ABSTRACTSoybean [Glycine max (L.) Merr.] resistance to soybean rust (SBR) caused by Phakopsora pachyrhizi could reduce reliance on fungicides to manage this disease. The objective of this study was to identify soybean germplasm with resistance to field populations of P. pachyrhizi in the United States. Field evaluations of 576 accessions from the USDA Soybean Germplasm Collection for resistance to SBR were conducted at seven locations in the southern United States between 2006 and 2008. Accessions from maturity groups (MG) 000 to X and North American susceptible check cultivars from each MG except X were rated for disease severity in all year–location environments, and for disease incidence, fungal sporulation, lesion type, and/or uredinia density in certain environments. While none of the accessions was immune in all environments, 64 were resistant in two or more locations each year that they were tested. Some accessions appeared to be more resistant in certain environments than in others. Of the original four Rpp genes described in the literature, Rpp1 provided the highest level of resistance, and among the accessions with uncharacterized Rpp genes, PI 567104B had the highest overall resistance across environments. The plant introductions confirmed to be resistant in these evaluations should be useful sources of genes for resistance to North American populations of P. pachyrhizi

A primary focus for soybean [Glycine max (L.) Merr.] breeders recently has been the development of cultivars with improved oil qualities such as reduced palmitic acid (16:0) and linolenic acid (18:3). A backcross breeding program was used to develop five low 16:0, two low 16:0 + 18:3, and one low 18:3 modified fatty acid breeding lines (MFALs). Research objectives were (i) to determine planting date effects on fatty acid content in the eight MFALs and (ii) to compare the MFALs to parental cultivars for seed composition and agronomic traits. The eight MFALs and four control cultivars were evaluated at two planting dates at Clemson, SC, in 2001, 2003, and 2004. Planting dates were chosen to simulate full season and double crop planting dates for South Carolina soybean production. Agronomic traits including seed yield, plant height, lodging, maturity date, seed size, and seed quality were measured, and seeds were analyzed for protein, oil, and fatty acid levels. Planting date had a significant effect on all agronomic variables, as well as on protein, oil, and palmitic and linolenic acid. There was a decrease in palmitic acid at the late planting date, while the early planting date resulted in a decrease in linolenic acid levels. The effect of genotype was significant for all agronomic and seed composition variables measured when averaged across planting dates. It appears that planting date may be manipulated to reduce palmitic or linolenic acid of MFALs, although the extent of the reduction varies with genotype.

Partitioning of soybean [Glycine max (L.) Merr.] seed yield between mainstem and branch fractions across row widths and genotypes at recommended seeding rates is not well understood. A field experiment was conducted to evaluate the distribution of seed yield between mainstem and branch fractions of eight soybean genotypes grown in narrow (19 cm) and wide (97 cm) rows at recommended seeding rates. In contrast to adequate rainfall throughout the crop season in 2002, a lack of rainfall during reproductive development in 2003 caused differences in mainstem and branch yield components between years. Mainstem seed yields, averaged over years and genotypes, accounted for 45 and 69% of the total yield in wide and narrow rows, respectively. Mainstem seed yields, averaged over years and row widths, ranged from 62 to 142 g m−2 among genotypes. Ranking of mainstem and branch yields among genotypes was stable over environments. Similarly, row width did not influence mainstem yields among genotypes, but genotype branch yields in wide rows were different from those in narrow rows. Branch seed yields in narrow rows, averaged over years, ranged from 14 to 57% of total seed yield while 47 to 74% of total seed yield was produced on branches in wide rows. This research demonstrates considerable differences exist in mainstem and branch yields among genotypes and that genotypes having superior branch yield should be selected for wide rows while mainstem yield should be used as a selection criteria for narrow rows.

Crop ScienceVolume 43, Issue 6 p. 2305-2306 Registrations Of Cultivar Registration of ‘Santee’ Soybean E.R. Shipe, Corresponding Author E.R. Shipe eshipe@clemson.edu Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Corresponding author (eshipe@clemson.edu)Search for more papers by this authorJ.D. Mueller, J.D. Mueller Dep. of Plant Pathology and Physiology, Edisto Res. and Educ. Ctr., Blackville, SC, 29817Search for more papers by this authorS.A. Lewis, S.A. Lewis Dep. of Plant Pathology and Physiology, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorP.F. Williams, P.F. Williams Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorR.K. Stephens, R.K. Stephens Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Search for more papers by this author E.R. Shipe, Corresponding Author E.R. Shipe eshipe@clemson.edu Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Corresponding author (eshipe@clemson.edu)Search for more papers by this authorJ.D. Mueller, J.D. Mueller Dep. of Plant Pathology and Physiology, Edisto Res. and Educ. Ctr., Blackville, SC, 29817Search for more papers by this authorS.A. Lewis, S.A. Lewis Dep. of Plant Pathology and Physiology, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorP.F. Williams, P.F. Williams Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorR.K. Stephens, R.K. Stephens Dep. of Crop and Soil Environmental Science, Clemson Univ., Clemson, SC, 29634Search for more papers by this author First published: 01 November 2003 https://doi.org/10.2135/cropsci2003.2305Citations: 3 Technical Contribution no. 4822 of the South Carolina Agriculture and Forestry Research System, Clemson Univ. Research supported by state and Hatch funds allocated to the South Carolina Agriculture and Forestry Research System and by grants from the South Carolina Soybean Board. Registration by CSSA. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume43, Issue6November–December 2003Pages 2305-2306 RelatedInformation

Reproduction of reniform nematode Rotylenchulus reniformis on 139 soybean lines was evaluated in a greenhouse in the summer of 2001. Cultivars and lines (119 total) were new in the Arkansas and Mississippi Soybean Testing Programs, and an additional 20 were submitted by C. Overstreet, Louisiana State Extension Nematologist. A second test of 32 breeding lines and 2 cultivars from the Clemson University soybean breeding program was performed at the same time under the same conditions. Controls were the resistant cultivars Forrest and Hartwig, susceptible Braxton, and fallow infested soil. Five treatment replications were planted in sandy loam soil infested with 1,744 eggs and vermiform reniform nematodes, grown for 10 weeks in 10 cm-diam.- pots. Total reniform nematodes extracted from soil and roots was determined, and a reproductive factor (final population (Pf)/ initial inoculum level (Pi)) was calculated for each genotype. Reproduction on each genotype was compared to the reproduction on the resistant cultivar Forrest (RF), and the log ratio [log(RF + 1) is reported. Cultivars with reproduction not significantly different from Forrest (log ratio) were not suitable hosts, whereas those with greater reproductive indices were considered suitable hosts. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode and to select useful breeding lines as parent material for future development of reniform nematode resistant cultivars and lines.

Frogeye leaf spot (FLS) caused by Cercospora sojina Hara is a disease of soybean (Glycine max (L.) Merr.) that causes significant seed yield losses in warm, humid environments of southeastern United States. The Rcs 3 gene in soybean has been reported to condition resistance to all known races of C. sojina. The objectives of this study were to determine the effectiveness of Rcs 3 in limiting seed yield loss due to FLS and to compare the seed yield of the resistant and susceptible near-isolines (NILs) in the absence of significant FLS disease. Four pairs of NILs—Colquitt/Colquitt-Rcs 3 , Gordon/Gordon-Rcs 3 , Thomas/Thomas-Rcs 3 , and Wright/Wright-Rcs 3 —were evaluated in 23 field experiments in Alabama, Florida, Georgia, Louisiana, Mississippi, and South Carolina during 1992 to 1994. The amount of damage to susceptible soybean caused by FLS was dependent on the specific environment. All four of the Rcs 3 NILs were resistant to the prevalent races of FLS in all environments. In the absence of significant FLS disease, each of the Rcs 3 NILs was at least equal to the respective susceptible line in its seed yield. In the presence of FLS infestation, the susceptible lines suffered significant seed yield loss (up to 31%) compared to their Rcs 3 NILs. The effect of FLS on seed yield was dependent on cumulative disease severity over the growing season. Thus, the area under disease progress curve was more useful than percent of leaf area infected at the end of the growing season (R7 stage of development) in explaining the seed yield loss due to FLS.

Germplasm line J87-233 is resistant to soybean cyst nematode (SCN) races 1, 2, 3, 5 and moderately resistant to race 14 with resistance derived from 3 primitive sources, ‘Peking’, PI 88788 and PI 90763. F2:3 progeny of J87-233 and SCN-susceptible ‘Hutcheson’ cross were evaluated for response to SCN races 1, 2, 3, 5 and 14. Linkage groups (LG) A, B, F, G, J, M, N, S were tested with 215 genomic clones and 45 decamers for parental genotypes. QTL for race 1 and QTL for race 3 were detected on LG A2, the region of BLT65V and SCAR 548/5631100/1025,975. The cluster analysis of 12 soybean cultivars and 38 plant introductions confirmed association of SCAR1100/1025,975 with resistance to races 1 and 3, and suggested possible DNA rearrangements that might give rise to new resistance specificities in the region. The highly significant association of K69T marker with SCN race 1 resistance in conjunction with its location, 18.5 cM from the reported QTL, exemplifies the importance of the QTL locus on LG G and suggests expansion of the linkage map in the LG G-terminal region. Detected interaction between loci on LG A2 and LG G, and also with loci on LG F and LG M, may play a significant role in the genotype-specific response to SCN. Identification of two major regions on LG A2 and LG G for SCN resistance shows their applicability to advanced germplasm, however, transmission of molecular marker alleles indicates that applied markers are not yet reliable in revealing all possible recombination events in breeding for SCN resistance.

Soybean, Glycine max (L.) Merr., genotypes are known to differ in chlorimuron ethyl sensitivity (CS). Earlier we have reported two putatively independent marker loci linked to two quantitative trait loci (QTLs) controlling CS in a soybean population derived from a cross of PI97100 (sensitive to chlorimuron ethyl) and ‘Coker 237’ (tolerant to chlorimuron ethyl). The objective of the present study was to quantify the association of the two marker loci with seed yield and related traits in this soybean population following application of chlorimuron ethyl. Phenotypic data were collected for 111 F 2 -derived lines of the cross grown in replicated plots at Athens, G.A., in 1994 and 1995, and at Blackville, S.C., in 1995. The two CS marker loci explained as much as 50% of the genetic variation in seed yield and seed number m -2 , but had no association with seed weight, plant height, lodging, seed protein, and seed oil. There were no epistatic interactions between the two marker loci for any of the traits. The marker locus (cr168-1 on USDA linkage group E) linked to the major CS QTL explained between 13 and 23% of the variation in seed yield. The Coker 237 allele at this locus was associated with decreased CS and increased seed yield. The marker locus (Blt015-2 on an unknown linkage group) linked to the minor CS QTL accounted for a maximum of 11% of the variation in seed yield. The Coker 237 allele at this locus was associated with an increase in CS and a decrease in seed yield. The association of the two marker loci with seed number m -2 strongly resembled their association with seed yield. Seed yield had a strong positive correlation ( r =0.74 – 0.94) with seed number m -2 , and the effect of chlorimuron ethyl on seed yield was due mainly to its effect on seed number m -2 rather than seed weight.

Soybean [Glycine max (L.) Merr.] genotypes are known to differ in their chlorimuron ethyl sensitivity (CS). These differences are believed to be controlled by a few major genes. However, the genes controlling CS are probably not the same for all soybean genotypes. Information on the number of genes and their genomic location can be determined by molecular mapping of CS. A restriction fragment length polymorphism (RFLP) map was constructed from a soybean population of 111 F2-derived lines of a PI 97100 X Coker 237 cross. The purpose of this study was to identify and map the loci controlling CS in soybean. The F2-derived lines were grown at Athens, Georgia, and Blackville, South Carolina, in 1995, treated with chlorimuron ethyl, and scored for CS. The genetic map, involving 162 marker loci, covered about 1600 cM, with an average distance of 10.7 cM between two adjacent marker loci. In this population CS was conditioned by one major locus on the USDA linkage group (LG) E and one minor locus on an unknown linkage group at both locations as well as combined over locations. The most probable genomic location of the major locus was 2.8 cM from the RFLP locus cr168-1 on LG E. This locus explained as much as 88% of the variation in CS, whereas the minor locus explained about 11% of the variation. Thus, we have identified and located the single major locus along with a previously unknown minor locus for CS in soybean.

A long-juvenile (LJ) trait that delays powering under short-day conditions has been incorporated into adapted soybean [Glycine max CL.) Merr.] germplasm. Little is known about the performance of recently developed LJ cultivars and elite strains as influenced by planting systems typical of the southeastern USA. Therefore, a field study was undertaken using two LJ cultivars and four elite LJ Florida strains at Blackville and Pendleton, SC. Planting dates were early Gate April), normal Gate May), and late Gate June), in 1993 and 1994. The LJ genotypes exhibited neither genotype x planting date nor genotype x location interactions for seed yield or seed quality, indicating consistency of genotype performance across environments. Although variation among LJ genotypes for yield was not detected, all four elite strains all ranked higher in yield than the two cultivars. Maturity varied among LJ genotypes but seed yield did not, indicating the possibility of developing LJ genotypes that have relatively short life cycles and high seed yield. Additionally, LJ genotypes were compared with two conventional cultivars: Maturity Groups (MG) IV, V, and VI at early plantings; MG V, VI, and VII at normal plantings; and MG VI, VII, and Vm at late plantings. As planting date was delayed, growth and agronomic responses of LJ genotypes became similar to those of successively later conventional cultivars. The LJ genotypes were similar in yield to conventional cultivars in maturity groups V to VIII across planting dates, but had 56% higher yields than MG IV cultivars at the early planting. Seed quality ratings of LJ genotypes were 54 and 23% better than MG IV and V cultivars, respectively, at the early planting. In general, LJ genotypes showed superior photoperiodic adaptation to different planting date environments.

Crop ScienceVolume 37, Issue 6 cropsci1997.0011183X003700060062x p. 1983-1983 Registration of Cultivars Registration of ‘Dillon’ Soybean E. R. Shipe, Corresponding Author E. R. Shipe [email protected] Dep. of AgronomyCorresponding author ([email protected]).Search for more papers by this authorJ. D. Mueller, J. D. Mueller Dep. of Plant Pathology and Physiology, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorS. A. Lewis, S. A. Lewis Dep. of Plant Pathology and Physiology, Edisto Res. & Educ. Ctr., Blackville, SC, 29817Search for more papers by this authorP. F. Williams Jr., P. F. Williams Jr. Dep. of AgronomySearch for more papers by this authorJ. P. Tomkins, J. P. Tomkins Dep. of AgronomySearch for more papers by this author E. R. Shipe, Corresponding Author E. R. Shipe [email protected] Dep. of AgronomyCorresponding author ([email protected]).Search for more papers by this authorJ. D. Mueller, J. D. Mueller Dep. of Plant Pathology and Physiology, Clemson Univ., Clemson, SC, 29634Search for more papers by this authorS. A. Lewis, S. A. Lewis Dep. of Plant Pathology and Physiology, Edisto Res. & Educ. Ctr., Blackville, SC, 29817Search for more papers by this authorP. F. Williams Jr., P. F. Williams Jr. Dep. of AgronomySearch for more papers by this authorJ. P. Tomkins, J. P. Tomkins Dep. of AgronomySearch for more papers by this author First published: 01 November 1997 https://doi.org/10.2135/cropsci1997.0011183X003700060062xCitations: 23AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume37, Issue6November–December 1997Pages 1983-1983 RelatedInformation

The use of molecular markers to identify quantitative trait loci (QTLs) has the potential to enhance the efficiency of trait selection in plant breeding. The purpose of the present study was to identify additional QTLs for plant height, lodging, and maturity in a soybean, Glycine max (L.) Merr., population segregating for growth habit. In this study, 153 restriction fragment length polymorphisms (RFLP) and one morphological marker (Dt1) were used to identify QTLs associated with plant height, lodging, and maturity in 111 F2-derived lines from a cross of PI 97100 and 'Coker 237'. The F2-derived lines and two parents were grown at Athens, Ga., and Blackville, S.C., in 1994 and evaluated for phenotypic traits. The genetic linkage map of these 143 loci covered about 1600 cM and converged into 23 linkage groups. Eleven markers remained unlinked. Using interval-mapping analysis for linked markers and single-factor analysis of variance (ANOVA), loci were tested for association with phenotypic data taken at each location as well as mean values over the two locations. In the combined analysis over locations, the major locus associated with plant height was identified as Dt1 on linkage group (LG) L. The Dt1 locus was also associated with lodging. This locus explained 67.7% of the total variation for plant height, and 56.4% for lodging. In addition, two QTLs for plant height (K007 on LG H and A516b on LG N) and one QTL for lodging (cr517 on LG J) were identified. For maturity, two independent QTLs were identified in intervals between R051 and N100, and between B032 and CpTI, on LG K. These QTLs explained 31.2% and 26.2% of the total variation for maturity, respectively. The same QTLs were identified for all traits at each location. This consistency of QTLs may be related to a few QTLs with large effects conditioning plant height, lodging, and maturity in this population.

Seed weight (SW) is a component of soybean, Glycine max (L.) Merr., seed yield, as well as an important trait for food-type soybeans. Two soybean populations, 120 F4-derived lines of 'Young'xPI416937 (Pop1) and 111 F2-derived lines of PI97100x'Coker 237' (Pop2), were mapped with RFLP makers to identify quantitative trait loci (QTLs) conditioning SW across environments and populations. The genetic map of Pop1 consisted of 155 loci covering 973 cM, whereas Pop2 involved 153 loci and covered 1600 cM of map distance. For Pop1, the phenotypic data were collected from Plains, GA., Windblow, N.C., and Plymouth, N.C., in 1994. For Pop2, data were collected from Athens, GA., in 1994 and 1995, and Blackville, S.C., in 1995. Based on single-factor analysis of variance (ANOVA), seven and nine independent loci were associated with SW in Pop1 and Pop2, respectively. Together the loci explained 73% of the variability in SW in Pop1 and 74% in Pop2. Transgressive segregation occurred among the progeny in both populations. The marker loci associated with SW were highly consistent across environments and years. Two QTLs on linkage group (LG) F and K were located at similar genomic regions in both populations. The high consistency of QTLs across environments indicates that effective marker-assisted selection is feasible for soybean SW.

A long‐juvenile (LJ) trait that delays flowering has been incorporated into temperate soybean [Glycine max (L.) Merr.] genotypes for adaptation to short‐day conditions. Growth and agronomic effects of the LJ trait as influenced by maturity group are not well documented. A study was undertaken in which five LJ near‐isoline pairs in Maturity Groups IV, V, and VI were evaluated at early (late April), normal (late May), and late (late June) sowing dates near Pendleton, SC (34° N lat) in 1993 and 1994. Growth stages, plant morphology, and agronomic characteristics were determined. Extended periods of vegetative growth in response to the LJ trait resulted in one to three additional V‐stages and increased branch growth during the vegetative period. The LJ trait lengthened the period between flowering and pod set (R1 to R5) 38, 17, and 11% at early, normal, and late sowings, respectively, in Maturity Group IV isolines and shortened it 18 and 12% at early and normal sowings for Maturity Group VI isolines. The period of seed fill (R5 to RT) was unaffected by the LJ trait. The LJ trait influenced reproductive morphology and plant seed yield distribution with responses being affected by maturity group. Seed yield in response to the trait increased 43 and 16% at early and normal sowings in Maturity Group IV isolines and 22% at early sowings in the Maturity Group V isoline. Seed quality of LJ genotypes in Maturity Group IV isoline pairs was improved 49 and 35% at early and normal sowings. Our results indicate that maturity group influences growth and agronomic responses related to the LJ trait and that early maturing genotypes are more suited for its introgression to maximize potential benefits of the trait.

Molecular markers provide the opportunity to identify marker-quantitative trait locus (QTL) associations in different environments and populations. Two soybean [Glycine max (L.) Merr.] populations, ‘Young’ x PI 416 937 and PI 97100 x ‘Coker 237’, were evaluated with restriction fragment length polymorphism (RFLP) markers to identify additional QTLs related to seed protein and oil. For the Young x PI 416937 population, 120 F4-derived lines were secored for segregation at 155 RFLP loci. The F4-derived lines and two parents were grown at Plains, G.a., and Windblow and Plymouth, N.C. in 1994, and evaluated for seed protein and oil. For the PI 97100 x Coker 237 population, 111 F2-derived lines were evaluated for segregation at 153 RFLP loci. Phenotypic data for seed protein and oil were obtained in two different locations (Athens, G.a., and Blackville, S.C.) in 1994. Based on single-factor analysis of variance (ANOVA) for the Young x PI 416937 population, five of seven independent markers associated with seed protein, and all four independent markers associated with seed oil in the combined analysis over locations were detected at all three locations. For the PI 97 100 x Coker 237 population, both single-factor ANOVA and interval mapping were used to detect QTLs. Using single-factor ANOVA, three of four independent markers for seed protein and two of three independent markers for seed oil were detected at both locations. In both populations, singlefactor ANOVA, revealed the consistency of QTLs across locations, which might be due to the high heritability and the relatively few QTLs with large effects conditioning these traits. However, interval mapping of the PI 97100 x Coker 237 population indicated that QTLs identified at Athens for seed protein and oil were different from those at Blackville. This might result from the power of QTL mapping being dependent on the level of saturation of the genetic map. Increased seed protein was associated with decreased seed oil in the PI 97100 x Coker 237 population (r = −0.61). There were various common markers (P⩽0.05) on linkage groups (LG) E, G,H,K, and UNK2 identified for both seed protein and oil. One QTL on LG E was associated with seed protein in both populations. The other QTLs for protein and oil were population specific.

Crop ScienceVolume 35, Issue 1 cropsci1995.0011183X003500010058x p. 283-283 Registration of Cultivars Registration of ‘Maxcy’ Soybean E. R. Shipe, E. R. ShipeSearch for more papers by this authorJ. D. Mueller, J. D. MuellerSearch for more papers by this authorS. A. Lewis, S. A. LewisSearch for more papers by this authorP. F. Williams Jr., P. F. Williams Jr.Search for more papers by this author E. R. Shipe, E. R. ShipeSearch for more papers by this authorJ. D. Mueller, J. D. MuellerSearch for more papers by this authorS. A. Lewis, S. A. LewisSearch for more papers by this authorP. F. Williams Jr., P. F. Williams Jr.Search for more papers by this author First published: 01 January 1995 https://doi.org/10.2135/cropsci1995.0011183X003500010058xCitations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume35, Issue1January–February 1995Pages 283-283 RelatedInformation

Fields in a concentrated area of soybean production in South Carolina were chosen for soil sampling to determine the distribution of plant-parasitic nematodes. Five hundred sampling sites were distributed over 19 counties according to county soybean acreage. Helicotylenchus and Scutellonema were identified most frequently from soil samples; together, these genera occurred in over 70% of the samples. Pratylenchus and Paratrichodorus were each observed in more than 60% of fields. Meloidogyne spp. were found in 27% of the fields and Hoplolaimus columbus in 14%. Rotylenchulus reniformis and Belonolaimus sp. each occurred in less than 10% of the fields. Tylenchorhynchus and Mesocriconema (Criconemella) were each present in over 40% of the fields, but numbers from each field were low. Of the fields sampled, 14% contained Heterodera glycines. Of these, 47% were race 14 and 32% were race 3. Races 9, 6, and 10 were also observed.

Nematode losses in South Carolina soybeans are caused primarily by Southern root-knot, soybean cyst, Columbia lance, and reniform nematodes. Sting, lesion, and peanut root-knot nematodes also cause losses in some fields. Soybean is an excellent host for these nematode species and therefore often sustains significant yield losses. In a survey of 500 soybean fields in South Carolina more than 90% of the fields had one of the previously listed nematode species present. Almost a third of the fields had at least one nematode species at damaging levels.

A technique was developed to evaluate Heterodera glycines development in susceptible and resistant soybean. Roots of 3-day-old soybean were exposed to infective juveniles of H. glyci.nes in sand for 8 hours followed by washing and transfer to hydroponic culture. The cotyledons and apical meristem were removed and plants were maintained under constant light, which resulted in a dwarfed plant system. After 15 or 20 days at 27 C, nematodes were rated for development. Emerged males were sieved from the culture water and females were counted directly from the roots. Nematodes remaining in the roots were rated for development after staining and clearing the tissues. The proportion of nematodes at each stage of development and the frequency of completed molts for each stage were calculated from these data. This technique showed that resistance to H. glycines was stage related and did not affect males and females equally in all resistant hosts. The resistance of plant introduction PI 209332 primarily affected development of third and fourth-stage juveniles; 'Pickett' mainly affected second and third-stage juveniles, whereas PI 89772 affected all stages. Male development was markedly affected in PI 89772 and 'Pickett' but not in PI 209332.