Mapping Of QTLs Research Articles

Development and validation of whole genome-wide and genic microsatellite markers in oil palm (Elaeis guineensis Jacq.): First microsatellite database (OpSatdb)

The availability of large expressed sequence tag (EST) and whole genome databases of oil palm enabled the development of a data base of microsatellite markers. For this purpose, an EST database consisting of 40,979 EST sequences spanning 27 Mb and a chromosome-wise whole genome databases were downloaded. A total of 3,950 primer pairs were identified and developed from EST sequences. The tri and tetra nucleotide repeat motifs were most prevalent (each 24.75%) followed by di-nucleotide repeat motifs. Whole genome-wide analysis found a total of 245,654 SSR repeats across the 16 chromosomes of oil palm, of which 38,717 were compound microsatellite repeats. A web application, OpSatdb, the first microsatellite database of oil palm, was developed using the PHP and MySQL database (https://ssr.icar.gov.in/index.php). It is a simple and systematic web-based search engine for searching SSRs based on repeat motif type, repeat type, and primer details. High synteny was observed between oil palm and rice genomes. The mapping of ESTs having SSRs by Blast2GO resulted in the identification of 19.2% sequences with gene ontology (GO) annotations. Randomly, a set of ten genic SSRs and five genomic SSRs were used for validation and genetic diversity on 100 genotypes belonging to the world oil palm genetic resources. The grouping pattern was observed to be broadly in accordance with the geographical origin of the genotypes. The identified genic and genome-wide SSRs can be effectively useful for various genomic applications of oil palm, such as genetic diversity, linkage map construction, mapping of QTLs, marker-assisted selection, and comparative population studies.

Genetic Analysis and Mapping of QTLs for Soybean Biological Nitrogen Fixation Traits Under Varied Field Conditions.

Soybean is an important economic and green manure crop that is widely used in intercropping and rotation systems due to its high biological nitrogen fixation (BNF) capacity and the resulting reduction in N fertilization. However, the genetic mechanisms underlying soybean BNF are largely unknown. Here, two soybean parent genotypes contrasting in BNF traits and 168 F9:11 recombinant inbred lines (RILs) were evaluated under four conditions in the field. The parent FC1 always produced more big nodules, yet fewer nodules in total than the parent FC2 in the field. Furthermore, nodulation in FC1 was more responsive to environmental changes than that in FC2. Broad-sense heritability (h2b) for all BNF traits varied from 0.48 to 0.87, which suggests that variation in the observed BNF traits was primarily determined by genotype. Moreover, two new QTLs for BNF traits, qBNF-16 and qBNF-17, were identified in this study. The qBNF-16 locus was detected under all of the four tested conditions, where it explained 15.9–59.0% of phenotypic variation with LOD values of 6.31–32.5. Meanwhile qBNF-17 explained 12.6–18.6% of observed variation with LOD values of 4.93–7.51. Genotype group analysis indicated that the FC1 genotype of qBNF-16 primarily affected nodule size (NS), while the FC2 genotype of qBNF-16 promoted nodule number (NN). On the other hand, the FC1 genotype of qBNF-17 influenced NN and the FC2 genotype of qBNF-17 impacted NS. The results on the whole suggest that these two QTLs might be valuable markers for breeding elite soybean varieties with high BNF capacities.

Identification of quantitative trait loci governing subgynoecy in cucumber

QTL-seq analysis identified three major QTLs conferring subgynoecy in cucumbers. Furthermore, sequence and expression analyses predicted candidate genes controlling subgynoecy. The cucumber (Cucumis sativus L.) is a typical monoecious having individual male and female flowers, and sex differentiation is an important developmental process that directly affects its fruit yield. Subgynoecy represents a sex form with a high degree of femaleness and would have alternative use as gynoecy under limited resource conditions. Recently, many studies have been reported that QTL-seq, which integrates the advantages of bulked segregant analysis and high-throughput whole-genome resequencing, can be a rapid and cost-effective way of mapping QTLs. Segregation analysis in the F2 and BC1 populations derived from a cross between subgynoecious LOSUAS and monoecious BMB suggested the quantitative nature of subgynoecy in cucumbers. Both genome-wide SNP profiling of subgynoecious and monoecious bulks constructed from F2 and BC1 plants consistently identified three significant genomic regions, one on chromosome 3 (sg3.1) and another two on short and long arms of chromosome 1 (sg1.1 and sg1.2). Classical QTL analysis using the F2 confirmed sg3.1 (R2 = 42%), sg1.1 (R2 = 29%) and sg1.2 (R2 = 18%) as major QTLs. These results revealed the unique genetic inheritance of subgynoecious line LOSUAS through two distinct major QTLs, sg3.1 and sg1.1, which mainly increase degree of femaleness, while another QTL, sg1.2, contributes to decrease it. This study demonstrated that QTL-seq allows rapid and powerful detection of QTLs using preliminary generation mapping populations such as F2 or BC1 population and further that the identified QTLs could be useful for molecular breeding of cucumber lines with high yield potential.

Identification and mapping of QTLs associated with drought tolerance traits in rice by a cross between Super Basmati and IR55419-04.

Water stress, in a climate change scenario is one of the major threats for sustainable rice productivity. Combining drought resistance with yield and desirable economic traits is the most promising solution for the researchers. Although several studies resulted in the identification of QTLs for drought resistance in rice, but none of them serve as a milestone. Therefore, there is always a quest to find the new QTLs. The present investigation was carried out to map QTLs involved in drought resistance and yield related parameter in a cross of IR55419-04 and Super Basmati. An F2 population of 418 individuals was used as the mapping population. The raised nursery was transplanted in lyzimeters. Two extreme sets of tolerant (23 Nos.) and sensitive (23 Nos.) individuals were selected based on total water uptake under water stress conditions. Two hundred thirty microsatellite markers staggered on the whole genome were used for identifying polymorphic markers between the two parents. The selected 73 polymorphic microsatellites were used to genotype individuals and were scattered on a distance of 1735 cM on all 12 linkage groups. QTL analysis was performed by using the WinQTL Cartographer 2.5 V. A total of 21 QTLs were detected using composite interval mapping. The QTLs relating to drought tolerance at the vegetative stage were found on chromosome 1. Novel genomic regions were detected in the marker interval RM520-RM143 and RM168-RM520. The region has a significant QTL qTWU3.1 for total water uptake. Root morphological trait QTLs were found on chromosome 3. QTLs responsible for additive effects were due to the alleles of the IR55419-04. These novel QTLs can be used for marker assisted breeding to develop new drought-tolerant rice varieties and fine mapping can be used to explore the functional relationship between the QTLs and phenotypic traits.

Mapping of Tolerant Salinity QTLs in the Progeny of Gaspard and Kharchia Cultivars in Bread Wheat

Mapping of Tolerant Salinity QTLs in the Progeny of Gaspard and Kharchia Cultivars in Bread Wheat

Genome-Wide Association Mapping of Major Root Length QTLs Under PEG Induced Water Stress in Wheat.

Roots are vital plant organs that determine adaptation to various soil conditions. The present study evaluated a core winter wheat collection for rooting depth under PEG induced early stage water stress and non-stress growing conditions. Analysis of phenotypic data indicated highly significant (p < 0.01) variation among genotypes. Broad sense heritability of 59 and 73% with corresponding genetic gains of 7.6 and 9.7 (5% selection intensity) were found under non-stress and stress conditions, respectively. The test genotypes were grouped in to three distinct clusters using unweighted pair group method with arithmetic mean (UPGMA) clustering based on maximum Euclidian distance. The first three principal components gave optimum mixed linear model for genome wide association study (GWAS). Linkage disequilibrium (LD) analysis showed significant LD (p < 0.05) amongst 15% of total marker pairs (25,125). Nearly 16% of the significant LDs were among inter chromosomal marker pairs. GWAS revealed five significant root length QTLs spread across four chromosomes. None of the identified QTLs were common between the two growing conditions. Stress specific QTLs, combined explaining 31% of phenotypic variation were located on chromosomes 2B (wPt6278) and 3B (wPt1159). Similarly, two of the three QTLs (wPt0021 and wPt8890) identified under the non-stress condition were found on chromosomes 3B and 5B, respectively. The B genome showed significant importance in controlling root growth both under stress and non-stress conditions. The identified markers can potentially be validated and used for marker assisted selection.

Mapping of QTLs controlling seed weight and seed-shape traits in Brassica napus L. using a high-density SNP map

Thousand seed weight (TSW) is an important trait in oilseed rape. Seed shape and seed size, which directly affect seed weight, can be characterized by seed length, seed width, length–width ratio, seed cross-section area, seed circumference, seed diameter and seed roundness. In the present study, a high-density SNP map containing 2812 bins (involving 11,458 SNPs) was used for the QTL analysis of the eight traits. As a result, 177 identified QTLs were detected in five environments, 25 for TSW and 152 for seven seed-shape traits. These QTLs were integrated into 149 consensus QTLs by a meta-analysis, including one (TSW, length–width ratio, seed length and seed width), two (seed circumference and seed diameter) and three (seed roundness) QTLs accounted for more than 10.0% of the phenotypic variation (PV). The further integration of these consensus QTLs resulted in 63 unique QTLs, of which 34 controlled at least two different traits. Notably, the unique QTL uqC2-1 affected all eight traits and explained 6.60–7.57% of the PV. Furthermore, 19 pairs of epistatic loci were detected and explained 2.39–19.17% of the PV. These results provide useful information to increase the understanding of the genetic basis of TSW and seed-shape traits.

Construction of a high-density genetic map and QTLs mapping with GBS from the interspecific F1 population of P. ostii ‘Fengdan Bai’ and P. suffruticosa ‘Xin Riyuejin’

Tree peony (Paeonia suffruticosa Andrews.) is an important ornamental and medicinal plant in China. However, the genetic mechanisms controlling the traits of interest have not been extensively investigated. In this study, an F1 hybrid population, derived from the cross of P. ostti (‘Feng Dan’) as the female parent and P. suffruticosa (‘Xin Riyuejin’) as the male parent, was used to construct the genetic linkage map using genotyping-by-sequencing (GBS) technique. From the high–throughput sequencing, a total of 243.35 Gb raw data were generated. And then 257,335,738 high-quality GBS markers were detected. Finally, an integrated genetic map containing 3868 markers was constructed, which distributed on 5 linkage groups (LGs). The genetic linkage map spanned 13175.5 cM with an average distance of 3.406 cM between adjacent markers. Based on this map, QTL analysis was performed. A total of 6 QTLs for 4 phenotypic traits of flower number, petal length, petal number and flowering stage were detected. This high-density genetic linkage map and QTL mapping for important flower-related traits using GBS with an F1 population of tree peony in this study will provide a solid foundation for gene positional cloning and molecular marker-assisted breeding in the near future.

An EST-SSR based genetic linkage map and identification of QTLs for anthracnose disease resistance in water yam (Dioscorea alata L.).

Water yam (Dioscorea alata L.) is one of the most important food yams with wide geographical distribution in the tropics. One of the major constraints to water yam production is anthracnose disease caused by a fungus, Colletotrichum gloeosporioides (Penz.). There are no economically feasible solutions as chemical sprays or cultural practices, such as crop rotation are seldom convenient for smallholder farmers for sustainable control of the disease. Breeding for development of durable genetic resistant varieties is known to offer lasting solution to control endemic disease threats to crop production. However, breeding for resistance to anthracnose has been slow considering the biological constraints related to the heterozygous and vegetative propagation of the crop. The development of saturated linkage maps with high marker density, such as SSRs, followed by identification of QTLs can accelerate the speed and precision of resistance breeding in water yam. In a previous study, a total of 1,152 EST-SSRs were developed from >40,000 EST-sequences generated from two D. alata genotypes. A set of 380 EST-SSRs were validated as polymorphic when tested on two diverse parents targeted for anthracnose disease and were used to generate a saturated linkage map. Majority of the SSRs (60.2%) showed Mendelian segregation pattern and had no effect on the construction of linkage map. All 380 EST-SSRs were mapped into 20 linkage groups, and covered a total length of 3229.5 cM. Majority of the markers were mapped on linkage group 1 (LG 1) comprising of 97 EST-SSRs. This is the first genetic linkage map of water yam constructed using EST-SSRs. QTL localization was based on phenotypic data collected over a 3-year period of inoculating the mapping population with the most virulent strain of C. gloeosporioides from West Africa. Based on threshold LOD scores, one QTL was consistently observed on LG 14 in all the three years and average score data. This QTL was found at position interval of 71.1–84.8 cM explaining 68.5% of the total phenotypic variation in the average score data. The high marker density allowed identification of QTLs and association for anthracnose disease, which could be validated in other mapping populations and used in marker-assisted breeding in D. alata improvement programmes.

Association mapping of salt tolerance traits at germination stage of rapeseed (Brassica napus L.)

Soil salinization has a major effect on crop yield. Seed germination is a crucial prerequisite for the successful cultivation of rapeseed in saline soils. Limited information is available about rapeseed salt tolerance at germination stage. Here, we carried out an association mapping of salt tolerance QTLs at seed germination stage. We evaluated salt tolerance of 214 rapeseed inbred lines at germination stage, and the 60 K Brassica Infinium® SNP array was used to genotype the association panel. Finally, a total of 110 single nucleotide polymorphisms (SNPs) were associated with three salt tolerance indices and these SNPs were integrated into 44 QTLs. In addition, 56 possible candidate genes were located in or near the genomic region where the above QTLs were mapped. Thus, our results provide valuable information for understanding the genetic control of rapeseed salt tolerance at germination stage and may facilitate marker-based breeding for rapeseed salt tolerance.

Construction of a high-density genetic map and mapping of QTLs for soybean (Glycine max) agronomic and seed quality traits by specific length amplified fragment sequencing

BackgroundSoybean is not only an important oil crop, but also an important source of edible protein and industrial raw material. Yield-traits and quality-traits are increasingly attracting the attention of breeders. Therefore, fine mapping the QTLs associated with yield-traits and quality-traits of soybean would be helpful for soybean breeders. In the present study, a high-density linkage map was constructed to identify the QTLs for the yield-traits and quality-traits, using specific length amplified fragment sequencing (SLAF-seq).ResultsSLAF-seq was performed to screen SLAF markers with 149 F8:11 individuals from a cross between a semi wild soybean, ‘Huapidou’, and a cultivated soybean, ‘Qihuang26’, which generated 400.91 M paired-end reads. In total, 53,132 polymorphic SLAF markers were obtained. The genetic linkage map was constructed by 5111 SLAF markers with segregation type of aa×bb. The final map, containing 20 linkage groups (LGs), was 2909.46 cM in length with an average distance of 0.57 cM between adjacent markers. The average coverage for each SLAF marker on the map was 81.26-fold in the male parent, 45.79-fold in the female parent, and 19.84-fold average in each F8:11 individual. According to the high-density map, 35 QTLs for plant height (PH), 100-seeds weight (SW), oil content in seeds (Oil) and protein content in seeds (Protein) were found to be distributed on 17 chromosomes, and 14 novel QTLs were identified for the first time. The physical distance of 11 QTLs was shorter than 100 Kb, suggesting a direct opportunity to find candidate genes. Furthermore, three pairs of epistatic QTLs associated with Protein involving 6 loci on 5 chromosomes were identified. Moreover, 13, 14, 7 and 9 genes, which showed tissue-specific expression patterns, might be associated with PH, SW, Oil and Protein, respectively.ConclusionsWith SLAF-sequencing, some novel QTLs and important QTLs for both yield-related and quality traits were identified based on a new, high-density linkage map. Moreover, 43 genes with tissue-specific expression patterns were regarded as potential genes in further study. Our findings might be beneficial to molecular marker-assisted breeding, and could provide detailed information for accurate QTL localization.

Mapping QTLs for physiological and biochemical traits related to grain yield under control and terminal heat stress conditions in bread wheat (Triticum aestivum L.).

In order to detect genomic regions with different effects for some of the physiological and biochemical traits of wheat, four experiments were conducted at Research Farm of Agricultural and Natural Resources Research Center of Zabol in 2015-2016 and 2016-2017 growing seasons. The experiments were carried out using four alpha lattice designs with two replications under non-stress and terminal heat stress conditions. Plant materials used in this study included 167 recombinant inbred lines and their parents ('SeriM82' and 'Babax'). Six traits including grain yield (GY), proline content (PRO), water soluble carbohydrates (WSC), maximum efficiency of photosystem II (Fv/Fm), cytoplasmic membrane stability (CMS) and chlorophyll content (CHL) were evaluated. Genetic linkage map consisted of 211 AFLP marker, 120 SSR marker and 144 DArT markers with 1864cm length and 4.4cm mean distance. QTL analysis was carried out using a mixed-model-based composite interval mapping (MCIM) method. By the combined analysis of normal phenotypic values, 27 additive QTLs and five pairs of epistatic effects were identified for studied traits, among which two additive and one epistatic QTL showed significant QTL × environment interactions. By the combined analysis of stress phenotypic values, a total of 26 QTLs with additive effects and 5 epistatic QTLs were detected, among which one additive and one epistatic QTL showed QTL × environment interactions. Six QTLs with major effects (QGY-2B, QGY-2D, QPro-5B, QWSC-4A, QFv/Fm-6A and QCMS-4B), which were common between two conditions could be useful for marker-assisted selection (MAS) in order to develop heat tolerant and high-performance wheat varieties.

Genome\u2010wide mapping of plasma protein QTLs identifies putatively causal genes and pathways for cardiovascular disease

Identifying genetic variants associated with circulating protein concentrations (protein quantitative trait loci; pQTLs) and integrating them with variants from genome-wide association studies (GWAS) may illuminate the proteome’s causal role in disease and bridge a knowledge gap regarding SNP-disease associations. We provide the results of GWAS of 71 high-value cardiovascular disease proteins in 6861 Framingham Heart Study participants and independent external replication. We report the mapping of over 16,000 pQTL variants and their functional relevance. We provide an integrated plasma protein-QTL database. Thirteen proteins harbor pQTL variants that match coronary disease-risk variants from GWAS or test causal for coronary disease by Mendelian randomization. Eight of these proteins predict new-onset cardiovascular disease events in Framingham participants. We demonstrate that identifying pQTLs, integrating them with GWAS results, employing Mendelian randomization, and prospectively testing protein-trait associations holds potential for elucidating causal genes, proteins, and pathways for cardiovascular disease and may identify targets for its prevention and treatment.

Construction of a high-density genetic map and its application for leaf shape QTL mapping in poplar.

High-quality and dense genetic maps were constructed, and leaf shape variation was dissected by QTL mapping in poplar. Species in the genus Populus, also known as poplars, are important woody species and considered model plants for perennial trees. High-density genetic maps are valuable genomic resources for population genetics. Here, we generated a high-quality and dense genetic map for an F1 poplar population using high-throughput NGS-based genotyping. A total of 92,097 high-quality SNP markers were developed by stringent filtering and identification. In total, 889 and 1650 SNPs formed the female and male genetic maps, respectively. To test the application of the genetic maps, QTL mapping of leaf shape was conducted for this F1 population. A total of nine parameters were scored for leaf shape variation in three different environments. Combining genetic maps and measurements of the nine leaf shape parameters, we mapped a total of 42 significant QTLs. The highest LOD score of all QTLs was 9.2, and that QTL explained the most (15.13%) trait variation. A total of nine QTLs could be detected in at least two environments, and they were located in two genomic regions. Within these two QTL regions, some candidate genes for regulating leaf shape were predicted through functional annotation. The successful mapping of leaf shape QTLs demonstrated the utility of our genetic maps. According to the performance of this study, we were able to provide high-quality and dense genetic maps and dissect the leaf shape variation in poplar.

Association mapping of cadmium-tolerant QTLs in Brassica napus L. and insight into their contributions to phytoremediation

Cadmium (Cd) contamination in soil is one of the major global environmental issues. Rapeseed (Brassica napus L.), as one of the most important oil crops, bio-energy resources and Cd accumulator, is an ideal plant for phytoremediation. But the Cd tolerance mechanisms in rapeseed are not known. Thus, both phenotypic and genotypic identification of Cd tolerance were conducted in a rapeseed natural population. Twelve Cd-tolerant genotypes were selected among 472 worldwide collection of natural rapeseeds based on the criterion of relative radicle length (RRL) >60%. Nine associated SNPs localized in four QTLs were identified by genome-wide association study (GWAS) in which 60 K Brassica Infinium® SNP array was used. Seven candidate genes for Cd tolerance, including HIPP27, EXPB4, EMB1793 and CDSP32 orthologues, were obtained in these loci. The expression of these genes were induced by Cd stress in Cd-tolerant genotype and reduced or not affected by Cd stress in Cd-sensitive genotype in qRT–PCR assays. These genes may contribute to Cd tolerance in rapeseed through the regulation of cell wall development, metal chelation, detoxification and antioxidant defense, respectively. In addition, we suggested that Cd tolerance in rapeseed could be improved by gene pyramiding, as our study has demonstrated the additive effect in both intra- and inter-QTL. Collectively, these findings could provide several breeding materials for producing Cd-tolerant rapeseeds that could be utilized in phytoremediation of heavy Cd polluted field.

QTL mapping for heading date, leaf area and chlorophyll content under cold and drought stress in two related recombinant inbred line populations (Japonica rice) and meta‐analysis

AbstractRice is highly susceptible to drought and cold. The goal of this study was to identify the QTLs affecting the rice heading date (HD), leaf area (LA) and chlorophyll content (CC) under cold and drought stress. A total of twenty‐nine and thirty‐eight additive QTLs were detected from two crosses of ‘Dongnong422’/‘Kongyu131’ and ‘Xiaobaijingzi’/‘Kongyu131’, respectively. qHD1‐7‐1, qHD1‐7‐2, qHD1‐2‐1, qLA1‐7‐1, qLA1‐6‐3 and qCC1‐7‐1 show adaptive effects under cold treatment, while qHD2‐2‐3, qHD2‐2‐2, qLA2‐7‐3 and qCC2‐5‐1 were important for explaining the genetic mechanism during drought tolerance. Additionally, nine and five additive × environment interaction QTLs were detected for two RILs, respectively. RIL26 and RIL73 were two lines that are associated with cold and drought for HD. 339 QTLs related to HD, CC and LA of rice from database and our research were projected onto the genetic map. Nine cloned genes and nineteen homologous candidate genes related to HD, CC, cold tolerance and drought tolerance were mapped by meta‐analysis. These results lay the foundation for the fine mapping of QTLs related to HD, LA and CC for marker‐assisted selection.

Prioritization of Candidate Genes in QTL Regions for Physiological and Biochemical Traits Underlying Drought Response in Barley (Hordeum vulgare L.).

Drought is one of the most adverse abiotic factors limiting growth and productivity of crops. Among them is barley, ranked fourth cereal worldwide in terms of harvested acreage and production. Plants have evolved various mechanisms to cope with water deficit at different biological levels, but there is an enormous challenge to decipher genes responsible for particular complex phenotypic traits, in order to develop drought tolerant crops. This work presents a comprehensive approach for elucidation of molecular mechanisms of drought tolerance in barley at the seedling stage of development. The study includes mapping of QTLs for physiological and biochemical traits associated with drought tolerance on a high-density function map, projection of QTL confidence intervals on barley physical map, and the retrievement of positional candidate genes (CGs), followed by their prioritization based on Gene Ontology (GO) enrichment analysis. A total of 64 QTLs for 25 physiological and biochemical traits that describe plant water status, photosynthetic efficiency, osmoprotectant and hormone content, as well as antioxidant activity, were positioned on a consensus map, constructed using RIL populations developed from the crosses between European and Syrian genotypes. The map contained a total of 875 SNP, SSR and CGs, spanning 941.86 cM with resolution of 1.1 cM. For the first time, QTLs for ethylene, glucose, sucrose, maltose, raffinose, α-tocopherol, γ-tocotrienol content, and catalase activity, have been mapped in barley. Based on overlapping confidence intervals of QTLs, 11 hotspots were identified that enclosed more than 60% of mapped QTLs. Genetic and physical map integration allowed the identification of 1,101 positional CGs within the confidence intervals of drought response-specific QTLs. Prioritization resulted in the designation of 143 CGs, among them were genes encoding antioxidants, carboxylic acid biosynthesis enzymes, heat shock proteins, small auxin up-regulated RNAs, nitric oxide synthase, ATP sulfurylases, and proteins involved in regulation of flowering time. This global approach may be proposed for identification of new CGs that underlies QTLs responsible for complex traits.

Meta-analysis of soybean amino acid QTLs and candidate gene mining

The composition and quantity of amino acids influence the protein content and nutritional value of soybeans and also have an important impact upon soybean quality. After integrating and proofreading 140 original QTLs associated with amino acid contentfrom soybase (http://www.soybase.org/), 138 QTLs were further analyzed to determine high-confidence QTL regions. Meta-analysis was first carried out using the BioMercator ver. 2.1 software, yielding 33 consensus QTLs. The consensus QTL confidence intervals (CIs) ranged from 0.07 to 19.85 Mb. Next, the overview method was used to optimize the CIs, and 57 “real” QTLs were mapped. Candidate genes in the consensus QTL regions were obtained from Phytozome and were annotated using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Swissprot, and gene annotation databases. Finally, 16 unpublished candidate genes controlling the content of five types of amino acids were identified with Blast. These results laid the foundation for fine mapping of soybean amino acid-related QTLs and marker-assisted selection.

Genotyping by sequencing of rice interspecific backcross inbred lines identifies QTLs for grain weight and grain length

Grain weight and grain length are the most stable components of rice yield and important indicators of consumer preference. Considering the potentials of wild rice and to enhance the rice yields to meet the increasing demands, 185 Backcross Inbred Lines (BILs) in the background of O. sativa ssp. indica cv. PR114, including 63 rufi-BILs derived from O. rufipogon IRGC104433 and 122 glumae-BILs from O. glumaepatula IRGC104387 were evaluated for mapping QTLs for yield and yield component traits using Genotyping by Sequencing (GBS). Phenotypic evaluation of BILs in three seasons spanning two locations revealed significant differences compared with recurrent parent. BILs which did not show significant differences for any trait under investigation, or similar based on pedigree, were excluded from GBS. Some glumae-BILs had to be excluded from mapping QTLs due to less sequence information. A custom designed approach for GBS data analysis identified 3322 informative SNPs in 55 rufi-BILs and 3437 informative SNPs in 79 glumae-BILs. QTL mapping identified one QTL for thousand grain weight (qtgw5.1), two for grain width (qgw5.1, qgw5.2) and one for grain length (qgl7.1) in rufi-BILs. In the glumae-BILs, three QTL for thousand grain weight (qtgw2.1, qtgw3.1, qtgw6.1) and two for grain length (qgl3.1, qgl7.1) were identified. Most of the grain weight and width QTL showed positive additive effect contributed by wild species allele, whereas the grain length QTL showed positive additive effect contributed by recurrent parent allele. Based on their physical position, none of the QTLs were found similar to previously cloned QTLs. QTLs for grain traits identified from low yielding wild relatives of rice reveals their significance in improving further the rice yields and widen the genetic base of cultivated rice.

Mapping of QTLs Associated with °Brix and Biomass-Related Traits in Sorghum Using SSR Markers

The non-renewability and greenhouse gas emission nature of crude oil led to the use of renewable plant-based biofuels as alternative energy. Sweet sorghum offers one of the best plant-based bioethanol production from its sugary stalk. Identification and mapping of quantitative trait loci associated with sugar-related traits in sorghum is a crucial step toward the improvement of the sugar content of the crop. The present study was carried out to identify and map QTLs associated with °Brix, stalk diameter and plant height using F2:3 segregating mapping populations derived from a cross between grain sorghum (Sorcoll 163) and sweet sorghum (Gambella). Phenotypic evaluation was conducted in two different environments. A genetic map was constructed using 192 F2 populations genotyped using 76 SSR markers. Estimated heritability for °Brix, stem diameter and plant height amounted to 0.88, 0.41 and 0.65, respectively. A total of seven QTLs distributed across five linkage groups that controls °Brix content were detected using Inclusive Composite Interval Mapping. Each QTL contributed 17.2–44.3% of the total phenotypic variation. The two QTLs located on linkage group SBI-05 and SBI-06 repeated in both environments. These QTLs can be the target of the breeding programs in the future due to high heritability as well as stability in two different environments. The number of SSR markers used in present study is relatively fewer and fine mapping of the target regions should be considered in order to further dissecting the region. All the detected QTLs in this study are categorized as major QTLs, and it could be used further in sweet sorghum improvement program.