F1 Hybrid Population Research Articles

Genome-wide analysis of spatiotemporal allele-specific expression in F1 hybrids of meat- and egg-type chickens

In diploid organisms, each gene locus is composed of two parental alleles, which would interact with each other for determining the phenotypic variation. Better understanding of the allele-specific expression (ASE) in farm animals is much important to explore the genetic basis underlying economically important traits, which have been poorly understood yet. In this study, genome-wide analysis was applied to explore the spatiotemporal pattern of ASE in the F1 hybrids of chicken. First, meat- and egg-type chickens were selected for producing a full-sib F1 hybrid population (n = 57). Then, genome resequencing of two parents and 38 offspring were performed and liver and breast muscle samples (n = 38) were subjected to strand-specific RNA sequencing (ssRNA-seq) for ASE detection at 1, 28, and 56 days of age, respectively. The results accurately identified a total of 465 informative genes that could be distinguished with respect to their parental origins. There were 0.4% − 4.1% of informative genes showing ASE, and 57 of them were found across different tissues and time points. Besides, most ASE genes in chickens were tissue-specific, and no matter what the time-point pattern of one ASE gene, the same parental allele of this gene almost showed consistently higher or lower expression across all time points in the same type tissue. In conclusion, this study indicated that most of ASE genes were tissue-specific and time-dependent.

In Arabidopsis thaliana Heterosis Level Varies among Individuals in an F1 Hybrid Population

Heterosis or hybrid vigour is a phenomenon in which hybrid progeny exhibit superior yield and biomass to parental lines and has been used to breed F1 hybrid cultivars in many crops. A similar level of heterosis in all F1 individuals is expected as they are genetically identical. However, we found variation in rosette size in individual F1 plants from a cross between C24 and Columbia-0 accessions of Arabidopsis thaliana. Big-sized F1 plants had 26.1% larger leaf area in the first and second leaves than medium-sized F1 plants at 14 days after sowing in spite of the identical genetic background. We identified differentially expressed genes between big- and medium-sized F1 plants by microarray; genes involved in the category of stress response were overrepresented. We made transgenic plants overexpressing 21 genes, which were differentially expressed between the two size classes, and some lines had increased plant size at 14 or 21 days after sowing but not at all time points during development. Change of expression levels in stress-responsive genes among individual F1 plants could generate the variation in plant size of individual F1 plants in A. thaliana.

De Novo Genome Assembly of Populus simonii Further Supports That Populus simonii and Populus trichocarpa Belong to Different Sections.

Populus simonii is an important tree in the genus Populus, widely distributed in the Northern Hemisphere and having a long cultivation history. Although this species has ecologically and economically important values, its genome sequence is currently not available, hindering the development of new varieties with wider adaptive and commercial traits. Here, we report a chromosome-level genome assembly of P. simonii using PacBio long-read sequencing data aided by Illumina paired-end reads and related genetic linkage maps. The assembly is 441.38 Mb in length and contain 686 contigs with a contig N50 of 1.94 Mb. With the linkage maps, 336 contigs were successfully anchored into 19 pseudochromosomes, accounting for 90.2% of the assembled genome size. Genomic integrity assessment showed that 1,347 (97.9%) of the 1,375 genes conserved among all embryophytes can be found in the P. simonii assembly. Genomic repeat analysis revealed that 41.47% of the P. simonii genome is composed of repetitive elements, of which 40.17% contained interspersed repeats. A total of 45,459 genes were predicted from the P. simonii genome sequence and 39,833 (87.6%) of the genes were annotated with one or more related functions. Phylogenetic analysis indicated that P. simonii and Populus trichocarpa should be placed in different sections, contrary to the previous classification according to morphology. The genome assembly not only provides an important genetic resource for the comparative and functional genomics of different Populus species, but also furnishes one of the closest reference sequences for identifying genomic variants in an F1 hybrid population derived by crossing P. simonii with other Populus species.

Morphological and genetic characteristics of F1 hybrids introgressed from Brassica napus to B. rapa in Taiwan

BackgroundUnintentional introgression from genetically modified (GM) oilseed rape (Brassica napus) to a relative is inevitable in the open field. A feasible and practical strategy for restricting the spread of GM offspring is to set a reasonable isolated distance between GM B. napus and the relatives. To define the isolated distance, a pollen donor/recipient pair is a prerequisite to conducting the field trial of pollen flow. However, because the cultivation of GM B. napus is prohibited in Taiwan, it is difficult to obtain relevant information. Thus, this study explored the morphological and genetic characteristics of five varieties of B. napus (donor), three varieties of B. rapa (recipient), and the 15 corresponding F1 hybrids, aiming to construct phenotypic data and genetic variation data and to select the most appropriate pollen donor/recipient for future field trials of pollen flow.ResultsThe genome size of all F1 hybrids estimated using flow cytometry showed intermediate DNA content between B. napus and B. rapa varieties. Most of the F1 hybrids had intermediate plant height and blooming period, and the rosette leaves type and colors resembled those of B. napus varieties. The results of sequence-related amplified polymorphism (SRAP) showed an average of 9.52 bands per primer combination and 67.87 polymorphic bands among the F1 hybrid population. Similarity and cluster analyses revealed higher similarity between F1 hybrids and B. napus varieties than between F1 hybrids and B. rapa varieties. Furthermore, we identified a specific 1100-bp band (LOC106302894) in F1 hybrids and B. napus varieties but not in B. rapa varieties.ConclusionsThe rosette leaves and the DNA marker LOC106302894 observed in F1 hybrids are consistent phenotypic and genetic characteristics that can be used to identify the presence of unintentional hybridization from B. napus to B. rapa in Taiwan. Due to the prohibition of GM crop cultivation, the hybridization system of non-GM Brassica species in this study can be utilized as a mimic scheme to conduct pollen flow trials, thus facilitating the determination of the proper isolated distance.

Screening of mango hybrid population for identifying nutritionally rich hybrids - A special focus on carotenoids

In the present study 109 F1 hybrids were evaluated for nutraceuticals such as total antioxidants, total phenols,total flavonoids and total carotenoids to identify nutritionally rich superior hybrids in mango. Genetic variabilityassessed for genetic parameters viz., genotypic variance, phenotypic variance, genotypic coefficient of variation(GCV), phenotypic coefficient of variation (PCV), heritability and genetic advance shown the presence of widegenetic variability in F1 hybrid population of mango for nutritional compounds. The total phenol content variedfrom 22.78 to 170.14 mg 100g−1 of pulp, total flavonoids from 5.07- 37.33 mg 100g−1, total carotenoids rangedfrom 1.42 - 16.79 mg 100g−1 and the total antioxidants were in the range of 0.26-1.43 μmol Trolox 100g−1 of pulp.The narrow difference between phenotypic coefficient of variation and genotypic coefficient of variation forall the traits indicated the predominance of genotypic variability. The broad sense heritability (H2) for all thecompounds was high indicating that phenotype aptly reflects its genotype. In conclusion, the four carotenoidsrich hybrids viz. H-4509 H-3432 H-4252 and H-3946 were identified with 16.79 100g−1, 11.37 100g−1, 10.42 100g−1 and 10.03 100g−1 carotenoids content respectively. These hybrids could possibly serve as elite parents in cropimprovement programme.

Mouse Phenome Database: a data repository and analysis suite for curated primary mouse phenotype data.

The Mouse Phenome Database (MPD; https://phenome.jax.org) is a widely accessed and highly functional data repository housing primary phenotype data for the laboratory mouse accessible via APIs and providing tools to analyze and visualize those data. Data come from investigators around the world and represent a broad scope of phenotyping endpoints and disease-related traits in naïve mice and those exposed to drugs, environmental agents or other treatments. MPD houses rigorously curated per-animal data with detailed protocols. Public ontologies and controlled vocabularies are used for annotation. In addition to phenotype tools, genetic analysis tools enable users to integrate and interpret genome–phenome relations across the database. Strain types and populations include inbred, recombinant inbred, F1 hybrid, transgenic, targeted mutants, chromosome substitution, Collaborative Cross, Diversity Outbred and other mapping populations. Our new analysis tools allow users to apply selected data in an integrated fashion to address problems in trait associations, reproducibility, polygenic syndrome model selection and multi-trait modeling. As we refine these tools and approaches, we will continue to provide users a means to identify consistent, quality studies that have high translational relevance.

Recombining Your Way Out of Trouble: The Genetic Architecture of Hybrid Fitness under Environmental Stress.

Hybridization between species can either promote or impede adaptation. But we know very little about the genetic basis of hybrid fitness, especially in nondomesticated organisms, and when populations are facing environmental stress. We made genetically variable F2 hybrid populations from two divergent Saccharomyces yeast species. We exposed populations to ten toxins and sequenced the most resilient hybrids on low coverage using ddRADseq to investigate four aspects of their genomes: 1) hybridity, 2) interspecific heterozygosity, 3) epistasis (positive or negative associations between nonhomologous chromosomes), and 4) ploidy. We used linear mixed-effect models and simulations to measure to which extent hybrid genome composition was contingent on the environment. Genomes grown in different environments varied in every aspect of hybridness measured, revealing strong genotype–environment interactions. We also found selection against heterozygosity or directional selection for one of the parental alleles, with larger fitness of genomes carrying more homozygous allelic combinations in an otherwise hybrid genomic background. In addition, individual chromosomes and chromosomal interactions showed significant species biases and pervasive aneuploidies. Against our expectations, we observed multiple beneficial, opposite-species chromosome associations, confirmed by epistasis- and selection-free computer simulations, which is surprising given the large divergence of parental genomes (∼15%). Together, these results suggest that successful, stress-resilient hybrid genomes can be assembled from the best features of both parents without paying high costs of negative epistasis. This illustrates the importance of measuring genetic trait architecture in an environmental context when determining the evolutionary potential of genetically diverse hybrid populations.

Developing genetically segregating populations for localization of novel sugarcane brown rust resistance genes

Brown rust caused by Puccinia melanocephala H. Sydow & P. Sydo is an important sugarcane disease that severely threatens sugarcane production in China. Breeding and planting resistant cultivars is the most cost-effective and efficient strategy for the control the disease. In addition, exploration, research, and utilization of resistant genes are the basis for resistance breeding. In the present study, four sugarcane varieties without the Bru1 gene and highly resistant to brown rust were used as male parents, and four varieties highly susceptible to brown rust were used as the female parents to configure hybrids. Six F1 hybrid populations were subjected to authenticity determination using SSR markers, brown rust resistance phenotype identification using artificial inoculation, and molecular detection of Bru1 gene. The results showed that the genetic segregation ratios in F1 hybrid populations of Yuetang 03-393 (HS) × ROC24 (HR) and Liucheng 03-1137 (HS) × Dezhe 93-88 (HR) were 3R:1S and 1R:3S, respectively, and Bru1 gene was not detected in their F1 hybrids. The results indicated that two dominant novel genes controlled brown rust resistance in Yuetang 03-393 (HS) × ROC24 (HR) and two recessive novel genes controlled brown rust resistance in Liucheng 03-1137 (HS) × Dezhe 93-88 (HR). Two genetically segregating populations that could be used for the localization of novel brown rust resistance genes were developed in the present study, and could lay a suitable foundation and provide theoretical reference for the analysis of the genetic mechanism of brown rust resistance, genetic map construction, mapping of novel resistance genes and the development of closely associated molecular markers in the future.

Time course of transient expression of pre-α-pro-GDNF and pre-β-pro-GDNF transcripts, and mGDNF mRNA region in Krushinsky–Molodkina rat brain after audiogenic seizures

The expression of glial cell line-derived neurothrophic factor (GDNF) transcript forms pre-(α)pro-gdnf, pre-(β)pro-gdnf, and their common region m-gdnf in the pons as well as the inferior (IC) and superior colliculi in Krushinsky–Molodkina (KM) rats and in the strain “0” was analyzed by quantitative real-time polymerase chain reaction (PCR) in the control (unstimulated KM and “0” rats) and 1.5, 4.5, and 8 h after auditory stimulation. Such stimulation induced audiogenic seizures (AS) in KM rats. Audiogenic seizure was not observed in “0” rats, which was obtained by selection for the absence of AS in a population of F2 hybrids between KM and Wistar rats not predisposed to AS. A significant drop in the level of all transcripts was observed 1.5 h after auditory stimulation in both KM and “0” rats. In most cases, the average expression of α and β isoforms and m-region 4.5 h after stimulation was greater than those after 1.5 and 8 h. At the same time, the expression of pre-(β)pro-gdnf in the IC of KM rats 4.5 h after the stimulation was significantly lower than after 1.5 or 8 h. This work presents the first demonstration of different time courses of expression of the α and β GDNF isoforms during physiological processes in genotype-specific pathology.

Heritability and Combining Ability Studies in Strawberry Population

The most efficient breeding strategies in crop improvement is the selection based on heritability and combing ability estimates for the traits of economic importance or commercial value. Therefore, the present study was to obtain estimates of heritability and to estimate the phenotypic and genotypic correlations among the characteristics of interest. The commercial cultivars ‘Aromas’, ‘Camarosa’, ‘Dover’, ‘Festival Flórida’, ‘Oso Grande’, ‘Sweet Charlie’ and ‘Milsei-Tudla’, and 103 F1 hybrids from the crossbreeding experiments were evaluated for four traits of commercial fruit yield and 13 traits of fruit physical and chemical quality. The estimated genetic parameters were general combining ability, specific combining ability, genotypic correlation among traits, estimates of heritability, genetic and phenotypic variance. The ‘Camarosa’ and ‘Aromas’ cultivars were the most promising cultivars for use as parents in the commercial fruit production, while ‘Dover’ and ‘Sweet Charlie’ cultivars were selected for taste of fruit in strawberry breeding, as they showed higher concentrations of favorable alleles in the F1 hybrid population. It was also verified some strong genetic correlations for some pairs of characteristics in the present study that may allow indirect selection. The estimation of these parameters is an important basis for decision making on the genetic engineering of strawberry.

Genetic structure of Spartina hybrids between native Spartina maritima and invasive Spartina densiflora in Southwest Europe

Interspecific hybridization represents an evolutionary force resulting in novel genotypes. The genomic changes that occur as a result of hybridization affect both genome structure and gene expression and consequently determine hybrid phenotypes and ecology. This study provides new data on the dynamics of hybrid invasions, integrating effects of the genetic, phenotypic, geographical and environmental scenarios with hybridization following invasion of a halophyte community by an exotic plant species. We analyzed the spatial genetic structure of sterile Spartina F1 hybrid populations established at the Gulf of Cadiz (Southwest Iberian Peninsula) and that of their parental species native S. maritima and invasive S. densiflora using nuclear DNA (Simple Sequence Repeats) and chloroplast DNA sequences. We also analyzed the relationships between the spatial genetic structure of the hybrids, their phenotypic variability and their marsh environment. The studied populations of Spartina hybrids were establishing hybrid zones with a spatial genetic structure inherited from both parental species. The hybrids were genetically more similar to the native than to the invasive species. The hybrid populations with greater genetic differentiation were those more spatially separated from each other and that were present in more contrasted sedimentary environments, revealing respective isolation processes by distance and by environment. The hybrids in the Guadiana Estuary were the most genetically differentiated and with the highest transgressive behavior in terms of tiller height.

Mendelian segregation of leaf phenotypes in experimental F2hybrids elucidates origin of morphological diversity of the apomicticRanunculus auricomuscomplex

AbstractApomictic plant complexes exhibit a stunning morphological diversity. TheRanunculus auricomuscomplex with more than 800 morphologically recognized asexual species and just 4 known sexual species is a model group to study origins of high morphological diversity in asexually reproducing lineages. During the Pleistocene, the sexuals of theR. auricomuscomplex diverged in Central Europe into two morphological groups of contrasting basal leaf phenotypes, the undivided forms represented by diploidR. carpaticolaand the deeply divided forms represented by diploidR. notabilis. An experimental interspecific crossing ofR. carpaticola×R. notabilisrevealed an extensive phenotypic diversity of the sexually formed F2hybrid generation. We hypothesize that apomictic species of the EuropeanR. auricomuscomplex might have established from hybrid derivatives ofcarpaticola‐andnotabilis‐like sexual ancestors. Here we investigate segregation of F2basal leaf phenotypes from experimentalR. carpaticola×R. notabiliscrosses. We tested the hypothesis whether F2hybrid leaf phenotypes segregate in a Mendelian manner and whether any segregant phenotypes matchR. variabilis, an apomictic species and natural hybrid derivative ofR. notabilis. Using landmark‐based geometric morphometrics of basal leaves, we recognized two major morphological clusters within theR. carpaticola×R. notabilisF2hybrid population. Thecarpaticola‐like morphological cluster included undivided or less‐divided leaf phenotypes without lateral sinuses and thenotabilis‐like morphological cluster contained deeply divided leaf phenotypes with 1–2 lateral sinuses. The overall ratio of the both morphological clusters within the F2hybrid population was approximately 1 : 1, suggesting Mendelian inheritance and partial dominance of the allele for the divided leaf phenotype. The morphological cluster of divided leaf phenotypes included 11% of F2individuals with a higher similarity to the apomictic speciesR. variabilisthan to the parental sexuals. Thevariabilis‐like F2segregant phenotypes often resulted from F1 crosses ofcarpaticola‐like mother plants withnotabilis‐like pollen donors; such crossing lines reached the highest morphological disparity. Equivalent hybridizations in nature followed by Mendelian segregation of phenotypes, which became later on fixed via the shift to apomictic reproduction, might have established the extant diversity of apomictic complexes. Microsatellite genotyping with six SSR loci revealed no correlation of genetic and phenotypic variation. We conclude that former “morpho‐groups” or “main species” based on phenotypic similarity only are unsuitable units for taxonomic classification.

GmRAD: an integrated SNP calling pipeline for genetic mapping with RADseq across a hybrid population.

Restriction site-associated DNA sequencing (RADseq) is a powerful technology that has been extensively applied in population genetics, phylogenetics and genetic mapping. Although many software packages are available for ecological and evolutionary studies, a few effective tools are available for extracting genotype data with RADseq for genetic mapping, a prerequisite for quantitative trait locus mapping, comparative genomics and genome scaffold assembly. Here, we present an integrated pipeline called gmRAD for generating single nucleotide polymorphism (SNP) genotypes from RADseq data, de novo, across a genetic mapping population derived by crossing two parents. As an analytical strategy, the software takes five steps to implement the whole algorithms, including clustering the first (forward) reads of each parent, building two parental references, generating parental SNP catalogs, calling SNP genotypes across all individuals and filtering the genotype data for genetic linkage mapping. All the steps can be completed with a simple command line, but they can be also performed optionally if prerequisite files are available. To validate its application, we also performed a real data analysis with RADseq data from an F1 hybrid population derived by crossing Populus deltoides and Populus simonii. The software gmRAD is freely available at https://github.com/tongchf/gmRAD.

A metabolome-based core hybridisation strategy for the prediction of rice grain weight across environments.

SummaryMarker‐based prediction holds great promise for improving current plant and animal breeding efficiencies. However, the predictabilities of complex traits are always severely affected by negative factors, including distant relatedness, environmental discrepancies, unknown population structures, and indeterminate numbers of predictive variables. In this study, we utilised two independent F1 hybrid populations in the years 2012 and 2015 to predict rice thousand grain weight (TGW) using parental untargeted metabolite profiles with a partial least squares regression method. A stable predictive model for TGW was built based on hybrids from the population in 2012 (r = 0.75) but failed to properly predict TGW for hybrids from the population in 2015 (r = 0.27). After integrating hybrids from both populations into the training set, the TGW of hybrids could be predicted but was largely dependent on population structures. Then, core hybrids from each population were determined by principal component analysis and the TGW of hybrids in both environments were successfully predicted (r > 0.60). Moreover, adjusting the population structures and numbers of predictive analytes increased TGW predictability for hybrids in 2015 (r = 0.72). Our study demonstrates that the TGW of F1 hybrids across environments can be accurately predicted based on parental untargeted metabolite profiles with a core hybridisation strategy in rice. Metabolic biomarkers identified from early developmental stage tissues, which are grown under experimental conditions, may represent a workable approach towards the robust prediction of major agronomic traits for climate‐adaptive varieties.

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.

DNA markers of AHAS1 gene for screening and identification of sunflower genotypes of hybrid origin

Aim. A molecular genetic study of sunflower F1 and F2 hybrids on a microsatellite markers of mutant AHAS1 gene associated with herbicide resistance was performed. The aim of the work was to screen of F1 and F2 sunflower hybrid populations with usage of DNA markers and identification of homozygous segregants containing of the gene for resistance to SU herbicides. Methods. It was used PCR amplification to detect alleles of microsatellite locus located within the mutant AHAS1 gene. Results. The possibility of identification of hybrid plants with different alleles of the AHAS1 gene was shown. The efficiency of the allele of 191 b. p. in the homo- and heterozygous state for marker selection of genotypes resistant to the herbicide of the sulfonylurea group was confirmed. 10 homozygous F2 plants of SURES-2 x OS 1019B and 18 homozygous F2 plants of SURES-2 x OS 1029B, which according to the genotype correspond to the donor line of the mutant AHAS1 gene, were obtained. Conclusions. F2 plants that are carriers of this gene in the homozygous state can be used as an initial material in breeding for the purpose of creating new inbred lines with genetically determined resistance to SU herbicides. Keywords: DNA markers, AHAS1 gene, sunflower, herbicides, resistance.

Identification of recombination events in outbred species with next-generation sequencing data

BackgroundMeiotic recombination events include crossovers and non-crossovers or gene conversions. Although the rate of crossovers is often used for genetic mapping, the gene conversion events are not well studied especially in outbred species, which could produce distorted markers and thus affect the precision of genetic maps.ResultsWe proposed a strategy for identifying gene conversion events in Populus with the next-generation sequencing (NGS) data from the two parents and their progeny in an F1 hybrid population. The strategy first involved phasing the heterozygous SNPs of the parents to obtain the parental haplotype blocks by NGS analytical tools, permitting to identify the parental gene conversion events with progeny genotypes. By incorporating available genetic linkage maps, longer haplotype blocks each corresponding to a chromosome can be created, not only allowing to detect crossover events but also possibly to locate a crossover in a small region. Our analysis revealed that gene conversions are more abundant than crossovers in Populus, with a higher probability to generate distorted markers in the regions involved than in the other regions on genome. The analytical procedures were implemented with Perl scripts as a freely available package, findGCO at https://github.com/tongchf/findGCO.ConclusionsThe novel strategy and the new developed Perl package permit to identify gene conversion events with the next-generation sequencing technology in a hybrid population of outbred species. The new method revealed that in a genetic mapping population some distorted genetic markers are possibly due to the gene conversion events.

High-Density Genetic Map Construction and Stem Total Polysaccharide Content-Related QTL Exploration for Chinese Endemic Dendrobium (Orchidaceae).

Plants of the Dendrobium genus are orchids with not only ornamental value but also high medicinal value. To understand the genetic basis of variations in active ingredients of the stem total polysaccharide contents (STPCs) among different Dendrobium species, it is of paramount importance to understand the mechanism of STPC formation and identify genes affecting its process at the whole genome level. Here, we report the first high-density single-nucleotide polymorphism (SNP) integrated genetic map with a good genome coverage of Dendrobium. The specific-locus amplified fragment sequencing (SLAF-seq) technology led to identification of 7,013,400 SNPs from 1,503,626 high-quality SLAF markers from two parents (Dendrobium moniliforme ♀ × Dendrobium officinale ♂) and their interspecific F1 hybrid population. The final genetic map contained 8, 573 SLAF markers, covering 19 linkage groups (LGs). This genetic map spanned a length of 2,737.49 cM, where the average distance between markers is 0.32 cM. In total, 5 quantitative trait loci (QTL) related to STPC were identified, 3 of which have candidate genes within the confidence intervals of these stable QTLs based on the D. officinale genome sequence. This study will build a foundation up for the mapping of other medicinal-related traits and provide an important reference for the molecular breeding of these Chinese herb.

Heterosis Analysis of Leaf Stomatal Characteristics on F 1 Population of Cocoa (Theobroma cacao L.) Related to Vascular-Streak Dieback Resistance

Breeding for cocoa resistance to VSD is the main goal in breeding program in Indonesia. Research for selection criteria on cocoa (Theobroma cacaoL.) resistance to vascular-streak dieback (VSD) has being carried out by exploring leaf stomatal characteristics corresponding to VSD damages. This research had objectives to select best crosses by observing the estimated value of heterosis and heterobeltiosis on F1 hybrid populations based on leaf stomata characteristics related to VSD resistance. Trial was established at Kaliwining Experimental Station of Indonesian Coffee and Cocoa Research Institute (ICCRI) in a VSD endemic area. Treatments consisted of 5 F1 hybrid populations generated by biparental crosses of TSH 858(S) x Sulawesi 1 (R), TSH 858 (S) x KEE 2 (R), TSH 858 (S) x Sulawesi 3 (R), Sca 6 (R) x KW 264 (S) and KW 617 (R) x KW 264 (S). Each cross consisted of 100-300 genotypes planted in high planting density of 0.5 m x 0.5 m. Theresistance was evaluated by scoring the plant damage in the scale of 0-3 at three years after planting. Stomata characteristics were assessed microscopically based on the variables of density, length, width and diameter of stomata and width of opening stomata. Analysis of correlation indicated that most of stomatal charac-teristicssignificantly correlated to VSD damage but the width of opening stomata performedthe highest coefficient of correlation (r = 0.49) and contributed to VSD damage (0.45). Meanwhile, path analysis indicated higher value of the char-acteristics performed less resistance of the tested hybrids, KW 617 x KW 264 showed lower value of heterosis and heterobeltiosis for the characteristics which of the best crosses for generating VSD-resistant genotype.

Inheritance of resistance to downy mildew by F1 and F2 sunflower hybrids

Inheritance of resistance to downy mildew by F1 and F2 sunflower hybrids