Isoflavone Content of Soybean Cultivars from Maturity Group 0 to VI Grown in Northern and Southern China

Soybean isoflavone content has long been considered to be a desirable trait to target in selection programs for their contribution to human health and plant defense systems. The objective of this study was to determine isoflavone concentrations of various soybean cultivars from maturity groups 0 to VI grown in various environments and to analyze their relationship to other important seed characters. Forty soybean cultivars were grown in replicated trials at Wuhan and Beijing of China in 2009/2010 and their individual and total isoflavone concentrations were determined by HPLC. Their yield and quality traits were also concurrently analyzed. The isoflavone components had abundant genetic variation in soybean seed, with a range of coefficient variation from 45.01% to 69.61%. Moreover, individual and total isoflavone concentrations were significantly affected by cultivar, maturity group, site and year. Total isoflavone concentration ranged from 551.15 to 7584.07 μg g(−1), and averaged 2972.64 μg g(−1) across environments and cultivars. There was a similar trend regarding the isoflavone contents, in which a lower isoflavone concentration was generally presented in early rather than late maturing soybean cultivars. In spite of significant cultivar × year × site interactions, cultivars with consistently high or low isoflavone concentrations across environments were identified, indicating that a genetic factor plays the most important role for isoflavone accumulation. The total isoflavone concentration had significant positive correlations with plant height, effective branches, pods per plant, seeds per plant, linoleic acid and linolenic acid, while significant negative correlations with oleic acid and oil content, indicating that isoflavone concentration can be predicted as being associated with other desirable seed characteristics

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, high-resolution 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 marker-assisted selection in soybean breeding programs. Keywords: Soybean (Glycine max L. Merrill), QTL mapping, Isoflavones, Specific-locus amplified fragment sequencing (SLAF-seq

Development of a Serotype-Specific DNA Microarray for Identification of Some Shigella and Pathogenic Escherichia coli Strains

Shigella and pathogenic Escherichia coli are major causes of human infectious diseases and are responsible for millions of cases of diarrhea worldwide every year. A convenient and rapid method to identify highly pathogenic serotypes of Shigella and E. coli is needed for large-scale epidemiologic study, timely clinical diagnosis, and reliable quarantine of the pathogens. In this study, a DNA microarray targeting O-serotype-specific genes was developed to detect 15 serotypes of Shigella and E. coli, including Shigella sonnei; Shigella flexneri type 2a; Shigella boydii types 7, 9, 13, 16, and 18; Shigella dysenteriae types 4, 8, and 10; and E. coli O55, O111, O114, O128, and O157. The microarray was tested against 186 representative strains of all Shigella and E. coli O serotypes, 38 clinical isolates, and 9 strains of other bacterial species that are commonly present in stool samples and was shown to be specific and reproducible. The detection sensitivity was 50 ng genomic DNA or 10(4) CFU per ml in mock stool specimens. This is the first report of a microarray for serotyping Shigella and pathogenic E. coli. The method has a number of advantages over traditional bacterial culture and antiserum agglutination methods and is promising for applications in basic microbiological research, clinical diagnosis, food safety, and epidemiological surveillance