Soybean Linkage Group Research Articles

Identification of Low-Light-Resistant Germplasm and Related Loci of Soybean

Low-light stress will lead to abnormal soybean growth and a subsequent yield reduction. Association mapping is a useful alternative to linkage mapping for the detection of marker–phenotype associations. This study aimed to evaluate low-light-resistant soybean accessions and identify markers associated with low-light resistance. We assessed the plant height, stem diameter, number of bean pods, and cotyledon height of soybean plants under low and normal light conditions. These traits were evaluated in 185 soybean accessions, and the accessions 11HX-020, 11HX-025, 11HX-029, 11HX-064, 11HX-127, 11HX-166, 11HX-183, and 11HX-216 showed stable performance under low-light conditions. These 185 accessions were genotyped with 639 single-nucleotide polymorphism (SNP) markers and 98 simple sequence repeat (SSR) markers. A total of 75 markers—i.e., traits associated with low-light resistance—were identified. These associated markers were distributed on 14 linkage groups (LGs) of soybean, and some markers were associated with two or more traits. According to the results, excellent germplasm material and low-light-resistance related markers can be used for low-light resistance breeding of soybean and will help identify the low-light resistance genes.

Phenotypic and molecular diversity among soybean cultivars as a function of growing season

The identification of divergence among cultivars adapted to specific soil and climatic conditions is of fundamental importance for the realization of promising hybridizations. This diversity can be accessed through phenotypic characteristics and molecular markers. In this sense, the objective of this study was to evaluate genetic diversity of soybean cultivars in the summer and winter from agromorphological traits and molecular markers. Two experiments were conducted, one in the summer (2011) and another in the winter (2012). The experiments were conducted in a randomized block design with four replications. Six widely grown cultivars were used and they showed striking differences in regards to morphological markers. The cultivars are: M 7211 RR, TMG 123 RR, TMG 1176 RR, M 7908 RR, TMG 127 RR and TMG 7188 RR. During the development of the plant, as well after harvesting were evaluated 18 traits. The DNA of six cultivars was amplified with 16 primers (microsatellite markers) flanking microsatellite regions in soybean located in sixteen of the twenty soybean linkage groups. Genetic dissimilarity between cultivars from agromorphological traits varies depending on the growing season. The molecular markers showed genetic variability between cultivars with different results for clusters formed from the agronomic characters. Thus, both phenotypic and the molecular data proved to beinformative tools to characterize the existing conflict between soybean cultivars.

Genetic Analysis of Relative Water Content (RWC) in Two Recombinant Inbred Line Populations of Soybean [Glycine max (L.) Merr.

Drought affects soybean [Glycine max (L.) Merr.] and other crops productivity in the US and other parts of the world. Relative water content (RWC) is an important indicator for plant water deficit tolerance (WDT). The objective of this study is to map quantitative trait loci (QTL) for RWC and several other leaf traits such as leaf dry weight (LDW), leaf fresh weight (LFW), and leaf turgid weight (LTW) in two soybean recombinant inbred line (RIL) populations, one derived from a cross of ‘Essex’ and ‘Forrest’ (ExF, n=94) and the other is derived from a cross of ‘PI 438489B’ and ‘Hamilton’ (PIxH, n=50). In the PIxH RIL population, eight QTL were identified and mapped on 6 different linkage groups (LGs) of the soybean genome. No QTL for LFW were identified in this population. In the ExF RIL population, 10 QTL were identified and mapped on 5 different LGs of soybean. Chromosome 18 (LG G) contains clusters of QTL for LFW, LTW, and RWC in the ExF RIL population. This same chromosome contains a QTL for RWC in the PIxH RIL population. The QTL found here are important to be included in breeding programs for soybean water deficit tolerance (WDT).

Pyramids of QTLs enhance host-plant resistance and Bt-mediated resistance to leaf-chewing insects in soybean.

Key messageQTL-M and QTL-E enhance soybean resistance to insects. Pyramiding these QTLs withcry1Ac increases protection against Bt-tolerant pests, presenting an opportunity to effectively deploy Bt with host–plant resistance genes.Plant resistance to leaf-chewing insects minimizes the need for insecticide applications, reducing crop production costs and pesticide concerns. In soybean [Glycine max (L.) Merr.], resistance to a broad range of leaf-chewing insects is found in PI 229358 and PI 227687. PI 229358’s resistance is conferred by three quantitative trait loci (QTLs): M, G, and H. PI 227687’s resistance is conferred by QTL-E. The letters indicate the soybean Linkage groups (LGs) on which the QTLs are located. This study aimed to determine if pyramiding PI 229358 and PI 227687 QTLs would enhance soybean resistance to leaf-chewing insects, and if pyramiding these QTLs with Bt (cry1Ac) enhances resistance against Bt-tolerant pests. The near-isogenic lines (NILs): BenningME, BenningMGHE, and BenningME+cry1Ac were developed. BenningME and BenningMGHE were evaluated in detached-leaf and greenhouse assays with soybean looper [SBL, Chrysodeixis includens (Walker)], corn earworm [CEW, Helicoverpa zea (Boddie)], fall armyworm [FAW, Spodoptera frugiperda (J.E. Smith)], and velvetbean caterpillar [VBC, Anticarsia gemmatalis (Hübner)]; and in field-cage assays with SBL. BenningME+cry1Ac was tested in detached-leaf assays against SBL, VBC, and Southern armyworm [SAW, Spodoptera eridania (Cramer)]. In the detached-leaf assay, BenningME showed the strongest antibiosis against CEW, FAW, and VBC. In field-cage conditions, BenningME and BenningMGHE suffered 61 % less defoliation than Benning. BenningME+cry1Ac was more resistant than BenningME and Benningcry1Ac against SBL and SAW. Agriculturally relevant levels of resistance in soybean can be achieved with just two loci, QTL-M and QTL-E. ME+cry1Ac could present an opportunity to protect the durability of Bt genes in elite soybean cultivars. These results should assist the development of effective pest management strategies, and sustainable deployment of Bt genes in soybean.

Identification and mapping of resistance genes to Phakopsora pachyrhizi in soybean (Glycine max L.) accession PI 594767-A

The goal of this study was to study resistance inheritance in the soybean (Glycine max L.) accession PI 594767-A to the Phakopsora pachyrhizi isolate PPUFV02, and map the resistance gene(s) identified using microsatellite markers. Crosses between PI 594767-A and the susceptible cultivar 'Conquista' gave rise to the segregating subpopulations 26C-2 and 26C-5, which in the F2 generation were evaluated for their reactions to PPUFV02. In addition, analyses with microsatellite markers linked to the Rpp1-Rpp5 loci were also performed. The segregation pattern obtained in 26C-2 revealed that resistance was governed by a recessive gene; a 1:2:1 segregation pattern was observed in 26C-5, indicating control by a gene with partial dominance. This variability may have been caused because environmental conditions, particularly temperature, when 26C-5 was assessed were unfavorable for pathogen development, allowing the phenotypic expression of heterozygous alleles in PI 594767-A. A resistance gene was located in the soybean linkage group G, in the genomic region between Sct_187r2 and Sat_064 that contains the Rpp1 locus. Resistance in PI 594767-A is probably conferred by a new Rpp1 gene allele, because this accession has a haplotype for Sct_187r2 and Sat_064, which differs from haplotypes of accessions that also contain resistance alleles that map the Rpp1 locus. The use of Sct_187r2 and Sat_064 will facilitate the introgression of the resistance allele from PI 594767-A and its pyramiding with other resistance genes into genotypes with superior agronomic characteristics, in order to obtain cultivars with broad-spectrum resistance to P. pachyrhizi.

Analysis of QTLs for the micromorphology on the seed coat surface of soybean using recombinant inbred lines

AbstractThe seed coat of soybean (Glycine max (L.) Merrill) must protect the seed but allow water intake. Overprotection, causing impermeability, is assumed to be due to the presence of an impermeable layer in the seed coat, although validation of this assumption has relied on imbibition testing, which tends to be influenced by microfractures in the seed coat. Recent micromorphological analyses using laser-assisted topography microscopy revealed links to the surface roughness (SR) of the seed coat. To verify genetic links between hardseededness and SR, we analysed quantitative trait loci (QTLs) governing SR formation using 148 recombinant inbred lines (RILs) with a genetic linkage map covering 2663.6 cM of all 20 linkage groups of soybean, with 355 DNA markers and 5 phenotype markers. Five QTLs were detected, including previously identified hardseededness QTLs for ratio of seeds absorbing water, namely RAS1 and RAS2, which accounted for 20% of the phenotypic variance, and one near a locus inhibiting seed coat colour (I). These results indicate that the impermeability of soybean seed is genetically related to the reduction of SR.

Genetic Analysis of Relative Water Content (RWC) in Two Recombinant Inbred Line Populations of Soybean [Glycine max (L.) Merr.

Drought affects soybean [Glycine max (L.) Merr.] and other crops productivity in the US and other parts of the world. Relative water content (RWC) is an important indicator for plant water deficit tolerance (WDT). The objective of this study is to map quantitative trait loci (QTL) for RWC and several other leaf traits such as leaf dry weight (LDW), leaf fresh weight (LFW), and leaf turgid weight (LTW) in two soybean recombinant inbred line (RIL) populations, one derived from a cross of ‘Essex’ and ‘Forrest’ (ExF, n=94) and the other is derived from a cross of ‘PI 438489B’ and ‘Hamilton’ (PIxH, n=50). In the PIxH RIL population, eight QTL were identified and mapped on 6 different linkage groups (LGs) of the soybean genome. No QTL for LFW were identified in this population. In the ExF RIL population, 10 QTL were identified and mapped on 5 different LGs of soybean. Chromosome 18 (LG G) contains clusters of QTL for LFW, LTW, and RWC in the ExF RIL population. This same chromosome contains a QTL for RWC in the PIxH RIL population. The QTL found here are important to be included in breeding programs for soybean water deficit tolerance (WDT).

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.

QTL underlying the resistance to soybean aphid (Aphis glycines Matsumura) through isoflavone-mediated antibiosis in soybean cultivar ‘Zhongdou 27’

Soybean aphid (Aphis glycines Matsumura) results in severe yield loss of soybean in many soybean-growing countries of the world. A few loci have been previously identified to be associated with the aphid resistance in soybean. However, none of them was via isoflavone-mediated antibiosis process. The aim of the present study was to conduct genetic analysis of aphid resistance and to identify quantitative trait loci (QTL) underlying aphid resistance in a Chinese soybean cultivar with high isoflavone content. One hundred and thirty F(5:6) derived recombinant inbred lines from the 'Zhongdou 27'×'Jiunong 20' cross were used. Two QTL were directly associated with resistance to aphid as measured by aphid damage index. qRa_1, close to Satt470 on soybean linkage group (LG) A2 (chromosome 8), was consistently detected for 3- and 4-week ratings and explained a large portion of phenotypic variations ranging from 25 to 35%. qRa_2, close to Satt144 of LG F (chromosome 13), was detected for 3- and 4-week ratings and could explain 7 and 11% of the phenotypic variation, respectively. These two QTL were highly associated with high isoflavone content and both positive alleles were derived from 'Zhongdou 27', a cultivar with higher isoflavone content. The results revealed that higher individual or total isoflavones contents in soybean lines could protect soybean against aphid attack. These two QTL detected jointly provide potential for marker-assisted selection to improve the resistance of soybean cultivars to aphid along with the increase of isoflavone content.

Selection of a core set of RILs from Forrest x Williams 82 to develop a framework map in soybean.

Soybean BAC-based physical maps provide a useful platform for gene and QTL map-based cloning, EST mapping, marker development, genome sequencing, and comparative genomic research. Soybean physical maps for “Forrest” and “Williams 82” representing the southern and northern US soybean germplasm base, respectively, have been constructed with different fingerprinting methods. These physical maps are complementary for coverage of gaps on the 20 soybean linkage groups. More than 5,000 genetic markers have been anchored onto the Williams 82 physical map, but only a limited number of markers have been anchored to the Forrest physical map. A mapping population of Forrest × Williams 82 made up of 1,025 F8 recombinant inbred lines (RILs) was used to construct a reference genetic map. A framework map with almost 1,000 genetic markers was constructed using a core set of these RILs. The core set of the population was evaluated with the theoretical population using equality, symmetry and representativeness tests. A high-resolution genetic map will allow integration and utilization of the physical maps to target QTL regions of interest, and to place a larger number of markers into a map in a more efficient way using a core set of RILs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-010-1522-3) contains supplementary material, which is available to authorized users.

Preliminary Mapping of Soybean Dominant Locus <em>Hrcs7</em> Conferring Resistance to <em>Cerocospara sojina</em> Race 7

Molecular marker-assisted selection can significantly improved resistance breeding efficiency. The soybean frogeye leaf spot (FLS) is caused by the fungus Cercospora sojina Hara. In order to find the resistant markers linked to C. sojina race 7 in soybean, we carried out the resistant genetic ananlysis and the resistant locus mapping. The F 2 population derived from the cross of 'Gang 95144-1' and 'Gongjiao 9723-6' was employed to analyze the resistance genetics. it was sure that the resistance conferring to FLS was controlled by one major dominant gene.. Bulk Segregant Analysis (BSA) and Simple Sequence Repeat (SSR) method were used to map the resistant locus. Among the 600 selected SSR primers, there were four primer pairs exhibiting the polymorphisms between DNA bulk of resistant and susceptible as well as both parents. Segregation distribution of the SSR markers, satt 414 and satt384, were conformed significantly to be as 1:2:1.of Mendel Segregation. The marker, satt411 and satt384 were assigned to link with the resistant locus based on estimation of MAPMAKER/EXP 3.0 software. The linkage order and distance would be Satt384 -5.7cM - Satt411 -7.9cM - Hrcs7 . The resistant locus was integrated to soybean linkage group E based on the Cregen ' s genetic linkage map of soybean.Molecular marker-assisted selection can significantly improved resistance breeding efficiency. The soybean frogeye leaf spot (FLS) is caused by the fungus Cercospora sojina Hara. In order to find the resistant markers linked to C. sojina race 7 in soybean, we carried out the resistant genetic ananlysis and the resistant locus mapping. The F 2 population derived from the cross of 'Gang 95144-1' and 'Gongjiao 9723-6' was employed to analyze the resistance genetics. it was sure that the resistance conferring to FLS was controlled by one major dominant locus named Hrcs7 .. Bulk Segregant Analysis (BSA) and Simple Sequence Repeat (SSR) method were used to map the resistant locus. Among the 600 selected SSR primers, there were four primer pairs exhibiting the polymorphisms between DNA bulk of resistant and susceptible as well as both parents. Segregation distribution of the SSR markers, satt 414 and satt384, were conformed significantly to be as 1:2:1.of Mendel Segregation. The marker, satt411 and satt384, were assigned to link with the resistant locus based on estimation of MAPMAKER/EXP 3.0 software. The linkage order and distance would be Satt384 -5.7cM -Satt411 -7.9cM - Hrcs7 . The resistant locus was integrated to soybean linkage group E based on the Cregen ' s genetic linkage map of soybean.

Origin Analysis of Resistance Gene to Soybean Mosaic Virus in Soybean Line ICGR95-5117

Soybean mosaic virus (SMV) is a prevalent viral pathogen of soybean. The soybean mosaic virus N3 (SMV3) is the most toxic strain in northeast China. Soybean lines ICGR95-5117 and ICGR95-5383 with high resistance to SMV3,which were all derived from ICGR661,are recently released from Chinese Academy of Agricultural Sciences. Several genes resistant to soybean mosaic virus have been identified and mapped on different soybean linkage groups by molecular markers. The re-sistance gene in ICGR95-5383 has been mapped on soybean linkage group F near Rsv1 gene. A dominant marker developed from the candidate gene of Rsv1 has been reported recently. The purpose of this research was to find the origin of the SMV3 resistance gene in ICGR95-5117 and the relationship of this resistance gene with Rsv1 by analyzing the pedigree. Thirty four SSR markers selected from linkage group F and two markers,SCAR marker (SCN11) tightly linked with resistance gene in ICGR95-5383 and Rsv1-f/r makers co-segregated with resistance gene Rsv1,were used to detect the materials in pedigree of ICGR95-5117. The similarity coefficient of the two lines between ICGR95-5117,ICGR95-5383 and ICGR661 was the highest. All the material except for Mangnolid(F-53)B had SMV3 resistance allele at locus SCN11. Williams 82 and ICGR661 had the same allelic variation at Rsv1-f/r locus with ICGR95-5117,revealing that the Rsv1 gene in ICGR95-5117 was inherited from Williams 82 via ICGR661. But ICGR95-5117 had higher resistance than ICGR661,indicating it might inherit different genes from SMV3 resistance parent Ludou4.

Origin of Resistance Gene to Soybean Mosaic Virus in Soybean Line ICGR95-5117

Abstract Soybean ( Glycine max L. Merr.) lines ICGR95-5117 and ICGR95-5383, which were derived from ICGR661, carry genes for high resistance to Soybean mosaic virus strain N3 (SMV3). The resistance gene in ICGR95-5383 has been mapped in soybean linkage group F near Rsv1 gene. A dominant marker developed from the candidate gene of Rsv1 has been reported recently. The purposes of this study were to find the origin of the SMV3 resistance gene in ICGR95-5117 and to understand the relationship of this gene with Rsv1 based on pedigree analysis. A total of 34 simple sequence repeat (SSR) markers in linkage group F and 2 markers tightly linked to the resistance gene in ICGR95-5383 (SCN11 and Rsv1-f/r) were used to detect the cultivars or lines in the pedigree of ICGR95-5117. Both ICGR95-5117 and ICGR95-5383 had the highest similarity coefficients with its parent ICGR661 and were distant from the other parent Ludou 4. All the materials except for Mangnolid(F-53)B had SMV3 resistance allele at locus SCN11. Williams 82, ICGR661, and ICGR95-5117 showed the same allelic variation at Rsv1-f/r locus. The result of resistance identification showed that Ludou 4 (absent of Rsv1) was highly resistant to SMV3, and ICGR95-5117 had stronger resistance than ICGR661. These results indicated that ICGR95-5117 inherited the Rsv1 gene from Williams 82 via ICGR661, and Ludou 4 contributed different resistance gene to ICGR95-5117.

Identification of a major QTL allele from wild soybean (Glycine soja Sieb. & Zucc.) for increasing alkaline salt tolerance in soybean

Salt-affected soils are generally classified into two main categories, sodic (alkaline) and saline. Our previous studies showed that the wild soybean accession JWS156-1 (Glycine soja) from the Kinki area of Japan was tolerant to NaCl salt, and the quantitative trait locus (QTL) for NaCl salt tolerance was located on soybean linkage group N (chromosome 3). Further investigation revealed that the wild soybean accession JWS156-1 also had a higher tolerance to alkaline salt stress. In the present study, an F(6) recombinant inbred line mapping population (n = 112) and an F(2) population (n = 149) derived from crosses between a cultivated soybean cultivar Jackson and JWS156-1 were used to identify QTL for alkaline salt tolerance in soybean. Evaluation of soybean alkaline salt tolerance was carried out based on salt tolerance rating (STR) and leaf chlorophyll content (SPAD value) after treatment with 180 mM NaHCO(3) for about 3 weeks under greenhouse conditions. In both populations, a significant QTL for alkaline salt tolerance was detected on the molecular linkage group D2 (chromosome 17), which accounted for 50.2 and 13.0% of the total variation for STR in the F(6) and the F(2) populations, respectively. The wild soybean contributed to the tolerance allele in the progenies. Our results suggest that QTL for alkaline salt tolerance is different from the QTL for NaCl salt tolerance found previously in this wild soybean genotype. The DNA markers closely associated with the QTLs might be useful for marker-assisted selection to pyramid tolerance genes in soybean for both alkaline and saline stresses.

Genetic diversity in soybean germplasm identified by SSR and EST-SSR markers

The objectives of this work were to investigate the genetic variation in 79 soybean (Glycine max) accessions from different regions of the world, to cluster the accessions based on their similarity, and to test the correlation between the two types of markers used. Simple sequence repeat markers present in genomic (SSR) and in expressed regions (EST-SSR) were used. Thirty SSR primer-pairs were selected (20 genomic and 10 EST-SSR) based on their distribution on the 20 genetic linkage groups of soybean, on their trinucleotide repetition unit and on their polymorphism information content. All analyzed loci were polymorphic, and 259 alleles were found. The number of alleles per locus varied from 2-21, with an average of 8.63. The accessions exhibit a significant number of rare alleles, with genotypes 19, 35, 63 and 65 carrying the greater number of exclusive alleles. Accessions 75 and 79 were the most similar and accessions 31 and 35, and 40 and 78, were the most divergent ones. A low correlation between SSR and EST-SSR data was observed, thus genomic and expressed microsatellite markers are required for an appropriate analysis of genetic diversity in soybean. The genetic diversity observed was high and allowed the formation of five groups and several subgroups. A moderate relationship between genetic divergence and geographic origin of accessions was observed.

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 Composition of Elite Soybean Cultivar Hefeng 25

This study evaluated the genetic composition of elite soybean [ Glycine max (L.) Merr.] cultivar Hefeng 25, and the genetic relationship between Hefeng 25 and its parents Hefeng 23 and Ke 4430-20. A total of 463 simple sequence repeat (SSR) markers were analyzed on 20 soybean linkage groups, and 177 SSR markers were monomorphic and 57 SSR loci were mutated (novel alleles to the parents). The overall genetic contributions of Hefeng 23 and Ke 4430-20 to Hefeng 25 were 39.4% and 48.3%, respectively. On the 20 linkage groups of Hefeng 25, alleles of loci tested originated differently. All alleles on linkage group G and most alleles on linkage group E were inherited from Ke 4430-20 and most alleles on linkage group L were from Hefeng 23. The combination of alleles on linkage groups in Hefeng 25 is conjectured in relation to the quantitative trait loci (QTLs) for favorable traits, such as yield and disease resistance, and has been selected during breeding process. For evaluating the effect of mutated loci on genetic purity, 12 seed samples of Hefeng 25 obtained from different companies were evaluated using 207 SSR markers including the markers for the 57 mutated loci. Only 4 seed samples had hybrid alleles at 13 loci, indicating that most of the mutated loci were purified. The elite genotype and high seed purity are probably the major factors for the long-term utilization in production of Hefeng 25.

QTL Analysis of Yield, Yield Components, and Lodging in Soybean

To date,more than 80 QTLs for yield have been mapped on 18 linkage groups of soybean(Glycine max L.Merr.) using over 20 segregation populations.However,only QTLs that expressed stably in different populations and environments are of great value for soybean breeding.Except for QTLs associated with seed weight,there are few reports on QTLs for other yield-related traits.The objectives of this study were to detect yield-related QTLs in soybean and to compare linkage groups obtained from different mapping populations.A total of 165 recombinant inbred lines(RILs) derived from a cross between Zhongdou 29 and Zhongdou 32 were used to analyze the relationships of yield per plant,yield components,and lodging percentage as well as their genetic effects,and to map the QTLs in 2006-2007.Thirty-eight QTLs for yield,seed and pod traits,and lodging related traits were detected using composite interval mapping(CIM) method.Most of the QTLs were located on C2,F,and I linkage groups.QTL qLD-15-1 for lodging percentage on F linkage group was detected in both years,which explained more than 20% of the phenotypic variation.This QTL had the same or adjacent marker intervals to QTLs for 100-seed weight and pod number on branch,showing correlation between yield-related traits and lodging.On I linkage group,the QTLs for seeds per pod,two-seed pods,three-seed pods,and four-seed pods were detected on the same position across years and explained 32-65% of the phenotypic variation.The positive alleles at loci of seeds per pod,four-seed pods,two-seed-pods,and three-seed pods were from different parents.The four QTLs for seed and pod traits mapped on the same position,which was consistent with the correlation analysis result of phenotypic traits.This suggests that the regulatory mechanisms of the four traits for seed and pod are different.

Inheritance of Resistance to the Soybean Aphid in Soybean PI 200538

The soybean aphid (Aphis glycines Matsumura) is a major soybean [Glycine max (L.) Merr.] insect pest. Soybean plant introduction (PI) 200538 has strong resistance to the aphid. The objectives of our research were to determine the inheritance of resistance and to map gene(s) controlling resistance in PI 200538. F2 populations developed from crosses between PI 200538 and three susceptible genotypes were tested for resistance and with DNA markers. F2 plants from the cross ‘Ina’ × PI 200538 segregated 114 resistant to 37 susceptible and F2 plants from the cross ‘Williams 82’ × PI 200538 segregated 203 resistant to 65 susceptible when tested for resistance to soybean aphid biotype 1. F2 plants from the cross LD02‐4485 × PI 200538 segregated 167 resistant to 62 susceptible when tested for resistance to biotype 2. These populations fit a 3:1 genetic ratio (P = 0.89, 0.78, and 0.52, respectively) with resistance dominant over susceptibility. Segregation among F2:3 families from the crosses supported the dominant resistance gene hypothesis. The gene mapped to soybean linkage group F, flanked by the simple sequence repeat marker loci Satt510, Soyhsp176, Satt114, and Sct_033, located in the same region as the aphid resistance gene Rag2 Since the resistance gene in PI 200538 also gave resistance to soybean aphid biotypes 1 and 2, it is possible that the gene is Rag2 and not a new aphid resistance gene. Therefore, PI 200538 may be an additional source of Rag2

Constructing Molecular Identity for Soybean Varieties from Heilongjiang Province, China

To distinguish major soybean [ Glycine max (L.) Merr.] varieties in Heilongjiang Province, China, a total of 83 varieties from 6 accumulative-temperature zones in the province were used to construct their molecular identity (ID). One hundred and fifty-seven polymorphic alleles were detected with 43 SSR primers that covered 19 linkage groups of soybean with 2 to 7 alleles (averagely 3.65 alleles) per locus. All fragments at each locus detected with polyacrylamide gel electrophoresis (PAGE) were digitized to fit the requirement of the software ID Analysis 1.0 that was developed by the authors. The 83 varieties were differentiated with 9 primers, i.e., Satt100, Sat_218, Satt514, Satt551, Satt380, Satt193, Satt191, Satt442, and Sat_084. Therefore, the PAGE pattern of each variety amplified with the 9 primers could be used as a molecular ID of these varieties.