Science Letters:Optimization of soybean (Glycine max (L.) Merrill) in planta ovary transformation using a linear minimal gus gene cassette

Soybean transformation by ovary-drip was improved by optimizing the length of the transformation pathway by cutting the styles. These modifications facilitated soybean transformation manipulation and improved transformation reproducibility and efficiency. Using a linear minimal gus gene cassette as the foreign DNA, a maximum transformation frequency of 11% was obtained in flowers of the soybean cultivar ‘Liaodou 14’ with their styles mostly removed, whereas removal of only the stigma, partial style cutting and partial ovary cutting gave transformation frequencies of 0%, 1%, and 2%, respectively. An average transformation frequency of 8.2% was obtained when 619 flowers from three soybean cultivars (‘Liaodou 14’, ‘Liaodou 13’, and ‘Tiefeng 29’) were transformed by this optimized method. Southern blotting analysis showed that the gus reporter gene (encoding β-glucuronidase) was stably inherited with a simple pattern. Reverse transcription-polymerase chain reaction (RT-PCR) and GUS staining confirmed the expression of the gus gene in transgenic plants.

Identification of novel QTL associated with soybean isoflavone content

Soybean isoflavones are essential secondary metabolites synthesized in the phenylpropanoid pathway and benefit human health. In the present study, highresolution QTL mapping for isoflavone components was performed using specific-locus amplified fragment sequencing(SLAF-seq) with a recombinant inbred line(RIL) population(F5:7) derived from a cross between two cultivated soybean varieties, Luheidou 2(LHD2) and Nanhuizao(NHZ). Using a high-density genetic map comprising 3541 SLAF markers and the isoflavone contents of soybean seeds in the 200 lines in four environments, 24 stable QTL were identified for isoflavone components, explaining 4.2%–21.2% of phenotypic variation.Of these QTL, four novel stable QTL(qG8, qMD19, qMG18, and qTIF19) were identified for genistin, malonyldaidzin, malonylgenistin, and total isoflavones, respectively. Gene annotation revealed three genes involved in isoflavone biosynthesis(Gm4CL, GmIFR, and GmCHR) and 13 MYB-like genes within genomic regions corresponding to stable QTL intervals, suggesting candidate genes underlying these loci. Nine epistatic QTL were identified for isoflavone components, explaining 4.7%–15.6% of phenotypic variation. These results will facilitate understanding the genetic basis of isoflavone accumulation in soybean seeds. The stable QTL and tightly linked SLAF markers may be used for markerassisted selection in soybean breeding programs.

Effects of Lipoxygenase Null Genes of Soybean in Controlling Beany-flavor of Soymilk and Soyflour

The flavor of the soymilk and soyflour obtained from the lipoxygenase mutant isolines was concentrated by simultaneous distillation and extraction (SDE), and its constituents were identified by gas chro-matography (GC) and gas chromatography-mass spectrometry. Results showed that the same 24 flavor constituents were isolated in both soymilk and soyflour, and most of them were aldehydes and alcohols. Lox2 was most responsible for the production of the volatile and beany-flavor components, and Lox1 less responsible. Lox3 was least responsible and can reduce the yield of hexanal. Either Lx1 or Lx2 could significantly reduce the volatile and beany-flavor, and Lx3 could significantly increase the yield of hexanal. Primary and secondary interactions existed among the null mutant genes, and the major effects and interactions could be affected by processing conditions. The isoline with triple lipoxygenase null genes yielded the least volatile and beany-flavor components, and the isoline without the lipoxygenase gene Lx3 produced the greatest amount of the volatile and beany-flavor components. The amounts of volatile and beany-flavor components produced by the other isolines were between that of the isoline with triple lipoxygenase null genes and the isoline without lipoxygenase gene Lx3. According to the correlation analysis, the hexanal amount could be used as an index in evaluating the importance of lipoxygenase isozymes in the yield of beany-flavor compounds, and the effects of the different types of lipoxygenase null mutants in controlling beany-flavor compounds. The cultivars with triple lipoxygenase null genes will be a quality raw material for soy food processing.

Studies on the Correlations Between Isoflavone Contents in Soybean Seed and the Eco-Physiological Factors

The soybean cultivar Yudou25 was sown at 5 locations of Henan Province on 13 differentdates in 2001 and 2002. The data of isoflavone contents for the 109 samples of soybeanseed and 33 eco-physiological factors including meteorological factors, soil nutritionand altitudes were received and used for statistical analysis. The step-wise regressionwas used to screen the correlated factors, which significantly effected isoflavonecontents. Results showed that 9 eco-physiological factors were highly correlated withisoflavones. Low mean temperature, high diurnal temperature range at seed filling andmaturity, more sunlight hours and low mean temperature at emergence were favorable toisoflavone accumulation. The rainfall at emergence showed a nonlinear relationship withisoflavone content and its optimum value was 75 mm for isoflavone formation. Low diurnaltemperature range at branching, high organic matter and low sulfur content in soil weresuitable for the formation of isoflavones. The isoflavone contents would not be affectedby other eco-physiological factors in this study.

Natural variations and geographical distributions of seed carotenoids and chlorophylls in 1167 Chinese soybean accessions

Understanding the composition and contents of carotenoids in various soybean seed accessions is important for their nutritional assessment.This study investigated the variability in the concentrations of carotenoids and chlorophylls and revealed their associations with other nutritional quality traits in a genetically diverse set of Chinese soybean accessions comprised of cultivars and landraces.Genotype,planting year,accession type,seed cotyledon color,and ecoregion of origin significantly influenced the accumulation of carotenoids and chlorophylls.The mean total carotenoid content was in the range of 8.15–14.72μg g–1 across the ecoregions.The total carotenoid content was 1.2-fold higher in the landraces than in the cultivars.Soybeans with green cotyledons had higher contents of carotenoids and chlorophylls than those with yellow cotyledons.Remarkably,lutein was the most abundant carotenoid in all the germplasms,ranging from 1.35–37.44μg g–1.Carotenoids and chlorophylls showed significant correlations with other quality traits,which will help to set breeding strategies for enhancing soybean carotenoids without affecting the other components.Collectively,our results demonstrate that carotenoids are adequately accumulated in soybean seeds,however,they are strongly influenced by genetic factors,accession type,and germplasm origin.We identified novel germplasms with the highest total carotenoid contents across the various ecoregions of China that could serve as the genetic materials for soybean carotenoid breeding programs,and thereby as the raw materials for food sectors,pharmaceuticals,and the cosmetic industry.

Stability of Soybean Genotypes and Their Classification into Relative Maturity Groups in Brazil

The stability of soybean genotypes is very important in breeding programs for not only the evaluation, selection, and production of cultivars but also the establishment of parameters required for the classification of genotypes into relative maturity groups (RMG). The aim of this study was to define stable genotypes for traits, such as days to flowering, days to maturity, and length of the reproductive period, and to classify them into RMG. For this purpose, 20 commercial soybean cultivars were evaluated in 12 environments distributed in the major producing regions of Brazil. Assessments according to the Eberhart and Russell method and the additive main effects and multiplicative interaction (AMMI) method were effective in the identification of stable genotypes and their classification into RMG. These methods can also be used collectively for this purpose. Our results showed that the AMMI method led to a better interpretation of genotype-environment interactions. Thus, RMG obtained on the basis of stable genotypes represented a good estimate of the relative maturity of soybean crops throughout Brazil. *Corresponding author.

Profiling seed soluble sugar compositions in 1164 Chinese soybean accessions from major growing ecoregions

Soluble sugar is a key quality trait of soybean seeds.We developed rapid and economic extraction and quantification methods for seed soluble sugars using an ultra-high performance liquid chromatography system with a refractive index detector.We evaluated the soluble sugar compositions of 1164 soybean accessions collected from diverse ecoregions and grown in multiple locations and years.Total soluble sugar(TSS)content was influenced by accession type,year of cultivation,and ecoregion.The mean contents of fructose,glucose,sucrose,raffinose,stachyose and TSS were 3.31,5.21,55.60,6.60,35.47,and 106.19 mg g^(-1),respectively.The highest mean TSS content(108.71 mg g^(-1)) was observed in accessions from Northern Region of China.Cultivars contained higher contents of sucrose,raffinose,and TSS,whereas landraces had a higher content of stachyose.Fourteen accessions with mean TSS contents>130 mg g^(-1) were identified as elite soybean resources.TSS was correlated with sucrose,raffinose,stachyose,protein,oil and total tocopherol.The main soluble sugar components were correlated with latitude and longitude,indicating that the geographical origin of the accessions affected their seed soluble sugar compositions.The developed methods and elite identified accessions can be used in the food and feed industry and in soybean breeding programs aimed at improving soybean seed nutrition.

Evaluation of Soybean Cultivars of Contrasting Cycles according to the Level of Investment in Fertilization

The objective of the present study was to characterize the duration of the phenological stages, the agronomic characteristics and grain yield in soybean cultivars with contrasting cycles and indeterminate growth type, submitted to different fertilization investment environments under no-tillage system in the central region of Minas Gerais. The work was conducted under field conditions, in an experimental area of Embrapa Maize and Sorghum, in Sete Lagoas, MG, in the harvest of 2015/2016. Ten soybean cultivars with different relative maturity groups (RMG) were studied, representing almost all RMG materials currently sown in Minas Gerais, in two environments with different levels of fertilizer investment. The variables were submitted to analysis of joint variance, in order to verify the existence of interaction between cultivars and investment in fertilization environments. Fertilizer investment levels influence grain yield of soybean cultivars of contrasting cycles. The higher height of the soybean plants implies higher lodging and lower grain yield. This situation is aggravated by the greater investment in fertilization. The difference between the cycles of the cultivars is in the duration of the vegetative stages, being greater in the later cultivars.