Commercial Soybean Cultivars Research Articles

Genetic diversity of European commercial soybean [Glycine max (L.) Merr.] germplasm revealed by SSR markers

There are numerous soybean [Glycine max (L.) Merr.] breeding programs in Europe focused on development of elite non genetically modified (GM) cultivars for fast growing market of GM-free proteins for animal feed. Due to low variability of visual descriptors and mostly unknown pedigrees, divergent parents’ selection for crosses is a great challenge. Another challenge is cultivar distinction and protection of plant breeders’ rights of ever-increasing number of cultivars. By using 42 microsatellite (SSR) markers, we performed characterization of 97 commercial soybean cultivars and experimental lines developed at various research and breeding institutions in Europe (86) and in North and South America (11) in order to assess their genotype distinction power as well as utility for estimating genetic diversity and genetic structure. A set of 27 most polymorphic SSR markers was sufficient to discriminate all 97 genotypes. Discrimination of, by pedigree very related cultivars, was somewhat difficult due to the low polymorphism but still possible. Cluster analysis showed that European germplasm is mainly distributed into clusters reflecting breeding programs and maturity groups. Performed genetic characterization provides an insight into genetic structure of European soybean germplasm and might serve as a starting point for future breeding decisions. Disclosed SSR data of the analyzed commercial European germplasm can serve for genetic fingerprinting purpose as well as for foundation of public soybean cultivar database.

Somatic Embryogenesis and Plant Regeneration from Commercial Soybean Cultivars.

The efficient regeneration of plants from commercial genotypes is a pre-requisite for successful genetic transformation, to apply modern crop improvement techniques such as CRISPR-based genome editing. Plant regeneration through the somatic embryogenesis pathway offers an advantage over the organogenesis approach, avoiding the risk of developing chimeras. Plant genotype, explant type, and media compositions play an essential role in the in-vitro regeneration of plants. This study aimed to characterize the commercially grown Australian soybean genotypes for their potential to induce somatic embryos, embryo proliferation, maturation, germination, and plant regeneration. Overall, nine soybean cultivars belonging to different maturity groups were evaluated. Immature cotyledon ranging from 2–4 and 4–6 mm in size were used as explants for somatic embryogenesis induction. Maximum somatic embryo induction frequency (86%) was observed from 4–6 mm immature cotyledons of the cv. Jack (MG III), followed by 66%, 26%, 21%, and 6% in cultivars Williams (MG III), Snowy (MG III), MoonB1 (MG V), and PNR791 (MG V), respectively. On the other hand, cv. Snowy showed maximum somatic-embryo-inducing potential (67%) in 2–4 mm immature cotyledons followed by Williams, Jack, MoonB1, and PNR791. Somatic embryos from Jack, Williams, and Snowy cultivars were further tested for embryo proliferation, maturation, and germination. Maximum proliferation and maturation were observed in cv. Jack, followed by Snowy and Williams. However, cv. Snowy showed a significantly higher conversion of cotyledonary stage embryos to plantlets (85%), than both Jack and Williams cultivars (53% each). In conclusion, this study outlined a protocol for somatic embryogenesis and plant regeneration from three soybean cultivars. Our findings suggest commercial cv. Snowy could be a good candidate for developing transgenic plants through somatic embryogenesis.

Different soybean cultivars respond differentially to damage in a herbivore-specific manner and decreas herbivore performance

This study demonstrates that soybean cultivars respond differentially to damage in a herbivore-specific manner, and trigger responses decreasing herbivore performance. Soybean crops are affected by a great number of insect herbivores, resulting in devastating yield losses. Secondary metabolites like proteinase inhibitors and phenolic compounds are part of plants’ defense mechanisms against insect pests. However, the specificity of soybean defense responses to different attacking herbivores is poorly known. To investigate species-specific foliage responses to herbivory, we used two different commercial soybean cultivars (DM 4210 and DM 5.8i) widely used in Argentina with diverse susceptibility to insects’ attack and two species of phytophagous insects, thrips (Caliothrips phaseoli; Thysanoptera) and lepidopteran larvae (Spodoptera frugiperda; Lepidoptera) with a different way of feeding. Benzoic acid derivative levels were increased by damage of both insect species in the foliage of the field-grown soybean cultivars, whereas trypsin protease inhibitors activity was induced in cultivar (cv) DM 4210 by fall armyworm damage and malonyl genistein content in cv DM 5.8i after thrips’ attack. Although survivorship and mass of fall armyworm larvae were not differentially affected in field conditions by soybean cultivars, larvae reared in the laboratory that fed on cv DM 5.8i gained more mass than those on DM 4210. Conversely, thrips performance, natural colonization, and preference of feeding were higher on cv DM 4210 than on cv DM 5.8i. The differential effects of soybean cultivars on insectspecies’ performance were explained not only by induced defenses, but also by differences of constitutive defenses between cultivars. This study demonstrated that soybean cultivars responded differentially to damage in a herbivore-specific manner, and triggered responses decreased herbivore performance.

Enhanced resistance to sclerotinia stem rot in transgenic soybean that overexpresses a wheat oxalate oxidase.

Sclerotinia stem rot (SSR), caused by the oxalate-secreting necrotrophic fungal pathogen Sclerotinia sclerotiorum, is one of the devastating diseases that causes significant yield loss in soybean (Glycine max). Until now, effective control of the pathogen is greatly limited by a lack of strong resistance in available commercial soybean cultivars. In this study, transgenic soybean plants overexpressing an oxalic acid (OA)-degrading oxalate oxidase gene OXO from wheat were generated and evaluated for their resistance to S. sclerotiorum. Integration and expression of the transgene were confirmed by Southern and western blot analyses. As compared with non-transformed (NT) control plants, the transgenic lines with increased oxalate oxidase activity displayed significantly reduced lesion sizes, i.e., by 58.71-82.73% reduction of lesion length in a detached stem assay (T3 and T4 generations) and 76.67-82.0% reduction of lesion area in a detached leaf assay (T4 generation). The transgenic plants also showed increased tolerance to the externally applied OA (60mM) relative to the NT controls. Consecutive resistance evaluation further confirmed an enhanced and stable resistance to S. sclerotiorum in the T3 and T4 transgenic lines. Similarly, decreased OA content and increased hydrogen peroxide (H2O2) levels were also observed in the transgenic leaves after S. sclerotiorum inoculation. Quantitative real-time polymerase chain reaction analysis revealed that the expression level of OXO reached a peak at 1h and 4h after inoculation with S. sclerotiorum. In parallel, a significant up-regulation of the hypersensitive response-related genes GmNPR1-1, GmNPR1-2, GmSGT1, and GmRAR occurred, eventually induced by increased release of H2O2 at the infection sites. Interestingly, other defense-related genes such as salicylic acid-dependent genes (GmPR1, GmPR2, GmPR3, GmPR5, GmPR12 and GmPAL), and ethylene/jasmonic acid-dependent genes (GmAOS, GmPPO) also exhibited higher expression levels in the transgenic plants than in the NT controls. Our results demonstrated that overexpression of OXO enhances SSR resistance by degrading OA secreted by S. sclerotiorum and increasing H2O2 levels, and eliciting defense responses mediated by multiple signaling pathways.

Identification of quantitative trait loci for seed isoflavone concentration in soybean (Glycine max) against soybean cyst nematode stress

AbstractIsoflavones are plant secondary metabolites produced in soybean (Glycine max), which provide plant defense against pathogens and are beneficial to human health. Soybean cyst nematode (SCN) is a major yield‐limiting pest in most soybean‐producing area across the world. Traits, seed isoflavones and SCN resistance are quantitative in nature, and their phenotypic evaluations are expensive. Quantitative trait loci (QTL) underlying the two traits will be helpful to develop SCN‐resistant lines with elevated isoflavones using marker‐assisted‐selection (MAS). This study aims to identify isoflavones and SCN‐related QTL in a soybean population consisting of 109 RILs, which was developed from a cross between two commercial soybean cultivars viz. ‘RCAT1004’ and ‘DH4202’ and grown in four non‐SCN and SCN‐infested fields during 2015 and 2016. While single marker ANOVA identified 10 QTL for isoflavones and five for SCN (p < 0.01), simple interval and multiple QTL mappings identified four QTL associated with isoflavones (LOD ≥ 2.2). These results contribute to a better understanding of the genetics of the two traits and provide molecular markers that can be used in MAS to facilitate developing SCN‐resistant soybeans with increased isoflavones.

Evaluation of Commercial Soybean Cultivars for Reaction to Phomopsis Seed Decay.

Phomopsis seed decay (PSD), caused by Phomopsis longicolla (syn. Diaporthe longicolla), is an economically important soybean disease causing poor seed quality. Planting resistant cultivars is one of the most effective means to control PSD. In this study, 16 commercially available maturity groups IV and V soybean cultivars, including two previously identified PSD-resistant and two PSD-susceptible checks, were evaluated for seed infection by P. longicolla in inoculated and noninoculated plots, and harvested promptly or with a 2-week delay in harvest. The test was conducted at Stoneville, Mississippi, in 2012 and 2013. Seed infection by P. longicolla ranged from 0.5 to 76%, and seed germination ranged from 18 to 97%. One MG IV cultivar (Morsoy R2 491) and five MG V cultivars (Progeny 5650, Progeny 5706, Asgrow 5606, Asgrow 5831, and Dyna-Gro33C59) had significantly (P ≤ 0.05) lower percent seed infected by P. longicolla than their respective susceptible checks and other cultivars in the same tests. Information obtained from this study will be useful for soybean growers and breeders for selection of cultivars for planting or breeding and future genetic studies in the development of cultivars with improved resistance to PSD.

Development and Evaluation of Glycine max Germplasm Lines with Quantitative Resistance to Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot, is a devastating fungal pathogen of soybean that can cause significant yield losses to growers when environmental conditions are favorable for the disease. The development of resistant varieties has proven difficult. However, poor resistance in commercial cultivars can be improved through additional breeding efforts and understanding the genetic basis of resistance. The objective of this project was to develop soybean germplasm lines that have a high level of Sclerotinia stem rot resistance to be used directly as cultivars or in breeding programs as a source of improved Sclerotinia stem rot resistance. Sclerotinia stem rot-resistant soybean germplasm was developed by crossing two sources of resistance, W04-1002 and AxN-1-55, with lines exhibiting resistance to Heterodera glycines and Cadophora gregata in addition to favorable agronomic traits. Following greenhouse evaluations of 1,076 inbred lines derived from these crosses, 31 lines were evaluated for resistance in field tests during the 2014 field season. Subsequently, 11 Sclerotinia stem rot resistant breeding lines were moved forward for field evaluation in 2015, and seven elite breeding lines were selected and evaluated in the 2016 field season. To better understand resistance mechanisms, a marker analysis was conducted to identify quantitative trait loci linked to resistance. Thirteen markers associated with Sclerotinia stem rot resistance were identified on chromosomes 15, 16, 17, 18, and 19. Our markers confirm previously reported chromosomal regions associated with Sclerotinia stem rot resistance as well as a novel region of chromosome 16. The seven elite germplasm lines were also re-evaluated within a greenhouse setting using a cut petiole technique with multiple S. sclerotiorum isolates to test the durability of physiological resistance of the lines in a controlled environment. This work presents a novel and comprehensive classical breeding method for selecting lines with physiological resistance to Sclerotinia stem rot and a range of agronomic traits. In these studies, we identify four germplasm lines; 91–38, 51–23, SSR51–70, and 52–82B exhibiting a high level of Sclerotinia stem rot resistance combined with desirable agronomic traits, including high protein and oil contents. The germplasm identified in this study will serve as a valuable source of physiological resistance to Sclerotinia stem rot that could be improved through further breeding to generate high-yielding commercial soybean cultivars.

The endogenous transposable element Tgm9 is suitable for generating knockout mutants for functional analyses of soybean genes and genetic improvement in soybean.

In soybean, variegated flowers can be caused by somatic excision of the CACTA-type transposable element Tgm9 from Intron 2 of the DFR2 gene encoding dihydroflavonol-4-reductase of the anthocyanin pigment biosynthetic pathway. DFR2 was mapped to the W4 locus, where the allele containing Tgm9 was termed w4-m. In this study we have demonstrated that previously identified morphological mutants (three chlorophyll deficient mutants, one male sterile-female fertile mutant, and three partial female sterile mutants) were caused by insertion of Tgm9 following its excision from DFR2. Analyses of Tgm9 insertion sites among 105 independent mutants demonstrated that Tgm9 hops to all 20 soybean chromosomes from its original location on Chromosome 17. Some genomic regions are prone to increased Tgm9-insertions. Tgm9 transposed over 25% of the time into exon or intron sequences. Tgm9 is therefore suitable for generating an indexed insertional mutant collection for functional analyses of most soybean genes. Furthermore, desirable Tgm9-induced stable knockout mutants can be utilized in generating improved traits for commercial soybean cultivars.

Legume biotechnology: towards development of a genetic transformation system for commercial cultivars of soybean (Glycine maxL.)

Legume biotechnology: towards development of a genetic transformation system for commercial cultivars of soybean (<i>Glycine max</i>L.)

In Vitro Plant Regeneration from Commercial Cultivars of Soybean.

Soybean, a major legume crop, is the source of vegetable oil and protein. There is a need for transgenic approaches to breeding superior soybean varieties to meet future climate challenges. Efficient plant regeneration is a prerequisite for successful application of genetic transformation technology. Soybean cultivars are classified into different maturity groups based on photoperiod requirements. In this study, nine soybean varieties belonging to different maturity group were regenerated successfully from three different explants: half split hypocotyl, complete hypocotyl, and cotyledonary node. All the genotypes and explant types responded by producing adventitious shoots. Shoot induction potential ranged within 60–87%, 50–100%, and 75–100%, and regeneration rate ranged within 4.2–10, 2.7–4.2, and 2.6–10.5 shoots per explant using half split hypocotyl, complete hypocotyl, and cotyledonary explants, respectively, among all the tested genotypes. Bunya variety showed the best regeneration response using half split and complete hypocotyl explants and the PNR791 with cotyledonary node. The regenerated shoots were successfully rooted and acclimatized to glasshouse conditions. This study shows that commercial varieties of soybean are amenable to shoot regeneration with high regeneration frequencies and could be exploited for genetic transformation. Further, our results show no correlation between shoots regeneration capacity with the maturity grouping of the soybean cultivars tested.

Exogenous application of methyl jasmonate induces defence against Meloidogyne hapla in soybean

Phytohormones play important roles in plant defence against plant-parasitic nematodes, although the role of jasmonate (JA) in defence against root-knot nematodes (RKN, Meloidogyne spp.) in soybean (Glycine max) was unknown. In this study, two commercial soybean cultivars, cvs DongSheng1 (DS1) and SuiNong14 (SN14), were identified as susceptible and resistant, respectively, to M. hapla. Quantitative reverse transcription (qRT)-PCR analysis showed that the expression of genes involved in JA synthesis or signalling was significantly induced in both susceptible and resistant roots at 24 and 48 h after inoculation. Exogenous application of methyl jasmonate induced defence against RKN in susceptible cv. DS1, which might be involved in altered activities of defence-related enzymes (chitinase and β-1,3 glucanase) and pathogenesis-related gene PR5 expression. The results indicate that exogenous application of JA might be an alternative strategy to induce soybean resistance against RKN.

Assessment of Commercial Soybean Cultivars for Resistance Against Prevalent Heterodera glycines Populations of South Dakota

Soybean cyst nematode (SCN; Heterodera glycines) is the most important yield limiting factor of soybean production in South Dakota and the main management practice is planting SCN-resistant cultivars. The effectiveness of host resistance is often limited by the diversity of SCN populations that can reproduce on resistant varieties. A greenhouse study was set up to determine the response of SCN-resistant commercial soybean cultivars with PI 88788 as the source of SCN resistance genes to the three commonly found SCN H. glycines (HG) types in South Dakota. To screen the soybean cultivars, 3,000 SCN eggs and juveniles of the prevalent HG types 0, 2.5.7, and 7 were each inoculated to 34 commercial soybean cultivars and also a susceptible cultivar, Williams 82, as the control. The female index (FI) was calculated based on the average number of females (cysts) found on each cultivar relative to the susceptible check after 35 days. Cultivars showed a varied response to HG types with all 34 cultivars showing resistance or moderate resistance to HG 0. Less than 9% of the cultivars tested had resistance response and between 82 to 88% had moderate resistance response to both HG 7 and 2.5.7 types. Only one cultivar was rated as susceptible to both HG 7 and 2.5.7. These results indicate that host resistance is still effective in managing SCN in South Dakota. However, use of these cultivars should be combined with crop rotation and rotation within soybean cultivars derived from different resistance sources for sustainable SCN management.

Natural resistance of soybean cultivars to the soybean looper larva Chrysodeixis includens (Lepidoptera: Noctuidae)

Abstract: The objective of this work was to evaluate the natural resistance of soybean cultivars to Chrysodeixis includens. For this, four commercial soybean cultivars recommended for the Southern region of Brazil were used: BR 36, NA 5909 RG, BMX Turbo RR, and Benso 1RR. In the laboratory, larvae were subjected to the antixenosis feeding assay, in which they were free or not to choose among old leaves, new leaves, and pods. Neonate larvae were subjected to two antibiosis tests: in the first one, they were fed with leaves from the middle third of the plants of the four cultivars; and, in the second one, with leaves or pods of the NA 5909 RG cultivar. Chrysodeixis includens larvae prefer leaves over pods and old leaves over new ones. The Benso 1RR cultivar extends the development cycle of C.includens, but only BMX Turbo RR will reduce the population growth of larvae in the next generations.

Adaptability and stability of soybean cultivars for grain yield and seed quality.

This study aimed at verifying the adaptability and stability of soybean cultivars, considering the grain yield and quality of seeds, adopting univariate and multivariate approaches. The experiments were conducted in two crops, three environments, in 2013/2014 and 2014/2015 crop seasons, in the county of Inconfidentes, Lavras, and Patos de Minas, in the Minas Gerais State, Brazil. We evaluated 17 commercial soybean cultivars. For adaptability and stability evaluations, the Graphic and GGE biplot methods were employed. Previously, a selection index was estimated based on the sum of the standardized variables (Z index). The data relative to grain yield, mass of one thousand grain, uniformity test (sieve retention), and germination test were standardized (Zij) per cultivar. With the sum of Zij, we obtained the selection index for the four traits evaluated together. In the Graphic method evaluation, cultivars NA 7200 RR and CD 2737 RR presented the highest values for selection index Z. By the GGE biplot method, we verified that cultivar NA 7200 RR presented greater stability in both univariate evaluations, for grain yield, and for selection index Z.

Trends of Soybean Yields under Climate Change Scenarios

Soybean is a very important crop, cultivated mainly as stock feed for animal production, but also for other uses such as biodiesel. Brazil is the second largest producer of soybeans, and the main exporter. About 10% of total Brazilian production is aimed for biodiesel production. The aim of this work was to assess the impact of climate change scenarios on soybean yield and evaluate two simple adaptation strategies: cultivar and planting date. Tests were done for soil profiles from two important producing regions: Chapecó-Red Oxisol, and Passo Fundo-Rodic Hapludox. Two commercial soybean cultivars (CD202 and CD204) and seven regional circulation models (RCM) were used. All simulations were done with DSSAT. After model calibration, eleven planting dates were run for two periods (2011–2040 and 2071–2100) using the RCM’s. There were no differences between cultivars. For Chapecó, the majority of RCM’s projected yield reductions, with few RCM’s projecting increments, and for only few planting dates (November). The response pattern for both time periods were identical, although the end-of-century period presented a further yield reduction. The main reason was reduced water holding capacity in soil, high temperatures, and changes in rainfall distribution along the cropping season. For Passo Fundo, 2011–2040 yields were distinct, depending on the RCM. Simulated yields tended to follow the actual yield pattern along the different planting dates, besides discrepancies. For 2071–2100, all but one RCM indicated yields equal or lower to actual levels. Regarding planting dates, no significant changes were identified, although reductions were observed for the early planting dates (August–September). The scenarios suggest that soybean yields will be reduced, jeopardizing the viability of this crop and biodiesel production in the studied regions.

English

The relationship between seed vigor test and seedling emergence is crucial to predict easily the seed performance under field conditions and the seed producers continuously explore the best vigor test to enhance stand establishment. This study was conducted to determine the suitable seed vigor test and mineral element in the seed to predict accurately the field performance of soybean. Fifty seed lots of 22 commercial soybean cultivars were assessed for seedling emergence under field conditions and germination, emergence, cool and cold tests, electrical conductivity (EC) and pH for 4, 8 and 24 h, accelerated ageing (AA) at 41, 43 and 45°C for 48, 72, 96, 120 and 144 h in the laboratory. Initial seed weight, oil, protein, P, K, Ca, Fe, Mn and Zn concentration in seed lots were also investigated. Their results were correlated with field emergence percentage of seed lots to detect the most suitable indicator for vigorous seed lot. The germination percentage varied from 56% to 100%, while the field emergence percentage ranged between 0% and 84%. No significant correlation was noticed between field emergence and seed weight, oil and protein contents. AA test at 41°C for 72 h gave the highest significantly positive correlation with r=0.831**, but the highest significant and negative correlation coefficient (r=-0.801**) with field emergence percentage were observed in EC test for 24 h. Only Mn concentration of six elements investigated was significantly correlated with field emergence (r=-0.376*). It was concluded that the AA condition of 72 h at 41°C are recommended as an ideal seed vigor test to estimate closely field emergence performance of soybean seeds. © 2016 Friends Science Publishers

In Vitro Regeneration Potential of Seven Commercial Soybean Cultivars (Glycine max L.) for Use in Biotechnology

Abstract This work is aimed to evaluate in vitro regeneration potential of seven commercial soybean varieties Bohemians, Cardiff, Gallec, Merlin, Moravians, Naya and Silensia (Glycine max L.) cultivated in Central Europe. Our results showed the half-seeds could be effectively used as an explant source for all tested cultivars. The regeneration was initiated on the media containing growth regulators 1.67 mg.l-1 BAP and 0.25 mg.l-1 GA3. Within the first five days culture, green chlorophyll-containing explants were observed with frequency from 18.3% to 55.9%. Two weeks later, the explants responded by production of calli with the efficiency up to 83.0%. First shoots appeared after 2–3 weeks of subculture on the media. The soybean regeneration showed to be genotype-dependent with variable efficiencies from 5.7% (cv. Naya) to 37.7% (cv. Gallec). The cultivars Cardiff, Merlin and Gallec appear to be the most promising candidates for further biotechnological use. Application of antioxidants such as L-cysteine, dithiothreitol and sodium thiosulfate does not have effect on the explant regeneration for the first five days.

A pigeonpea gene confers resistance to Asian soybean rust in soybean.

Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most economically important crop diseases, but is only treatable with fungicides, which are becoming less effective owing to the emergence of fungicide resistance. There are no commercial soybean cultivars with durable resistance to P. pachyrhizi, and although soybean resistance loci have been mapped, no resistance genes have been cloned. We report the cloning of a P. pachyrhizi resistance gene CcRpp1 (Cajanus cajan Resistance against Phakopsora pachyrhizi 1) from pigeonpea (Cajanus cajan) and show that CcRpp1 confers full resistance to P. pachyrhizi in soybean. Our findings show that legume species related to soybean such as pigeonpea, cowpea, common bean and others could provide a valuable and diverse pool of resistance traits for crop improvement.

Glycone-rich Soy Isoflavone Extracts Promote Estrogen Receptor Positive Breast Cancer Cell Growth

ABSTRACTDue to the association of hormone replacement therapy (HRT) with breast cancer risk, estrogenically active soy isoflavones are considered as an HRT alternative to alleviate menopausal symptoms. However, several recent reports challenged the health benefits of soy isoflavones and associated them with breast cancer promotion. While glyconic isoflavones are the major constituents of soybean seeds, due to their low cell permeability, they are considered to be biologically inactive. The glyconic isoflavones may exert their effects on membrane-bound estrogen receptors or could be converted to aglycones by extracellular β-glucosidases. Therefore, we hypothesized that despite their low cell permeability, soybean cultivars with high glyconic isoflavones may promote breast cancer cell growth. To test this, composition and estrogenic activity of isoflavones from 54 commercial soybean cultivars were determined. Soybean seeds produced in identical climate and growth conditions were used to minimize the effects of extraneous factors on isoflavone profile and concentrations. The glyconic daidzin concentration negatively correlated with genistin and with other aglycones. Relative to control, isoflavone extracts from 51 cultivars were estrogenic and promoted the growth of estrogen receptor positive (ER+) breast cancer cell line MCF-7 from 1.14 to 4.59 folds and other three cultivars slightly reduced the growth. Among these, extracts from three cultivars were highly estrogenic and promoted MCF-7 cell growth by 2.59–4.64 folds (P<0.005). Among six isoflavones, daidzin was positively associated with MCF-7 cell growth (P<0.005, r = 0.13966), whereas the negative correlation between genistin and MCF-7 cell growth was nearly significant (P≤0.0562, r = −0.026141). Furthermore, in drug interaction studies daidzin-rich isoflavone extracts antagonized tamoxifen, an ER inhibitor. Taken together, our results suggest that the glyconic daidzin-rich soy isoflavone extracts may exert estrogenic effects and promote ER+ breast cancer growth.

Host Plant Resistance to Megacopta cribraria (Hemiptera: Plataspidae) in Diverse Soybean Germplasm Maturity Groups V Through VIII.

Initially discovered in Georgia in 2009, the exotic invasive plataspid, Megacopta cribraria (F.), has become a serious pest of soybean ( Glycine max (L.) Merrill). Managing M. cribraria in soybean typically involves the application of broad-spectrum insecticides. Soybean host plant resistance is an attractive alternative approach; however, no commercial soybean cultivars have been identified as resistant. During 2013 and 2014, we compared 40 and 44 soybean genotypes, respectively, for resistance to M. cribraria in a split-plot design under natural insect infestation in small-plot experiments. Soybean genotypes were selected to maximize diversity with respect to maturity group, pubescence type, leaf shape, seed size, nitrogen fixation, drought tolerance, seed protein content, and pest resistance. Megacopta cribraria egg masses, nymphs, and adults were counted during the growing season to identify potentially resistant soybean genotypes. Soybean seed yield was measured in insecticide-protected and unprotected conditions to determine tolerance to M. cribraria feeding. In both years, a range of host plant resistance was observed. The fewest M. cribraria adults and nymphs were found on narrow-leaf, small-seeded cultivars 'N7103' and 'Vance,' as well as the nonnodulating cultivar 'Nitrasoy.' Additionally, N7103 and Vance were among the least susceptible genotypes to M. cribraria oviposition in the field. Most 'Benning' cultivar insect-resistant near-isogenic breeding lines also displayed moderate levels of resistance to M. cribraria . Seed yields of Vance and N7103 were less affected by M. cribraria in 2013 than most other soybean genotypes. These results may be useful to soybean breeders to develop cultivars with resistance to M. cribraria.