Frogeye Leaf Spot Of Soybean Research Articles

First Report of Races 11 and 12 of Cercospora sojina, the Causal Agent of Soybean Frogeye Leaf Spot, in Argentina.

During the growing seasons of 2008 to 2009 and 2009 to 2010, severe outbreaks of soybean (Glycine max (L.) Merr.) frogeye leaf spot, a disease caused by Cercospora sojina Hara, occurred in several areas in Argentina (1). Two surveys were conducted in soybean fields, one in 2008 that included the provinces of Buenos Aires, Córdoba, and Santa Fe, and another that was performed in 2009 in the same provinces plus three others: Entre Ríos, Santiago del Estero, and Tucumán. In both surveys, plants presented circular lesions with reddish brown-to-gray spots and bordered by typical, narrow, reddish purple margins (3). To promote sporulation and to enable identification of the causal agent, leaves of diseased plants were collected and placed in a moist chamber for 24 h with a 12-h light cycle at 25°C. Conidia were plated on potato dextrose agar medium amended with streptomycin and were incubated at 25°C and 12 h of fluorescent light. Isolated cultures sporulated in 10 days and, on the basis of their morphology, were identified as C. sojina. A total of 147 isolates were deposited at the Culture Collection of CEREMIC (Centro de Referencia de Micología). They produced one- to nine-septate hyaline, elongate to fusiform conidia that measured 54.9 ± 16.2 × 5.7 ± 1.0 μm. Six isolates of C. sojina, each representing a province, were inoculated on a set of 12 differential soybean cultivars: Lee, Davis, Hood, Richland, Lincoln, Kent, Tracy, S 100, Palmetto, Peking, CNS, and Blackhawk (2). Fifteen plants of each differential were sprayed at V3 growth stage with a suspension of 6 × 104 conidia/ml. The test was conducted twice in a complete randomized design with three replicates. Control plants were sprayed with sterile distilled water. After inoculation, plants were placed in a greenhouse bench humidity chamber at 26 to 28°C for 72 h. Disease was rated 14 days after inoculation; plants with numerous lesions were considered susceptible and each of the 15 plants was given a score of 1. Plants with small or no lesions were classified as resistant and given a score of 0. Control plants remained healthy. The pathogen was reisolated from symptomatic plants and morphological characteristics were consistent with C. sojina. Based on the response of the differentials to each isolate and on the race designations, the isolates from Buenos Aires, Córdoba, Santa Fe, and Tucumán belong to race 11, while those from Santiago del Estero and Entre Ríos province to race 12. The finding of these two races threatening soybean cultivars in Argentina may be indicative of additional races. Thus, the incorporation of multiple resistance genes may reduce the impact of the disease on soybean. To our knowledge, this is the first report of the identification of races of C. sojina in Argentina.

First Report of the Soybean Frogeye Leaf Spot Fungus (Cercospora sojina) Resistant to Quinone Outside Inhibitor Fungicides in North America.

Quinone outside inhibitor (QoI; also known as strobilurin) fungicides sometimes are applied to soybean (Glycine max) fields to help manage frogeye leaf spot of soybean (caused by Cercospora sojina) in the United States. In August 2010, soybean leaflets exhibiting severe frogeye leaf spot symptoms were collected from a field in Lauderdale County, TN that had been treated twice with pyraclostrobin during that growing season. The field had been planted into soybean annually since at least 2008, and a QoI fungicide had been applied to the field in each of those years. Fifteen single-spore isolates of C. sojina were recovered from the affected soybean leaflets. These isolates were identified as C. sojina based on the observed symptoms on the soybean leaflets and the morphology and size of conidiophores and conidia (3). In addition, DNA was extracted from the cultures, PCR amplification of the small subunit rDNA and internal transcribed spacer (ITS) region was conducted (2), and the resulting PCR product was sequenced at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequences were compared with sequences deposited in the nucleotide database ( http://www.ncbi.nlm.nih.gov ) and showed highest homology to sequences of C. sojina. The isolates were tested for their sensitivity to technical-grade formulations of the QoI fungicides azoxystrobin, pyraclostrobin, and trifloxystrobin with an in vitro conidial germination assay with fungicide + salicylhydroxamic acid (SHAM)-amended potato dextrose agar as described by Bradley and Pedersen (1). The effective concentration at which 50% conidial germination was inhibited (EC50) was determined for all 15 C. sojina isolates, with mean values of 3.1644 (2.7826 to 4.5409), 0.3297 (0.2818 to 0.6404), and 0.8573 (0.3665 to 2.5119) μg/ml for azoxystrobin, pyraclostrobin, and trifloxystrobin, respectively. When compared with previously established mean EC50 values of C. sojina baseline isolates (4), EC50 values of the C. sojina isolates collected from the Lauderdale County, TN soybean field were approximately 249- to 7,144-fold greater than the EC50 values of the baseline isolates. These results indicate that all isolates recovered from the Lauderdale County, TN soybean field were highly resistant to QoI fungicides. To our knowledge, this is the first report of QoI fungicide resistance occurring in C. sojina, and surveys for additional QoI fungicide-resistant C. sojina isolates are needed to determine their prevalence and geographic distribution. In light of these findings, soybean growers in Tennessee and adjacent states should consider utilizing alternative frogeye leaf spot management practices such as planting resistant cultivars, rotating to nonhost crops, and tilling affected soybean residue (3).

ダイズ斑点病 (病原菌Cercospora sojina Hara) の種子伝染

ダイズ斑点病 (病原菌Cercospora sojina Hara) の種子伝染

First Report of Frogeye Leaf Spot of Soybean Caused by Cercospora sojina Race 11 in Virginia.

Frogeye leaf spot of soybean (FLS) (Glycine max (L.) Merr.), caused by Cercospora sojina Hara, was first detected in Virginia in 1942 (1). During the 2008 growing season, a FLS survey was conducted in soybean fields in Virginia. This was the first FLS race survey conducted in Virginia. Typical frogeye leaf spot symptoms, as reported by Phillips (4), were observed on soybean leaves in Westmoreland County. During 2008, Westmoreland County planted 7,365 ha of soybean. Symptomatic leaves were collected from V06-1891, V06-1365, V05-4394, V04-8405, and Hutcheson cultivars from plants in growth stages R5 to R6. Leaves were placed in a moist chamber for 24 h at 21°C with 12-h light to induce sporulation. C. sojina was only recovered from V06-1365. Conidia were removed from the leaves, placed into V8 juice agar amended with rifampicin (10 mg ml-1) and ampicillin (0.25 g liter-1) and incubated at 21°C with 12-h light. Cultures with dark pigmentation and presence of conidia were observed after 3 weeks. Conidia matched the description of C. sojina (4). Conidia had three to nine septa, were hyaline, elongate to fusiform, and measured 3 to 6 × 25 to 40 μm. Race identification was conducted using the set of differentials reported by Mian et al. (3). Spores for inoculation were produced on soybean stem lima bean agar (SSLBA) media. Tencentimeter-diameter pots, each containing four plants, were used. The test was conducted twice in a complete randomized design with three replications. Seedlings were inoculated at the V3 growth stage with a spore suspension of 6 × 104 spores/ml. Control plants were sprayed with sterile distilled water. Plants were placed in a greenhouse bench humidity chamber at 21°C for 72 h. Disease rating was conducted 14 days after inoculation. Since the resistance to FLS is known to be controlled by single dominant genes, the FLS was scored as a qualitative trait (i.e., resistant versus susceptible) as previously done by Mian et al. (2). Plants that showed numerous, large, spreading lesions were classified as susceptible and each plant was given a score of 1. Plants that showed no lesions or only small lesions or flecks were classified as resistant and each plant was given a score of 0. Control plants remained healthy. On the basis of the reaction response of the isolate on the set of differentials and comparison with the proposed race designations of Mian et al. (3), the isolate was classified as race 11. Race 11 shows compatible reaction (susceptibility) on the soybean cv. Lincoln, which is the source of Rcs1 resistance gene, and incompatible reactions (resistance) on cvs. Peking, Davis, and Kent. The latter two cultivars are sources of the Rcs3 and Rcs2 genes, respectively. Successful development of soybean cultivars with FLS resistance not only depends on knowledge of the presence of resistance genes, but also on the understanding of the pathogen population structure. To our knowledge this is the first report of C. sojina race 11 from soybean in Virginia. Resistance to this race is conditioned by Rcs2, Rcs3, and the single dominant gene in Peking (3). We recommend use of Rcs3 and Rcs2 genes and the single dominant gene in Peking for resistance to FLS in Virginia.

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.

Severe Outbreaks of Soybean Frogeye Leaf Spot Caused by Cercospora sojina in the Pampean Region, Argentina.

Frogeye leaf spot of soybean (Glycine max (L.) Merr.) caused by Cercospora sojina Hara was reported to be severe from 1998 to 1999 in northwest Argentina (2). Although the disease was detected at low prevalence (5 to 25%), incidence, and severity in the Pampean Region from 2005 to 2008, no severe outbreaks have been recorded in the provinces of Córdoba, Santa Fe, and Buenos Aires. During the 2008-2009 growing season, disease spread rapidly throughout most soybean-growing areas of the Pampean Region. Disease was observed on almost all varieties of maturity group (MG) III, IV, and V. Symptoms on leaves were circular, reddish brown-to-gray spots (1 to 6 mm) and bordered by typical, narrow, reddish purple margins. Morphology of the fungi was examined on infected tissues. Conidiophores were light-to-dark brown, fasciculate, geniculate, and measured 110 to 203 μm long. Conidia were 1 to 9 septate, hyaline, elongate to fusiform, and measured 26 to 111 (47.3 ± 14.7) × 5.2 to 7.4 μm (6.1 ± 0.7). Pathogenicity tests were conducted on seedlings of a susceptible cultivar by spraying leaves of each of 80 plants at the V3 growth stage with 18 ml of a conidial suspension (3 × 104 conidia/ml) with a hand-held atomizer. Plants were covered with plastic bags and placed in a greenhouse at 28 to 30°C for 48 h. The plastic bags were removed and plants were maintained in high humidity at the same temperature. The same number of noninoculated plants was used as controls. After 10 to 12 days, all inoculated plants showed typical symptoms. Koch's postulates were fulfilled by isolating C. sojina from inoculated plants. Control plants remained healthy. Foliar lesions and morphological characteristics of the pathogen were consistent with C. sojina (1). Disease assessments were made for the middle and upper canopy from 15 arbitrarily collected plants. Soybean plants were in growth stages between R3 and R5 during the survey. Incidence (percentage of plants affected) and severity (percentage of leaf area affected with lesions) were visually estimated from each of the 30 soybean-production fields located in Monte Cristo, Alta Gracia, Jesús María, W. Escalante, Monte Buey, (10 fields, Córdoba Province), Venado Tuerto, Villa Cañás, Cristophersen, María Teresa, (12 fields, Santa Fe Province), Pergamino, Rojas, and Salto (8 fields, Buenos Aires Province). Incidence was 100% in all fields from Córdoba and Santa Fe. Incidence in Buenos Aires was 0 to 100%. Highest severity levels were quantified from fields in Córdoba (severity of 30 to 60%). Lesions also developed on stems and pods. In samples from Buenos Aires, severity levels were ≤10% in the eight soybean fields. Number of lesions per leaflet was recorded from central leaflets in samples from Monte Cristo, Alta Gracia, Venado Tuerto, and María Teresa with 20 to 55 typical lesions per leaflet. Since the disease was always more important in northwest Argentina, genetic resistance is more commonly available in varieties of MG VII to VIII, so most of the varieties of MG III, IV, and V frequently planted in Pampean Region are susceptible. This fact in combination with rainfall, warm temperatures, and high relative humidity in no-till fields during this summer have encouraged the severe outbreak of frogeye leaf spot, especially in the province of Córdoba and in some regions of Santa Fe.

Frogeye Leaf Spot of Soybean: A Review and Proposed Race Designations for Isolates of Cercospora sojina Hara

Frogeye leaf spot (FLS), caused by Cercospora sojina K. Hara, is a common disease of soybean [Glycine max (L.) Merr.] in most soybean‐growing countries of the world. Significant yield losses of soybean (10–60%) have been attributed to FLS under hot and humid growing conditions. The FLS in the southern United States has been kept under control by planting resistant cultivars. Cercospora sojina is a dynamic pathogen with extensive virulence or race diversity. The current number of C. sojina isolates at the University of Georgia collection is 93. Assigning race designations to this large number of isolates has been difficult because of the lack of a well‐defined set of differentials. To facilitate future studies of the genetics of soybean resistance to FLS and the identification and comparison of existing and future races of C. sojina, we have reassessed both the soybean differentials and the C. sojina races. Based on the reactions of 93 isolates of C. sojina on 38 putative soybean differentials, we propose a core set of 12 differentials and 11 races that represent the major diversity among the 93 C. sojina isolates. The definition of these 12 differentials and 11 races should provide the foundation for the identification and comparison of additional soybean resistance genes and new races of C. sojina

Single Nucleotide Polymorphism Detection of the Rcs3 Gene for Resistance to Frogeye Leaf Spot in Soybean

Frogeye leaf spot (FLS), caused by Cercospora sojina Hara, has become a more frequent disease in soybean, Glycine max (L.) Merr., across the USA. The Rcs3 gene provides resistance to all known races of C. sojina To provide resources for efficient marker‐assisted selection (MAS) of Rcs3, we developed and evaluated several single nucleotide polymorphisms (SNP) and insertions or deletions (InDels) markers linked to Rcs3 We surveyed 13 bacterial artificial chromosome (BAC) end sequences that were anchored with simple sequence repeat (SSR) markers Satt244 and Satt547 along with the two SSRs containing clones in six soybean cultivars (Davis, Cook, and Young that have the Rcs3 allele and Blackhawk, Bragg, and Lee that have the rcs3 allele) for SNPs. A total of 19 SNPs/InDels were identified and validated, but only 11 mapped near Rcs3 in a F2 population of Davis × Blackhawk. The Rcs3 gene was positioned near Satt244 and 0.50 cM from SNPs AZ573TA150 and AZ573CA393. None of the SNPs or InDels identified appeared to contribute directly to the Rcs3 phenotype, but 11 mapped within a 3‐cM interval surrounding Rcs3 These 11 markers were further validated for association with Rcs3 and for their potential in MAS in 64 lines and cultivars. Our results suggest that the two markers AZ573TA150 and AZ573CA393 could be used in MAS for Rcs3. Allele specific oligonucleotide probes specific for MAS were developed for a direct hybridization assay on a Luminex 100 flow cytometry platform.

Frogeye Leaf Spot of Soybean Caused by Cercospora sojina in Northwestern Argentina

Frogeye leaf spot of soybean (Glycine max (L.) Merr.), caused by Cercospora sojina Hara, was first detected during the 1997-98 growing season at low incidence and severity (<1% of the leaf diseased) levels in the provinces of Tucumán, Salta, Jujuy, Catamarca, and Santiago del Estero in northwestern Argentina. During the 1998-1999 growing season, disease incidence increased and disease severity grew to 10% of the leaf surface diseased on highly susceptible cultivars in a few locations. An outbreak of frogeye leaf spot occurred throughout northwestern Argentina during the 1999-2000 growing season. Frogeye leaf spot was severe on susceptible cultivars in the provinces of Salta, Santiago del Estero and Catamarca with the greatest intensity in the northeastern part of the Province of Tucumán. Symptoms on leaves were circular lesions that ranged in size from 1 to 5 mm, were reddish-brown to gray or tan, and were bordered by a narrow, reddish-brown to purple margin. Conidiophores and conidia of C. sojina developed on the abaxial leaf surface (1,2). Severely diseased leaves were desiccated and dropped during the R6 stage of growth. Lesions also developed on stems, pods, and seeds. Field surveys indicated that this disease reduced the yields of the highly susceptible cultivars Anta 82 RR, Coker 6738, and A 6445 RG by 48, 34, and 25%, respectively. C. sojina was cultured from diseased tissue on PDA acidified with 0.2% lactic acid and maintained on V-8 juice agar amended with streptomycin sulfate (100 mg/l). Conidia were elongated, dark, 38 to 62 × 5 to 9 μm, with 2 to 6 septa, and borne on dark conidiophores with 1 to 4 septa. Pathogenicity tests were conducted on seedlings of the susceptible cultivars A 6445 RG and Coker 6738 and on the resistant cultivars A 8000 RG and Shulka. Seedlings were inoculated at the V3 growth stage by spraying the leaves with a conidial suspension (4 × 104 conidia/ml) using a hand-held atomizer. Control plants were sprayed with sterile distilled water. Plants were placed in a moist chamber at 26°C for 2 days and then transferred to a greenhouse bench where they were kept at 25 to 30°C. Symptoms identical to those observed in the field became visible after 7 to 10 days. Ratings were made 14 days after inoculation by estimating the percentage of leaf area affected using a standard area diagram. Lesions covered 60 to 65% of the leaf area of susceptible cultivars, but less than 2% on resistant cultivars. Control plants remained healthy. C. sojina was reisolated from lesions on leaves of susceptible plants. Above-average rainfall and high relative humidity in northwestern Argentina during the first three months of 2000 may have encouraged the severe outbreak of frogeye leaf spot of soybean. The outbreak was aggravated by the widespread use of notillage systems in the region and the large hectarage planted with susceptible cultivars.

Outbreaks of Soybean Frogeye Leaf Spot in Iowa.

Frogeye leaf spot of soybean, caused by Cercospora sojina, is typically a disease of warm and humid regions (2). Although the disease was reported in the Midwest in the 1920s (1), no outbreaks have been recorded in Iowa. Outbreaks of frogeye leaf spot occurred during 1999 in soybean fields in Ames and Grand Junction in central Iowa. During the 2000 growing season, the disease occurred in southwestern, southcentral, central, southeastern, and east-central Iowa. Occurrences of the disease with severity (reduction of green leaf area) greater than 50% were observed in production soybean fields at Grand Junction in central Iowa and Central City in eastern Iowa. In a 12-ha no-till field planted with cv. Asgrow 2501, the disease was noticeable and uniformly distributed in the entire field in mid July. Disease severity in this field was greater than 70% by the end of August. Disease incidence, however, was less than 10% in three adjacent soybean fields. In a soybean performance test at a central Iowa location where the disease occurred in 1999 and 2000, the disease was observed on all 80 varieties, with four having a severity equal to or greater than 40%. Fourteen entries had less than a 10% disease severity and 19 entries had a disease severity equal to or greater than 30%. Infected leaves in these locations had typical lesions of frogeye leaf spot, which appeared as reddish brown margins surrounding light brown or ash gray centers. On the infected tissues, hyaline, straight, and multiseptate conidia from clustered conidiophores were found, isolated, and identified to C. sojina. The relatively warm winter temperatures in 1998 to 1999 and 1999 to 2000 were associated with frogeye leaf spot epidemics. Because of the seedborne nature of C. sojina, efforts are warranted to monitor and survey the occurrence of frogeye leaf spot in Iowa, an important seed production state in the northern soybean production region.

Incidence and severity of frogeye leaf spot and associated yield losses in soybeans in agroecological zone II of Zambia.

The incidence and severity of frogeye leaf spot of soybean (Glycine max (L.) Merr.) was studied in agroecological region II of Zambia during the 1997/98 crop growing season. A survey was conducted on farmers' fields on SCSI Kaleya, Magoye and Hernon-147 cultivars. Disease incidence and severity was assessed by monitoring disease increments at two weeks interval (beginning of January to April) from nine fields, three from each province. Soybean cultivars were evaluated for yield losses resulting from frogeye leaf spot. Field plots of each cultivar were either sprayed twice with benomyl (benlate) or not sprayed at all. The results showed that the incidence of frogeye leaf spot was highest in Southern province (5.1), followed by Lusaka province (4.9) while Central province had the lowest disease incidence (1.8). Values for area under disease progress curve (AUDPC) were significantly greater (P < 0.05) for Lusaka and Southern provinces than for Central province. Yields in benomyl protected plots ranged from 1444 kg ha-1 to 2320 kg ha-1 and were significantly different among the cultivars. Average yields of non protected plants were reduced by 30.5% for Kaleya, 35.6% for Hernon-147 and 37.2% for SCS1. Incidence and severity increased with time and varied depending on weather parameters and susceptibility of cultivars to the disease. Yield losses due to frogeye leaf spot occurred through a reduction in seed size. Differences in weather conditions and amount of inocula are believed to contribute to the observed variation in incidence and severity of the disease at different locations.

Molecular characterization of RAPD and SCAR marker linked to the frog-eye leaf spot resistance gene in soybean

Two fragments SCS3620 and SCS3580 of the co-dominant marker OPS03620 & 580 that were linked to the resistance gene of soybean frog-eye leaf spot have been completely sequenced. A significant insertion of 30 bp is the main reason of the polymorphism between the two fragments. The results of Southern hybridization indicate that SCS3620 derives from a single-or low-copy sequence and can be used as an RFLP probe. A co-dominant SCAR marker SCS3620 & 580 has been developed based on the sequences. The segregation of SCS3620 & 580 is similar to that of RAPD marker OPS03620 & 580-Significant polymorphism has been shown between resistant and susceptible genotypes when 62 soybean genotypes were surveyed for the SCAR marker. Therefore, the marker can be used in the resistance breeding of soybean frog-eye leaf spot by marker-assisted selection.

Molecular Mapping of the Rcs3 Gene for Resistance to Frogeye Leaf Spot in Soybean

ABSTRACTFrogeye leaf spot (FLS) (caused by Cercospora sojina Hara) is a foliar disease of soybean [Glycine max (L.) Merr.] that causes significant yield loss in southeastern USA. The Rcs 3 gene in soybean has been reported to condition resistance to all known races of C. sojina. Molecular mapping of the Rcs3 gene will be helpful in breeding soybean for resistance to FLS. The objective of this study was to map the Rcs3 gene with DNA markers. The parents, 123 F2 plants, and the F2:3 families from the cross of ‘Blackhawk’ (susceptible) × ‘Davis’ (resistant and original source of the Rcs3 gene) were scored for FLS reaction in the greenhouse after inoculation with race 5 of C. sojina. In addition, ‘Wright’ and the Wright6‐Rcs 3 (near isoline of Wright) were also scored for FLS by the same protocol. A resistant and a susceptible DNA bulk were created by pooling the DNA of 15 resistant and 15 susceptible F2 plants, respectively, from the Blackhawk × Davis population. The two bulks and resistant–susceptible near isolines (NILs) of Wright were screened with simple sequence repeat (SSR) markers from soybean linkage groups with known disease resistance gene clusters. The bulks and the NILs of Wright both showed a putative association between the Rcs 3 locus and a SSR marker Satt244 from linkage group (LG) J. A molecular map of the relevant segment of the LG J for the Blackhawk × Davis population was then created by screening the DNA of 95 F2 plants with the available polymorphic SSR and RFLP markers. We have mapped the Rcs3 gene for resistance to FLS in soybean near a previously known disease resistance gene cluster on LG J. The gene was closely linked to SSR markers Satt244 and Satt547. Close proximity of this gene with these SSR markers provides soybean breeders with an opportunity to use these markers for marker assisted selection (MAS) for FLS resistance in soybean.