27.2 alleles per primer. All primers showed 100 polymorphism percentage, and higher PIC values exceeded 0.90. Jaccard similarity values varied between 0.04 to 0.43, with an average of 0.31, which showed a weak relationship among the accessions and their origin. Based on UGPMA and principal coordinate analysis, accessions collected from the same region showed less aggregation. Genetic diversity parameters showed that both Aflaj and Joodah populations recorded the highest mean values for the effective number of alleles (1.26 and 1.24). Shannon index and genetic heterozygosity (0.23 and 0.15 for both populations), and percent of polymorphism 45.45% for Aflaj and 43.87 for Joodah population. Most of the genetic variation was because of differences within populations (77%) and 23% among populations. SRAP markers explored the genetic diversity among and within S. persica populations. In this work, genetic diversity within populations was high, and the population structure was weak. We detected no specific geographic structure, which may reveal an active movement of plants among populations.

Genetic relationships and diversity among populations of Paris polyphylla assessed using SCoT and SRAP markers.

The genetic diversity of 33 Paris polyphylla samples collected from the Dabie Mountains was analyzed using SCoT and SRAP molecular markers, revealing the genetic relationships among Paris polyphylla resources in the Dabie Mountains at the molecular level and providing a theoretical basis for genetic improvement and conservation. As a result, a total of 134 bands were amplified with 9 SCoT primers, the percentage of polymorphic bands was 100%, the average number of primers amplified was 14.89, the PIC value was 94.83% and the genetic similarity coefficient ranged from 0.463 to 0.896. Ten pairs of SRAP primer combinations amplified 135 bands, including 129 polymorphic bands, and the percentage of polymorphic bands was 95.56%. The average number of polymorphic bands obtained with each pair of SRAP primer combinations was 12.9, the PIC value was 93.91%, and the genetic similarity coefficient ranged from 0.533 to 0.904. This study showed that both SCoT and SRAP markers were suitable for the genetic diversity analysis of P. polyphylla, which belongs to a genus in which SRAP marker technology has not previously been applied, despite its application in a variety of other plants.

[Establishment of DNA fingerprints for Chrysosplenium using SRAP Markers].

As a traditional Chinese medicinal material, Chrysosplenium is urgently needed for genetic resource investigation and protection research due to the decrease of its wild resources in recent years. After investigating the wild resources, we conducted genetic polymorphism and clustering studies of 24 species(a total of 36 samples) of Chrysosplenium using SRAP technique. The results showed that a total of 374 polymorphic bands were obtained using 18 pairs of SRAP primers to amplify these samples, on average of 20.7 bands for each primer pair. We used the biological software to analyze the population's genetic parameter and got the N_a value as 2.000 0, N_(e )value as 1.408 4, the average Nei's index as 0.263 5, and the average Shannon information index as 0.419 1. UPGMA cluster analysis showed that all the samples can be divided into three major groups at the genetic similarity coefficient of 0.70: there are 18 species(24 samples) gathered for the Ⅰ groups, 3 species or variation(7 samples) for Ⅱ groups, and 3 species(5 samples) for Ⅲ groups. The differences of these Chrysosplenium species at the molecular level are consistent with that of their geographical and ecological distribution. At the same time, we used SRAP technology to construct 36 DNA digital fingerprints of Chrysosplenium and obtained the unique molecular identification band type of each material. These results will provide effective methods and reliable basis for the identification, protection and genetic diversity analysis of the germplasm resources of Chrysosplenium, and lay a foundation for the further development and utilization of them.

A multilevel exploration of Avena strigosa diversity as a prelude to promote alternative crop.

BACKGROUND: Sand oat (Avena strigosa Schreb.), one of the four cultivated species of the genus Avena, could be considered as another alternative crop. In gene banks 865 germplasm samples of this species have been preserved that have not been thoroughly investigated so far. The results of phenotyping (36 traits), isoenzymatic (12 systems) and genetic (8 pairs of Sequence-related amplified polymorphism markers) variation were used to obtain the complete description of 56 accessions diversity originated from different parts of world. RESULTS: Breeded and weedy forms represented similar pool of morphological traits that indicated a short-term and extensive breeding process, albeit all accessions which we classified as cultivated were characterized by better grain and green mass parameters compared to the weedy ones. Isoenzymes showed relationships with geographical origin, which was not possible to detect by SRAP markers. There was no similarity between morphological and biochemical results. The polymorphism level of SRAP markers was lower than indicated by the available literature data for other species, however it may result from the analysis of pooled samples of accessions with a high internal variability. The extensive type of breeding and its relatively short duration was also reflected in the population structure results. Joint analysis revealed that a secondary centre of diversity is being created in South America and that it has its genealogy from the Iberian Peninsula. CONCLUSIONS: Despite the relatively large representation of this species is in various gene banks, it is highly probable that the vast majority of stored worldwide accessions are duplicates, and the protected gene pool is relatively narrow. Sand oat meets all the requirements for an alternative crop species, but further studies are needed to identify the genotypes/populations with the most favourable distribution of utility and quality parameters.

Genetic diversity in Corchorus olitorius L. revealed by morphophysiological and molecular analyses.

Assessment of genetic diversity has an efficient role in plant breeding and improvement programs. There is a limit number of investigations dealing with the evaluation of genetic diversity in Jew's mallow (Corchorus olitorius L.), despite its valuable importance as a leafy vegetable and a delicious dish rich in vitamins and antioxidants. Therefore, in this study, 18 landraces of Jew's mallow-collected from different locations in Egypt-were used for genetic diversity assessment based on morphophysiological and molecular evaluations. A high degree of variability was found among the evaluated landraces at both levels, indicating the appropriateness of such collection to be involved in breeding approaches. Some morphophysiological traits offered a high level of diversity and effectively discriminated the landraces. Thus, they are recommended to be used in successive morphological evaluation studies. On the other hand, molecular evaluation using the random amplified polymorphic DNA (RAPD) and the sequence related amplified polymorphism (SRAP) efficiently supported the morphological results by exposing a clear genetic relationship among the landraces. In addition, the principal coordinate analysis based on combined data of RAPD and SRAP divided the landraces into two main groups, reflecting their relationship molecularly. The first group included nine landraces related to Upper Egypt and the second gathered three landraces from Delta, while the other six landraces were distinctly distributed around these two groups. The two groups may have two distinct ancestors in addition to the different ancestors of the scattered landraces. Findings of this study are valuable and could assist in Jew's mallow breeding programs.

Genetic diversity between two Egyptian clover varieties and QTL analysis for some agro-morphological traits.

Genetic diversity between two ecotypes of Egyptian clover varieties, namely Fahl (mono-cut) and Helaly (multi-cut) have been assessed based on forage yield and yield components as well as molecular marker systems. The two parental genotypes were crossed to produce seeds of F1 and F2 progenies. Analyses of variance indicated significant differences between four populations (P1 (Fahl), P2 (Helaly), F1 and F2) for fresh forage yield, number of florets/inflorescence, number of seeds/inflorescence and 1000 seed weight. The mean of F1 hybrid indicated over-dominance of the higher performance. The phenotypic and genotypic coefficients of variation were high for fresh forage yield, intermediate for 1000-seed weight and low for number of florets/inflorescence and number of seeds/inflorescence. Four molecular marker systems with 80 primers, 30 RAPD, 10 ISSR, 10 SRAP and 30 SSR were used for studying the genetic diversity between the two parents, out of which 64 primers (26 RAPD, 7 ISSR, 7 SRAP and 24 SSR) were polymorphic between the parents. The four molecular marker systems generated unique DNA bands for each parent. Twenty-one primers which produced higher unique bands in both parents were surveyed on bulked DNA from the extremes of four agro-morphological traits within and between the two ecotypes in F2 generations. Twenty-one primers produced bands distinguish between the bulked extremes for at least one trait within each ecotype or between the two ecotypes. All polymorphic primers were subjected to QTL analysis, out of them 23 only were mapped on three linkage groups with four agro-morphological traits and showed 24 putative QTLs.