Linkage Group D1b Research Articles

Recessive Resistance Governed by a Major Quantitative Trait Locus Restricts Clover Yellow Vein Virus in Mechanically but Not Graft-Inoculated Cultivated Soybeans.

Clover yellow vein virus (ClYVV) infects and causes disease in legume plants. However, here, we found that ClYVV isolate No. 30 (ClYVV-No.30) inefficiently multiplied or spread via cell-to-cell movement in mechanically inoculated leaves of a dozen soybean (Glycine max) cultivars and resulted in failure to spread systemically. Soybean plants also had a similar resistance phenotype against additional ClYVV isolates. In contrast, all but one of 24 tested accessions of wild soybeans (G. soja) were susceptible to ClYVV-No.30. Graft inoculation of cultivated soybean TK780 with ClYVV-No.30-infected wild soybean B01167 scion resulted in systemic infection of the cultivated soybean rootstock. This suggests that, upon mechanical inoculation, the cultivated soybean inhibits ClYVV-No.30, at infection steps prior to the systemic spread of the virus, via vascular systems. Systemic infection of all F1 plants from crossing between TK780 and B01167 and of 68 of 76 F2 plants with ClYVV-No.30 indicated recessive inheritance of the resistance. Further genetic analysis using 64 recombinant inbred lines between TK780 and B01167 detected one major quantitative trait locus, designated d-cv, for the resistance that was positioned in the linkage group D1b (chromosome 2). The mapped region on soybean genome suggests that d-cv is not an allele of the known resistance genes against soybean mosaic virus.

Molecular mapping of three male-sterile, female-fertile mutants and generation of a comprehensive map of all known male sterility genes in soybean.

In soybean, an environmentally stable male sterility system is vital for making hybrid seed production commercially viable. Eleven male-sterile, female-fertile mutants (ms1, ms2, ms3, ms4, ms5, ms6, ms7, ms8, ms9, msMOS, and msp) have been identified in soybean. Of these, eight (ms2, ms3, ms5, ms7, ms8, ms9, msMOS, and msp) have been mapped to soybean chromosomes. The objectives of this study were to (i) locate the ms1, ms4, and ms6 genes to soybean chromosomes; (ii) generate genetic linkage maps of the regions containing these genes; and (iii) develop a comprehensive map of all known male-sterile, female-fertile genes in soybean. The bulked segregant analysis technique was used to locate genes to soybean chromosomes. Microsatellite markers from the corresponding chromosomes were used on F2 populations to generate genetic linkage maps. The ms1 and ms6 genes were located on chromosome 13 (molecular linkage group F) and ms4 was present on chromosome 2 (molecular linkage group D1b). Molecular analyses revealed markers Satt516, BARCSOYSSR_02_1539, and AW186493 were located closest to ms1, ms4, and ms6, respectively. The ms1 and ms6 genes, although present on the same chromosome, were independently assorting with a genetic distance of 73.7 cM. Using information from this study and compiled information from previously published male sterility genes in soybean, a comprehensive genetic linkage map was generated. Eleven male sterility genes were present on seven soybean chromosomes. Four genes were present in two regions on chromosome 2 (molecular linkage group D1b) and two genes were present on chromosome 13 (molecular linkage group F).

Mapping quantitative trait loci for yield-related traits in soybean (Glycine max L.).

Development of soybean cultivars with high seed yield is a major focus in soybean breeding programs. This study was conducted to identify genetic loci associated with seed yield-related traits in soybean and also to clarify consistency of the detected QTLs with QTLs found by previous researchers. A population of 135 F2:3 lines was developed from a cross between a vegetable soybean line (MJ0004-6) and a landrace cultivar from Myanmar (R18500). They were evaluated in the experimental field of Kasetsart University, Kamphaeng Saen, Nakhon Pathom, Thailand in a randomized complete block design with two replications each in 2011 and 2012 growing seasons. The two parents exhibited contrasting characteristics for most of the traits that were mapped. Analysis of variance showed that the main effects of genotype and environment (year) were significant for all studied traits. Genotype by environment interaction was also highly significant for all the traits. The population was genotyped by 149 polymorphic SSR markers and the genetic map consisted of 129 SSR loci which converged into 38 linkage groups covering 1156 cM of soybean genome. There were 10 QTLs significantly associated with seed yield-related traits across two seasons with single QTLs explaining between 5.0% to 21.9% of the phenotypic variation. Three of these QTLs were detected in both years for days to flowering, days to maturity and 100 seed weight. Most of the detected QTLs in our research were consistent with earlier QTLs reported by previous researchers. However, four novel QTLs including SF1, SF2 and SF3 on linkage groups L and N for seed filling period and PN1 on linkage group D1b for pod number were identified in the present study.

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 soybean mosaic virus resistance alleles in Jindou 1 soybean

Jindou 1 is a soybean cultivar from China, which is resistant to all seven Soybean mosaic virus (SMV) strains identified in the U.S. An F2 population consisted of 91 plants derived from the cross Jindou 1× Essex were used for genetic analysis of SMV resistance. The segregation analysis of the F2 population indicated that Jindou 1 contained a dominant gene for SMV G1 resistance. Co-segregating analyses showed that the gene was tightly linked to a SNP marker, 3gG2-snp2, which was derived from the SMV Rsv1 candidate gene 3gG2, with a genetic distance 1.1 cM and the gene was independent to the single nucleotide polymorphism (SNP) marker, Barc-040713-07825, which is linked to Rsv4 on chromosome 2 (linkage group D1b). The gene in Jindou 1 was assumed to be Rsv1-y based on an Rsv1-specific PCR-based marker 3gG2-f1/r1 and the SNP maker 3gG2-snp1. Beside Rsv1-y, Jindou 1 was postulated to have Rsv3 based on the reaction pattern to 7 SMV strains G1–G7 in comparisons with the patterns in SMV differential lines.

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.

Quantitative trait loci associated with soybean tolerance to low phosphorus stress based on flower and pod abscission

With 2 figures and 5 tables AbstractLow phosphorus (P) stress limits soybean production. A population of 152 recombinant inbred lines (RILs) derived from a cross between ‘Bogao’ (P sensitive variety) and ‘Nannong 94‐156’ (P tolerant variety) and 248 markers were used to map quantitative trait loci (QTLs) for low‐P tolerance. Two pot culture trials were conducted and low‐P tolerance evaluated using flower and pod abscission rate under low P and normal P. Conditional QTLs and epistasis for tolerance to low P were also analysed. A conditional QTL (near Satt274) on linkage group D1b+W was identified which conferred low‐P tolerance epistatic effects and coincided with previously discovered QTLs. An additive QTL, qFARLPG‐07, for flower abscission rate under low P was detected with a LOD score of 7.79 and explained 32.3% of phenotypic variation. It was detected at the same interval of the corresponding QTL for other traits across years. This region coincided with two conditional QTLs (cqFARLPG‐07 and cqPARLPG‐07), from the P‐tolerant parent ‘Nannong 94‐156’ related to low‐P tolerance. These results will provide a basis for further fine mapping and eventual cloning of the P‐efficiency genes in soybean.

Detection of quantitative trait loci for phosphorus deficiency tolerance at soybean seedling stage

Phosphorus deficiency is a primary constraint to soybean productivity in acid and calcareous soils. Our aim was to map quantitative trait loci (QTL) controlling phosphorus deficiency tolerance using 152 recombinant inbred lines derived from a cross between the P stress tolerant variety Nannong94-156 and the P stress sensitive variety Bogao. Five traits were used as parameters to evaluate phosphorus deficiency tolerance at seedling stage under different phosphorus levels in experiments 2005 and 2006. As a result, thirty-four additive QTLs were detected on nine linkage groups, with corresponding contribution ratios of 6.6–19.3%. There were three clusters of QTL found in genomic regions S506-Satt534 (on linkage group B2-1), Sat_183-Satt274 (on linkage group D1b + W), and Sat_185-Satt012 (on linkage group G). The locus flanked by Sat_183-Satt274 on linkage group D1b + W was coincident with four previously discovered QTLs with phosphorus efficiency. Another interesting locus flanked by Sat_185-Satt012 on linkage group G was detected across years. The identified QTL will be useful to improve the stress resistance of soybean against a complex nutritional disorder caused by phosphorus deficiency. In addition, more QTLs were detected under low phosphorus condition and some QTLs were detected that specifically expressed under different phosphorus levels. These particular QTLs could help provide greater understanding of the genetic basis of phosphorus efficiency in soybean.

콩에서 microsatellite marker를 이용한 불포화지방산 함량의 양적형질 유전자좌의 분석

Soybean oil is an important source of vegetable oil for human food and nonfood applications and accounts for approximately 22% of the world's total edible oil production. Improvement of the quality and quantity of soybean seed oil constituents is one of the most important objectives in soybean breeding. The objective of this study was to identify quantitative trait loci (QTLs) that control oleic, linoleic, and linolenic acid contents in soybean. The 117 F 2:10 recombinant inbred lines (RIL) developed from a cross of 'Keunolkong' and 'Shinpaldalkong' were used. Narrow-sense heritability estimates based on a plot mean on seed weight, protein and oil content were 0.85, 0.82 and 0.81, respectively. Eight independent QTLs for oleic acid content were identified from linkage group (LG) A2, C1, D2, F, G, L, and O. Seven QTLs for linoleic acid content were located on LG D1b, E, H, I and L. Oil content was related with five QTLs located on LG C1, H, J, K, and L. Oleic, linoleic, and linolenic acid have two common QTLs on LG C1 and L. Thus, we identified major loci improving soybean oil quality.

Mapping candidate genes for oleate biosynthesis and their association with unsaturated fatty acid seed content in soybean

The development of high-oleate soybean germplasm is hindered by the lack of knowledge of the genetic factors controlling oleate phenotypic variation. In the present study, several candidate genes implicated in oleate biosynthesis were mapped and their cosegregation with oleate, linoleate and linolenate quantitative trait loci (QTLs) was investigated. FAD2-2C, a previously described ω-6 desaturase isoform, was localized on linkage group E; whereas, a novel FAD2-2 isoform, designated as FAD2-2D, mapped on linkage group N. In addition, two isoforms were identified for the aminoalcoholphosphotransferase-encoding GmAAPT1 gene, denoted AAPT1a and AAPT1b. A database query suggested that only one functional copy of the FAD6 gene, encoding a plastid localized ω-6 desaturase, exists in the soybean genome. AAPT1a and FAD6 mapped on linkage group D1b, 23.40 cM apart. Linolenate QTLs with minor effects were identified near the FAD6 and AAPT1a markers in two segregating populations.

Mapping QTLs of Resistance to &lt;I&gt;Megacota cribraria&lt;/I&gt; (Fabricius) in Soy-bean

Globular stink bug [Megacota cribraria (Fabricius)] is one of the important pests for soybean [Glycine max (L.) Merr.] in the central and southern China. However, very few reports on soybean resistant to M. cribraria were found in the literature. The objectives of the present study were to find QTLs associated with resistance to M. cribraria in soybean and to analyze the stability of mapped QTLs among years by using two RIL populations, NJRIKY (or KY) and NJRIWT (or WT) derived from the crosses of Kefeng 1×Nannong 1138-2 and Wan 82-178×Tongshanbopihuangdoujia, respectively. The 184 lines of KY and 142 lines of WT were tested and the percentage of black mildew on stem and purple spots on leaves was used as indicator to evaluate their resistance to M. cribraria under natural infestation during 2004-2006. There existed significant differences among lines in the two RIL populations during the three years, with heritability of 66.5%-88.8% in KY and 61.3%-84.8% in WT. The composite interval mapping (CIM) of the software Windows QTL Cartographer Version 2.5 was used to map QTLs. The linkage group D1a and C2 in KY and the linkage group H and D1b in WT were found to be related with resistance to M. crubrarua. The QTL qRMC-d1a-1 on Linkage group D1a was detected consistently associated with reaction to M. cribraria in KY during the three years, which accounted for 7.6%-31.4% of phenotypic variation; the QTL qRMC-c2-1 on linkage group C2 was detected in 2005-2006, which accounted for less phenotypic variation than the former one; the resistance alleles were from Nannong 1138-2. There appeared significant interactions between qRMC-d1a-1 and qRMC-h-1 in KY in 2005 and 2006. The QTL qRMC-h-1 on linkage group H was detected also consistently associated with reaction to M. cribraria in WT during the three years, which accounted for 16.3%-36.2% of phenotypic variation; the QTL qRMC-d1b-2 on linkage group D1b was detected in 2004-2005, which accounted for less phenotypic variation than the former one; the resistant alleles were from Tongshanbopihuangdoujia. Therefore, different QTLs conferred resistance to M. cribraria in KY and WT basically although the two QTLs in the latter population were also identified in one year in the former population. The fact that the QTLs were repeatedly detected in different environments indicated the resistance was controlled stably by the main QTLs. Based on the results, it is inferred that the markers linked to the detected QTLs should be useful for marker-assisted selection for resistance to M. cribraria in soybean.

Mapping QTL tolerance to Phytophthora root rot in soybean using microsatellite and RAPD/SCAR derived markers

Broad tolerance to phytophthora root rot (PRR) caused by Phytophthora sojae has become an important goal for the improvement of soybean (Glycine max) because of the rapid spread of races that defeat the available resistance genes. The aim of this research was to identify the location of quantitative trait loci (QTL) in ‘Conrad’, a soybean cultivar with broad tolerance to many races of P. sojae. A PRR susceptible breeding line ‘OX760-6-1’was crossed with Conrad. Through single-seed-descent, 112, F2 derived, F7 recombinant inbred lines (RILs) were advanced. A total of 39 random amplified polymorphic DNA bands (RAPDs) and 89 type 1 microsatellite (simple sequence repeat; SSR) markers were used to construct a genetic linkage map. In the greenhouse, RILs were inoculated with four P. sojae isolates (three from China and one from Canada). Disease was measured as the percent of dead plants 20 days after germination in P. sojae inoculated vermiculite in the greenhouse. Three QTLs (QGP1, QGP2, QGP3) for PRR tolerance in the greenhouse were detected using WinQTLCart 2.0 with a log-likelihood (LOD) score 27.14 acquired through permutations (1,000 at P ≤ 0.05). QGP1 (near Satt509) was located at linkage group F and explained 13.2%, 5.9%, and 6.7% of the phenotypic variance for tolerance to the JiXi, JianSanJiang and ShuangYaShan isolates, respectively. QGP2 (near Satt334) was located in a different interval on linkage group F and explained 5.1% and 2.4% of the phenotypic variance for JiXi and ShuangYaShan isolates, respectively. QGP3 was located on linkage group D1b + W (near OPL18800/SCL18659) and explained 10.2% of the phenotypic variance for Woodslee isolate. QGP1 and QGP2 appeared to be associated with PRR tolerance across a range of isolates but QGP3 was active only against the Woodslee isolate. At Woodslee and Weaver (in Ontario) in 2000, the interval associated with QGP3 explained 21.6% and 16.7% of phenotypic variance in resistance to PRR, respectively and was referred as QFP1. The identified QTLs would be beneficial for marker assistant selection of PRR tolerance varieties against both China and North America P. sojae races.

콩에서 종실의 무게와 oil 및 단백질 함량을 조절하는 양적 형질 유전자좌와 연관된 simple sequence repeat marker

콩은 전 세계 시장의 48%를 차지하는 중요한 유료작물이다. 콩 종자를 구성하는 양적인 부분과 질적인 부분의 개선은 콩 육종 목표의 중요한 부분이다. 단백질함량과 종실의 크기는 두부와 콩나물의 질을 평가하는 중요한 특성이다. 따라서 본 연구는 콩에서 종실의 크기와 단백질 및 oil 함량을 조절하는 양적형질유전자좌(QTLs)를 확인하기 위하여 실시하였다. 시험재료로는 큰올콩과 신팔달콩을 교배한 후 <TEX>$F_2$</TEX>유래 <TEX>$F_10$</TEX>세대의 RIL을 이용하였으며, 이를 바탕으로 종실의 무게와 oil 및 단백질 함량과 관련된 QTLs를 탐색하였다. 종실의 무게와 단백질 및 oil 함량의 협의의 유전력은 각각 0.8과 0.78 및 0.71을 나타내었다. 종실의 무게와 관련된 QTLs는 연관군 F, I와 K의 세 개의 독립적인 QTLs를 확인하였다. 단백질함량과 관련된 QTLs는 연관군 D1b, E, H, I와 L의 다섯 개의 독립적인 QTLs를 확인하였다. 그리고 oil 함량과 관련된 QTLs는 연관군 D1b, E, G, I, J와 N의 여섯 개의 독립적인 QTLs를 확인하였다. oil 및 단백질 함량과 관련된 QTLs는 연관군 D1b, E와 I에서 공통적으로 나타났다. 따라서 이들 주요 QTL은 콩 품종 육성과정에서 품질의 개선하기 위한 선발 마커로서 활용가치가 높은 것으로 판단된다. Soybean [Glycine max (L.) Merr.] is an important crop, accounting for 48% of the world market in oil crops. Improvement of the quality and quantity of soybean seed constituents is one of the most important objectives in soybean breeding. Protein content and seed size are important properties to determine the quality of tofu and soy sprouts respectively. The objective of this study was to identify quantitative trait loci (QTLs) that control seed weight, protein and oil content in soybean. The 117 <TEX>$F_{2:10}$</TEX> recombinant inbred lines (RlL) developed from a cross of 'Keunolkong' and 'Shinpaldalkong' were used. Narrow-sense heritability estimates based on a plot mean on seed weight, protein and oil content were 0.8, 0.78 and 0.71, respectively. Four independent QTLs for seed weight were identified from linkage group (LG) F, I and K. Five QTL for protein content were located on LG D1b, E, H, I and L. Oil content was related with six QTLs located on LG D1b, E, G, I, J and N. Protein and oil content have three common QTLs on LG D1b, E and I. Thus, we identified major loci improving soybean seed quality.

Quantitative trait loci associated with oligosaccharide and sucrose contents in soybean (Glycine max L.)

Oligosaccharides and sucrose are very important nutritional components in soybean seeds. However, little information is available about their inheritance. We used molecular markers to identify the genomic regions significantly associated with the quantitative trait locus (QTL) that controls oligosaccharide and sucrose contents in segregating F2:10 Rl lines. Two related, but independent, QTLs were identified for oligosaccharides — near marker satt546 on linkage group (LG) D1b+W and satt278 on LG L. Four others, for sucrose content, were located at LG B1 (satt197), D1b+W (satt546), and L (satt523 and satt278). Finally, we found two common QTLs, on LG D1b+W and L, that are associated with both oligosaccharides and sucrose.

Marker-assisted Analysis for Soybean Hard Seededness with Isozyme and Simple Sequence Repeat Loci

We determined the genomic regions of wild soybean (Glycine max subsp. soja) carrying quantitative trait loci (QTL) for hard seededness, a distinct character between the wild and cultivated soybeans. The segregation of hard seededness, as evaluated using seed coat permeability (SCP), was examined in the progeny of a cross between wild and cultivated soybeans. The high parent-offspring correlation coefficient between F 2 and F 3 indicated that SCP was a highly heritable character. A marker-assisted analysis of five isozyme and 131 simple sequence repeat (SSR) loci revealed that at least two major and one minor QTL were involved in controlling the trait. The QTL near an SSR marker (Satt459) in molecular linkage group D1b+W had the greatest effect on SCP, and accounted for 23.8 and 38.5% of the phenotypic variance observed in the F 2 and F 3 mean, respectively. Seed coat color, determined by a locus inhibiting seed coat color (I) and a pubescence color locus (T), was also closely associated with SCP in F 4 to F 6 , although seed coat color did not appear to be associated with SCP in the F 2 . The results of this and a previous study suggest that different sets of QTL contribute to the phenotypic difference of seed coat permeability in wild and cultivated soybeans to different degrees.

Genetic identification of a female partial-sterile mutant in soybean.

We report here the genetic identification of a female partial-sterile mutant derived from soybean mutant L67-3483. L67-3483, which originated from the cultivar Clark after X-ray irradiation, is male and female fertile. All F1 plants in reciprocal pollinations of L67-3483 with 'Clark', 'Minsoy', or 'BSR 101' were female partial sterile. Partial sterility is expressed in the heterozygous condition at a single locus and upon self-pollination this locus exhibits a 1:1 segregation pattern. This locus is located on the terminus of the soybean molecular linkage group D1b+W, between simple sequence repeat (SSR) markers Satt157 and Satt266, and is linked to each by 5.3 and 1.2 cM, respectively. This gene is transmitted through both female and male gametes and there was no segregation distortion of SSR markers linked to this gene. We concluded that this female partial-sterile gene is a new mutation class, and differs from the previously reported mutation classes in soybean, i.e., sporophytic mutation, gametophytic female-specific mutation, and general gametophytic mutation. Restriction of recombination around the mutant gene suggested that this gene is located near or within (a) small inversion(s) or adjacent to (a) chromosomal deletion(s).

A Retrospective DNA Marker Assessment of the Development of Insect Resistant Soybean

There has been limited success over the past 30 yr in the development of superior soybean cultivars [Glycine max (L.) Merr] with insect resistance. Success may be hampered by the quantitative nature of resistance and by linkage drag from resistant plant introduction (PI) donor parents. Soybean insect resistance quantitative trait loci (SIR QTLs) have been identified from PI 229358 and PI 171451 by restriction fragment length polymorphism (RFLP) analysis. The objective of this study was to tag the SIR QTLs from PI 229358 with simple sequence repeat (SSR) markers and to determine the extent to which the SIR QTLs have been introgressed in registered cultivars, germplasm releases, or breeding lines that have resistance derived from this PI or from PI 171451. Marker analysis defined intervals by 5 centimorgans (cM) or less for a SIR QTL on linkage group D1b (SIR‐D1b), and for SIR‐G, SIR‐H, and SIR‐M. SIR QTLs were tracked through pedigrees by evaluating the inheritance of PI alleles at marker loci tightly linked to the QTLs during the phenotypic selection for insect resistance. It was inferred that at least 13 of the 15 SIR genotypes studied had introgressed SIR‐M. PI genome introgression around SIR‐M was measured to assess linkage drag. Some genotypes exhibited a dramatic reduction in the amount of linked PI genome, which likely occurred in response to phenotypic selection for agronomic performance as a means of reducing linkage drag. Only a few genotypes were inferred to possess SIR‐G or SIR‐H, and no genotypes possessed SIR‐D1b. The results of this study indicate that marker‐assisted selection for SIR QTLs is needed to introgress these loci into elite genetic backgrounds.

Positioning the wp Flower Color Locus on the Soybean Genome Map

The wp allele generates a pink flowered phenotype in soybean [Glycine max (L.) Merr.]. Genotypes with W1_wp wp are associated with larger seed size and higher seed protein content. The influence of a single locus on the anthocyanin pathway and seed protein accumulation has not been documented in other species. It is of interest to clone wp by initially identifying linked molecular markers. The objective of this research was to use restriction fragment length polymorphism (RFLP) and simple sequence repeat (SSR) molecular markers to position the wp locus on the soybean public genetic map. Of the 74 markers tested, two RFLP and 14 SSR markers were identified as linked to wp The two RFLP markers linked to wp in this study were previously reported to be associated with quantitative trait loci (QTL) controlling seed protein in a G. soja Siebold &amp; Zucc. × G. max population. It is proposed that wp is located between RFLP locus K011 and SSR locus Satt600. The molecular markers linked to wp were located on linkage group D1b+W of the public soybean genetic map. The knowledge of linked molecular markers will assist in cloning wp, potentially leading to further characterization of how wp influences the anthocyanin pathway and seed protein accumulation.

Molecular Mapping of a Male‐Sterile Gene in Soybean

A newly identified genie male‐sterile mutant in soybean [Glycine max (L.) Merr.] has high seed set under natural field conditions and is potentially useful in breeding programs. Meiosis is normal in the mutant line. Sterility in this mutant is caused by failure of cailose dissolution at the tetrad stage, which results in microspore abortion; however, little is known about the male‐sterile gene at the molecular level. The objective of this study was to identify molecular markers linked with the male‐sterile gene (ms) and to place the ms gene onto the soybean molecular genetic map. An F2 population of 107 individuals was constructed from a cross between the mutant msMOS (ms ms) and the cultivar Minsoy (Ms Ms). Two hundred seventy markers, including 219 RFLP and 51 SSRs, were evaluated. Of these, 102 RFLP probes and 31 SSR markers detected polymorphisms between the parents. The F2 population was screened for segregation of these polymorphic molecular markers. Analyses revealed that the male‐sterile locus, designated ‘ms’, was located on linkage group D1b of the USDA/ISU soybean molecular genetic map. The availability of linked DNA markers will facilitate the genetic analysis of this male‐sterility gene in relation to soybean breeding programs, and will be a starting point for the isolation of the ms gene by map‐based cloning.