Linkage Group B1 Research Articles

Identification and validation of quantitative trait loci controlling seed isoflavone content across multiple environments and backgrounds in soybean

Soybean is important throughout the world not only due to the high seed protein and oil but also owing to the seed isoflavone. To improve the isoflavone concentration in seeds, detecting and mining the stable and reliable quantitative trait loci (QTLs) and related genes in multiple environments and genetic backgrounds become more and more important. In view of this, a F6:7 recombinant inbred line (RIL) population of 345 lines derived from a cross between Zheng 92116 and Liaodou14 (ZL) was genotyped using 1739 polymorphic SNP and 127 SSR markers in this study and was phenotyped for individual and total seed isoflavone in four environments over 2 years. In total, 48 additive QTLs, which explained 3.00–29.83% of seed isoflavone variation, were identified. Of them, eight QTLs (qDA1_1, qGA1_1, qTIA1_1, qDA1_2, qGA1_2, qTIA1_2, qDA1_3, qTIA1_3) with phenotypic variation explained (PVE) ranging from 14.09 to 28.59% for daidzin, genistin, and total isoflavone were located on the same region of linkage group (LG) A1. These QTLs were further verified in another RIL population derived from Zheng 92116 × Qihuang 30 (ZQ). Meanwhile, the other four overlapping QTLs on linkage group B1, which were associated with glycitin content (qGLB1_1, qGLB1_2, qGLB1_3, qGLB1_4) and explained 16.52 to 29.83% of phenotypic variation, were also verified using the ZQ population. Moreover, the individuals with different genotypes at the common flanking SNP markers for these QTLs on LGs A1 and B1 in the two mapping populations showed significant different isoflavone content, which further validate the QTL mapping results. And also, some candidate genes might participate in the isoflavone biosynthesis processes were found in these stable QTL regions. Thus, the novel and stable QTLs identified and verified in this study could be applied in marker-assisted selection breeding or map-based candidate genes cloning in soybean seed isoflavone genetic improvement in future.

Fine mapping the BjPl1 gene for purple leaf color in B2 of Brassica juncea L. through comparative mapping and whole-genome re-sequencing

Purple plants with higher anthocyanin content have attracted increasing attention in recent years due to their advantageous biological functions and nutritional value. A spontaneous mutant with purple leaves, designated 1280-1, was discovered in Brassica juncea line 1280. A previous genetic analysis indicated that the purple leaf trait in 1280-1 was controlled by a dominant gene (BjPl1). In the present study, an analysis of total anthocyanin content further indicated that the purple leaf trait was controlled by a complete dominance gene. According to a survey of 426 primers available from public resources, BjPl1 was assigned to linkage group B2 of B. juncea. In the early stage of this research, based on comparative mapping in Brassica, two simple sequence repeat (SSR) markers developed from A2 of B. rapa delimited the BjPl1 gene to a 0.7-cM genetic interval in the corresponding linkage map. According to information on the B. juncea genome released recently, the location of BjPl1 was further narrowed to a 225-kb interval (17.74–17.97 Mb). Within the target region, whole-genome re-sequencing identified two candidate regions (17.74–17.78 Mb and 17.93–17.96 Mb). Through Blast analysis of the two candidate intervals, four homologous anthocyanin biosynthetic genes were identified and localized to a 17.93–17.96 Mb interval of B2 (approximately 27 kb), which might include BjPl1. This work lays the foundation for the isolation of BjPl1 and will further improve our understanding of the molecular mechanisms of the anthocyanin metabolic pathway in Brassica.

Microsomal Omega-3 Fatty Acid Desaturase Genes in Low Linolenic Acid Soybean Line RG10 and Validation of Major Linolenic Acid QTL.

High levels of linolenic acid (80 g kg−1) are associated with the development of off-flavors and poor stability in soybean oil. The development of low linolenic acid lines such as RG10 (20 g kg−1 linolenic acid) can reduce these problems. The level of linolenic acid in seed oil is determined by the activities of microsomal omega-3 fatty acid desaturases (FAD3). A major linolenic acid QTL (>70% of variation) on linkage group B2 (chromosome Gm14) was previously detected in a recombinant inbred line population from the RG10 × OX948 cross. The objectives of this study were to validate the major linolenic acid QTL in an independent population and characterize all the soybean FAD3 genes. Four FAD3 genes were sequenced and localized in RG10 and OX948 and compared to the genes in the reference Williams 82 genome. The FAD3A gene sequences mapped to the locus Glyma.14g194300 [on the chromosome Gm14 (B2)], which is syntenic to the FAD3B gene (locus Glyma.02g227200) on the chromosome Gm02 (D1b). The location of the FAD3A gene is the same as was previously determined for the fan allele, that conditions low linolenic acid content and several linolenic acid QTL, including Linolen 3-3, mapped previously with the RG10 × OX948 population and confirmed in the PI 361088B × OX948 population as Linolen-PO (FAD3A). The FAD3B gene-based marker, developed previously, was mapped to the chromosome Gm02 (D1b) in a region containing a newly detected linolenic acid QTL [Linolen-RO(FAD3B)] in the RG10 × OX948 genetic map and corresponds well with the in silico position of the FAD3B gene sequences. FAD3C and FAD3D gene sequences, mapped to syntenic regions on chromosomes Gm18 (locus Glyma.18g062000) and Gm11 (locus Glyma.11g227200), respectively. Association of linolenic acid QTL with the desaturase genes FAD3A and FAD3B, their validation in an independent population, and development of FAD3 gene-specific markers should simplify and accelerate breeding for low linolenic acid soybean cultivars.

Identification of a New Allele at the Rsv3 Locus for Resistance to Soybean Mosaic Virus in PI 61944 Soybean Accession

ABSTRACTSoybean mosaic virus (SMV) is a prevalent pathogen in soybean [Glycine max, (L.) Merr.]. Several SMV resistance genes have been discovered, but most of them do not provide resistance to all strains of SMV. The objective of this research was to identify new genes or alleles displaying differential reactions to SMV strains in the SMV‐resistant soybean genotype, PI 61944. Cross combinations were made to develop F2 and F2:3 populations, followed by mapping analyses and greenhouse screenings using G1 and G7 virus strains. A resistant parent, PI 61944 (Rsv‐?), was crossed with a susceptible parent, Essex (rsv), and with differential parents, PI 96983 (Rsv1), L29 (Rsv3), V94‐5152 (Rsv4), and PI 507389 (Rsv1‐n), for allelism tests. Results indicated that resistance to SMV in PI 61944 was controlled by a single, dominant gene. This gene did not appear to be allelic to the Rsv1 locus as was previously reported. Allelism test revealed that the resistance allele in PI 61944 is located at the Rsv3 locus. A molecular marker analysis further revealed that the resistance allele in PI 61944 is located at linkage group B2 (chromosome 14). Additionally, PI 61944 exhibited unique SMV reaction patterns when compared with the reported Rsv3 allele in L29. Therefore, we propose that the new allele, Rsv3‐n, be assigned to the SMV resistance locus in PI 61944. The Rsv3 alleles are rare to find among the soybean germplasm, but can confer resistance to aggressive SMV strains; therefore, we expect PI 61944 to be useful in future breeding efforts.

Mapping of QTL Associated with Seed Amino Acids Content in “MD96-5722” by “Spencer” RIL Population of Soybean Using SNP Markers

Limited information is available on the genetic analysis of amino acid composition in soybean seeds. Previously, quantitative trait loci (QTLs) for seed isoflavones, protein, oil, and fatty acids were identified in the MD96-5722 by Spencer and other RIL populations. There were wide variations for these seed constituents among the RIL populations. Therefore, the objective of this study was to identify QTLs controlling different amino acids content in soybean seeds. To achieve this objective, ninety-two F5:7 recombinant inbred lines (RIL), developed from a cross of MD96- 5722 and Spencer, using a total 5376 Single Nucleotide Polymorphism (SNPs) markers, were used. The RILs were genotyped by using 537 polymorphic, reliably segregating SNP markers, developed from the Illumina Infinium SoySNP6K BeadChip array. A total of 13 QTLs were identified with three QTLs for threonine on the linkage group (LG) A1, C2, and B2. Two QTLs were identified for each of the amino acids proline on LG D1a and B2, serine on LG A1 and C2, tryptophan on LG K and G, and cysteine on LG A1 and K. One QTL was identified for arginine on LG N and histidine on LG J. The new QTLs findings for seed amino acid will facilitate the development of soybean cultivars with higher protein and amino acid quality to help meet the industry and consumer needs. * Corresponding author.

Quantitative Trait Loci for Seed Isoflavone Contents in ‘MD96-5722’ by ‘Spencer’ Recombinant Inbred Lines of Soybean

Isoflavones from soybeans [ Glycine max (L.) Merr.] have a significant impact on human health to reduce the risk of several major diseases. Breeding soybean for high isoflavone content in the seed is possible through marker-assisted selection (MAS) which can be based on quantitative trait loci (QTL). The objective of this study was to identify QTL controlling isoflavone content in a set of 'MD96-5722' by 'Spencer' recombinant inbred line (RIL) populations of soybean. Wide variations were found for seed concentrations of daidzein, glycitein, genistein, and total isoflavones among the RIL populations. Three QTL were identified on three different linkage groups (LG) represented by three different chromosomes (Chr). One QTL that controlled daidzein content was identified on LG A1 (Chr 5), and two QTL that underlay glycitein content were identified on LG K (Chr 9) and LG B2 (Chr 14). Identified QTL could be functional in developing soybean with preferable isoflavone concentrations in the seeds through MAS.

Identification of germplasm with stacked QTL underlying seed traits in an inbred soybean population from cultivars Essex and Forrest

Soybean (Glycine max (L.) Merr.) seed provides valuable oil (~200 g/kg) and protein (~400 g/kg) co-products. Seed composition variations result from several quantitative trait loci (QTL) that act through development. The objectives here were to identify loci underlying seed traits in the Essex × Forrest (EF94)-derived recombinant inbred line (RIL) population which has low frequencies of marker polymorphisms. Seed weight, protein, and oil were measured over 3 years: 2001, 2003, and 2005. Essex’s seeds were larger (141 mg/seed), higher in protein (406 g/kg), and lower in oil (190 g/kg) than Forrest’s (115 mg/seed, 395 g protein/kg, and 203 g oil/kg). Marker analysis included 413 markers for trait associations used for ANOVA, interval mapping, and composite interval mapping. Eleven QTL in nine genomic regions were associated (LOD >2; P < 0.0077) with seed traits. Two QTL, for mean protein and seed size, were clustered on linkage group (LG) E (chromosome Gm16). QTL for protein content alone were found on LG C2 (Gm6), LG D1b (Gm2), LG H (Gm12), and LG I (Gm20). The alleles from Essex, the high-protein parent, underlay higher protein (4–10 g/kg) at four of five loci. A QTL for mean oil was found on LG A2 (Gm18) and on LG I (Gm 20). The alleles from Forrest underlay higher oil (3–4 g/kg). Five separate QTL for mean seed weight were found on LG A1 (Gm05), LG N (Gm15), two on LG B1 (Gm11) and one on LG N (Gm3). The alleles from Essex underlay greater seed weight (0.4–0.66 g/100 seeds). The QTL positions were consistent with reported loci. Germplasm that contained all five beneficial alleles at the QTL underlying protein was significantly higher in protein and yield than Essex (409.7–412.3 g/kg) and included RILs 49 and 62. The germplasm identified can be useful for further breeding of the many traits and QTL measured in each line.

Identification of Quantitative Trait Loci Associated with Fructose, Glucose, and Sucrose Concentration in Snap Bean Pods

ABSTRACTSugars, including fructose, glucose, and sucrose, contribute significantly to the flavor and consumer acceptance of snap beans (Phaseolus vulgaris L.). Differences between dry and snap bean cultivars and among snap bean cultivars in the patterns of accumulation of sugars have been observed. In ‘Eagle’, a white‐seeded, large‐sieve snap bean cultivar, fructose and glucose concentrations in developing pods decreased while sucrose concentration increased with increasing pod size. In contrast, fructose and glucose concentrations increased while sucrose remained unchanged with increasing pod size in Puebla 152, a black‐seeded dry bean landrace from Mexico. A population derived from the cross Eagle × Puebla 152 consisting of 75 F9:10 recombinant inbred lines (RILs) was developed by single seed descent. Significant differences in fructose, glucose, and sucrose concentrations of sieve size 4 (8.33–9.52 mm) pods were observed among RILs. No significant genotype × year interactions were observed. Heritability estimates for fructose, glucose, and sucrose were 0.85 ± 0.16, 0.81 ± 0.16, and 0.85 ± 0.16, respectively. A single quantitative trait locus (QTL) on linkage group B1 was identified that is closely linked to random amplified polymorphic DNA (RAPD) marker W9.1050 and explains 28.8 and 26.6% of the variation in pod fructose and sucrose concentration, respectively. A two‐QTL model, including W9.1050 and RAPD marker F8.500 on linkage group B6, explained 36.4% of the variation in glucose concentration in pods.

Genomic Location of a Gene Conditioning a Miniature Phenotype in Soybean [Glycine max (L.) Merr.

The potential for global warming and climate change has increased the focus of research on plant genes that respond to high temperatures. Previous research identified a temperature-sensitive miniature soybean mutant that was controlled by a single gene. The objectives of our research were to confirm the single-gene control and to determine the genomic location of this gene. Segregation of the combined progeny of four BC6F5 plants heterozygous for the miniature trait in a Tracy-M background confirmed that the trait was conditioned by a single gene (1:2:1, χ 2 = 4.38, P = 0.1120). Molecular marker analysis identified three SSR markers and a SNP marker on molecular linkage group B2 (chromosome 14) associated with segregation for the miniature trait. One of these, marker Satt560, co-segregated perfectly with the miniature trait. The data from these four polymorphic markers indicated that the gene conditioning this miniature phenotype is at or near Satt560. Given this newly identified location of the gene and the recently published soybean genomic sequence, it may be feasible to isolate the gene and determine its mechanism of action in responding to temperature. Such knowledge may be of use in understanding how plants respond to increased temperature.

Nonsense Mutation of an MYB Transcription Factor Is Associated with Purple-Blue Flower Color in Soybean

Previous studies revealed that the recessive allele of the W2 locus generated purple-blue color and high vacuolar pH of flower petals in soybean. The location of W2 gene was reportedly close to simple sequence repeat marker Satt318 in molecular linkage group B2. We used information from the soybean genome to clone a candidate gene for W2. An MYB transcription factor gene belonging to G20 group was found in the vicinity of Satt318. Full-length cDNAs were cloned from purple-flowered cultivar Harosoy (W2 allele) and purple-blue flowered cultivars, Nezumisaya and w2-20 (w2 allele), by reverse transcription-PCR and designated as GmMYB-G20-1. Its open reading frame was 1083 bp long that encoded 361 amino acids in Harosoy. GmMYB-G20-1 had 53.7% similarity in amino acid sequence with the PH4 gene of petunia controlling blueness and vacuolar pH of flower petals. GmMYB-G20-1 of Nezumisaya and w2-20 had 3 base substitutions compared with that of Harosoy. The first substitution generated a stop codon in the MYB domain, resulting in truncated polypeptides. Cleaved amplified polymorphic sequence (CAPS) marker was developed to detect the base substitution. The polymorphic CAPS marker co-segregated with alleles at the W2 locus in the F(2) population. These results suggest that GmMYB-G20-1 might correspond to the W2 gene.

The Rsv3 Locus Conferring Resistance to Soybean Mosaic Virus is Associated with a Cluster of Coiled‐Coil Nucleotide‐Binding Leucine‐Rich Repeat Genes

The Soybean mosaic virus (SMV) resistance locus, Rsv3, previously mapped between markers A519F/R and M3Satt in the soybean molecular linkage group B2 (chromosome 14), has been characterized by examination of the soybean genome sequence. The 154 kbp interval encompassing Rsv3 contains a family of closely related coiled‐coil nucleotide‐binding leucine‐rich repeat (CC‐NB‐LRR) genes. Tightly linked to this region are additional CC‐NB‐LRR genes and several leucine‐rich repeat receptor‐like kinase (LRR‐RLK) genes, thereby indicating that members of both multigene families constitute a heterogeneous cluster at the Rsv3 chromosomal region. To further confirm the sequence and genetic map concordance, we developed 16 markers from the genomic sequence including predicted CC‐NB‐LRR genes and their flanking sequences. Mapping of the resultant markers in three populations showed parallel alignment between the genetic and sequence maps in the Rsv3‐containing region. Phylogenetic analysis of five CC‐NB‐LRR genes including a pseudogene showed they were highly similar to each other and formed a subclade within a CC‐NB‐LRR gene clade with representatives from several plant families including legume species. These results demonstrate that the Rsv3 locus is associated with this cluster of CC‐NB‐LRR genes, thereby suggesting that the Rsv3 gene most likely encodes a member of this gene family. In addition, information from this study should facilitate marker‐assisted selection and pyramiding of resistance genes.

Variation in Reaction to Fusarium spp. Identified in a Common Bean (Phaseolus vulgaris L.) Population Developed for Field‐Based Resistance to Root Rot and Wilt

Fusarium oxysporum f. sp. phaseoli (FOP) and Fusarium solani f. sp. phaseoli (FSP) cause wilt and root rot symptoms in beans (Phaseolus vulgaris L.) and frequently cause a reduction in pod yield. The objectives of this study were to determine the degree of phenotypic variation for reaction to FOP and FSP present in an ‘Eagle’ × Puebla 152 (EP) recombinant inbred line (RIL) population and to determine if previously identified quantitative trait loci (QTLs) associated with resistance to Aphanomyces euteiches were consistent with those associated with resistance to FOP and FSP. Transgressive segregation was observed among the EP RILs for reaction to FOP. The narrow sense heritabilities for resistance to FOP based on foliar and root symptoms were 0.25 ± 0.07 and 0.29 ± 0.07, respectively. Similarly, the narrow sense heritability for resistance to FSP was 0.23 ± 0.12. Random amplified polymorphic DNA (RAPD) markers W13.350 on linkage group B6 and AG13.600 on linkage group B8 were associated with QTLs for root and foliar response to FOP; an additional RAPD marker, U12.500 on linkage group B2, was associated with foliar response to FOP. Selection for QTLs associated with resistance to FOP should result in bean lines with reduced severity to both foliar and root symptoms caused by FOP. Two QTLs, AM2.400 and U20.1150 on linkage groups B3 and B8, respectively, were identified as associated with resistance to FSP. The QTLs associated with FOP, FSP, and A. euteiches are independent, indicating that it may be possible to use RAPD markers to pyramid resistance to all three soil borne pathogens.

Multiplex single nucleotide polymorphism (SNP) assay for detection of soybean mosaic virus resistance genes in soybean

Soybean mosaic virus (SMV) is one of the most destructive viral diseases in soybean (Glycine max). Three independent loci for SMV resistance have been identified in soybean germplasm. The use of genetic resistance is the most effective method of controlling this disease. Marker assisted selection (MAS) has become very important and useful in the effort of selecting genes for SMV resistance. Single nucleotide polymorphism (SNP), because of its abundance and high-throughput potential, is a powerful tool in genome mapping, association studies, diversity analysis, and tagging of important genes in plant genomics. In this study, a 10 SNPs plus one insert/deletion (InDel) multiplex assay was developed for SMV resistance: two SNPs were developed from the candidate gene 3gG2 at Rsv1 locus, two SNPs selected from the clone N11PF linked to Rsv1, one 'BARC' SNP screened from soybean chromosome 13 [linkage group (LG) F] near Rsv1, two 'BARC' SNPs from probe A519 linked to Rsv3, one 'BARC' SNP from chromosome 14 (LG B2) near Rsv3, and two 'BARC' SNPs from chromosome 2 (LG D1b) near Rsv4, plus one InDel marker from expressed sequence tag (EST) AW307114 linked to Rsv4. This 11 SNP/InDel multiplex assay showed polymorphism among 47 diverse soybean germplasm, indicating this assay can be used to investigate the mode of inheritance in a SMV resistant soybean line carrying Rsv1, Rsv3, and/or Rsv4 through a segregating population with phenotypic data, and to select a specific gene or pyramid two or three genes for SMV resistance through MAS in soybean breeding program. The presence of two SMV resistance genes (Rsv1 and Rsv3) in J05 soybean was confirmed by the SNP assay.

QTL Mapping of Isoflavone, Oil and Protein Contents in Soybean ( Glycine max L. Merr.)

Soybean ( Glycine max L. Merr.) is the world's foremost source of edible plant oil and proteins, meantime, the biologically active secondary metabolites such as saponins and isoflavones are benefit to human health. The objective of this study was to identify quantitative trait loci (QTL) and epistatic interactions associated with isoflavone, protein, and oil contents in soybean seeds. An F 13 recombinant inbred line (RIL) comprising 474 lines was derived from a cross between Jindou 23 and Huibuzhi cultivars. SSR technique was employed for mapping of the QTLs. The QTLs for isoflavone, protein, and oil contents were analyzed and 23 QTLs were detected based on the constructed linkage map. Six QTLs for isoflavone content were localized in linkage groups J, N, D2, and G, eleven QTLs for oil content were localized in the linkage groups A1, A2, B2, C2, and D2, and six QTLs for protein content were localized in linkage groups B2, C2, G, and H1. The correlative analysis demonstrated that the isoflavone content had significant correlation with protein content, while significantly negative correlations was existed between oil and protein content, and significantly positive correlations was existed between protein and oil content. All these findings have laid an important basis for the marker assisted breeding in soybean. The phenotypic correlations of quantitative traits may be resulted from the correlation of the QTL controlling those traits.

Discovery and transmission of functional QTL in the pedigree of an elite soybean cultivar Suinong14

With 3 figures and 5 tables AbstractIn this study, we extended in silico mapping for single trait to analyse data from multiple environments by calculating intraclass correlations and to mapping pleiotropic QTL for multiple traits by defining new statistic to measure the correlation between multiple traits and the marker. Data sets include phenotypes of eight agronomic traits obtained from six different ecologic environments and years, and genotypic information from 477 polymorphic markers on 14 ancestral lines in the pedigree of ‘Suinong14’. With in silico mapping, a total of 39 markers distributed on 14 linkage groups are detected as QTL responsible for eight agronomic traits and 10 QTL are identified as having pleiotropic effects. Tracing transmission of functional QTL in the pedigree indicated that certain QTL, such as Sat_036 on linkage group D1a, Satt182 on linkage group L, and Satt726 on linkage group B2 may be responsible for the contribution of exotic germplasm to the improved cultivars.

Identification of QTL in soybean underlying resistance to herbivory by Japanese beetles (Popillia japonica, Newman)

Soybean [Glycine max (L.) Merr.] was one of the most important legume crops in the world in 2010. Japanese beetles (JB; Popillia japonica, Newman) in the US were an introduced and potentially damaging insect pest for soybean. JBs are likely to spread across the US if global warming occurs. Resistance to JB in soybean was previously reported only in plant introductions. The aims here were to identify loci underlying resistance to JB herbivory in recombinant inbred lines (RILs) derived from the cross of Essex x Forrest cultivars (EF94) and to correlate those with loci with factors that confer insect resistance in soybean cultivars. The RIL population was used to map 413 markers, 238 satellite markers and 177 other DNA markers. Field data were from two environments over 2 years. Pest severity (PS) measured defoliation on a 0-9 scale. Pest incidence (PI) was the percentage of plants within each RIL with beetles on them. Antibiosis and antixenosis data were from feeding assays with detached leaves in petri plates. Five QTL were detected for the mean PS field trait (16% < R (2) < 27%). The loci were within the intervals Satt632-A2D8 on linkage group (LG) A2 (chromosome 8); Satt583-Satt415 on LG B1 (11); Satt009-Satt530 on LG N (3); and close to two markers OB02_140 (LG E; 20 cM from Satt572) and OZ15_150 LG (19 cM from Satt291 C2). Two QTL were detected for the mean PI field trait (16% < R (2) < 18%) close to Satt385 on LG A1 and Satt440 on LG I. The no choice feeding studies detected three QTL that were significant; two for antixenosis (22% < R (2) < 24%) between Satt632-A2D8 on LG A2 (8) and Sat_039-Satt160 on LG F (13); and a major locus effect (R (2) = 54%) for antibiosis on LG D2 (17) between Satt464-Satt488. Therefore, loci underlying resistance to JB herbivory were a mixture of major and minor gene effects. Some loci were within regions underlying resistance to soybean cyst nematode (LGs A2 and I) and root knot nematode (LG F) but not other major loci underlying resistance to nematode or insect pests (LGs G, H and M).

Genetic Analysis of Genes Controlling Natural Variation of Seed Coat and Flower Colors in Soybean

Soybean exhibits natural variation in flower and seed coat colors via the deposition of various anthocyanin pigments in the respective tissues. Although pigmentation in seeds or flowers has been well dissected at molecular level in several plant species, the genes controlling natural variation in anthocyanin traits in the soybean are not completely understood. To evaluate the genetic correlation between genetic loci and genes, 8 enzyme-encoding gene families and a transcription factor were localized in a soybean genome-wide genetic map. Among the seed coat color-controlling loci, the genetic location of the gene encoding for W1 was substantiated in the context of the current soybean molecular genetic map and O was postulated to correspond to anthocyanidin reductase. Among the genetic loci that regulate flower pigmentation, the genetic locations of the genes encoding for W1, W4, and Wp were identified, W3 was mapped on soybean linkage group B2 (chromosome 14), and W2 was postulated to correspond to an MYB transcription factor. Correlation studies between the developed markers and 3 color-controlling loci provided important empirical data that should prove useful in the design of marker-assisted breeding schemes as well as future association studies involving soybean.

Genetic Mapping of Resistance to Phomopsis Seed Decay in the Soybean Breeding Line MO/PSD-0259 (PI562694) and Plant Introduction 80837

Resistance to Phomopsis seed decay (PSD) in soybean (Glycine max [L.] Merr.) could provide dependable control of this important disease that affects seed quality. Studies have shown that single dominant genes that are allelomorphically different confer low levels of PSD in MO/PSD-0259 and PI 80837. The objectives of this research were to identify simple sequence repeat (SSR) markers linked to genes for PSD resistance in PI 80837 and MO/PSD-0259 and to associate the resistance genes to known linkage groups. Crosses were made between the PSD-susceptible cultivar Agripro 350 and each of the resistant lines MO/PSD-0259 and PI 80837. F(2) populations from each cross were grown and inoculated in the field. Individual plant reactions were characterized by determining the levels of seed infection, and DNA of F(2) plants was extracted for SSR analysis and mapping. F(2) segregation data showed that different single dominant genes condition PSD resistance in MO/PSD-0259 and PI 80837. Resistance in PI 80837 was linked to Sat_177 (4.3 cM) and Sat_342 (15.8 cM) on molecular linkage group (MLG) B2. In MO/PSD-0259, resistance was linked to Sat_317 (5.9 cM) and Sat_120 (12.7 cM) on MLG F. These data support work by Berger and Minor (Berger RD, Minor HC. 1999. An restriction fragment length polymorphism (RFLP) marker associated with resistance to Phomopsis seed decay in soybean PI 417479. Crop Sci 39:800-805.) in which PSD resistance in PI 417479, the resistant parent used to develop MO/PSD-0259, was associated with RFLP marker A708 on MLG F. These SSR markers should be useful in selection for resistant genotypes in breeding programs.

Genetic dissection of the resistance to nine anthracnose races in the common bean differential cultivars MDRK and TU

Resistance to nine races of the pathogenic fungus Colletotrichum lindemuthianum, causal agent of anthracnose, was evaluated in F(3) families derived from the cross between the anthracnose differential bean cultivars TU (resistant to races, 3, 6, 7, 31, 38, 39, 102, and 449) and MDRK (resistant to races, 449, and 1545). Molecular marker analyses were carried out in the F(2) individuals in order to map and characterize the anthracnose resistance genes or gene clusters present in these two differential cultivars. The results of the combined segregation indicate that at least three independent loci conferring resistance to anthracnose are present in TU. One of them, corresponding to the previously described anthracnose resistance locus Co-5, is located in linkage group B7, and is formed by a cluster of different genes conferring specific resistance to races, 3, 6, 7, 31, 38, 39, 102, and 449. Evidence of intra-cluster recombination between these specific resistance genes was found. The second locus present in TU confers specific resistance to races 31 and 102, and the third locus confers specific resistance to race 102, the location of these two loci remains unknown. The resistance to race 1545 present in MDRK is due to two independent dominant genes. The results of the combined segregation of two F(4) families showing monogenic segregation for resistance to race 1545 indicates that one of these two genes is linked to marker OF10(530), located in linkage group B1, and corresponds to the previously described anthracnose resistance locus Co-1. The second gene conferring resistance to race 1545 in MDRK is linked to marker Pv-ctt001, located in linkage group B4, and corresponds to the Co-3/Co-9 cluster. The resistance to race 449 present in MDRK is conferred by a single gene, located in linkage group B4, probably included in the same Co-3/Co-9 cluster.

Epistatic Effects and QE Interaction Effects of QTLs for Protein Content in Soybean

Soybean [Glycine max(L).Merr.],widely grown in United States,Brazil,Argentina,and China,is one of the plant protein source.Protein content in soybean is a quantitative trait controlled by multiple genes,and Currently,SoyBase(2007) documented at least 76 QTL associated with protein content that have been mapped in many different populations and environ-ments.The objective of the paper was to investigate epistatic effects and QE interaction effects of QTLs for protein content by mixed linear model.QTLs for soybean protein content were detected in a five-year experiment with the recombination inbred lines(RIL) population derived from a cross between Charleston and Dongnong 594.Ten QTLs with additive effects for protein content were mapped in the linkage groups B2,C2,D1a,E,and N,one of which was the positive effect contributed by Charleston,the others of which were the negative effects donated by Dongnong 94.Fifteen QTLs pairs with epistatic effects for protein con-tent in the RIL were detected,accounting for 13.57% of the general phenotypic variation.There existed interaction between 9 QTLs and environment,and the general contribution to protein content was 4.47%.