Assessment of molecular markers and marker-assisted selection for drought tolerance in barley(Hordeum vulgare L.)

This review updates the present status of the field of molecular markers and marker-assisted selection(MAS),using the example of drought tolerance in barley.The accuracy of selected quantitative trait loci(QTLs),candidate genes and suggested markers was assessed in the barley genome cv.Morex.Six common strategies are described for molecular marker development,candidate gene identification and verification,and their possible applications in MAS to improve the grain yield and yield components in barley under drought stress.These strategies are based on the following five principles:(1)Molecular markers are designated as genomic‘tags’,and their‘prediction’is strongly dependent on their distance from a candidate gene on genetic or physical maps;(2)plants react differently under favourable and stressful conditions or depending on their stage of development;(3)each candidate gene must be verified by confirming its expression in the relevant conditions,e.g.,drought;(4)the molecular marker identified must be validated for MAS for tolerance to drought stress and improved grain yield;and(5)the small number of molecular markers realized for MAS in breeding,from among the many studies targeting candidate genes,can be explained by the complex nature of drought stress,and multiple stress-responsive genes in each barley genotype that are expressed differentially depending on many other factors.

Karyotype establishment and development of specific molecular markers of Aegilops geniculata Roth based on SLAF-seq

The constant evolution of pathogens poses a threat to wheat resistance against diseases,endangering food security.Developing resistant wheat varieties is the most practical approach for circumventing this problem.As a close relative of wheat,Aegilops geniculata,particularly accession SY159,has evolved numerous beneficial traits that could be applied to improve wheat.In this study,we established the karyotype of SY159 by fluorescence in situ hybridization(FISH)using the oligonucleotide probes Oligo-pTa535 and Oligo-pSc119.2 and a complete set of wheat–Ae.geniculata accession TA2899 addition lines as a reference.Using specific-locus amplified fragment sequencing(SLAF-seq)technology,400 specific markers were established for detecting the SY159 chromosomes with efficiencies reaching 81.5%.The SY159-specific markers were used to classify the different homologous groups of SY159 against the wheat-Ae.geniculata addition lines.We used these specific markers on the 7Mg chromosome after classification,and successfully confirmed their suitability for studying the different chromosomes of SY159.This study provides a foundation for accelerating the application of SY159 in genetic breeding programs designed to improve wheat.

Research Progress on Application of Molecular Markers in Breeding of Camellia oleifera

Camellia oleifera is an important woody oil tree species unique to China.It is known as the world s four major woody oil crops along with olive,oil palm and coconut.It is known as the‘king of oil’because of its high oil content.With the increase of people's attention to the yield of Camellia oleifera,its high yield has become the focus.In traditional breeding model,judgment is performed by phenotypic traits,but this method is single and easily affected by the environment,and can no longer meet the demand.In contrast,molecular marker breeding is not affected by the environment,and is stable and efficient and capable of accurately mapping target genes,so it has attracted much attention.In this paper,the research progress on C.oleifera germplasm resources diversity,DNA fingerprinting construction,genetic linkage map construction and QTL mapping was summarized,and the application of SSR molecular marker technique combined with association analysis in C.oleifera breeding in recent years was discussed,in order to provide new ideas for high-yield breeding of C.oleifera.

Fast tracking alien gene discovery by molecular markers in a late flowering Chinese cabbage-cabbage translocation line‘AT7–4'

Flowering time is an important agronomic trait of Chinese cabbage with late flowering being a primary breeding objective.In our previous work,we obtained Chinese cabbage-cabbage translocation lines that contained several beneficial cabbage genes.Cabbage-specific molecular markers show that these genes were coming from chromosome C01 of cabbage.In this study,we investigated the inheritance of flowering time in a couple of translocation lines and analyzed the transmission rate of molecular markers in the offspring.Consequently,we obtained the late flowering Chinese cabbage-cabbage translocation line‘AT7–4’in which the flowering time was later than that of‘85–1’by about 7 days under 4-week vernalization.Based on previous studies of the genomes of Chinese cabbage and cabbage,we located the cabbage-specific molecular markers that were closely linked at the top of the chromosome A01 in the F2mapping population generated by self-crossing F1s derived from a cross between the translocation line‘AT7–4’and Chinese cabbage‘14–36’.Five flowering-related genes in the alien fragment were found by functional annotation and their molecular markers were developed.This study lays the foundation for the future improvement of Chinese cabbage varieties using A-C translocation lines.

Genetic Relationships Among Soluble Carbohydrates, Anthocyanins and Growth Characteristics in Leymus (Gramineae) Detected with Molecular Markers

Low-temperature soluble carbohydrate accumulations are commonly associated with anthocyanin coloration, attenuated growth and cold adaptation of cool-season grasses. The vrn-1 gene has potent effects on vernalization requirement, growth, and soluble carbohydrate accumulations of the winter-annual Triticeae species. Two hundred and four unmapped AFLP markers and genome-specific DNA markers genetically linked to the vrn-1 gene were used to detect QTL controlling soluble carbohydrate accumulations, anthocyanin coloration and growth characteristics in a segregating population derived from open pollinated Leymus cinereus x L. triticoides hybrids. These perennial Triticeae grasses are distinguished by adaptation and growth habit. As expected, positive trait correlations and pleiotropic gene effects were detected for soluble carbohydrate accumulations and anthocyanin coloration. Likewise, positive trait correlations and pleiotropic gene effects were detected for tillering, leaf development, leaf growth, regrowth and rhizome spread. However, soluble carbohydrate accumulations were not associated with attenuated growth. In fact, several DNA marker alleles, including one near vrn-Ns1, had positive effects on soluble leaf carbohydrate concentrations and low temperature growth. The corresponding DNA marker near vrn-Ns1 had more specific effects on tillering. We speculate that vrn-1 exerts quantitative effects on low-temperature soluble leaf carbohydrate accumulations and growth habit of the perennial Leymus. However, a number of other DNA markers displayed highly significant effects on soluble carbohydrate accumulations and various growth characteristics. Findings indicate that anthocyanin coloration may be a useful phenotypic marker for soluble carbohydrate accumulation. Although variation for soluble carbohydrates was not associated with attenuated growth in this population, this trait was under genetic control.

Development and Utilization of 1S^1 Chromosomearm-specific Molecular Markers of Aegilops longissima

Introducing the 1S^1 chromosome of Aegilops longissima into wheat genome can significantly improve wheat grain quality and contents of iron and zinc. Therefore, the development of molecular markers specific to 1S^1 chromosome of A. longissima is of important significance for breeding high-quality wheat with high contents of iron and zinc in grains. In this study, nine molecular markers specific to 1S^1 chromosome of A. longissima were developed, including two 1S^1S specific markers,six 1S^1L specific markers and one 1S^1 specific marker which was located on both short and long arms. The practicability of these molecular markers were verified using hybrid population as materials. The results showed that hybrid population could be effectively screened and identified, which indicated that the developed 1S^1 chromosome-specific molecular markers could be used for screening and identification of hybrid population and could be used in marker-assisted breeding of high-quality wheat with high contents of Fe and Zn in grains.

Role of CD97^(stalk) and CD55 as molecular markers for prognosis and therapy of gastric carcinoma patients

Objectives： To explore the mechanism of development and aggressiveness in gastric carcinomas by investigating the expression and role of CD97 and its cellular ligand CD55 in gastric carcinomas. Methods： Tumor and corresponding normal mucosal tissue, collected from 39 gastric carcinoma patients, were examined by immunohistochemistry and RT-PCR for the expression of CD97 and CD55. Results： CD97^stalk was strongly stained on scattered tumor cells or small tumor cell clusters at the invasion front of gastric carcinomas. The expression of CD97^stalk was frequently observed in tumors of stage Ⅰ and T1 gastric carcinoma patients. The expression of CD97^stalk between Stage Ⅰ and Stage Ⅱ, Ⅲ, Ⅳ specimens showed significant difference （P〈0.05）, between T1 and T2, T3, T4 specimens also showed significant difference （P〈0.05）. Specimens with tumor invasion depth limited in mucosa of T1 specimens showed higher positive CD55 expression than specimens with the same tumor invasion depth in T2, T3, T4 specimens, the expression of CD55 between T1 and T2, T3, T4 specimens was significantly different （P〈0.05）. There was strong correlation between the distribution patterns of CD97^stalk and CD55 on tumor tissues （r=0.73, P〈0.05）. Signet ring cell carcinomas frequently contained strong CD97^stalk and CD55-staining. Conclusions： Our results suggest that CD97^stalk is probably involved in the growth, invasion and aggressiveness of gastric carcinomas by binding its cellular ligand CD55. CD97^stalk and CD55 could be useful as molecular markers for prognosis and therapy of gastric carcinoma patients.

Charaterization of Citrus Hybrid ＂Huangguogan＂ through the Combination of Morphological and Molecular Markers

Huangguogan, an obvious Citrus hybrid, is suitable for transportation and export and ripens in March or April. Because of late season, it may playa significant role in fruit market. However, its origin is still unconfirmed. The aim of this study was to clarify the possible parentage of Huangguogan via the combination of morphological and molecular markers including simple sequence repeat （SSR） and chloroplast simple sequence repeat （cpSSR）. Analysis of morphological traits including leaf stalk length, phylliform index and fruit shape index indicated that Huangguogan had similarities in morphology with Sweet orange. The SSR Cluster Analysis showed that Huangguogan was clustered together with Hongju tangerine and revealed -80% genetic similarity. They illustrated a close genetic distance between Huangguogan and Hongju tangerine. In addition, the bands of2 polymorphic cpSSR were identical in Huangguoggan and Sweet orange. Consequently, it is likely that its female parentage was the sweet orange （Citrus sinensis （L.） Osbeck） and its male parentage was the tangerine （Citrus reticulata Blanco）.

Relationship Between F_1,F_2 Hybrid Yield, Heterosis and Genetic Distance Measured by Molecular Markers and Parent Performance in Cotton

Genetic distance among 36 cotton cultivars measured by molecular markers of RAPDs, ISSRs, and SSRs was from 0.0701 to 0.4255 with the mean of 0.2844, and from 2.18 to 12.60 with the mean of 7.04 based on the genotype performance in two-year field experiments, which has a significant positive correlation (r = 0.3350). The correlative coefficients for boll number per plant, boll weight, yield per plant, lint percent and lint yield per plant were 0.8035,0.8877,0.7135,0.9640 and 0.8956 between F1 and F2 hybrid performance assessed by three-environment field experiments, respectively. The mean of F1 and F2 hybrid het-erosis of yield per plant and lint yield per plant were 13.62% , 16.31% , 7.90% and 9.02% , and the correlative coefficients between them were 0.3689 and 0.3787, respectively. The correlation between the genetic distance and heterosis was low, and influenced directly by the selected parents.

Rice molecular markers and genetic mapping:Current status and prospects

Dramatic changes in climatic conditions that supplement the biotic and abiotic stresses pose severe threat to the sustainable rice production and have made it a difficult task for rice molecular breeders to enhance production and productivity under these stress factors. The main focus of rice molecular breeders is to understand the fundamentals of molecular pathways involved in complex agronomic traits to increase the yield. The availability of complete rice genome sequence and recent improvements in rice genomics research has made it possible to detect and map accurately a large number of genes by using linkage to DNA markers. Linkage mapping is an effective approach to identify the genetic markers which are co-segregating with target traits within the family. The ideas of genetic diversity, quantitative trait locus（QTL） mapping, and marker-assisted selection（MAS） are evolving into more efficient concepts of linkage disequilibrium（LD） also called association mapping and genomic selection（GS）, respectively. The use of cost-effective DNA markers derived from the fine mapped position of the genes for important agronomic traits will provide opportunities for breeders to develop high-yielding, stress-resistant, and better quality rice cultivars. Here we focus on the progress of molecular marker technologies, their application in genetic mapping and evolution of association mapping techniques in rice.

Screening and Application of Molecular Markers for Starch Synthesis-related Genes in Rice

In this study, the genotypes of starch synthesis-related genes were systematically screened from different rice varieties using molecular markers. The results showed that starch synthesis-related genes were highly polymorphic between indica and japonica varieties, as they greatly variated among indica varieties, but were conserved among japonica varieties. The genotypes of two indica varieties9311 and Minghui 63 were more similar to that of japonica varieties. Two or three alleles of six starch synthesis-related genes were found in 28 japonica parental varieties. Four genotypes of two soluble starch synthase genes, SSIIa and SSIIIa,were detected in 88 stable lines derived from the cross of Kanto 194/ Wujing 13 using molecular markers.

Research Progresses of Sugarcane Brown Rust Resistance Gene and Molecular Markers

Brown rust is a main sugarcane disease in China, affecting stable development of sugarcane industry. Resistance breeding is an effective measure to control sugarcane rust, and looking for diverse sugarcane rust resistance alternative resources is another important way to improve rust resistance level. This article reviewed from the aspects of construction of sugarcane genetic map, research progress of rust resistance gene, development of rust resistance molecular markers, and research strategies of rust resistance gene, in order to provide scientific guidance and reference for rust resistance breeding.

Genetic Analysis of Segregation Distortion of Molecular Markers in Maize RIL Population

A RIL population was used in this study, which was derived from a cross between a temperate maize germplasm inbred line B31-1 and a tropical maize germplasm inbred lines Huangzao 4. A genetic linkage map was constructed comprising of 153 polymorphic markers. Among the 153 polymorphic markers, 82 markers showed the significantly segregation distortion（P〈0.05）, favoring either the marker alleles of female parent 1331-1（62.50%） or male parent Huangzao 4（37.50%）. Segregation distortion marker distribution along the present molecular maps of maize was far from uniform, with clusters of tightly linked loci and single marker. Nine segregation distortion regions were detected on 10 chromosomes, indicating that possible causes for segregation deviation of molecular markers are genetic selection.

Genetic Analysis of Cotton Fiber Traits by Molecular Markers

1.Development of EST-SSRs derived from G.barbadense:One hundred and nineteen EST-SSRs were developed based on 98 unique ESTs from a cDNA library constructed in our laboratory using developing fibers from G.barbadense cv.3-79.Among the SSRs,trinucleotide AAG appeared

Molecular Markers Associated with Starch Content and Implications for Sugarcane Introgression Breeding Using Saccharum spontaneum

Introgression with Saceharum spontaneum intended to broaden the genetic base of sugarcane resulted in an increase in desirable genes for broader adapt ability as well as undesirable genes for high starch content. Markers could provide a quick and efficient method of screening parental genotypes for low starch. The objectives of this study were to identify potential markers associated with starch in S. spontaneum population and evaluate their potential for screening for starch content. Data for starch content and （simple sequence repeats） SSR markers were collected from 51 S. spontaneum clones grown in replicated pots. The mixed procedure of statistical analysis system （SAS） was used to determine markers significantly associated with starch. Thirty-nine out of 357 polymorphic markers were significantly （P 〈 0.05） associated with starch content. Eighteen were positively associated and 21 were negatively associated. The presence of a positive marker produced 39% more starch than absence while the absence of a negative marker produced 57% more starch than presence. Selecting parents using negative markers may be more efficient than selecting using positive markers.

Genetic Diversity Analysis of 13 Maize Inbred Lines by SSR Molecular Markers

This paper used SSR molecular markers to perform the genetic diversity analysis on 13 ordinary inbred lines of maize of different sources in order to divide heterotic groups of maize inbred line and predict heterosis. Using 12 pairs of SSR primers,a total of 47 allelic variants were detected in 13 inbred lines,2-5 alleles were detected for each pair of primers,an average of 3. 9,and polymorphism information content varied from 0. 379 to 0. 828. According to the cluster analysis,the 13 inbred lines could be divided into 5 groups.

Molecular Markers in Improvement of Fiber Quality Traits in Cotton

Cotton is the worlds leading natural fiber crop,and it is the cornerstone of textile industries worldwide.The cotton industry is confronted with problems in cost of production and

Genetic Diversity in <i>Jatropha platyphylla</i>Accessions Based on Morphological Traits and Inter-Simple Sequence Repeats Molecular Markers

Seven accessions of Jatropha platyphylla were evaluated for their phenotypic traits and genetic diversity using inter-simple sequence repeats (ISSRs). Cluster analyses with nine traits were performed: number of branches per plant;fruit per bunch;bunch per branch;bunch per plant;total seed production;total fruit production, protein content, oil content, and fatty acid profile. Genotypes from Rosario, Sinaloa, Mexico (PR11) yielded the highest values in all traits. The correlation analysis of the quantitative traits showed high correlations between seed and total fruit production (r = 0.99). Unsaturated linoleic acid was the most abundant fatty acid (57.64% - 52.39%). Within a genetic improvement program, two of the most important variables to be considered are oil content and phenotypic characteristics of the plant. J. platyphylla has shown viable selection traits that provide a possibility of producing interspecies hybrids and giving them added value. ISSRs primers generated variable banding patterns that were found to be polymorphic;the polymorphic information content (PIC) of these loci ranged from 0.21 to 0.45 with an average of 0.34. The unweighted pair group method (UPGMA) cluster analysis of the data showed the formation of three groups, where the most divergent accession pair was the genotype from Quelite (QP11) and Rosario (PR11).

Study Genetic Variation Using DNA Molecular Markers and Identification Physiological Races of Wheat Stripe （yellow） Rust Puccinia striiformis f.sp tritici during 2010-2014 in Some Regions of Syria

Yellow Rust （stripe） rust （Puccinia striiformis West. f. sp. tritici） is one of the most epidemic diseases infect wheat in cold and wet regions. In 1988, this disease caused a loss of seasonal production amounted 70% on wheat variety Mexipak in Syria, and recurrent infection in 2010, caused by a virulent race called Yr27, caused a considerable loss in the production of bread wheat cultivars （Cham 8, Cham 6 particularly） amounted 90%. Recently, 15 races of yellow rust had been addressed in Syria for seasons 2010-2014; 159E256, 166E254, 166E256, 255 E112, 0 E0, 64 E 6, 230 El50, 0 E 18, 198 El30, 166 El50, 102 El60, 128 E0, 126 El50, 214E150, and 6E16. The race 6E16 was the most frequent during the two seasons, while the race 255El12 was the most virulent, followed by the race 230E222 and the race 0E0 was the weakest one. This study revealed the presence of fourteen newly observed races in Syria. Molecular Variance Analysis of Molecular Variance （AMOVA） of 55 yellow rust Puccinia striiformis f.sp tritici isolates examined by Amplify Fragment Length Polymorphism （AFLP） revealed high genetic variation within population, and the dimensional scale analysis （MSD） and tree diagram showed that the Syrian yellow rust isolates were clustered in three groups： the first group contained isolates derived from durum wheat, the second one contained bread wheat isolates, but the third was made of isolates derived from both durum and bread wheat species.

The Correlation between the Intrinsic and Extrinsic Molecular Markers in the Inhibition of the Lungs Carcinogenesis Growth by Mahkota Dewa Polyphenols on Balb/c Mouse

Phytochemical analysis shows that mahkota dewa fruit contains polyphenols. Mahkota dewa polyphenols have the ability to disrupt or reverse the stages of cancer or a carcinogenesis process by affecting the intracellular signaling tissue molecules involved in an initiation and/or promotion. This chemopreventive potential is highly anticipating. The use, effectiveness, and benefits of the polyphenol have been empirically and pre-clinically proved without side effects. A multivariate analysis using Spearman’s test was conducted to examine the correlation between variables. Meanwhile, to determine which dependent variables played the strong role, a discriminant function analysis was performed with a significance level of p < 0.05 and a reliability level of 95%. The results showed that the mahkota dewa polyphenols acted as the suppressor agent by inducing apoptosis. This finding proved that polyphenols addition might result in death signal transduction through an apoptosis pathway which is either mediated by death receptor or mitochondria. The results of this study indicate that there is a relationship between apoptotic cell death mediated by death receptor and mitochondria through the administration of mahkota dewa polyphenols, it can be argued that mahkota dewa polyphenols can function in lung cancer chemoprevention in mice strain Balb/c.