Soybean Flowering Research Articles

Functional Redundancy of FLOWERING LOCUS T 3b in Soybean Flowering Time Regulation.

Photoperiodic flowering is an important agronomic trait that determines adaptability and yield in soybean and is strongly influenced by FLOWERING LOCUS T (FT) genes. Due to the presence of multiple FT homologs in the genome, their functions in soybean are not fully understood. Here, we show that GmFT3b exhibits functional redundancy in regulating soybean photoperiodic flowering. Bioinformatic analysis revealed that GmFT3b is a typical floral inducer FT homolog and that the protein is localized to the nucleus. Moreover, GmFT3b expression was induced by photoperiod and circadian rhythm and was more responsive to long-day (LD) conditions. We generated a homozygous ft3b knockout and three GmFT3b-overexpressing soybean lines for evaluation under different photoperiods. There were no significant differences in flowering time between the wild-type, the GmFT3b overexpressors, and the ft3b knockouts under natural long-day, short-day, or LD conditions. Although the downstream flowering-related genes GmFUL1 (a, b), GmAP1d, and GmLFY1 were slightly down-regulated in ft3b plants, the floral inducers GmFT5a and GmFT5b were highly expressed, indicating potential compensation for the loss of GmFT3b. We suggest that GmFT3b acts redundantly in flowering time regulation and may be compensated by other FT homologs in soybean.

Evaluating the impact of increased pollinator habitat on bee visitation and yield metrics in soybean crops

Agricultural intensification has significantly altered ecosystem functioning and aided in the reduction of global biodiversity. While agriculture requires increased reliance on animal pollination, pollinator populations have declined. To combat this, adding pollinator habitat into agricultural landscapes is increasingly common, but many questions remain about its functionality and impact on agroecosystems, particularly in pollinator-independent crops. Our study uses pollinator habitats planted on experimental research stations in the southeastern USA to evaluate their impact on pollinator communities within a nearby cropping system (soybeans) and the resulting yield. We found the species composition of pollinator communities within the habitat to be significantly different than the communities in soybeans. Even still, we identified more than 30 bee species visiting soybean flowers and verified that a subset of these species had actively collected soybean pollen. Bees from soybean fields planted adjacent to the habitat had more habitat pollen types present, while some species had more non-habitat types present when in the negative control sites. The presence of habitat had a positive effect on some yield measurements with adjacent soybean sites having 6.52% heavier seeds per plant on average. These findings demonstrate that pollinator habitat can be an important resource for supporting pollinators and highlights the importance of considering pollinator habitat in pollinator-independent crops, as they may still benefit from and be attractive to pollinator communities.

Response of carbon, nitrogen and phosphorus concentration and stoichiometry of plants and soils during a soybean growth season to O3 stress and straw return in Northeast China

Carbon (C), nitrogen (N) and phosphorus (P) concentrations and stoichiometry play important roles in biogeochemical cycles of the ecosystems, yet it is still unclear how the allocations of C, N and P concentrations and stoichiometry among plant organs and soils related to O3 stress and straw return. Here, a pot experiment was conducted in open top chambers to monitor the response of C, N and P concentrations and stoichiometry of leaves, stems, roots and soils during a growing season (branching, flowering and podding stages) of soybean (Glycine max; a species highly sensitive to O3) to background O3 concentration (44.8 ± 5.6 ppb), O3 stress (79.7 ± 5.4 ppb) and straw treatment (no straw return and straw return). O3 stress significantly decreased root biomass. Straw return significantly increased root biomass under O3 stress at branching and flowering stages. Generally, O3 stress and straw return showed significant effects on the C, N and P concentrations of leaves and soils, and stoichiometric ratios of leaves, stems and microbial biomass. The C, N and P concentrations and stoichiometry of leaves, stems, roots and soils in response to O3 stress and straw return at the branching stage were inconsistent with the changes observed at the flowering and podding stages. The P conversion efficiency showed significant relationship with root P concentration under the combined effects of O3 stress and straw return. Altogether, the present study indicated that C, N and P concentrations of soybean might be more important than stoichiometric ratios as a driver of root defence against O3 stress in the case of straw return.

Transcriptome Profile of a Long-Juvenile Soybean Genotype Huaxia-3 Under Short and Long Photoperiod

The j allele delays flowering and enhances yield of long juvenile (LJ) soybean under short day (SD) condition. However, the underlying mechanism of j in flowering pathway of soybean is not fully known. The objective of the study is to profile the transcriptome of Huaxia-3 (HX3), a typical long juvenile soybean variety with a loss of function allele (j) for the J gene. This helps to identify the genes implicated in delayed flowering in the long juvenile soybean variety and the pathways involved. Phenotypic analysis revealed HX3-delayed flowering and matured later than the transgenic line with the functional J gene under SD. RNA-Seq analysis was conducted to compare the transcriptome of HX3 relative to the one overexpressing J gene under SD and long day (LD). A total of 674,800,494 clean reads were generated, of which 626,517,161 (93%) were uniquely mapped to the soybean reference genome. A total of 31 and 2311 genes were differentially expressed in the HX3 under SD and LD conditions respectively. The circadian rhythm pathway was the most significantly enriched pathway in the HX3 under SD condition. The GmELF3a (Glyma.04G050200) and FLOWERING LOCUS T (FT) genes such as GmFT2a (Glyma.16G150700) and GmFT5a (Glyma.16G044100) were downregulated, whiles GmFT4 (Glyma.08G363100) was upregulated in the HX3 under SD. Under LD FT homologs, GmFT4 (Glyma.08G363100) was downregulated and GmFT1a (Glyma.18G299000) was upregulated. Our study suggests that these FT homologs may be involved in delayed flowering of LJ soybean under SD.

Agronomic Performances of Compost Associated with Pollinating Insects on the Growth and Yield of <i>Glycine max</i> (L.) Merril under Field Conditions

Soybean is an oilseed crop legume cultivated for its benefits as a source of protein to human or animal food. The cultivation of soybean will promote the diversification of income sources for rural population. Like other crops, soybean flowers are visited by insects. It is expected that within the biodiversity conservation program, anthophilous insects including bees, generally increase fruit and seed yields of many plant species. Therefore, the effect of insect pollinators and compost on growth and yield parameters of Glycine max was assessed for two cropping seasons (2018 and 2019) in the field. The experiment was set up in a complete randomized block design with three treatments: subplots applied with compost; subplots applied with fertilizer-NPK; subplots applied neither with compost, nor with fertilizer-NPK. Two other treatments were designed by plants with flowers protected against insects or flowers pollination free. Results indicate that root nodules formed by soybean plants in plots that received compost were significantly higher (P G. max flowers respectively. Lipotriches collaris was the most insect species frequently observed in the field, with 44.20% and 43.34% visits yearly respectively. The synergistic effect of insects and compost increased the number of seeds per pod by 28.27% and the percentage of normal seeds by 24.47%. Hence, applying Glycine max seeds at sowing with compost and in an environment with hives close to field could be recommended in agricultural development programs of farmers for a sustainable improvement of pods and seed yield of this valuable crop.

Effect of Foliar Application of Liquid Biofertilizer of Buffalo Dung and Gram Bran with Combinations of Biopesticides on the Growth, Flowering and Productivity of Soybean (Glycine max L.) Crop

Excessive use of chemical fertilizers and pesticides in agricultural field for the huge production of agricultural products causes adverse effect on environment as well as on human health. Animal dungs and agricultural wastes are serious problem for society so it needs to be managed properly. Vermicomposting is the best process for the management of these wastes with the help of earthworm Eisenia fetida and the by-products released from these vermicompost are used in enhancing the agricultural productivity. Soybean (Glycine max L.) is a short season leguminous crop which has been recognised as pulse-oil seed. It is a highly nutritive crop which contains 43% of protein and 20% of oil approximately but due to various reasons its production rate is decreasing day by day. The vermiwash and neem, garlic and tobacco based biopesticides are being used as an alternative for chemical fertilizers and pesticides. The aim of present study was to observe the growth, flowering and productivity of soybean plant after foliar spray of vermiwash obtained from gram bran (GB) and buffalo dung (BD) with combinations of aqueous extracts of garlic, neem and tobacco leaves. The significant growth (cm) and productivity (g/m2) were observed after the foliar spray of vermiwash (GB+BD) and aqueous extracts of biopesticides (garlic, neem and tobacco leaves). The highest growth of soybean (49.2±2.6 cm) was observed after foliar application of vermiwash (GB+BD) with aqueous extract of neem leaves in ratio of 10:1 whereas, the maximum significant early flowering period (32.3±2.5 days) and productivity (423±14 g/m2) were obtained after treatment of vermiwash (GB+BD) with aqueous extract of neem, garlic and tobacco leaves in ratio of 10:1:1:1. The use of vermiwash with biopesticides in increasing agricultural product is a boon for crops as it is environmentally beneficial and costeffective alternative to chemical fertilizers and synthetic pesticides.

Flowering process in soybean under water deficit conditions: A review on genetic aspects.

Soybean is a key crop in many countries, being used from human food to the animal industry due to its nutritional properties. Financially, the grain chain moves large sums of money into the economy of producing countries. However, like other agricultural commodities around the world, it can have its final yield seriously compromised by abiotic environmental stressors, like drought. As flowers imply in pods and in grains inside it to minimize damages caused by water restriction, researchers have focused on understanding flowering-process related genes and their interactions. Here a review dedicated to the soybean flowering process and gene network involved in it is presented, describing gene interactions and how genes act in this complex mechanism, also ruled by environmental triggers such as day-light and circadian cycle. The objective was to gather information and insights on the soybean flowering process, aiming to provide knowledge useful to assist in the development of drought-tolerant soybean lines, minimizing losses due to delays or anticipation of flowering and, consequently, restraining financial and productivity losses.

Monitoring of photosynthetic activity indicators and its use to control the moisture supply of soybean crops

The paper presents the results of diagnostics of photosynthetic activity in soybean crops using the use of unmanned aircraft. Monitoring was carried out in two stages during the period of intensive growth of the green mass of crops before the onset of the soybean flowering phase in the agro-climatic conditions of the Central region of the Non-Chernozem zone of the Russian Federation. The purpose of the research: to study the possibilities of using unmanned aerial vehicles to control the photosynthetic activity of soybean plants and predict potential yields. For each of the varieties, the composition of photosynthetic pigments in the leaves of soybean plants, the average values of the clGreen vegetation index and the standard deviation in phases V2 – the second node and R2 – full flowering were determined. Forecast yield values were calculated based on the regression equation. The data obtained were evaluated using MAPE, the prediction accuracy was 92.4–97.3%.

Dependence of soybeans (Glycine Max Merril) to entomophile pollination and study of food resources of honey bees (Apis Mellifera L.) in contact with the crop

South America suffered strong modifications during the last decade due to the increase in anthropic activities and the expansion of agricultural areas, particularly soybeans, interacting with traditional productions such as Beekeeping. The objective of this research was to know the dependence of two soybean varieties on entomophilic pollination by means of meshing and to reveal the diversity of insects in contact with the crop, especially determining the interaction of the honeybee with it. In addition, a sample of bees was carried out in different areas of the country to compare the diversity of species between areas with anthropic management during 2015–2016 and 2016–2017. Specimens were collected and classified according to taxonomic keys. The main results: 1- Forty-five species of bees or taxa belonging to the subfamilies Megachilinae (11), Apinae (22), Halictinae (7), Colletinae (2) and Andreninae (3) were distinguished in the southern region of Uruguay and 6 of them were in contact with the crop. 2- The diversity of bees was greater for the southern region, with traditional agriculture and pastures, than that of the low-lying coastal region where an increasing use of agricultural land took place during the last decade, especially soybeans. 3 - At least two species of native bees use soy as a plant resource to make their nests. 4- Honey bees use soybeans as a source of pollen and nectar, but the flowers on the edge of the crop provide pollen and nectar that compete with soybeans. 5- Soy shows a different degree of dependence on insects to form seeds related to the amount of exchangeable K in the soil. 6- The edges of the crop are important to provide food and shelter for pollinators. This study addresses the interaction between soybeans, native bees and honeybees, showing the points of contact between them. In addition, complementary data are obtained on biotic and nutrient agents that intervene in the flowering of Soybeans, helping to think about strategies for coexistence of items.

Genome-wide identification of PME genes, evolution and expression analyses in soybean (Glycine max L.)

BackgroundPectin methylesterase (PME) is one of pectin-modifying enzyme that affects the pectin homeostasis in cell wall and regulates plant growth and diverse biological processes. The PME genes have been well explored and characterized in different plants. Nevertheless, systematic research on the soybean (Glycine max L.) PME genes remain lacking.ResultsWe identified 127 Glycine max PME genes (GmPME) from the soybean Wm82.a2.v1 genome, which unevenly distributed on 20 soybean chromosomes. Phylogenetic analysis classified the GmPME genes into four clades (Group I, Group II, Group III and Group IV). GmPME gene members in the same clades displayed similar gene structures and motif patterns. The gene family expansion analysis demonstrated that segmental duplication was the major driving force to acquire novel GmPME genes compared to the tandem duplication events. Further synteny and evolution analyses showed that the GmPME gene family experienced strong purifying selective pressures during evolution. The cis-element analyses together with the expression patterns of the GmPME genes in various tissues suggested that the GmPME genes broadly participate in distinct biological processes and regulate soybean developments. Importantly, based on the transcriptome data and quantitative RT-PCR validations, we examined the potential roles of the GmPME genes in regulating soybean flower bud development and seed germination.ConclusionIn conclusion, we provided a comprehensive characterization of the PME genes in soybean, and our work laid a foundation for the functional study of GmPME genes in the future.

Integrated Bioinformatics Analyses of PIN1, CKX, and Yield-Related Genes Reveals the Molecular Mechanisms for the Difference of Seed Number Per Pod Between Soybean and Cowpea.

There is limited advancement on seed number per pod (SNPP) in soybean breeding, resulting in low yield in China. To address this issue, we identified PIN1 and CKX gene families that regulate SNPP in Arabidopsis, analyzed the differences of auxin and cytokinin pathways, and constructed interaction networks on PIN1, CKX, and yield-related genes in soybean and cowpea. First, the relative expression level (REL) of PIN1 and the plasma membrane localization and phosphorylation levels of PIN1 protein were less in soybean than in cowpea, which make auxin transport efficiency lower in soybean, and its two interacted proteins might be involved in serine hydrolysis, so soybean has lower SNPP than cowpea. Then, the CKX gene family, along with its positive regulatory factor ROCK1, had higher REL and less miRNA regulation in soybean flowers than in cowpea ones. These lead to higher cytokinin degradation level, which further reduces the REL of PIN1 and decreases soybean SNPP. We found that VuACX4 had much higher REL than GmACX4, although the two genes essential in embryo development interact with the CKX gene family. Next, a tandem duplication experienced by legumes led to the differentiation of CKX3 into CKX3a and CKX3b, in which CKX3a is a key gene affecting ovule number. Finally, in the yield-related gene networks, three cowpea CBP genes had higher RELs than two soybean CBP genes, low RELs of three soybean-specific IPT genes might lead to a decrease in cytokinin synthesis, and some negative and positive SNPP regulation were found, respectively, in soybean and cowpea. These networks may explain the SNPP difference in the two crops. We deduced that ckx3a or ckx3a ckx6 ckx7 mutants, interfering CYP88A, and over-expressed DELLA increase SNPP in soybean. This study reveals the molecular mechanism for the SNPP difference in the two crops, and provides an important idea for increasing soybean yield.

The legume-specific transcription factor E1 controls leaf morphology in soybean

BackgroundThe leaf is a determinate organ essential for photosynthesis, whose size and shape determine plant architecture and strongly affect agronomic traits. In soybean, the molecular mechanism of leaf development is not well understood. The flowering repressor gene E1, which encodes a legume-specific B3-like protein, is known to be the gene with the largest influence on soybean flowering and maturity. However, knowledge of its potential other functions remains poor.ResultsHere, we identified a novel function of E1 protein in leaf development. Unifoliolate leaves of E1-overexpression (E1-OE) lines were smaller and curlier than those of wild type DongNong 50 (DN50) and Williams 82 (W82). Transverse histological sections showed disorganized cells and significantly elevated palisade tissue number, spongy tissue number, and bulliform cell number in E1-OE lines. Our results indicate that E1 binds to the promoters of the leaf- development-related CINCINNATA (CIN)-like TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factor genes to negatively regulate their expression.ConclusionsOur findings identify E1 as an important new factor in soybean leaf development.

Development of a marker panel for genotyping of domestic soybean cultivars for genes controlling the duration of vegetation and response to photoperiod.

Soybean, Glycine max L., is one of the most important agricultural crops grown in a wide range of latitude. In this regard, in soybean breeding, it is necessary to pay attention to the set of genes that control the transition to the f lowering stage, which will make it possible to adapt genotypes to local growing conditions as accurately as possible. The possibilities of soybean breeding for this trait have now signif icantly expanded due to identif ication of the main genes (E1–E4, GmFT2a, GmFT5a) that control the processes of f lowering and maturation in soybean, depending on the day length. The aim of this work was to develop a panel of markers for these genes, which could be used for a rapid and eff icient genotyping of domestic soybean cultivars and selection of plant material based on sensitivity to photoperiod and the duration of vegetation. Combinations of 10 primers, both previously developed and our own, were tested to identify different alleles of the E1–E4, GmFT2a, and GmFT5a genes using 10 soybean cultivars from different maturity groups. As a result, 5 combinations of dominant and recessive alleles for the E1–E4 genes were identif ied: (1) e1-nl(e1-as)/ e2-ns/e3-tr(e3-fs)/e4; (2) e1-as/e2-ns/e3-tr/E4; (3) e1-as/e2-ns/E3-Ha/e4; (4) E1/e2-ns/e3-tr/E4; (5) e1-nl/e2-ns/E3-Ha/E4. The studied cultivars contained the most common alleles of the GmFT2a and GmFT5a genes, with the exception of the ‘Cassidi’ cultivar having a rare dominant allele GmFT5a-H4. The degree of earliness of cultivars positively correlated with the number of recessive genes E1–E4, which is consistent with the data of foreign authors on different sets of cultivars from Japan and North China. Thus, the developed panel of markers can be successfully used in the selection of soybean for earliness and sensitivity to photoperiod.

Evaluating the Impact of Increased Pollinator Habitat on Surrounding Agricultural Systems

Agricultural intensification has majorly changed ecosystem functioning and aided in the reduction of global biodiversity. While agriculture requires increased reliance on animal pollination, pollinator populations have declined. To combat this, adding pollinator habitat into agricultural landscapes is increasingly common, but many questions remain about its functionality and impact on agroecosystems, particularly in pollinator-independent crops. Our study uses pollinator habitats planted on experimental research stations to evaluate their impact on pollinator communities within a nearby cropping system (soybeans) and the resulting yield. We found the species composition of pollinator communities within the habitat to be significantly different than the communities in soybeans. Even still, we identified more than 30 bee species visiting soybean flowers and verified that a subset of these species had actively collected soybean pollen. Bees from soybean fields planted adjacent to the habitat had more habitat pollen types present, while some species had more non-habitat types present when in the negative control sites. The presence of habitat had a positive effect on some yield measurements with adjacent soybean sites having 6.52% heavier seeds per plant on average. These findings demonstrate that pollinator habitat can be an important resource for supporting pollinators and highlights the importance of considering pollinator habitat in pollinator-independent crops, as they may still benefit from and be attractive to pollinator communities.

Effect of Source–Sink Ratio Manipulation on Growth, Flowering, and Yield Potential of Soybean

Trade-offs between growth and reproduction in soybean require resource availability manipulations. Decapitation and reducing sink strength through deflowering can affect the source–sink ratio that affects plant growth, development, and yield. The current study assesses the effect of decapitation (Decap) and removal of the two lowest racemes (R2LR) and their combination on growth, flowering, and yield capacity of soybean through controlling the source–sink ratio and inducing the “stay-green” phenotype. Two field experiments were conducted during 2018 and 2019 in the Agronomy Farm located at Mansoura University, Egypt. Decapitation was done at the V4 stage (35 days after sowing, DAS), during which four nodes on the main stem had fully developed leaves beginning with the unifoliolate nodes, whereas R2LR was performed at the R2 stage (50 DAS), during which the plants had one open flower at one of the two uppermost nodes on the main stem. Results indicated that Decap, R2LR, and their combination significantly increased seed yield per plant through increasing plant growth and flowering and improving biochemical attributes. The combination between Decap and R2LR was generally more effective in positively modulating plant vegetative, reproductive, and physiological capacity than either Decap or R2LR alone. Moreover, the number of branches as well as pods/plant and IAA content responded positively to Decap, whereas net assimilation rate, seed growth rate, number of flowers/node, and cytokinins content responded positively to R2LR. Decap and R2LR were interpreted in light of their effects on inducing the “stay-green” phenotype and altering the source–sink ratio. Based on the findings, it can be concluded that concealing the apical dominance in conjunction with reducing the sink strength through guided raceme removal would be beneficial for the reproductive potential in soybean.

Genome-Wide Association Study to Map Genomic Regions Related to the Initiation Time of Four Growth Stage Traits in Soybean.

The time to flowering (DF), pod beginning (DPB), seed formation (DSF), and maturity initiation (DMI) in soybean (Glycine max [L.] Merr) are important characteristics of growth stage traits (GSTs) in Chinese summer-sowing soybean, and are influenced by genetic as well as environmental factors. To better understand the molecular mechanism underlying the initiation times of GSTs, we investigated four GSTs of 309 diverse soybean accessions in six different environments and Best Linear Unbiased Prediction values. Furthermore, the genome-wide association study was conducted by a Fixed and random model Circulating Probability Unification method using over 60,000 single nucleotide polymorphism (SNP) markers to identify the significant quantitative trait nucleotide (QTN) regions with phenotypic data. As a result, 212 SNPs within 102 QTN regions were associated with four GSTs. Of which, eight stable regions were repeatedly detected in least three datasets for one GST. Interestingly, half of the QTN regions overlapped with previously reported quantitative trait loci or well-known soybean growth period genes. The hotspots associated with all GSTs were concentrated on chromosome 10. E2 (Glyma10g36600), a gene with a known function in regulating flowering and maturity in soybean, is also found on this chromosome. Thus, this genomic region may account for the strong correlation among the four GSTs. All the significant SNPs in the remaining 7 QTN regions could cause the significant phenotypic variation with both the major and minor alleles. Two hundred and seventy-five genes in soybean and their homologs in Arabidopsis were screened within ± 500 kb of 7 peak SNPs in the corresponding QTN regions. Most of the genes are involved in flowering, response to auxin stimulus, or regulation of seed germination, among others. The findings reported here provide an insight for genetic improvement which will aid in breeding of soybean cultivars that can be adapted to the various summer sowing areas in China and beyond.

Photons from NIR LEDs can delay flowering in short-day soybean and Cannabis: Implications for phytochrome activity.

Photons during the dark period delay flowering in short-day plants (SDP). Red photons applied at night convert phytochromes to the active far-red absorbing form (Pfr), leading to inhibition of flowering. Far-red photons (greater than 700 nm) re-induce flowering when applied after a pulse of red photons during the dark period. However, far-red photons at sufficiently high intensity and duration delay flowering in sensitive species. Mechanistically, this response occurs because phytochrome-red (Pr) absorbance is not zero beyond 700 nm. We applied nighttime photons from near infrared (NIR) LEDs (peak 850 nm) over a 12 h dark period. Flowering was delayed in Glycine max and Cannabis sativa (two photosensitive species) by 3 and 12 days, respectively, as the flux of photons from NIR LEDs was increased up to 83 and 116 μmol m-2 s-1. This suggests that long wavelength photons from NIR LEDs can activate phytochromes (convert Pr to Pfr) and thus alter plant development.

Soybean yield in succession to single and intercropping corn and brachiaria and submitted to differents irrigation intervals

The experiment was performed at a non-acclimatized protected screened environment. The objective of the study was to evaluate the influence predecessor crops of single and intercropping corn and brachiaria on soybean yield submitted to irrigation intervals. The experimental design adopted was in a split split-plot randomized block design with four repetitions. Two soil classes (dystroferric Red Latosol and dystrophic Red Latosol) were evaluated in the plots, three intervals between irrigations were used during the soybean flowering (each one day, two days and three days) in the subplots and three types straw in the crops autumn-winter (single corn, single brachiaria, intercropping corn and brachiaria) in the sub-subplots. The two soybean plants cultivated in polyethylene pots containing 20 liters of dystroferric Red Latosol or dystrophic Red Latosol corresponded to each repetition, according to the treatment. The irrigation intervals of three and two days, in dystroferric Red Latosol and dystrophic Red Latosol, respectively, with single brachiaria at the previous crop provided greater number and weight of pods, higher number of grains and higher soybean yield. Irrigation every three days with single corn at the previous crop in dystroferric Red Latosol and dystrophic Red Latosol, resulted in the lower soybean performance.

Allelic Variation of Soybean Maturity Genes E1–E4 in the Huang-Huai-Hai River Valley and the Northwest China

Soybean is planted in a wide span of the world, and flowering and maturity time is an important trait determining soybean yield formation and adaptation. Maturity loci E1, E2, E3 and E4 were frequently reported as the most influential genetic loci for soybean flowering and maturity. To understand the allelic variation and assess the phenological traits of cultivars with different E allelic combinations in natural environments, 251 cultivars of maturity group (MG) I–V were field tested in 42 locations across four sub-regions in the Huang-Huai-Hai and Northwest region of China and genotyped with KASP markers for E1–E4 loci. The results indicated that mutant alleles were only found in the E1 and E2 locus, all of the cultivars carried functional alleles in the E3 and E4 loci in this area, with the frequency of mutant allele to be higher in early maturity groups (MGs) than late MGs. Among nine E allelic combinations in this area, one photoperiodic insensitive mutation in E2 loci (E1/e2-ns/E3-Ha/E4 and E1/e2-ns/E3-Mi/E4) made up the largest proportion (25.10 and 18.33%), while two photoperiodic insensitive mutations in both E1 and E2 loci (e1-as/e2-ns/E3-Ha/E4) (1.20%) occupied the lowest proportion in this panel. The major combinations of E locus for MGI, MGII and MG III in this area were E1/E2-dl/E3-Mi/E4, E1/e2-ns/E3-Mi/E4 and E1/e2-ns/E3-Ha/E4, respectively. Cultivars carrying e1-as/e2-ns/E3-Ha/E4 genotype flowered earliest (34 days) on average, 7.6 days earlier than the latest-flowering E haplotype (E1/e2-ns/E3-Ha/E4). This study provided an opportunity to detect the E allelic combinations in the Huang-Huai-Hai River Valley and the Northwest China, which would facilitate the improvement of soybean adaptation in the future.

Molecular mechanisms for the photoperiodic regulation of flowering in soybean.

Photoperiodic flowering is one of the most important factors affecting regional adaptation and yield in soybean (Glycine max). Plant adaptation to long-day conditions at higher latitudes requires early flowering and a reduction or loss of photoperiod sensitivity; adaptation to short-day conditions at lower latitudes involves delayed flowering, which prolongs vegetative growth for maximum yield potential. Due to the influence of numerous major loci and quantitative trait loci (QTLs), soybean has broad adaptability across latitudes. Forward genetic approaches have uncovered the molecular basis for several of these major maturity genes and QTLs. Moreover, the molecular characterization of orthologs of Arabidopsis thaliana flowering genes has enriched our understanding of the photoperiodic flowering pathway in soybean. Building on early insights into the importance of the photoreceptor phytochrome A, several circadian clock components have been integrated into the genetic network controlling flowering in soybean: E1, a repressor of FLOWERING LOCUS T orthologs, plays a central role in this network. Here, we provide an overview of recent progress in elucidating photoperiodic flowering in soybean, how it contributes to our fundamental understanding of flowering time control, and how this information could be used for molecular design and breeding of high-yielding soybean cultivars.