Project description:Crop improvement is a long-term, expensive institutional endeavor. Genomic selection (GS), which uses single nucleotide polymorphism (SNP) information to estimate genomic breeding values, has proven efficient to increasing genetic gain by accelerating the breeding process in animal breeding programs. As for crop improvement, with few exceptions, GS applicability remains in the evaluation of algorithm performance. In this study, we examined factors related to GS applicability in line development stage for grain yield using a hard red winter wheat (Triticum aestivum L.) doubled-haploid population. The performance of GS was evaluated in two consecutive years to predict grain yield. In general, the semi-parametric reproducing kernel Hilbert space prediction algorithm outperformed parametric genomic best linear unbiased prediction. For both parametric and semi-parametric algorithms, an upward bias in predictability was apparent in within-year cross-validation, suggesting the prerequisite of cross-year validation for a more reliable prediction. Adjusting the training population's phenotype for genotype by environment effect had a positive impact on GS model's predictive ability. Possibly due to marker redundancy, a selected subset of SNPs at an absolute pairwise correlation coefficient threshold value of 0.4 produced comparable results and reduced the computational burden of considering the full SNP set. Finally, in the context of an ongoing breeding and selection effort, the present study has provided a measure of confidence based on the deviation of line selection from GS results, supporting the implementation of GS in wheat variety development.
Project description:Next-generation sequencing enables genome-wide genotyping of a large population and further facilitates the construction of a genetic linkage map. Low-coverage whole-genome sequencing has been employed for genetic linkage map construction in several species. However, this strategy generally requires available high-quality reference genomes and/or designed inbred pedigree lines, which restrict the scope of application for non-model and unsequenced species. Here, using torafugu (Takifugu rubripes) as a test model, we propose a new strategy for ultrahigh-density genetic linkage map construction using low-coverage whole-genome sequencing of a haploid/doubled haploid (H/DH) population without above requirements. Low-coverage (≈1×) whole-genome sequencing data of 165 DH individuals were used for de novo assembly and further performed single nucleotide polymorphisms (SNPs) calling, resulting in the identification of 1,070,601 SNPs. Based on SNP genotypes and de novo assembly, genotypes were associated with short DNA segments and an ultrahigh-density linkage map was constructed containing information of 802,277 SNPs in 3090 unique positions. Comparative analyses showed near-perfect concordance between the present linkage map and the latest published torafugu genome (FUGU5). This strategy would facilitate ultrahigh-density linkage map construction in various sexually reproducing organisms for which H/DH populations can be generated.
Project description:Doubled haploids in cucurbit species are produced through in situ parthenogenesis via pollination with irradiated pollen for further use as parental lines for hybrid F1 production. In this study, seven genotypes of melon "Piel de Sapo" were appraised for agronomic traits and pathogen resistances to evaluate its commercial value and used as donor plant material for the parthenogenetic process. Then, in situ parthenogenetic capacity of melon "Piel de Sapo" germplasm was evaluated and optimized. Several steps of the parthenogenetic process were assessed in this study such as melon fruit set after pollination with irradiated pollen, haploid embryo obtention, in vitro germination and growth of parthenogenetic embryos and plantlets, in vitro and in vivo chromosome doubling with colchicine or oryzalin and fruit set of doubled haploid lines. Parthenogenetic efficiencies of "Piel de Sapo" genotypes showed a high genotypic dependency during the whole process. Three different methods were assayed for parthenogenetic embryo detection: one-by-one, X-ray and liquid medium. X-ray radiography of seeds was four times faster than one-by-one method and jeopardized eight times less parthenogenetic embryo obtention than liquid medium. One third of melon fruits set after pollination with irradiated pollen contained at least one parthenogenetic embryo. The 50.94% of the embryos rescued did not develop into plantlets because failed to germinate or plantlet died at the first stages of development because of deleterious gene combination in haploid homozygosity. The distribution of the ploidy-level of the 26 parthenogenetic plantlets obtained was: 73.08% haploid, 23.08% spontaneous doubled haploid and 3.84% mixoploid. Two in vitro chromosome doubling methods, with colchicine or oryzalin, were compared with a third in vivo colchicine method. In vivo immersion of apical meristems in a colchicine solution for 2 h showed the highest results of plant survival, 57.33%, and chromosome doubling, 9.30% mixoploids and 20.93% doubled haploids. Fruit set and seed recovery of doubled haploids lines was achieved. In this study, doubled haploid lines were produced from seven donor genotypes of melon "Piel de Sapo," however, further improvements are need in order to increase the parthenogenetic efficiency.
Project description:BackgroundTwo-line hybrid wheat system using thermo-photo sensitive genic male sterility (TPSGMS) is currently the most promising approach for wheat heterosis utilization in China. However, during past 20 years only few TPSGMS lines were developed in hybrid wheat breeding, which has been the main limiting factor to create heterotic hybrids. Application of doubled haploid (DH) breeding provides a useful strategy to efficiently develop practically usable TPSGMS lines.ResultsF1s and selected F2 and F3 sterile plants of eight crosses made from two commercial TPSGMS lines were used to produce DH lines. We developed a total of 24 elite DH sterile lines with stable sterility, good outcrossing and yield potential, resistance to yellow rust and powdery mildew, as well as desirable plant height (50-60 cm). These DH lines were developed within 4 years through at least 1 year of evaluation. The stability of male sterility was confirmed for most (20/24) of these elite DH sterile lines by multiple tests in two or 3 years. These lines are expected to be used in hybrid wheat breeding. The percentage of elite lines developed from the tested DH lines produced from filial generations was in the order of F2 > F3 > F1.ConclusionsWe demonstrate that coupling DH techniques with conventional breeding is an efficient strategy for accelerating the development of more practical wheat TPSGMS lines. Generation of DHs from F2 generation appeared to be the better choice considering the balance of shortening breeding time and overall breeding efficiency.
Project description:For doubled haploid (DH) production in maize, F1 generation has been the most frequently used for haploid induction due to facility in the process. However, using F2 generation would be a good alternative to increase genetic variability owing to the additional recombination in meiosis. Our goals were to compare the effect of F1 and F2 generations on DH production in tropical germplasm, evaluating the R1-navajo expression in seeds, the working steps of the methodology, and the genetic variability of the DH lines obtained. Sources germplasm in F1 and F2 generations were crossed with the tropicalized haploid inducer LI-ESALQ. After harvest, for both induction crosses were calculated the haploid induction rate (HIR), diploid seed rate (DSR), and inhibition seed rate (ISR) using the total number of seeds obtained. In order to study the effectiveness of the DH working steps in each generation, the percentage per se and the relative percentage were verified. In addition, SNP markers were obtained for genetic variability studies. Results showed that the values for HIR, ISR, and DSR were 1.23%, 23.48%, and 75.21% for F1 and 1.78%, 15.82%, and 82.38% for F2, respectively. The effectiveness of the DH working step showed the same percentage per se value (0.4%) for F1 and F2, while the relative percentage was 27.2% for F1 and 22.4% for F2. Estimates of population parameters in DH lines from F1 were higher than F2. Furthermore, population structure and kinship analyses showed that one additional generation was not sufficient to create new genotype subgroups. Additionally, the relative efficiency of the response to selection in the F1 was 31.88% higher than F2 due to the number of cycles that are used to obtain the DH. Our results showed that in tropical maize, the use of F1 generation is recommended due to a superior balance between time and genetic variability.
Project description:A doubled haploid (DH) mapping population was obtained from microspore culture of an allohexaploid F1 from the cross between two recently-synthesized allohexaploid Brassica lines. We used single nucleotide polymorphism (SNP) genetic variation based on restriction-site associated DNA (RAD) sequencing to construct a high density genetic linkage map of the population. RAD libraries were constructed from the genomic DNA of both parents and 146 DH progenies. A total of 2.87 G reads with an average sequencing depth of 2.59 × were obtained in the parents and of 1.41 × in the progeny. A total of 290,422 SNPs were identified from clustering of RAD reads, from which we developed 7,950 high quality SNP markers that segregated normally (1:1) in the population. The linkage map contained all 27 chromosomes from the parental A, B and C genomes with a total genetic distance of 5725.19 cM and an average of 0.75 cM between adjacent markers. Genetic distance on non-integrated linkage groups was 1534.23 cM, or 21% of total genetic distance. Out of 146 DH progenies, 91 had a complete set of 27 chromosomes as expected of a hexaploid species, and 21 out of 27 chromosomes showed high collinearity between the physical and linkage maps. The loss of chromosome(s) or chromosome segment(s) in the DH population was associated with a reduction in pollen viability. Twenty-five additive QTL were associated with pollen viability and fertility-related traits (seed number, seed yield, pod length, plant height, 1000-seed weight). In addition, 44 intra-genomic and 18 inter-genomic epistatic QTL pairs were detected for 4 phenotypic traits. This provides confidence that the DH population may be selected for improved pollen viability and fertility in a future allohexaploid Brassica species.
Project description:Purpose: Next-generation sequencing (NGS) has revolutionized systems-based analysis of leaf color at different development stages. The goals of this study are to compare anthocyanin biosynthesis, chlorophyll metabolism and chloroplast organization transcriptome profiling (RNA-seq) to microarray and quantitative reverse transcription polymerase chain reaction (qRT–PCR) methods and to evaluate protocols for optimal high-throughput data analysis Methods: Leaf mRNA profiles of 12 RNA sequencing libraries (S1, S2, S3_S, and S3_C) were generated by deep sequencing, in triplicate, using an Illumina HiSeq 4000 system. After removing reads of low quality, those that remained were mapped to the reference genome (ftp://ftp.ensemblgenomes.org/pub/release-38/plants/genbank/brassica_oleracea/) using the HISAT package, allowing for a maximum of two mismatches and multiple alignments per read (up to 20 by default). qRT–PCR validation was performed using SYBR Green assays Results: Using an optimized data analysis workflow, we mapped about 571.74 million sequence reads per sample to the the reference genome (ftp://ftp.ensemblgenomes.org/pub/release-38/plants/genbank/brassica_oleracea/) and identified 99, 391, 74, and 543 DEGs were detected in pairwise comparison (S2 vs. S1, S3_S vs. S2, S3_C vs. S2, and S3_S vs. S3_C, respectively). The DEGs were associated with ‘photosynthesis’and other pathways in the Kyoto Encyclopedia of Genes and Genomes database; DEGs related to chloroplast organization were identified in the Gene Ontology analysis. The DEGs identified by RNA sequencing were confirmed by qRT-PCR analysis, indicating that the data were reliable. These findings provide information that can be useful for investigating the molecular basis for leaf variegation in ornamental kale and other plants. Conclusions: The results presented here reveal changes in the transcriptome profile of a bicolor leaf kale. DEGs related to anthocyanin biosynthesis, chlorophyll metabolism and chloroplast organization were detected. These results demonstrate that leaf color at different stages of development is influenced by anthocyanin biosynthesis, chloroplast and pigment metabolism, providing a foundation for investigating the molecular basis for bicolor leaf in ornamental kale and other plants.
Project description:Purpose: Next-generation sequencing (NGS) has revolutionized systems-based analysis of leaf color at different development stages. The goals of this study are to compare chlorophyll metabolism and chloroplast organization transcriptome profiling (RNA-seq) to microarray and quantitative reverse transcription polymerase chain reaction (qRT–PCR) methods and to evaluate protocols for optimal high-throughput data analysis Methods: leaf mRNA profiles of 12 RNA sequencing libraries (S1, S2, S3_S, and S3_C) were generated by deep sequencing, in triplicate, using an Illumina HiSeq 4000 system. After removing reads of low quality, those that remained were mapped to the reference genome (ftp://ftp.ensemblgenomes.org/pub/release-38/plants/genbank/brassica_oleracea/) using the HISAT package, allowing for a maximum of two mismatches and multiple alignments per read (up to 20 by default). qRT–PCR validation was performed using SYBR Green assays Results: Using an optimized data analysis workflow, we mapped about 571.74 million sequence reads per sample to the the reference genome (ftp://ftp.ensemblgenomes.org/pub/release-38/plants/genbank/brassica_oleracea/) and identified 1028, 4323, 428, and 1033 DEGs were detected in pairwise comparison (S2 vs. S1, S3_S vs. S2, S3_S vs. S2, and S3_S vs. S3_C, respectively). The DEGs were associated with ‘photosynthesis’, ‘carbon fixation in photosynthetic organisms’, ‘porphyrin and chlorophyll metabolism’ and other pathways in the Kyoto Encyclopedia of Genes and Genomes database; DEGs related to chloroplast organization were identified in the Gene Ontology analysis. The DEGs identified by RNA sequencing were confirmed by qRT-PCR analysis, indicating that the data were reliable. These findings provide information that can be useful for investigating the molecular basis for leaf variegation in ornamental kale and other plants. Conclusions: The results presented here reveal changes in the transcriptome profile of a variegated leaf kale. DEGs related to chlorophyll metabolism and chloroplast organization were detected. These results demonstrate that leaf color at different stages of development is influenced by chloroplast and pigment metabolism, providing a foundation for investigating the molecular basis for leaf variegation in ornamental kale and other plants.
Project description:Genomic selection and doubled haploids hold significant potential to enhance genetic gains and shorten breeding cycles across various crops. Here, we utilized stochastic simulations to investigate the best strategies for optimize a sweet corn breeding program. We assessed the effects of incorporating varying proportions of old and new parents into the crossing block (3:1, 1:1, 1:3, and 0:1 ratio, representing different degrees of parental substitution), as well as the implementation of genomic selection in two distinct pipelines: one calibrated using the phenotypes of testcross parents (GSTC scenario) and another using F1 individuals (GSF1). Additionally, we examined scenarios with doubled haploids, both with (DH) and without (DHGS) genomic selection. Across 20 years of simulated breeding, we evaluated scenarios considering traits with varying heritabilities, the presence or absence of genotype-by-environment effects, and two program sizes (50 vs 200 crosses per generation). We also assessed parameters such as parental genetic mean, average genetic variance, hybrid mean, and implementation costs for each scenario. Results indicated that within a conventional selection program, a 1:3 parental substitution ratio (replacing 75% of parents each generation with new lines) yielded the highest performance. Furthermore, the GSTC model outperformed the GSF1 model in enhancing genetic gain. The DHGS model emerged as the most effective, reducing cycle time from 5 to 4 years and enhancing hybrid gains despite increased costs. In conclusion, our findings strongly advocate for the integration of genomic selection and doubled haploids into sweet corn breeding programs, offering accelerated genetic gains and efficiency improvements.
Project description:Creating varieties with high nitrogen use efficiency (NUE) is crucial for sustainable agriculture development. In this study, a superior barley doubled haploid line (named DH45) with improved NUE was produced via F1 microspore embryogenesis with three rounds of screening in different nitrogen levels by hydroponic and field experiments. The molecular mechanisms responsible for the NUE of DH45 surpassing that of its parents were investigated by RNA-seq analysis. A total of 1027 differentially expressed genes (DEGs) were identified that were up- or down-regulated in DH45 under low nitrogen conditions but showed no significant differences in the parents. GO analysis indicated that genes involved in nitrogen compound metabolic processes were significantly enriched in DH45 compared with the parents. KEGG analysis showed the MAPK signaling pathway plant to be highly enriched in DH45 relative to its parents, as well as genes involved in alanine, aspartate and glutamate metabolism, and arginine biosynthesis. In conclusion, our study revealed the potential to fix trait superiority in a line by combining crossing with F1 microspore culture technologies in future crop breeding and also identified several candidate genes that are expressed in shoots and may enable barley to cope with low-nitrogen stress.