New statistical selection method for pleiotropic variants associated with both quantitative and qualitative traits.

BACKGROUND: Identification of pleiotropic variants associated with multiple phenotypic traits has received increasing attention in genetic association studies. Overlapping genetic associations from multiple traits help to detect weak genetic associations missed by single-trait analyses. Many statistical methods were developed to identify pleiotropic variants with most of them being limited to quantitative traits when pleiotropic effects on both quantitative and qualitative traits have been observed. This is a statistically challenging problem because there does not exist an appropriate multivariate distribution to model both quantitative and qualitative data together. Alternatively, meta-analysis methods can be applied, which basically integrate summary statistics of individual variants associated with either a quantitative or a qualitative trait without accounting for correlations among genetic variants. RESULTS: We propose a new statistical selection method based on a unified selection score quantifying how a genetic variant, i.e., a pleiotropic variant associates with both quantitative and qualitative traits. In our extensive simulation studies where various types of pleiotropic effects on both quantitative and qualitative traits were considered, we demonstrated that the proposed method outperforms the existing meta-analysis methods in terms of true positive selection. We also applied the proposed method to a peanut dataset with 6 quantitative and 2 qualitative traits, and a cowpea dataset with 2 quantitative and 6 qualitative traits. We were able to detect some potentially pleiotropic variants missed by the existing methods in both analyses. CONCLUSIONS: The proposed method is able to locate pleiotropic variants associated with both quantitative and qualitative traits. It has been implemented into an R package 'UNISS', which can be downloaded from http://github.com/statpng/uniss.

Transcriptome Analysis of Differentially Expressed Genes Associated with Salt Stress in Cowpea (Vigna unguiculata L.) during the Early Vegetative Stage.

Cowpea (Vigna unguiculata (L.), 2n = 22) is a tropical crop grown in arid and semiarid regions that is tolerant to abiotic stresses such as heat and drought. However, in these regions, salt in the soil is generally not eluted by rainwater, leading to salt stress for a variety of plant species. This study was conducted to identify genes related to salt stress using the comparative transcriptome analysis of cowpea germplasms with contrasting salt tolerance. Using the Illumina Novaseq 6000 platform, 1.1 billion high-quality short reads, with a total length of over 98.6 billion bp, were obtained from four cowpea germplasms. Of the differentially expressed genes identified for each salt tolerance type following RNA sequencing, 27 were shown to exhibit significant expression levels. These candidate genes were subsequently narrowed down using reference-sequencing analysis, and two salt stress-related genes (Vigun_02G076100 and Vigun_08G125100) with single-nucleotide polymorphism (SNP) variation were selected. Of the five SNPs identified in Vigun_02G076100, one that caused significant amino acid variation was identified, while all nucleotide variations in Vigun_08G125100 was classified as missing in the salt-resistant germplasms. The candidate genes and their variation, identified in this study provide, useful information for the development of molecular markers for cowpea breeding programs.

Development and Validation of SNP and InDel Markers for Pod-Shattering Tolerance in Soybean.

Pod-shattering causes a significant yield loss in many soybean cultivars. Shattering-tolerant cultivars provide the most effective approach to minimizing this loss. We developed molecular markers for pod-shattering and validated them in soybeans with diverse genetic backgrounds. The genes Glyma.16g141200, Glyma.16g141500, and Glyma.16g076600, identified in our previous study by quantitative trait locus (QTL) mapping and whole-genome resequencing, were selected for marker development. The whole-genome resequencing of three parental lines (one shattering-tolerant and two shattering-susceptible) identified single nucleotide polymorphism (SNP) and/or insertion/deletion (InDel) regions within or near the selected genes. Two SNPs and one InDel were converted to Kompetitive Allele-Specific PCR (KASP) and InDel markers, respectively. The accuracy of the markers was examined in the two recombinant inbred line populations used for the QTL mapping, as well as the 120 varieties and elite lines, through allelic discrimination and phenotyping by the oven-drying method. Both types of markers successfully discriminated the pod shattering-tolerant and shattering-susceptible genotypes. The prediction accuracy, which was as high as 90.9% for the RILs and was 100% for the varieties and elite lines, also supported the accuracy and usefulness of these markers. Thus, the markers can be used effectively for genetic and genomic studies and the marker-assisted selection for pod-shattering tolerance in soybean.

Genotyping by Sequencing-Based Discovery of SNP Markers and Construction of Linkage Map from F5 Population of Pepper with Contrasting Powdery Mildew Resistance Trait.

Powdery mildew (PM) is a common fungal disease infecting pepper plants worldwide. Molecular breeding of pepper cultivars with powdery mildew resistance is desirable for the economic improvement of pepper cultivation. In the present study, 188 F5 population derived from AR1 (PM resistant) and TF68 (PM sensitive) parents were subjected to high-throughput genotyping by sequencing (GBS) for the identification of single nucleotide polymorphism (SNP) markers. Further, the identified SNP markers were utilized for the construction of genetic linkage map and QTL analysis. Overall read mapping percentage of 87.29% was achieved in this study with the total length of mapped region ranging from 2,956,730 to 25,537,525 bp. A total of 41,111 polymorphic SNPs were identified, and a final of 1,841 SNPs were filtered for the construction of a linkage map. A total of 12 linkage groups were constructed corresponding to each chromosome with 1,308 SNP markers with the map length of 2506.8 cM. Further, two QTLs such as Pm-2.1 and Pm-5.1 were identified in chromosomes 2 and 5, respectively, for the PM resistance. Overall, the outcomes of the present endeavor can be utilized for the marker-assisted selection of pepper with powdery mildew-resistant trait.

Genetic Diversity and Genome-Wide Association Study of Seed Aspect Ratio Using a High-Density SNP Array in Peanut (Arachis hypogaea L.).

Peanut (Arachis hypogaea L.) is one of the important oil crops of the world. In this study, we aimed to evaluate the genetic diversity of 384 peanut germplasms including 100 Korean germplasms and 284 core collections from the United States Department of Agriculture (USDA) using an Axiom_Arachis array with 58K single-nucleotide polymorphisms (SNPs). We evaluated the evolutionary relationships among 384 peanut germplasms using a genome-wide association study (GWAS) of seed aspect ratio data processed by ImageJ software. In total, 14,030 filtered polymorphic SNPs were identified from the peanut 58K SNP array. We identified five SNPs with significant associations to seed aspect ratio on chromosomes Aradu.A09, Aradu.A10, Araip.B08, and Araip.B09. AX-177640219 on chromosome Araip.B08 was the most significantly associated marker in GAPIT and Regularization method. Phosphoenolpyruvate carboxylase (PEPC) was found among the eleven genes within a linkage disequilibrium (LD) of the significant SNPs on Araip.B08 and could have a strong causal effect in determining seed aspect ratio. The results of the present study provide information and methods that are useful for further genetic and genomic studies as well as molecular breeding programs in peanuts.

Population Structure and Genetic Diversity in Korean Cowpea Germplasm Based on SNP Markers.

Cowpea is one of the most essential legume crops providing inexpensive dietary protein and nutrients. The aim of this study was to understand the genetic diversity and population structure of global and Korean cowpea germplasms. A total of 384 cowpea accessions from 21 countries were genotyped with the Cowpea iSelect Consortium Array containing 51,128 single-nucleotide polymorphisms (SNPs). After SNP filtering, a genetic diversity study was carried out using 35,116 SNPs within 376 cowpea accessions, including 229 Korean accessions. Based on structure and principal component analysis, a total of 376 global accessions were divided into four major populations. Accessions in group 1 were from Asia and Europe, those in groups 2 and 4 were from Korea, and those in group 3 were from West Africa. In addition, 229 Korean accessions were divided into three major populations (Q1, Jeonra province; Q2, Gangwon province; Q3, a mixture of provinces). Additionally, the neighbor-joining tree indicated similar results. Further genetic diversity analysis within the global and Korean population groups indicated low heterozygosity, a low polymorphism information content, and a high inbreeding coefficient in the Korean cowpea accessions. The population structure analysis will provide useful knowledge to support the genetic potential of the cowpea breeding program, especially in Korea.

QTL Mapping and Candidate Gene Analysis for Pod Shattering Tolerance in Soybean (Glycine max).

Pod shattering is an important reproductive process in many wild species. However, pod shattering at the maturing stage can result in severe yield loss. The objectives of this study were to discover quantitative trait loci (QTLs) for pod shattering using two recombinant inbred line (RIL) populations derived from an elite cultivar having pod shattering tolerance, namely "Daewonkong", and to predict novel candidate QTL/genes involved in pod shattering based on their allele patterns. We found several QTLs with more than 10% phenotypic variance explained (PVE) on seven different chromosomes and found a novel candidate QTL on chromosome 16 (qPS-DS16-1) from the allele patterns in the QTL region. Out of the 41 annotated genes in the QTL region, six were found to contain SNP (single-nucleotide polymorphism)/indel variations in the coding sequence of the parents compared to the soybean reference genome. Among the six potential candidate genes, Glyma.16g076600, one of the genes with known function, showed a highly differential expression levels between the tolerant and susceptible parents in the growth stages R3 to R6. Further, Glyma.16g076600 is a homolog of AT4G19230 in Arabidopsis, whose function is related to abscisic acid catabolism. The results provide useful information to understand the genetic mechanism of pod shattering and could be used for improving the efficiency of marker-assisted selection for developing varieties of soybeans tolerant to pod shattering.

Identification of Key Genes for the Precise Classification between Solenopsis invicta and S. geminata Facilitating the Quarantine Process.

One of the 100 worst invasive exotic species, Solenopsis invicta (red imported fire ant), has the possibility to induce an allergic reaction that may eventually cause death from its aggressive stinging. In 2017, S. invicta was found at a container yard in Gamman Port, Busan, South Korea for the first time. It may result in an infestation of fire ants in the Korean environment. After this incident, sensitive quarantine procedures are required to detect possible contamination of fire ants in imported containers. However, currently, fire ant identification relies on phenotypic characteristics. This requires highly trained experts for identification and there are not enough to cover all imported containers. Here, we develop a key molecular marker to distinguish S. invicta from others using the whole genome sequence (WGS) of collected S. invicta from Gamman Port and NCBI-deposited WGS data of S.invicta and S. geminata. The consolidated genotypes of Solenopsis genus successfully indicate the distinguishable gene. The gel-based experimental validation confirmed expected classification and the developed cleaved amplified polymorphic sequences (CAPS) marker also gave a consistent result. Using the CAPS marker derived from our consolidated genotypes, the samples collected from containers in several ports can be easily tested by PCR in a few hours. The quick and easy test would increase not only the labor efficiency but also the environmental safety from fire ants.

Phosphoproteome data from abscisic acid and ethylene treated Glycine max leaves.

The data reported here are associated with the article "Comparative phosphoproteome analysis upon ethylene and abscisic acid treatment in Glycine max leaves" [1]. Phosphorylation plays a critical role in the regulation of the biological activities of proteins. However, phosphorylation-mediated regulation of proteins and pathways involved in ethylene (ET) and abscisic acid (ABA) signaling is currently poorly understood. Therefore, we used a shotgun proteomics approach to identify the phosphopeptides and phosphoproteins in response to ET, ABA and combined ET+ABA treatments. Here, we present the Mass spectrometry, protein-protein interaction, Gene ontology and KEGG data associated with the ET and ABA signaling in soybean leaves [1].

Whole Genome Resequencing of Capsicum baccatum and Capsicum annuum to Discover Single Nucleotide Polymorphism Related to Powdery Mildew Resistance.

The present study deals with genome wide identification of single-nucleotide polymorphism (SNP) markers related to powdery mildew (PM) resistance in two pepper varieties. Capsicum baccatum (PRH1- a PM resistant line) and Capsicum annuum (Saengryeg- a PM susceptible line), were resequenced to develop SNP markers. A total of 6,213,009 and 6,840,889 SNPs for PRH1 and Saengryeg respectively have been discovered. Among the SNPs, majority were classified as homozygous type SNPs, particularly in the resistant line. Moreover, the SNPs were differentially distributed among the chromosomes in both the resistant and susceptible lines. In total, 4,887,031 polymorphic SNP loci were identified between the two lines and 306,871 high-resolution melting (HRM) marker primer sets were designed. In order to understand the SNPs associated with the vital genes involved in diseases resistance and stress associated processes, chromosome-wise gene ontology analysis was performed. The results revealed the occurrence that SNPs related to diseases resistance genes were predominantly distributed in chromosome 4. In addition, 6281 SNPs associated with 46 resistance genes were identified. Among the lines, PRH1 consisted of maximum number of polymorphic SNPs related to NBS-LRR genes. The SNP markers were validated using HRM assay in 45 F4 populations and correlated with the phenotypic disease index.

Next-generation sequencing yields the complete chloroplast genome of C. goeringii acc. smg222 and phylogenetic analysis.

Spring orchid (Cymbidium goeringii) is one of the most important species belonging to Orchidaceae owing to its aesthetic appeal, fragrant flowers and ideal characteristics for using as a houseplant. In this study, the complete chloroplast genome of Korean C. goeringii acc. smg222 was determined by Illumina sequencing. The circular double-stranded DNA of 148,441 bp consisted of two inverted repeat regions of 25,610 bp each, a large single copy region of 83,311 bp, and a small single copy region of 13,910 bp. The genome contained 122 genes, of which 104 were unique and 18 were duplicated within the IRs. The 104 unique genes included 70 protein-coding genes, 30 distinct tRNA genes, and four rRNA genes. Phylogenetic tree analysis revealed that C. goeringii acc. smg222 was clustered with Cymbidium kanran, a cymbidium species native to Korea.

Transcriptomic dynamics in soybean near-isogenic lines differing in alleles for an aphid resistance gene, following infestation by soybean aphid biotype 2.

BACKGROUND: Genetic resistance of soybean [Glycine max (L.) Merr] against Aphis glycines provides effective management of this invasive pest, though the underlying molecular mechanisms are largely unknown. This study aimed to investigate genome-wide changes in gene expressions of soybean near-isogenic lines (NILs) either with the Rag5 allele for resistance or the rag5 allele for susceptibility to the aphid following infestation with soybean aphid biotype 2. RESULTS: The resistant (R)-NIL responded more rapidly to aphid infestation than the susceptible (S)-NIL, with differential expressions of 2496 genes during first 12 h of infestation (hai), compared to the aphid-free control. Although the majority of the differentially expressed genes (DEGs) in the R-NIL also responded to aphid infestation in S-NIL, overall the response time was longer and/or the magnitude of change was smaller in the S-NIL. In addition, 915 DEGs in R-NIL continued to be regulated at all time points (0, 6, 12, and 48 hai), while only 20 DEGs did so in S-NIL. Enriched gene ontology of the 2496 DEGs involved in plant defense responses including primary metabolite catalysis, oxidative stress reduction, and phytohormone-related signaling. By comparing R- vs. S-NIL, a total of 556 DEGs were identified. Of the 13 genes annotated in a 120-kb window of the Rag5 locus, two genes (Glyma.13 g190200 and Glyma.13 g190600) were differentially expressed (upregulated in S- or R-NIL), and another gene (Glyma.13 g190500) was induced up to 4-fold in the R-NIL at 6 and 12 h following aphid infestation. CONCLUSIONS: This study strengthens our understanding of the defense dynamics in compatible and incompatible interactions of soybean and soybean aphid biotype 2. Several DEGs (e.g., Glyma.13 g190200, Glyma.13 g190500, and Glyma.13 g190600) near the Rag5 locus are strong candidate genes for further investigations.

Resequencing of Capsicum annuum parental lines (YCM334 and Taean) for the genetic analysis of bacterial wilt resistance.

BACKGROUND: Bacterial wilt (BW) is a widespread plant disease that affects a broad range of dicot and monocot hosts and is particularly harmful for solanaceous plants, such as pepper, tomato, and eggplant. The pathogen responsible for BW is the soil-borne bacterium, Ralstonia solanacearum, which can adapt to diverse temperature conditions and is found in climates ranging from tropical to temperate. Resistance to BW has been detected in some pepper plant lines; however, the genomic loci and alleles that mediate this are poorly studied in this species. RESULTS: We resequenced the pepper cultivars YCM344 and Taean, which are parental recombinant inbred lines (RIL) that display differential resistance phenotypes against BW, with YCM344 being highly resistant to infection with this pathogen. We identified novel single nucleotide polymorphisms (SNPs) and insertions/deletions (Indels) that are only present in both parental lines, as compared to the reference genome and further determined variations that distinguish these two cultivars from one another. We then identified potentially informative SNPs that were found in genes related to those that have been previously associated with disease resistance, such as the R genes and stress response genes. Moreover, via comparative analysis, we identified SNPs located in genomic regions that have homology to known resistance genes in the tomato genomes. CONCLUSIONS: From our SNP profiling in both parental lines, we could identify SNPs that are potentially responsible for BW resistance, and practically, these may be used as markers for assisted breeding schemes using these populations. We predict that our analyses will be valuable for both better understanding the YCM334/Taean-derived populations, as well as for enhancing our knowledge of critical SNPs present in the pepper genome.

Optimization of a Virus-Induced Gene Silencing System with Soybean yellow common mosaic virus for Gene Function Studies in Soybeans.

Virus-induced gene silencing (VIGS) is an effective tool for the study of soybean gene function. Successful VIGS depends on the interaction between virus spread and plant growth, which can be influenced by environmental conditions. Recently, we developed a new VIGS system derived from the Soybean yellow common mosaic virus (SYCMV). Here, we investigated several environmental and developmental factors to improve the efficiency of a SYCMV-based VIGS system to optimize the functional analysis of the soybean. Following SYCMV: Glycine max-phytoene desaturase (GmPDS) infiltration, we investigated the effect of photoperiod, inoculation time, concentration of Agrobacterium inoculm, and growth temperature on VIGS efficiency. In addition, the relative expression of GmPDS between non-silenced and silenced plants was measured by qRT-PCR. We found that gene silencing efficiency was highest at a photoperiod of 16/8 h (light/dark) at a growth temperature of approximately 27°C following syringe infiltration to unrolled unifoliolate leaves in cotyledon stage with a final SYCMV:GmPDS optimal density (OD)600 of 2.0. Using this optimized protocol, we achieved high efficiency of GmPDS-silencing in various soybean germplasms including cultivated and wild soybeans. We also confirmed that VIGS occurred in the entire plant, including the root, stem, leaves, and flowers, and could transmit GmPDS to other soybean germplasms via mechanical inoculation. This optimized protocol using a SYCMV-based VIGS system in the soybean should provide a fast and effective method to elucidate gene functions and for use in large-scale screening experiments.

Identification of Soybean Proteins and Genes Differentially Regulated in Near Isogenic Lines Differing in Resistance to Aphid Infestation.

Soybean aphid is an important pest causing significant yield losses. The Rag2 locus confers resistance to soybean aphid biotypes 1 and 2. Transcriptomic and proteomic analyses were done over a 48 h period after aphid infestation using near isogenic lines (NILs) differing at the Rag2 locus. Comparing the Rag2 and/or rag2 lines identified 3445 proteins, of which 396 were differentially regulated between the two lines, including proteins involved in cell wall metabolism, carbohydrate metabolism, and stress response. RNA-seq transcriptomic analysis identified 2361 genes significantly regulated between the resistant and susceptible lines. Genes upregulated in the Rag2 line were annotated as being involved in cell wall, secondary, and hormone metabolism as well as in stress, signaling, and transcriptional responses. Genes downregulated in the Rag2 line were annotated as being involved in photosynthesis and carbon metabolism. Interestingly, two genes (unknown and mitochondrial protease) located within the defined Rag2 locus were expressed significantly higher in the resistant genotype. The expression of a putative NBS-LRR resistant gene within the Rag2 locus was not different between the two soybean lines, but a second NBL-LRR gene located just at the border of the defined Rag2 locus was. Therefore, this gene may be a candidate R gene controlling aphid resistance.

Identification and mapping of quantitative trait loci (QTL) conferring resistance to Fusarium graminearum from soybean PI 567301B.

KEY MESSAGE: A major novel QTL was identified in a recombinant inbred line population derived from a cross of 'Wyandot' × PI 567301B for Fusarium graminearum, a seed and seedling pathogen of soybean. Fusarium graminearum is now recognized as a primary pathogen of soybean, causing root, seed rot and seedling damping-off in North America. In a preliminary screen, 'Wyandot' and PI 567301B were identified with medium and high levels of partial resistance to F. graminearum, respectively. The objective of this study was to characterise resistance towards F. graminearum using 184 recombinant inbred lines (RILs) derived from a cross of 'Wyandot' × PI 567301B. The parents and the RILs of the mapping population were evaluated for resistance towards F. graminearum using the rolled towel assay in a randomized incomplete block design. A genetic map was constructed from 2545 SNP markers and 2 SSR markers by composite interval mapping. One major and one minor QTL were identified on chromosomes 8 and 6, respectively, which explained 38.5 and 8.1 % of the phenotypic variance. The major QTL on chromosome 8 was mapped to a 300 kb size genomic region of the Williams 82 sequence. Annotation of this region indicates that there are 39 genes including the Rhg4 locus for soybean cyst nematode (SCN) resistance. Based on previous screens, PI 567301B is susceptible to SCN. Fine mapping of this locus will assist in cloning these candidate genes as well as identifying DNA markers flanking the QTL that can be used in marker-assisted breeding to develop cultivars with high levels of resistance to F. graminearum.

Genome sequence of mungbean and insights into evolution within Vigna species.

Mungbean (Vigna radiata) is a fast-growing, warm-season legume crop that is primarily cultivated in developing countries of Asia. Here we construct a draft genome sequence of mungbean to facilitate genome research into the subgenus Ceratotropis, which includes several important dietary legumes in Asia, and to enable a better understanding of the evolution of leguminous species. Based on the de novo assembly of additional wild mungbean species, the divergence of what was eventually domesticated and the sampled wild mungbean species appears to have predated domestication. Moreover, the de novo assembly of a tetraploid Vigna species (V. reflexo-pilosa var. glabra) provides genomic evidence of a recent allopolyploid event. The species tree is constructed using de novo RNA-seq assemblies of 22 accessions of 18 Vigna species and protein sets of Glycine max. The present assembly of V. radiata var. radiata will facilitate genome research and accelerate molecular breeding of the subgenus Ceratotropis.

Population genetic structure and genetic diversity of soybean aphid collections from the USA, South Korea, and Japan.

Following its recent invasion of North America, the soybean aphid (Aphis glycines Matsumura) has become the number one insect pest of soybean (Glycine max L. Merr.) in the north central states of the USA. A few studies have been conducted on the population genetic structure and genetic diversity of the soybean aphid and the source of its invasion in North America. Molecular markers, such as simple sequence repeats (SSRs) are very useful in the evaluation of population structure and genetic diversity. We used 18 SSR markers to assess the genetic diversity of soybean aphid collections from the USA, South Korea, and Japan. The aphids were collected from two sites in the USA (Indiana and South Dakota), two sites in South Korea (Yeonggwang district and Cheonan city), and one site in Japan (Utsunomiya). The SSR markers were highly effective in differentiating among aphid collections from different countries. The level of differentiation within each population and among populations from the same country was limited, even in the case of the USA where the two collection sites were more than 1200 km apart.

Genetic mapping of the powdery mildew resistance gene in soybean PI 567301B.

Powdery mildew (PMD) of soybean [Glycine max (L.) Merr.] is caused by the fungus Microsphaera diffusa. Severe infection of PMD on susceptible varieties often causes premature defoliation and chlorosis of the leaves, which can result in considerable yield losses under favorable environmental conditions for disease development in the field. A total of 334 F(7)-derived recombinant inbred lines (RILs) from a cross of a PMD susceptible soybean cultivar Wyandot and PMD-resistant PI 567301B were used for genetic mapping of PMD resistance in PI 567301B and for development of molecular markers tightly linked to the gene. The result of the PMD screening for each line in the field was in agreement with that in the greenhouse test. The genetic map containing the PMD resistance gene was constructed in a 3.3 cM interval flanked by two simple sequence repeat (SSR) markers on chromosome 16. The PMD resistance gene was mapped at the same location with SSR marker BARCSOYSSR_16_1291, indicating that there was no recombination between the 334 RILs and this marker. In addition, a single nucleotide polymorphism (SNP) marker developed by high-resolution melting curve analysis and a cleaved amplified polymorphic sequence (CAPS) marker with Rsa1 recognition site were used for the genetic mapping. These two markers were also mapped to the same genomic location with the PMD resistance gene. We validated three tightly linked markers to the PMD resistance gene using 38 BC(6)F(2) lines and corresponding BC(6)F(2:3) families. The three marker genotypes of the backcross lines predicted the observed PMD phenotypes of the lines with complete accuracy. We have mapped a putatively novel single dominant PMD resistance gene in PI 567301B and developed three new molecular markers closely linked to the gene. Molecular markers developed from this study may be used for high-throughput marker-assisted breeding for PMD resistance with the gene from PI 567301B.

Genetic map of lps3: a new short petiole gene in soybeans.

The short petiole trait is valuable for the development of plant ideotypes with high yield by improving the plant canopy. The soybean breeding line SS98206SP has shown extremely short petioles in the greenhouse and fields. A new single recessive gene designated as lps3 confers the short petiole trait in SS98206SP. The objectives of this study were to map the short petiole gene in SS98206SP with PCR-based markers. In total, 187 F(2) plants and their F(2:3) families from a cross between the short petiole line SS98206SP and the long petiole cultivar 'Taekwang' along with the two parental lines were evaluated for their petiole lengths in a greenhouse. An SSR marker from each 10-cM section of a consensus soybean map was selected for bulked segregant analysis (BSA) to identify the tentative genomic location of the gene. The BSA technique was useful to localize the gene to a genomic region in the soybean linkage group F (chromosome 13). A linkage map with six SSR and two SNP markers flanking the gene was constructed. We positioned the gene between two SSR markers, Sat_234 and Sct_033, at distances of 8.5 and 3.5 cM from the marker, respectively. The makers flanking the gene (lps3) were located within 3-4 cM of the gene. These markers will be useful for maker-assisted selection in the development of new ideotype soybean plants.