Search

Despite the longstanding importance of silage as a critical feed source for ruminants, its quality improvement has been largely overlooked. Although numerous quantitative trait loci (QTL) and genes affecting silage quality in maize have been reported, only a few have been effectively incorporated into breeding programs. Addressing this gap, the present study undertook a comprehensive meta-QTL (MQTL) analysis involving 523 QTL associated with silage-quality traits collected from 14 published studies. Of the 523 QTL, 405 were projected onto a consensus map comprising 62,424 genetic markers, resulting in the identification of 60 MQTL and eight singletons. The average confidence interval (CI) of the MQTL was 3.9-fold smaller than that of the source QTL. Nine of the 60 identified MQTL were classified as breeder’s MQTL owing to their small CIs, involvement of more QTL, and large contribution to phenotypic variation. One-third of the MQTL co-localized with DNA marker-trait associations identified in previous genomewide association mapping studies. A set of 78 high-confidence candidate genes influencing silage quality were identified in the MQTL regions. These genes and associated markers may advance marker-assisted breeding for maize silage quality. [ABSTRACT FROM AUTHOR]

Submerged germination ability is a key trait of rice (Oryza sativa L.) in the success of water direct seeding. Therefore, mining submerged germination‐related loci and seeking high tolerant rice germplasms are important for developing rice direct seeding breeding strategies. Here, we treated 272 recombinant inbred lines (RILs, F15) from a cross from Luohui 9 (indica) and RPY geng (japonica) with simulated submergence for 7 days. We successfully bred several superior homozygous RILs with high submergence resistance, namely, R53, R137, R148, R176, and R180, via indica and japonica hybridization strategies. Then, the QTL mapping of coleoptile length trait was performed by R/qtl and IciMapping softwares based on the high‐density bin marker genetic map and two QTLs responsible for coleoptile length were detected in chromosomes 1 (qCL‐1.1) and 3 (qCL‐3.1). The haplotype results of RILs showed that the aggregation of elite alleles of these two QTLs in an individual was beneficial to improving the rice submergence tolerance. According to contrasting genotype of qCL‐1.1 and qCL‐3.1 with different coleoptile lengths, RIL07 (R07) and R180 were selected to further RNA‐seq analysis for analyzing the possible molecular mechanisms of rice under submergence stress. Finally, LOC_Os01g04430, LOC_Os01g04530, and LOC_Os03g22720 for qCL‐1.1 and qCL‐3.1 were characterized to affect submergence stress by the overlapped analysis of two independent sets of RNA‐seq data, qRT‐PCR verification, and gene sequence alignments. In this study, the submerged germination‐related QTLs/genes and high submergence‐tolerant RILs provided new genetic resources for breeding rice varieties suitable for direct seeding via molecular breeding strategies in the immediate future. [ABSTRACT FROM AUTHOR]

Coffee production has been limited by the coffee leaf rust (CLR) disease. Genetic markers linked to resistance have been utilized for molecular breeding programs. Some of these markers have been linked specifically to a hypothetical SH3 gene that confers resistance against CLR. Using PrimerBLAST, the binding sites of these SH3 markers have been localized to a region in chromosome 3 of the coffee genome. Protein-coding genes were obtained from the Ensembl Plants website and filtered using the Orange software according to the gene annotations of their predicted products. The candidate resistance and resistance-associated genes were then datamined and physical maps were constructed to visualize their locations. The data generated by this study may help guide future investigations regarding SH3-conferred resistance. [ABSTRACT FROM AUTHOR]

This study used SSR and AFLP markers to construct the genetic linkage map of Reyan5-11×PR107 population, integrated the published genetic linkage map and utilised the integrated map to perform QTL mapping of rubber yield-related traits. A genetic map consisting of 132 molecular markers (88 SSR and 44 AFLP markers) was constructed, and a joint map consisting of 143 molecular markers (99 SSR and 44 AFLP markers), which contained 19 linkage groups covering the rubber tree genome of 1298.5 cM, each linkage group containing 2–40 Mark, the average distance between the marks is 9.08 cM. Under the conditions of LOD ≥ 2.5, it was detected 2 QTLs related to girth, 3 QTLs related to dry rubber content, and 3 QTLs related to dry rubber yield per tree, 4 QTLs related to the unit secant length dry rubber yield, 5 QTLs related to the number of conducting phloem laticifer and 4 QTLs related to the number of yellow phloem laticifer. [ABSTRACT FROM AUTHOR]

Backcrossing is a powerful tool for plant breeding. The improved marker-assisted backcrossing intends to transfer targeted genes or quantitative trait loci (QTLs) of interest from a donor parent into a recurrent parent. In this study, a tobacco BC4F3 population was generated using Y3 and K326 as hybrid parents and YF1-1 as F1 parents. High-throughput sequencing data of 381 pedigree populations were used to construct high-density genetic maps containing 24 142 high-quality single nucleotide polymorphism (SNP) markers with an average genetic distance of 0.59 cM. A genome module analysis was then performed for all the offspring. A total of forty-three candidate QTLs for six agronomics traits were identified. This study provides original biomarkers for tobacco breeding and offers clues for prospective backcrossing applications in other plants. [ABSTRACT FROM AUTHOR]

Background: Genomic information for Allium cepa L. is limited as it is heterozygous and its genome is very large. To elucidate potential SNP markers obtained by NGS, we used a complete set of A. fistulosum L.-A. cepa monosomic addition lines (MALs) and doubled haploids (DHs). These were the parental lines of an A. cepa mapping population for transcriptome-based SNP genotyping. Results: We mapped the transcriptome sequence reads from a series of A. fistulosum-A. cepa MALs onto the unigene sequence of the doubled haploid shallot A. cepa Aggregatum group (DHA) and compared the MAL genotype call for parental bunching onion and shallot transcriptome mapping data. We identified SNP sites with at least four reads on 25,462 unigenes. They were anchored on eight A. cepa chromosomes. A single SNP site was identified on 3,278 unigenes and multiple SNPs were identified on 22,184 unigenes. The chromosome marker information was made public via the web database Allium TDB (http://alliumtdb.kazusa.or.jp/). To apply transcriptome based genotyping approach for genetic mapping, we gathered RNA sequence data from 96 lines of a DHA × doubled haploid bulb onion A. cepa common onion group (DHC) mapping population. After selecting co-dominant SNP sites, 16,872 SNPs were identified in 5,339 unigenes. Of these, at least two SNPs with identical genotypes were found in 1,435 unigenes. We developed a linkage map using genotype information from these unigenes. All unigene markers mapped onto the eight chromosomes and graphical genotyping was conducted based on the unigene order information. Another 2,963 unigenes were allocated onto the eight chromosomes. To confirm the accuracy of this transcriptome-based genetic linkage map, conventional PCR-based markers were used for linkage analysis. All SNP - and PCR-based markers were mapped onto the expected linkage groups and no inconsistency was found among these chromosomal locations. Conclusions: Effective transcriptome analysis with unique Allium resources successfully associated numerous chromosome markers with unigene information and a high-density A. cepa linkage map. The information on these unigene markers is valuable in genome sequencing and useful trait detection in Allium. [ABSTRACT FROM AUTHOR]

The main purposes of the study were (i) to develop a mapping population, (ii) to construct its genetic map for further identification of genes associated with important agronomic traits. To the best of our knowledge this is the first segregating population and genetic map developed for Kazakh bread wheat. The work is an example of how plant breeding programs in Kazakhstan have started successfully using next generation plant breeding methods to carry out systematic plant breeding to enhance final grain harvest. The KASP technology and SNP DNA-markers have been exploited to genotype and build a genetic map. The total length of the map was 1376 cM. A total 157, which spanned A, B and D subgenomes, out of the initial 178 SNP markers used formed 26 linkage groups leaving 1 duplicated and 20 unassigned markers. As threshold distance between markers was set ≤30 cM, two linkage groups were obtained for chromosomes such as 2А, 2В, 2D, 3A, 5A, 6B and 7A. Kosambi mapping function was employed to calculate recombination units. RILs were developed through SSD method up to F4 generation. Almost 97% of identified alleles were useful in evaluating the population's genetic diversity; the remaining 3% showed no outcome. As a result, 77 DNA markers were mapped for A, 74 for B and 27 for D genomes. The mapping population will be genotyped using a high marker density array platform such as Illumina iSelect to obtain a genetic map with a relatively high coverage. Then, the population and high-resolution genetic map will be used to identify genes influencing wheat adaptation in Kazakhstan. [ABSTRACT FROM AUTHOR]

Next-generation sequencing (NGS)-based genotyping methods can generate numerous genetic markers in a single experiment and have contributed to plant genetic mapping. However, for high precision genetic analysis, the complicated genetic segregation mode in polyploid organisms requires high-coverage NGS data and elaborate analytical algorithms. In the present study, we propose a simple strategy for the genetic mapping of polyploids using low-coverage NGS data. The validity of the strategy was investigated using simulated data. Previous studies indicated that accurate allele dosage estimation from low-coverage NGS data (read depth < 40) is difficult. Therefore, we used allele dosage probabilities calculated from read counts in association analyses to detect loci associated with phenotypic variations. The allele dosage probabilities showed significant detection power, although higher allele dosage estimation accuracy resulted in higher detection power. On the contrary, differences in the segregation patterns between the marker and causal genes resulted in a drastic decrease in detection power even if the marker and casual genes were in complete linkage and the allele dosage estimation was accurate. These results indicated that the use of a larger number of markers is advantageous, even if the accuracy of allele dosage estimation is low. Finally, we applied the strategy for the genetic mapping of autohexaploid sweet potato (Ipomoea batatas) populations to detect loci associated with agronomic traits. Our strategy could constitute a cost-effective approach for preliminary experiments done performed to large-scale studies. [ABSTRACT FROM AUTHOR]

Genotyping is an essential procedure for identifying agronomically useful genes and analyzing population structure. Various types of genetic marker systems have been developed in common buckwheat (Fagopyrum esculentum Moench). In the 1980s, morphological and allozyme markers were used to construct linkage maps. Until the early 2000s, allozyme markers were widely used in population genetics studies. Such studies demonstrated that cultivated common buckwheat likely originated in the Sanjiang area of China. In the late 1990s and early 2000s, advances in PCR technology led to the development of various DNA marker systems for use in linkage mapping. However, PCR-based markers did not completely cover the genome, making genetic analysis of buckwheat challenging. The subsequent development of next generation sequencing, a game-changing technology, has allowed genome-wide analysis to be performed for many species. Indeed, 8,884 markers spanning 756 loci were recently mapped onto eight linkage groups of common buckwheat; these markers were successfully used for genomic selection to increase yield. Furthermore, draft genome sequences are now available in the Buckwheat Genome DataBase (BGDB). In this review, I summarize advances in the breeding and genetic analysis of common buckwheat based on contemporary genetic marker systems. [ABSTRACT FROM AUTHOR]

Actinobacillus (A.) pleuropneumoniae is one of the most important respiratory pathogens in global pig production. Antimicrobial treatment and vaccination provide only limited protection, but genetic disease resistance is a very promising alternative for sustainable prophylaxis. Previous studies have discovered multiple QTL that may explain up to 30% of phenotypic variance. Based on these findings, the aim of the present study was to use genomic sequencing to identify genetic markers for resistance to pleuropneumonia in a segregating commercial German Landrace line. 163 pigs were infected with A. pleuropneumoniae Serotype 7 through a standardized aerosol infection method. Phenotypes were accurately defined on a clinical, pathological and microbiological basis. The 58 pigs with the most extreme phenotypes were genotyped by sequencing (next-generation sequencing). SNPs were used in a genome-wide association study. The study identified genome-wide associated SNPs on three chromosomes, two of which were chromosomes of QTL which had been mapped in a recent experiment. Each variant explained up to 20% of the total phenotypic variance. Combined, the three variants explained 52.8% of the variance. The SNPs are located in genes involved in the pathomechanism of pleuropneumonia. This study confirms the genetic background for the host's resistance to pleuropneumonia and indicates a potential role of three candidates on SSC2, SSC12 and SSC15. Favorable gene variants are segregating in commercial populations. Further work is needed to verify the results in a controlled study and to identify the functional QTN. [ABSTRACT FROM AUTHOR]

Platycladus orientalis is an ecologically important native conifer in Northern China and exotic species in many parts of the world; however, knowledge about the species' genetics and genome are very limited. The availability of well-developed battery of genetic markers, with large genome coverage, is a prerequisite for the species genetic dissection of adaptive attributes and efficient selective breeding. Here, we present a genome-wide genotyping method with double-digestion restriction site associated DNA sequencing (ddRAD-seq) that is effective in generating large number of Mendelian markers for genome mapping and other genetic applications. Using 139 megagametophytes collected from a single mother tree, we assembled 397,226 loci, of which 108,683 (27.4%) were polymorphic. After stringent filtering for 1:1 segregation ratio and missing rate of, 20%, the remaining 23,926 loci (22% of the polymorphic loci) were ordered into 11 linkage groups (LGs) and distributed across 7,559 unique positions, with a total map length of 1,443 cM and an average spacing of 0.2 cM between adjacent unique positions. The 11 LGs correspond to the species' 11 haploid genome chromosome number. This genetic map is among few high-density maps available for conifers to date, and represents the first genetic map for P. orientalis. The information generated serves as a solid foundation not only for marker-assisted breeding efforts, but also for comparative conifer genomic studies. [ABSTRACT FROM AUTHOR]

• Development of high-throughput 78 K Infinium® high density SNP array for oil palm. • SNP array is an important resource for genetic studies in oil palm. • Unintended selfing is observed in crosses generated via controlled pollination. • Array revealed the level of homozygosity and aberrations in chromosomes. • Comprehensive deciphering of oil palm genetics can influence improvement strategies. High-throughput and high-density (HD) genetic marker genotyping systems are critical to optimize the efficiency of oil palm breeding and improvement programmes. This study reports the development of the 78 K Infinium ® HD customized SNP array, which was used to genotype a thousand palms of a commercial Deli dura x AVROS pisifera family. A total 64,108 (∼82.0%) polymorphic SNP markers were identified of which, 57, 465 (89.6%) were mapped onto the genetic map that has the largest number of markers published so far in oil palm and holds 14,781 SNPs on 2,363 orphan scaffolds (whose chromosomal locations were unknown), which will improve the existing oil palm reference genome (EG5.1). The SNPs were highly informative based on the parent-to-progeny allelic inheritance analysis. The data demonstrated that 4.3% of the progeny resulted from unintentional self-fertilization of the dura female parent. These unintended 'selfs' are highly inbred, which will affect their yield. This study also for the first time, describes the homozygosity in the Deli dura and AVROS pisifera , two important parental lines widely used in commercial seed production. As expected, both the parental palms were highly homozygous, having 138 Mb homozygous regions in common, with 70.3% identical alleles. Such a detailed genetic analysis of the individual palm has been made possible with this customized HD SNP array, which will be a valuable tool for routine application in oil palm improvement programmes. The strategy used to design and apply the array will also be of interest for wider scientific research. [ABSTRACT FROM AUTHOR]

Summary Combinatorial association mapping aims to assess the statistical association of higher-order interactions of genetic markers with a phenotype of interest. This article presents combinatorial association mapping (CASMAP), a software package that leverages recent advances in significant pattern mining to overcome the statistical and computational challenges that have hindered combinatorial association mapping. CASMAP can be used to perform region-based association studies and to detect higher-order epistatic interactions of genetic variants. Most importantly, unlike other existing significant pattern mining-based tools, CASMAP allows for the correction of categorical covariates such as age or gender, making it suitable for genome-wide association studies. Availability and implementation The R and Python packages can be downloaded from our GitHub repository http://github.com/BorgwardtLab/CASMAP. The R package is also available on CRAN. Supplementary information Supplementary data are available at Bioinformatics online. [ABSTRACT FROM AUTHOR]

Marker-assisted selection (MAS) can effectively promote fiber yield improvement for ramie. However, so far, the lack of molecular markers associated with fiber yield traits impede the application of MAS in ramie breeding. The objectives of this study were to identify simple sequence repeat (SSR) loci associated with fiber yield traits in ramie and to infer population structure and evolutionary genetic relationships. Genetic diversity, population structure, and association mapping analyses were conducted using 107 ramie accessions and 95 pairs of SSR markers. The results indicate that the average number of alleles per locus was 2.64 and that Shannon diversity index values ranged from 0.3797 to 1.4298. The 107 accessions were divided into two subpopulations with extensive genetic variation, indicating that the natural population was representative and could be used for further association analysis of quantitative traits. Association analysis detected a total of 16 stable molecular markers related to yield traits in ramie, including six for plant height, two for ramet number, five for stem diameter, three for skin thickness, and three for fiber percentage. Of these, the SSR marker RAM290 was associated with stem diameter in three environments and can explain 8.32%–23.42% of the phenotypic variation, indicating its potential utility in molecular breeding. These findings will be useful in the genetic improvement of ramie yield traits through marker-assisted selection. [ABSTRACT FROM AUTHOR]

Background: Oil palm (Elaeis guineensis, Jacq.) is the most important source of edible oil. The improvement of oil yield is currently slow in conventional breeding programs due to long generation intervals. Marker-assisted selection (MAS) has the potential to accelerate genetic improvement. To identify DNA markers associated with oil content traits for MAS, we performed quantitative trait loci (QTL) mapping using genotyping by sequencing (GBS) in a breeding population derived from a cross between Deli Dura and Ghana Pisifera, containing 153 F1 trees. Results: We constructed a high-density linkage map containing 1357 SNPs and 123 microsatellites. The 16 linkage groups (LGs) spanned 1527 cM, with an average marker space of 1.03 cM. One significant and three suggestive QTL for oil to bunch (O/B) and oil to dry mesocarp (O/DM) were mapped on LG1, LG8, and LG10 in a F1 breeding population, respectively. These QTL explained 7.6-13.3% of phenotypic variance. DNA markers associated with oil content in these QTL were identified. Trees with beneficial genotypes at two QTL for O/B showed an average O/B of 30.97%, significantly (P < 0.01) higher than that of trees without any beneficial QTL genotypes (average O/B of 28.24%). QTL combinations showed that the higher the number of QTL with beneficial genotypes, the higher the resulting average O/B in the breeding population. Conclusions: A linkage map with 1480 DNA markers was constructed and used to identify QTL for oil content traits. Pyramiding the identified QTL with beneficial genotypes associated with oil content traits using DNA markers has the potential to accelerate genetic improvement for oil yield in the breeding population of oil palm. [ABSTRACT FROM AUTHOR]

Genetic diversity is critical in sweetpotato improvement as it is the source of genes for desired genetic gains. Knowledge of the level of genetic diversity in a segregating family contributes to our understanding of the genetic diversity present in crosses and helps breeders to make selections for population improvement and cultivar release. Simple sequence repeat (SSR) markers have become widely used markers for diversity and linkage analysis in plants. In this study, we screened 405 sweetpotato SSR markers for polymorphism on the parents and progeny of a biparental cross of New Kawogo x Beauregard cultivars. Thereafter, we used the informative markers to analyze the diversity in this population. A total of 250 markers were polymorphic on the parents and selected progeny; of these, 133 were informative and used for diversity analysis. The polymorphic information content (PIC) values of the 133 markers ranged from 0.1 to 0.9 with an average of 0.7, an indication of high level of informativeness. The pairwise genetic distances among the progeny and parents ranged from 0.2 to 0.9, and they were grouped into five main clusters. The 133 SSR primers were informative and are recommended for use in sweetpotato diversity and linkage analysis. [ABSTRACT FROM AUTHOR]

The prediction of the flowering time (FT) trait in Brassica napus based on genome-wide markers and the detection of underlying genetic factors is important not only for oilseed producers around the world but also for the other crop industry in the rotation system in China. In previous studies the low density and mixture of biomarkers used obstructed genomic selection in B. napus and comprehensive mapping of FT related loci. In this study, a high-density genome-wide SNP set was genotyped from a double-haploid population of B. napus. We first performed genomic prediction of FT traits in B. napus using SNPs across the genome under ten environments of three geographic regions via eight existing genomic predictive models. The results showed that all the models achieved comparably high accuracies, verifying the feasibility of genomic prediction in B. napus. Next, we performed a large-scale mapping of FT related loci among three regions, and found 437 associated SNPs, some of which represented known FT genes, such as AP1 and PHYE. The genes tagged by the associated SNPs were enriched in biological processes involved in the formation of flowers. Epistasis analysis showed that significant interactions were found between detected loci, even among some known FT related genes. All the results showed that our large scale and high-density genotype data are of great practical and scientific values for B. napus. To our best knowledge, this is the first evaluation of genomic selection models in B. napus based on a high-density SNP dataset and large-scale mapping of FT loci. [ABSTRACT FROM AUTHOR]

Identification of marker-trait associations is the first step towards marker-assisted selection in plant breeding. Here we assess genetic diversity and population structure of 94 diverse wheat elite lines and use genome-wide association mapping to identify marker-trait associations for five important traits: kernel hardness (KHA), thousand-kernel weight, grain protein content, test weight (TWT), and plant height (PHT). The 94 accessions employed in this study were grouped into three subpopulations based on the first three principal components, which accounted for 51.5 % of the variations. A mixed linear model was used to detect marker-trait associations incorporating covariance of population structure and relative kinship. A total of six marker loci was significantly associated with KHA, TWT, and PHT after the correction of false discovery rate ( α = 0.05). The gene pinB was found to be highly associated with KHA, and is reported to be a major determinant of KHA together with the gene pinA at the Ha locus on chromosome 5D. Marker XwPt- 7187 on chromosome 2A was also significantly associated with KHA, two Diversity Arrays Technology markers XwPt- 1250 and XwPt- 4628 with TWT, and marker Xgwm512 with PHT, making the first report of marker-trait associations in these genomic regions. [ABSTRACT FROM AUTHOR]

The large-scale validation and high-throughput genotyping of numerous informative genic microsatellite markers are required for association mapping to identify candidate genes for complex quantitative traits in chickpea. However, the screening and genotyping of such informative markers in individual genotypes/whole association panels for trait association mapping involves massive costs in terms of resources, time and labour due to low genetic polymorphism in chickpea. We have developed an alternative time-saving and cost-effective pool-based trait association mapping approach by combining pooled DNA analysis (with 616 genic microsatellite markers) and individual genotype (large structured association panel) genotyping. Using this approach we have identified seven seed weight-associated transcription factor gene-derived microsatellite markers (with minor allele frequency >15 %) in desi and kabuli chickpea. Strong marker allele effects of these five transcription factors with increasing seed weight in the contrasting desi and kabuli genotypes were evident. Bi-parental linkage mapping using 241 of the informative gene-based microsatellite markers resulted in the identification and mapping of nine such markers linked with three major quantitative trait loci (explaining a total phenotypic variance of 23.5-34.7 %) on chromosomes 1 (CaqSW1.1: 73.5-74.5 cM and CaqSW1.2: 79.3-81.3 cM) and 2 (CaqSW2.1: 65.7-67.5 cM) controlling 100-seed weight in chickpea. The integration of pool-based trait association mapping with differential expression profiling, traditional bi-parental linkage mapping and high-resolution microsatellite-single nucleotide polymorphism marker-based haplotyping/linkage disequilibrium mapping delineated four transcription factor genes (DUF3594, bZIP, DUF1635 and SBP) controlling seed weight in desi and kabuli chickpea. The strategies implemented in our study can be used in large-scale trait association mapping for the rapid identification of candidate genes and in the development of functional markers for traits of agricultural importance in crop species including chickpea. [ABSTRACT FROM AUTHOR]

The accuracy of genomic selection depends on the relatedness between the members of the set in which marker effects are estimated based on evaluation data and the types for which performance is predicted. Here, we investigate the impact of relatedness on the performance of marker-assisted selection for fungal disease resistance in hybrid wheat. A large and diverse mapping population of 1739 elite European winter wheat inbred lines and hybrids was evaluated for powdery mildew, leaf rust and stripe rust resistance in multi-location field trials and fingerprinted with 9 k and 90 k SNP arrays. Comparison of the accuracies of prediction achieved with data sets from the two marker arrays revealed a crucial role for a sufficiently high marker density in genome-wide association mapping. Cross-validation studies using test sets with varying degrees of relationship to the corresponding estimation sets revealed that close relatedness leads to a substantial increase in the proportion of total genotypic variance explained by the identified QTL and consequently to an overoptimistic judgment of the precision of marker-assisted selection. [ABSTRACT FROM AUTHOR]

Key message: After cloning and mapping of wheat TaSdr genes, both the functional markers for TaSdr - B1 and TaVp - 1B were validated, and the distribution of allelic variations at TaSdr - B1 locus in the wheat cultivars from 19 countries was characterized. Abstract: Seed dormancy is a major factor associated with pre-harvest sprouting (PHS) in common wheat ( Triticum aestivum L.). Wheat TaSdr genes, orthologs of OsSdr4 conferring seed dormancy in rice, were cloned by a comparative genomics approach. They were located on homoeologous group 2 chromosomes, and designated as TaSdr- A1, TaSdr- B1 and TaSdr- D1, respectively. Sequence analysis of TaSdr- B1 revealed a SNP at the position -11 upstream of the initiation codon, with bases A and G in cultivars with low and high germination indices (GI), respectively. A cleaved amplified polymorphism sequence marker Sdr2B was developed based on the SNP, and subsequently functional analysis of TaSdr- B1 was conducted by association and linkage mapping. A QTL for GI co-segregating with Sdr2B explained 6.4, 7.8 and 8.7 % of the phenotypic variances in a RIL population derived from Yangxiaomai/Zhongyou 9507 grown in Shijiazhuang, Beijing and the averaged data from those environments, respectively. Two sets of Chinese wheat cultivars were used for association mapping, and results indicated that TaSdr- B1 was significantly associated with GI. Analysis of the allelic distribution at the TaSdr- B1 locus showed that the frequencies of TaSdr- B1a associated with a lower GI were high in cultivars from Japan, Australia, Argentina, and the Middle and Lower Yangtze Valley Winter Wheat Region and Southwest Winter Wheat Region in China. This study provides not only a reliable functional marker for molecular-assisted selection of PHS in wheat breeding programs, but also gives novel information for a comprehensive understanding of seed dormancy. [ABSTRACT FROM AUTHOR]

Microsatellite or single sequence repeat (SSR) markers have been commonly used in genetic research in many crop species, including common bean ( Phaseolus vulgaris L.). A limited number of existing SSR markers have been designed from high-throughput sequencing of the genome, warranting the exploitation of new SSR markers from genomic regions. In this paper, we sequenced total DNA from the genotype Hong Yundou with a 454-FLX pyrosequencer and found numerous SSR loci. Based on these, a large number of SSR markers were developed and 90 genomic-SSR markers with clear bands were tested for mapping and diversity detection. The new SSR markers proved to be highly polymorphic for molecular polymorphism, with an average polymorphism information content value of 0.44 in 131 Chinese genotypes and breeding lines, effective for distinguishing Andean and Mesoamerican genotypes. In addition, we integrated 85 primers of the 90 polymorphism markers into the bean map using an F2 segregating population derived from Hong Yundou crossed with Jingdou. The distribution of SSR markers among 11 chromosomes was not random and tended to cluster on the linkage map, with 14 new markers mapped on chromosome Pv01, whereas only four loci were located on chromosome Pv04. Overall, these new markers have potential for genetic mapping, genetic diversity studies and map-based cloning in common bean. [ABSTRACT FROM AUTHOR]

Although rice yield has been doubled in most parts of the world since 1960s, thanks to the advancements in breeding technologies, the biological mechanisms controlling yield are largely unknown. To understand the genetic basis of rice yield, a number of quantitative trait locus (QTL) mapping studies have been carried out, but whole-genome QTL mapping incorporating all interaction effects is still lacking. In this paper, we exploited whole-genome markers of an immortalized F2 population derived from an elite rice hybrid to perform QTL mapping for rice yield characterized by yield per plant and three yield component traits. Our QTL model includes additive and dominance main effects of 1,619 markers and all pair-wise interactions, with a total of more than 5 million possible effects. The QTL mapping identified 54, 5, 28 and 4 significant effects involving 103, 9, 52 and 7 QTLs for the four traits, namely the number of panicles per plant, the number of grains per panicle, grain weight, and yield per plant. Most identified QTLs are involved in digenic interactions. An extensive literature survey of experimentally characterized genes related to crop yield shows that 19 of 54 effects, 4 of 5 effects, 12 of 28 effects and 2 of 4 effects for the four traits, respectively, involve at least one QTL that locates within 2 cM distance to at least one yield-related gene. This study not only reveals the major role of epistasis influencing rice yield, but also provides a set of candidate genetic loci for further experimental investigation. [ABSTRACT FROM AUTHOR]

Improvement of resistance to Fusarium head blight (FHB) is a continuous challenge for durum wheat breeders, particularly due to the limited genetic variation within this crop species. We accordingly generated a backcross-derived mapping population using the type 2 FHB resistant Triticum dicoccoides line Mt. Gerizim #36 as donor and the modern Austrian T. durum cultivar Helidur as recipient; 103 BCF lines were phenotyped for type 2 FHB resistance using single-spikelet inoculations and genotyped with 421 DNA markers (SSR and AFLP). QTL mapping revealed two highly significant QTL, mapping to chromosomes 3A and 6B, respectively. For both QTL the T. dicoccoides allele improved type 2 FHB resistance. Recombinant lines with both favorable alleles fixed conferred high resistance to FHB similar to that observed in the T. dicoccoides parent. The results appear directly applicable for durum wheat resistance breeding. [ABSTRACT FROM AUTHOR]

A durum wheat consensus linkage map was developed by combining segregation data from six mapping populations. All of the crosses were derived from durum wheat cultivars, except for one accession of T. ssp. dicoccoides. The consensus map was composed of 1,898 loci arranged into 27 linkage groups covering all 14 chromosomes. The length of the integrated map and the average marker distance were 3,058.6 and 1.6 cM, respectively. The order of the loci was generally in agreement with respect to the individual maps and with previously published maps. When the consensus map was aligned to the deletion bin map, 493 markers were assigned to specific bins. Segregation distortion was found across many durum wheat chromosomes, with a higher frequency for the B genome. This high-density consensus map allowed the scanning of the genome for chromosomal rearrangements occurring during the wheat evolution. Translocations and inversions that were already known in literature were confirmed, and new putative rearrangements are proposed. The consensus map herein described provides a more complete coverage of the durum wheat genome compared with previously developed maps. It also represents a step forward in durum wheat genomics and an essential tool for further research and studies on evolution of the wheat genome. [ABSTRACT FROM AUTHOR]

Three linkage maps of flax ( Linum usitatissimum L.) were constructed from populations CDC Bethune/Macbeth, E1747/Viking and SP2047/UGG5-5 containing between 385 and 469 mapped markers each. The first consensus map of flax was constructed incorporating 770 markers based on 371 shared markers including 114 that were shared by all three populations and 257 shared between any two populations. The 15 linkage group map corresponds to the haploid number of chromosomes of this species. The marker order of the consensus map was largely collinear in all three individual maps but a few local inversions and marker rearrangements spanning short intervals were observed. Segregation distortion was present in all linkage groups which contained 1-52 markers displaying non-Mendelian segregation. The total length of the consensus genetic map is 1,551 cM with a mean marker density of 2.0 cM. A total of 670 markers were anchored to 204 of the 416 fingerprinted contigs of the physical map corresponding to ~274 Mb or 74 % of the estimated flax genome size of 370 Mb. This high resolution consensus map will be a resource for comparative genomics, genome organization, evolution studies and anchoring of the whole genome shotgun sequence. [ABSTRACT FROM AUTHOR]

The common wheat cultivar Parula possesses a high level of slow rusting, adult plant resistance (APR) to all three rust diseases of wheat. Previous mapping studies using an Avocet- YrA/Parula recombinant inbred line (RIL) population showed that APR to leaf rust ( Puccinia triticina) in Parula is governed by at least three independent slow rusting resistance genes: Lr34 on 7DS, Lr46 on 1BL, and a previously unknown gene on 7BL. The use of field rust reaction and flanking markers identified two F RILs, Arula1 and Arula2, from the above population that lacked Lr34 and Lr46 but carried the leaf rust resistance gene in 7BL, hereby designated Lr68. Arula1 and Arula2 were crossed with Apav, a highly susceptible line from the cross Avocet- YrA/Pavon 76, and 396 F-derived F RILs were developed for mapping Lr68. The RILs were phenotyped for leaf rust resistance for over 2 years in Ciudad Obregon, Mexico, with a mixture of P. triticina races MBJ/SP and MCJ/SP. Close genetic linkages with several DNA markers on 7BL were established using 367 RILs; Psy1- 1 and gwm146 flanked Lr68 and were estimated at 0.5 and 0.6 cM, respectively. The relationship between Lr68 and the race-specific seedling resistance gene Lr14b, located in the same region and present in Parula, Arula1 and Arula2, was investigated by evaluating the RILs with Lr14b-avirulent P. triticina race TCT/QB in the greenhouse. Although Lr14b and Lr68 homozygous recombinants in repulsion were not identified in RILs, γ-irradiation-induced deletion stocks that lacked Lr68 but possessed Lr14b showed that Lr68 and Lr14b are different loci. Flanking DNA markers that are tightly linked to Lr68 in a wide array of genotypes can be utilized for selection of APR to leaf rust. [ABSTRACT FROM AUTHOR]

Cross-incompatibility genes known as gametophyte factors ( ga) are numerous in maize. Many popcorn strains carry these genes and cannot be fertilized by pollen of dent and flint maize strains although the reciprocal crosses are successful. A Chinese popcorn strain SDGa25 carries the strongest allele of Ga1 ( Ga1- S) and the majority of Chinese dent and flint maize germplasm are incompatible with SDGa25. The incompatibility is due to pollen tube growth obstruction 2 h after pollination. The pollen tube is arrested in the silk segment 5.5 cm distal to the pollination area and never reaches the ovule. The Ga1- S carried by SDGa25 behaves as a single dominant gene. This gene was mapped between markers SD3 on BAC AC200747 0.827 cM apart on the telomere side and SD12 on BAC AC204382 0.709 cM apart on the centromere side. The genetic region mapped spanning the Ga1- S locus was estimated to be 1.5 cM in length and the physical distance is 2,056,343 bp on ctg156 based on the B73 RefGen_v2 sequence. Gametophyte factors influence gene flow direction and the strongest Ga1- S allele is useful for isolating one category of commercial varieties from another. The eight tightly linked markers to Ga1- S developed in this study would greatly improve marker-assisted introgression efficiency and the fine mapping would facilitate the isolation of the Ga1- S. [ABSTRACT FROM AUTHOR]

In plant breeding, a large number of progenies that will be discarded later in the breeding process must be phenotyped and marker genotyped for conducting QTL analysis. In many cases, phenotypic preselection of lines could be useful. However, in QTL analyses even moderate preselection can have a significant effect on the power of QTL detection and estimation of effects of the target traits. In this study, we provide exact formulas for quantifying the change of allele frequencies within marker classes, expectations of marker contrasts and the variance of the marker contrasts under truncation selection, for the general case of two QTL affecting the target trait and a correlated trait. We focused on homozygous lines derived at random from biparental crosses. The effects of linkage between the marker and the QTL under selection as well as the effect of selection on a correlated trait can be quantified with the given formulas. Theoretical results clearly show that depending on the magnitude of QTL effects, high selection intensities can lead to a dramatic reduction in power of QTL detection and that approximations based on the infinitesimal model deviate substantially from exact solutions. The presented formulas are valuable for choosing appropriate selection intensity when performing QTL mapping experiments on the data on phenotypically preselected traits and enable the calculation and bias correction of the effects of QTL under selection. Application of our theory to experimental data revealed that selection-induced bias of QTL effects can be successfully corrected. [ABSTRACT FROM AUTHOR]

Genome-wide association analysis is a powerful approach to identify the causal genetic polymorphisms underlying complex traits. In this study, we evaluated a population of 191 soybean landraces in five environments to detect molecular markers associated with soybean yield and its components using 1,536 single-nucleotide polymorphisms (SNPs) and 209 haplotypes. The analysis revealed that abundant phenotypic and genetic diversity existed in the studied population. This soybean population could be divided into two subpopulations and no or weak relatedness was detected between pair-wise landraces. The level of intra-chromosomal linkage disequilibrium was about 500 kb. Genome-wide association analysis based on the unified mixed model identified 19 SNPs and 5 haplotypes associated with soybean yield and yield components in three or more environments. Nine markers were found co-associated with two or more traits. Many markers were located in or close to previously reported quantitative trait loci mapped by linkage analysis. The SNPs and haplotypes identified in this study will help to further understand the genetic basis of soybean yield and its components, and may facilitate future high-yield breeding by marker-assisted selection in soybean. [ABSTRACT FROM AUTHOR]

PK23-2, a line of six-rowed barley ( Hordeum vulgare L.) originating from Pakistan, has resistance to Japanese strains I and III of the barley yellow mosaic virus (BaYMV). To identify the source of resistance in this line, reciprocal crosses were made between the susceptible cultivar Daisen-gold and PK23-2. Genetic analyses in the F generation, F generation, and a doubled haploid population (DH45) derived from the F revealed that PK23-2 harbors one dominant and one recessive resistance genes. A linkage map was constructed using 61 lines of DH45 and 127 DNA markers; this map covered 1268.8 cM in 10 linkage groups. One QTL having a LOD score of 4.07 and explaining 26.8% of the phenotypic variance explained (PVE) for resistance to BaYMV was detected at DNA marker ABG070 on chromosome 3H. Another QTL having a LOD score of 3.53 and PVE of 27.2% was located at marker Bmag0490 on chromosome 4H. The resistance gene on chromosome 3H, here named Rym17, showed dominant inheritance, whereas the gene on chromosome 4H, here named rym18, showed recessive inheritance in F populations derived from crosses between several resistant lines of DH45 and Daisen-gold. The BaYMV recessive resistance genes rym1, rym3, and rym5, found in Japanese barley germplasm, were not allelic to rym18. These results revealed that PK23-2 harbors two previously unidentified resistance genes, Rym17 on 3H and rym18 on 4H; Rym17 is the first dominant BaYMV resistance gene to be identified in primary gene pool. These new genes, particularly dominant Rym17, represent a potentially valuable genetic resource against BaYMV disease. [ABSTRACT FROM AUTHOR]

The greenbug, Schizaphis graminum (Rondani), is an important aphid pest of small grain crops especially wheat ( Triticum aestivum L., 2 n = 6 x = 42, genomes AABBDD) in many parts of the world. The greenbug-resistance gene Gb3 originated from Aegilops tauschii Coss. (2 n = 2x = 14, genome DD) has shown consistent and durable resistance against prevailing greenbug biotypes in wheat fields. We previously mapped Gb3 in a recombination-rich, telomeric bin of wheat chromosome arm 7DL. In this study, high-resolution genetic mapping was carried out using an F segregating population derived from two Ae. tauschii accessions, the resistant PI 268210 (original donor of Gb3 in the hexaploid wheat germplasm line 'Largo') and susceptible AL8/78. Molecular markers were developed by exploring bin-mapped wheat RFLPs, SSRs, ESTs and the Ae. tauschii physical map (BAC contigs). Wheat EST and Ae. tauschii BAC end sequences located in the deletion bin 7DL3-0.82-1.00 were used to design STS (sequence tagged site) or CAPS (Cleaved Amplified Polymorphic Sequence) markers. Forty-five PCR-based markers were developed and mapped to the chromosomal region spanning the Gb3 locus. The greenbug-resistance gene Gb3 now was delimited in an interval of 1.1 cM by two molecular markers (HI067J6-R and HI009B3-R). This localized high-resolution genetic map with markers closely linked to Gb3 lays a solid foundation for map based cloning of Gb3 and marker-assisted selection of this gene in wheat breeding. [ABSTRACT FROM AUTHOR]

A unique broccoli × broccoli doubled haploid (DH) population has been created from the F of a cross between two DH broccoli lines derived from cultivars Green Duke and Marathon. We genotyped 154 individuals from this population with simple sequence repeat and amplified fragment length polymorphism markers to create a B. oleracea L. var. italica 'intra-crop' specific framework linkage map. The map is composed of nine linkage groups with a total length of 946.7 cM. Previous published B. oleracea maps have been constructed using diverse crosses between morphotypes of B. oleracea; this map therefore represents a useful breeding resource for the dissection of broccoli specific traits. Phenotype data have been collected from the population over five growing seasons; the framework linkage map has been used to locate quantitative trait loci for agronomically important broccoli traits including head weight (saleable yield), head diameter, stalk diameter, weight loss and relative weight loss during storage, as well as traits for broccoli leaf architecture. This population and associated linkage map will aid breeders to directly map agronomically important traits for the improvement of elite broccoli cultivars. [ABSTRACT FROM AUTHOR]

The modification of flowering date is considered an important way to escape the current or future climatic constraints that affect wheat crops. A better understanding of its genetic bases would enable a more efficient and rapid modification through breeding. The objective of this study was to identify chromosomal regions associated with earliness in wheat. A 227-wheat core collection chosen to be highly contrasted for earliness was characterized for heading date. Experiments were conducted in controlled conditions and in the field for 3 years to break down earliness in the component traits: photoperiod sensitivity, vernalization requirement and narrow-sense earliness. Whole-genome association mapping was carried out using 760 molecular markers and taking into account the five ancestral group structure. We identified 62 markers individually associated to earliness components corresponding to 33 chromosomal regions. In addition, we identified 15 other significant markers and seven more regions by testing marker pair interactions. Co-localizations were observed with the Ppd- 1, Vrn- 1 and Rht- 1 candidate genes. Using an independent set of lines to validate the model built for heading date, we were able to explain 34% of the variation using the structure and the significant markers. Results were compared with already published data using bi-parental populations giving an insight into the genetic architecture of flowering time in wheat. [ABSTRACT FROM AUTHOR]

Spike density in barley is under the control of several major genes, as documented previously by genetic analysis of a number of morphological mutants. One such class of mutants affects the rachis internode length leading to dense or compact spikes and the underlying genes were designated dense spike ( dsp). We previously delimited two introgressed genomic segments on chromosome 3H (21 SNP loci, 35.5 cM) and 7H (17 SNP loci, 20.34 cM) in BW265, a BCF nearly isogenic line (NIL) of cv. Bowman as potentially containing the dense spike mutant locus dsp.ar, by genotyping 1,536 single nucleotide polymorphism (SNP) markers in both BW265 and its recurrent parent. Here, the gene was allocated by high-resolution bi-parental mapping to a 0.37 cM interval between markers SC57808 (Hv_SPL14)-CAPSK06413 residing on the short and long arm at the genetic centromere of chromosome 7H, respectively. This region putatively contains more than 800 genes as deduced by comparison with the collinear regions of barley, rice, sorghum and Brachypodium, Classical map-based isolation of the gene dsp.ar thus will be complicated due to the infavorable relationship of genetic to physical distances at the target locus. [ABSTRACT FROM AUTHOR]

With 3 figures Abstract Genetic analysis of F2 and backcross populations of an induced temperature-sensitive genic male sterility (TGMS) mutant source F 61 with normal pollen parents revealed that TGMS trait was controlled by a single recessive gene. Molecular tagging of TGMS trait was attempted using polymorphic randomly amplified polymorphic DNA (RAPD) and simple sequence repeats (SSR) markers through bulked segregant analysis. The RAPD primers UBC 345830, UBC 313927, microsatellites RM224 and RM21 produced putative markers, which differentiate parents and bulks from sterile parent and sterile bulks. The RAPD analysis of individual F2 plants with the primer UBC345830 showed perfect marker-phenotype cosegregation. The 830-bp RAPD fragment, which segregated with TGMS locus at a distance of 1.33 cM, was eluted and cloned, and sequence information was used for designing sequence-characterized amplified region (SCAR) primer, which cosegregated with TGMS locus at a distance of 0.8 cM. TGMS locus was mapped onto chromosome 11 using RM21 and RM224, flanking it at a distance of 4.3 and 3.0 cM, respectively. The DNA markers tightly linked to TGMS gene ( tms8) in F 61 can be cost effectively used for marker-assisted selection of TGMS trait. [ABSTRACT FROM AUTHOR]

Abstract: Bioinformatic mining of EST datasets is an efficient and economical method for developing functional microsatellite markers. The aim of this work is to generate new tea plant EST-SSR markers and to evaluate their potentials for cross-species/genera amplification and in particular genetic linkage mapping. A total collection of 8008 untapped tea plant ESTs were retrieved from GenBank and then clustered into 2982 non-redundant unique sequences, in which 561 microsatellites were identified. Of these SSRs, the di-nucleotide repeats were the most common repeat types (255, 45.5%), then followed by tri- (18.9%), hexa- (14.3%), penta- (13.5%), tetra- (5.3%), hepta- (2.1%), octa- (0.2%), and deca-nucleotide repeats (0.2%). AG/CT and AGA/TCT predominated in dimeric and trimeric repeat motifs, respectively. BLASTX homology searches found that 319 SSR-containing ESTs had significant Arabidopsis protein hits (E-value<1.00E−05). In total, a set of 97 primer pairs was successfully designed for marker development and validation. Finally, fifty-four primers yielded repeatable and distinct amplification products among 21 tea plant genotypes, however, only 30 loci were polymorphic with an average allele number of 3.4/locus (range: 2–6 alleles/locus). Cross-amplification showed that 87% (26/30) primers could yield scorable products in at least one of nineteen Theaceae species. The transferability ranged from 7 to 77% with a mean of 30%. Furthermore, twenty-five SSR loci were polymorphic for the parents of a pseudo-testcross mapping population of tea plant, indicating they could be utilized for genetic linkage mapping. These novel informative EST-SSR markers will be a useful addition to genetic analysis and molecular breeding programs in tea plant and its related species. [Copyright &y& Elsevier]

The soybean aphid ( Aphis glycines Matsumura) is the most damaging insect pest of soybean [ Glycine max (L.) Merr.] in North America. New soybean aphid biotypes have been evolving quickly and at least three confirmed biotypes have been reported in USA. These biotypes are capable of defeating most known aphid resistant soybean genes indicating the need for identification of new genes. Plant Introduction (PI) 567301B was earlier identified to have antixenosis resistance against biotype 1 and 2 of the soybean aphid. Two hundred and three F recombinant inbred lines (RILs) developed from a cross of soybean aphid susceptible cultivar Wyandot and resistant PI 567301B were used for mapping aphid resistance genes using the quantitative trait loci (QTL) mapping approach. A subset of 94 RILs and 516 polymorphic SNP makers were used to construct a genome-wide molecular linkage map. Two candidate QTL regions for aphid resistance were identified on this linkage map. Fine mapping of the QTL regions was conducted with SSR markers using all 203 RILs. A major gene on chromosome 13 was mapped near the previously identified Rag2 gene. However, an earlier study revealed that the detached leaves of PI 567301B had no resistance against the soybean aphids while the detached leaves of PI 243540 (source of Rag2) maintained aphid resistance. These results and the earlier finding that PI 243540 showed antibiosis resistance and PI 567301B showed antixenosis type resistance, indicating that the aphid resistances in the two PIs are not controlled by the same gene. Thus, we have mapped a new gene near the Rag2 locus for soybean aphid resistance that should be useful in breeding for new aphid-resistant soybean cultivars. Molecular markers closely linked to this gene are available for marker-assisted breeding. Also, the minor locus found on chromosome 8 represents the first reported soybean aphid-resistant locus on this chromosome. [ABSTRACT FROM AUTHOR]

The intervals containing two major quantitative trait loci (QTL) from a Spanish barley landrace conferring broad spectrum resistance to Blumeria graminis were subjected to marker saturation. First, all the available information on recently developed marker resources for barley was exploited. Then, a comparative genomic analysis of the QTL regions with other sequenced grass model species was performed. As a result of the first step, 32 new markers were added to the previous map and new flanking markers closer to both QTL were identified. Next, syntenic integration revealed that the barley target regions showed homology with regions on chromosome 6 of rice ( Oryza sativa), chromosome 10 of Sorghum bicolor and chromosome 1 of Brachypodium distachyon. A nested insertion of ancestral syntenic blocks on Brachypodium chromosome 1 was confirmed. Based on sequence information of the most likely candidate orthologous genes, 23 new barley unigene-derived markers were developed and mapped within the barley target regions. The assessment of colinearity revealed an inversion on chromosome 7HL of barley compared to the other three grass species, and nearly perfect colinearity on chromosome 7HS. This two-step marker enrichment allowed for the refinement of the two QTL into much smaller intervals. Inspection of all predicted proteins for the barley unigenes identified within the QTL intervals did not reveal the presence of resistance gene candidates. This study demonstrates the usefulness of sequenced genomes for fine mapping and paves the way for the use of these two loci in barley breeding programs. [ABSTRACT FROM AUTHOR]

A population derived from a cross between grapevine breeding strain Gf.Ga-52-42 and cultivar 'Solaris' consisting of 265 F1-individuals was genetically mapped using SSR markers and screened for downy mildew resistance. Quantitative trait locus (QTL) analysis revealed two strong QTLs on linkage groups (LGs) 18 and 09. The locus on LG 18 was found to be identical with the previously described locus Rpv3 and is transmitted by Gf.Ga-52-42. 'Solaris' transmitted the resistance-related locus on LG 09 explaining up to 50% of the phenotypic variation in the population. This downy mildew resistance locus is named Rpv10 for resistance to Plasmopara viticola. Rpv10 was initially introgressed from Vitis amurensis, a wild species of the Asian Vitis gene pool. The one-LOD supported confidence interval of the QTL spans a section of 2.1 centi Morgan (cM) corresponding to 314 kb in the reference genome PN40024 (12x). Eight resistance gene analogues (RGAs) of the NBS-LRR type and additional resistance-linked genes are located in this region of PN40024. The F1 sub-population which contains the Rpv3 as well as the Rpv10 locus showed a significantly higher degree of resistance, indicating additive effects by pyramiding of resistance loci. Possibilities for using the resistance locus Rpv10 in a grapevine breeding programme are discussed. Furthermore, the marker data revealed 'Severnyi' × 'Muscat Ottonel' as the true parentage for the male parent of 'Solaris'. [ABSTRACT FROM AUTHOR]

Wheat yellow mosaic (WYM) caused by wheat yellow mosaic bymovirus (WYMV) has been growing as one of the most serious diseases affecting wheat production in China. In this study, the association of quantitative trait loci (QTLs) governing WYMV resistance with molecular markers was established using 164 recombinant inbred lines (RILs) derived from 'Xifeng Wheat' (highly resistant) × 'Zhen 9523' (highly susceptible). Phenotypic data of WYMV resistance of the RILs were collected from 4-year, two-location replicated field trials. A molecular marker-based linkage map, which was comprised of 273 non-redundant loci and represented all the 21 wheat chromosomes, was constructed with the JoinMap 4.0 software. Using the Windows QTL Cartographer V2.5 software, three QTLs associated with WYMV resistance, QYm.njau- 3B.1, QYm.njau- 5A.1 and QYm.njau- 7B.1, were detected on chromosomes 3BS, 5AL, and 7BS, respectively. The favorable allele effects were all contributed by 'Xifeng Wheat'. Among the three QTLs, QYm.njau- 3B.1 and QYm.njau- 5A.1 were detected in all the four trials and the overall mean, and could explain 3.3-10.2% and 25.9-53.7% of the phenotypic variation, respectively, while QYm.njau- 7B.1 was detected in one trial and the overall mean and explained 4.9 and 3.3% of the phenotypic variation, respectively. A large portion of the variability for WYMV response was explained by a major QTL, QYm.njau- 5A.1. The relationship of the molecular markers linked with QYm.njau- 5A.1 and the WYMV resistance was further validated using a secondary F population. The results showed that three markers, i.e., Xwmc415.1, CINAU152, and CINAU153, were closely linked to QYm.njau- 5A.1 with the genetic distances of 0.0, 0.0, and 0.1 cM, respectively, indicating they should be useful in marker-assisted selection (MAS) wheat breeding for WYMV resistance. A panel of germplasm collection consisting of 46 wheat varieties with known WYMV response phenotypes was further used to validate the presence and effects of QYm.njau- 5A.1 and the above three markers. It was found that QYm.njau- 5A.1 was present in 12 of the 34 WYMV-resistant varieties. [ABSTRACT FROM AUTHOR]

Allotetraploid (2 n = 4 x = 28) Leymus triticoides and Leymus cinereus are divergent perennial grasses, which form fertile hybrids. Genetic maps with n = 14 linkage groups (LG) comprised with 1,583 AFLP and 67 heterologous anchor markers were previously used for mapping quantitative trait loci (QTLs) in these hybrids, and chromosomes of other Leymus wildryes have been transferred to wheat. However, identifications of the x = 7 homoeologous groups were tenuous and genetic research has been encumbered by a lack of functional, conserved gene marker sequences. Herein, we mapped 350 simple sequence repeats and 26 putative lignin biosynthesis genes from a new Leymus EST library and constructed one integrated consensus map with 799 markers, including 375 AFLPs and 48 heterologous markers, spanning 2,381 centiMorgans. LG1b and LG6b were reassigned as LG6b* and LG1b*, respectively, and LG4 Ns and LG4 Xm were inverted so that all 14 linkage groups are aligned to the x = 7 Triticeae chromosomes based on EST alignments to barley and other reference genomes. Amplification of 146 mapped Leymus ESTs representing six of the seven homoeologous groups was shown for 17 wheat- Leymus chromosome introgression lines. Reciprocal translocations between 4L and 5L in both Leymus and Triticum monococcum were aligned to the same regions of Brachypodium chromosome 1. A caffeic acid O-methyltransferase locus aligned to fiber QTL peaks on Leymus LG7a and brown midrib mutations of maize and sorghum. Glaucousness genes on Leymus and wheat chromosome 2 were aligned to the same region of Brachypodium chromosome 5. Markers linked to the S self-incompatibility gene on Leymus LG1a cosegregated with markers on LG2b, possibly cross-linked by gametophytic selection. Homoeologous chromosomes 1 and 2 harbor the S and Z gametophytic self-incompatibility genes of Phalaris, Secale, and Lolium, but the Leymus chromosome-2 self-incompatibility gene aligns to a different region on Brachypodium chromosome 5. Nevertheless, cosegregation of self-incompatibility genes on Leymus presents a powerful system for mapping these loci. [ABSTRACT FROM AUTHOR]

Deep-seeding tolerant seeds can emerge from deep soil where the moisture is suitable for seed germination. Breeding deep-seeding tolerant cultivars is becoming increasingly important in arid and semi-arid regions. To dissect the quantitative trait loci (QTL) controlling deep-seeding tolerance traits, we selected a tolerant maize inbred line 3681-4 and crossed it with the elite inbred line-X178 to generate an F population and the derivative F families. A molecular linkage map composed of 179 molecular markers was constructed, and 25 QTL were detected including 10 QTL for sowing at 10 cm depth and 15 QTL for sowing at 20 cm depth. The QTL analysis results confirmed that deep-seeding tolerance was mainly caused by mesocotyl elongation and also revealed considerable overlap among QTL for different traits. To confirm a major QTL on chromosome 10 for mesocotyl length measured at 20 cm depth, we selected and self-pollinated a BCF plant that was heterozygous at the markers around the target QTL and homozygous at other QTL to generate a BCF population. We found that this QTL explained more phenotypic variance in the BCF population than that in the F population, which laid the foundation for fine mapping and NIL (near-isogenic line) construction. [ABSTRACT FROM AUTHOR]

The article offers information on development and characterization of (bacterial artificial chromosomes)BAC-end sequence derived (simple sequence repeat)SSRs for cultivated peanut. A large set of BAC-end sequences, were used for developing SSR markers, and was applied in genetic linkage mapping. Majority of BESs had no detectable homology to known genes followed by sequences with similarity to known genes and in miscellaneous sequences.This can be used for molecular analysis of the genome.

In this study, high-resolution melting (HRM) analysis was evaluated for gene mapping in rice with sequence-tagged site (STS) and simple sequence repeat (SSR) markers. A total of 103 out of 353 normal STS and SSR markers revealed polymorphic melting curves among the parental genotypes, and 12 of these were successfully used to genotype the F mapping population for HRM analysis. Additional electrophoresis findings demonstrated that HRM genotyping matched with traditional electrophoresis results. To optimize the HRM-marker screening efficiency, different HRM reaction conditions were evaluated. A 5-μl touchdown-polymerase chain reaction (PCR) system provided no significant improvement in screening efficiency but in a 10-μl touchdown-PCR system, the marker screening efficiency increased by 75%. Twenty-one markers were obtained for mapping purposes under the optimized reaction conditions. This study indicates that HRM analysis can speed up the gene mapping progress in rice, while saving a lot of manpower. [ABSTRACT FROM AUTHOR]

Flax ( Linum usitatissimum L.) seeds contain nearly 50% oil which is high in linolenic acid (an omega-3 fatty acid). In this study, a genetic linkage map was constructed based on 114 expressed sequence tag-derived simple sequence repeat (SSR) markers in addition to five single nucleotide polymorphism markers, five genes ( fad2A, fad2B, fad3A, fad3B and dgat1) and one phenotypic trait (seed coat color), using a doubled haploid (DH) population of 78 individuals generated from a cross between SP2047 (a yellow-seeded Solin™ line with 2-4% linolenic acid) and UGG5-5 (a brown-seeded flax line with 63-66% linolenic acid). This map consists of 24 linkage groups with 113 markers spanning ~833.8 cM. Quantitative trait locus (QTL) analysis detected two major QTLs each for linoleic acid (LIO, QLio.crc- LG7, QLio.crc- LG16), linolenic acid (LIN, QLin.crc- LG7, QLin.crc- LG16) and iodine value (IOD, QIod.crc- LG7, QIod.crc- LG16), and one major QTL for palmitic acid (PAL, QPal.crc- LG9). The mutant allele of fad3A, mapped to the chromosomal segment inherited from the parent SP2047, underlies the QTL on linkage group 7 and was positively associated with high LIO content but negatively associated with LIN and IOD. This fad3A locus accounted for approximately 34, 25 and 29% of the phenotypic variation observed in this DH population for these three traits, respectively. The QTL localized on linkage group 16 explained approximately 20, 25 and 13% of the phenotypic variation for these same traits, respectively. For palmitic acid, QPal.crc- LG9 accounted for ~42% of the phenotypic variation. This first SSR-based linkage map in flax will serve as a resource for mapping additional markers, genes and traits, in map-based cloning and in marker-assisted selection. [ABSTRACT FROM AUTHOR]

Resistance to Fusarium head blight (FHB) is of great importance in wheat breeding programs in the northern hemisphere. In Europe, breeders prefer adapted germplasm as resistance donor because of high grain yield and quality demands. Our objective was to identify chromosomal regions affecting FHB resistance among 455 European soft winter wheat ( Triticum aestivum L.) lines using a genome-wide association mapping approach and to analyze the importance of epistatic interactions. All entries were evaluated for FHB resistance by inoculation in two environments and several ratings. Wheat was genotyped by 115 simple sequence repeat markers randomly distributed across the genome and two allele-specific markers for Rht- B1 and Rht- D1 genes. The genome-wide scan revealed nine significant ( P < 0.05) marker-phenotype associations on seven chromosomes including dwarfing gene Rht- D1. Using a Bonferroni-Holm correction, three significant associations remained on chromosomes 1B, 1D, and 2D. The proportion of the genotypic variance explained simultaneously by individual markers was 36% and increased to 50% when two digenic epistatic interactions were considered, one of them associated with Rht- B1. In conclusion, new genomic regions on chromosomes 1D and 3A could be found for FHB resistance in European wheat and the effect of epistatic interactions was substantial. [ABSTRACT FROM AUTHOR]

Depending on the position on the panicle, grain filling differs for spikelets on primary branches and secondary branches of upper and lower portions in rice ( Oryza sativa L.). With the objective of identifying candidate genes associated with the grain-filling process across the panicle, a candidate gene (CG)-based mapping approach was attempted in an F population derived from the cross between Rasi, a rice variety known for its good grain filling, and IC114927, a local landrace. The grain filling (%) was characterized for 444 F individual plants across the panicle. Within the F population, thirteen plants were identified with >90% grain filling across the panicle. For 120 markers designed from 1 kb upstream and within the candidate genes reported to be involved in translocation process of sugars, 18.3% polymorphism was observed. Using a selective genotyping approach comprising 24 individuals from eight groups based on their filling and position, two associated CG markers were identified. Further analysis of the mapping population showed a CG marker based on the sucrose phosphate synthase gene on chromosome 2 to be significantly associated with filling of grains on primary branches of the upper half of the panicle and another CG marker based on the transporter gene on chromosome 11 to be associated with filling of grains on primary branches of the lower half; secondary branches of the upper half and lower half of the panicle. Both the positive alleles were contributed by the variety Rasi. With a candidate gene-based marker mapping approach, two genes involved in sugar translocation and transport were identified to be directly associated with grain filling in rice. [ABSTRACT FROM AUTHOR]

Introgressions into wheat from related species have been widely used as a source of agronomically beneficial traits. One such example is the introduction of the potent eyespot resistance gene Pch1 from the wild relative Aegilops ventricosa onto chromosome 7DL of wheat. In common with genes carried on many other such introgressions, the use of Pch1 in commercial wheat varieties has been hindered by linkage drag with yield-limiting traits. Attempts to break this linkage have been frustrated by a lack of co-dominant PCR markers suitable for identifying heterozygotes in F populations. We developed conserved orthologous sequence (COS) markers, utilising the Brachypodium distachyon (Brachypodium) genome sequence, to provide co-dominant markers in the Pch1 region. These were supplemented with previously developed sequence-tagged site (STS) markers and simple sequence repeat (SSR) markers. Markers were applied to a panel of varieties and to a BC F population, segregating between wheat and Ae. ventricosa over the distal portion of 7DL, to identify recombinants in the region of Pch1. By exploiting co-linearity between wheat chromosome 7D, Brachypodium chromosome 1, rice chromosome 6 and sorghum chromosome 10, Pch1 was located to an interval between the flanking markers Xwg7S and Xcos7- 9. Furthermore candidate gene regions were identified in Brachypodium (364 Kb), rice (178 Kb) and sorghum (315 Kb) as a prelude to the map-based cloning of the gene. In addition, using homoeologue transferable markers, we obtained evidence that the eyespot resistances Pch1 and Pch2 on chromosomes 7D and 7A, respectively, are potentially homoeoloci. It is anticipated that the COS marker methodology could be used for the identification of recombinants in other introgressions into wheat from wild relatives. This would assist the mapping of genes of interest and the breaking of deleterious linkages to enable greater use of these introgressions in commercial varieties. [ABSTRACT FROM AUTHOR]

The use of resistant varieties is an important tool in the management of late blight, which threatens potato production worldwide. Clone Ma R8 from the Mastenbroek differential set has strong resistance to Phytophthora infestans, the causal agent of late blight. The F1 progeny of a cross between the susceptible cultivar Concurrent and Ma R8 were assessed for late blight resistance in field trials inoculated with an incompatible P. infestans isolate. A 1:1 segregation of resistance and susceptibility was observed, indicating that the resistance gene referred to as R8, is present in simplex in the tetraploid Ma R8 clone. NBS profiling and successive marker sequence comparison to the potato and tomato genome draft sequences, suggested that the R8 gene is located on the long arm of chromosome IX and not on the short arm of chromosome XI as was suggested previously. Analysis of SSR, CAPS and SCAR markers confirmed that R8 was on the distal end of the long arm of chromosome IX. R gene cluster directed profiling markers CDP4 and CDP5 flanked the R8 gene at the distal end (1 cM). CDP1-1, CDP1-2 and CDP2 flanked the R8 gene on the proximal side (2 cM). An additional co-segregating marker (CDP3) was found, which will be useful for marker assisted breeding and map based cloning of R8. [ABSTRACT FROM AUTHOR]