Mark A Edwards Copyright (c) 2012 All rights reserved. http://works.bepress.com/markedwards Recent documents in Mark A Edwards en-us Sun, 25 Nov 2012 15:15:52 PST 3600 Chloroplast genome sequences from total DNA for plant identification http://works.bepress.com/markedwards/8 http://works.bepress.com/markedwards/8 Tue, 21 Sep 2010 19:55:30 PDT Chloroplast DNA sequence data are a versatile tool for plant identification or barcoding and establishing genetic relationships among plant species. Different chloroplast loci have been utilized for use at close and distant evolutionary distances in plants, and no single locus has been identified that can distinguish between all plant species. Advances in DNA sequencing technology are providing new cost-effective options for genome comparisons on a much larger scale. Universal PCR amplification of chloroplast sequences or isolation of pure chloroplast fractions, however, are nontrivial. We now propose the analysis of chloroplast genome sequences from massively parallel sequencing (MPS) of total DNA as a simple and cost-effective option for plant barcoding, and analysis of plant relationships to guide gene discovery for biotechnology. We present chloroplast genome sequences of five grass species derived from MPS of total DNA. These data accurately established the phylogenetic relationships between the species, correcting an apparent error in the published rice sequence. The chloroplast genome may be the elusive single-locus DNA barcode for plants.

]]> Catherine J. Nock et al. Next generation genotyping http://works.bepress.com/markedwards/7 http://works.bepress.com/markedwards/7 Sun, 28 Feb 2010 22:04:00 PST Robert J. Henry et al. Next-generation sequencing of plant genomes http://works.bepress.com/markedwards/6 http://works.bepress.com/markedwards/6 Sun, 28 Feb 2010 22:03:59 PST Nicole F. Rice et al. Studies into the genetics of wheat endosperm rheology and microstructure http://works.bepress.com/markedwards/5 http://works.bepress.com/markedwards/5 Tue, 09 Feb 2010 22:14:13 PST Despite considerable gains in wheat flour milling yield through conventional breeding strategies and milling technologies, the theoretical maximum yield still has not been attained. Discovery of genes in wheat that control flour yield would provide a means for breeders to develop new wheats that fulfill their potential in relation to this trait. A more targeted approach is to improve the understanding of the role of grain microstructure in determining high flour yield. Previous research has shown that increased flour yield in hard wheat is associated with increased endosperm rheology index, calculated from strength and stiffness as measured by the SKCS (Osborne et al, 2005; Osborne et al, 2007). Edwards et al (2007) demonstrated, through microscopy and particle size analysis of the crushed material from the SKCS 4100 and a first break roll stand, that the SKCS data for unconditioned wheat averaged over 300 grains provided a useful indicator of milling performance of a wheat sample. The Pina-D1 and Pinb-D1 alleles, tightly linked to the Ha locus on the short arm of Chromosome 5D, determine the hardness phenotype (Greenwell and Schofield, 1986). However, this does not fully account for the observed genetic variation in hardness, especially within each hardness class, and it is thought that additional modifying genes account for the range of hardness within hard or soft classes (Martin et al, 2001). Others have investigated the relationship between endosperm starch granule size and hardness. Igrejas et al (2002) reported that harder wheat had a higher content of small starch granules but could not find a QTL for starch granule size on the 5D Chromosome; they concluded that “starch size distribution is influenced by genes which have yet to be analysed”. The aim of the present study was to test the hypothesis that a genetic association exists in hard wheat between starch granule type and flour yield.

]]> Mark A. Edwards et al. Effect of endosperm starch granule size distribution on milling yield in hard wheat http://works.bepress.com/markedwards/4 http://works.bepress.com/markedwards/4 Tue, 09 Feb 2010 22:14:12 PST Increased flour yield in hard wheat is associated with increased endosperm rheology index, calculated from strength and stiffness as measured by the SKCS. A study of the fractured endosperm of hard wheat varieties grouped according to similar rheology index values was performed using environmental scanning electron microscopy (ESEM). Differing microstructures and fracture patterns were observed between each group. Specifically, the group representing high rheology index had a greater concentration of small starch granules in prismatic cells. Samples of diverse wheat germplasm were grown at two sites and subjected to laboratory milling. Starch granule size distribution (SGSD) analysis using a laser diffraction method was undertaken on a subset of samples in triplicate representing a range in flour yield. The results supported an hypothesis for a significant influence of SGSD on flour yield of hard wheat varieties. In addition, a significant part (R2>0.40 (p<0.05) at two sites) of the association appeared to be under genetic control. Results indicate a more even gradation of distributions involving an increase in the sample volume % of small granule (types B and C) and decrease in type A granules. This was associated with increased rheology index values and higher flour yield. The ratio of type A:C starch granules accounted for up to 58% (p<0.05) of the variation in flour yield in the samples studied. Thus, rheological parameters measured using a rapid SKCS screening method can be linked to the genetic regulation of SGSD with implications for the improvement of commercial processing performance of hard wheat.

]]> Mark A. Edwards et al. Grain endosperm microstructure and milling quality of hard wheat http://works.bepress.com/markedwards/3 http://works.bepress.com/markedwards/3 Tue, 09 Feb 2010 22:14:11 PST Milling quality is considered to be a combination of the potential yield, bran content, colour and starch damage of flour. It is a complex trait because these factors interact with one another, with the milling process and with the requirements for the end product to be made from the flour. Despite considerable gains in wheat flour milling yield through conventional breeding strategies and milling technologies, the theoretical maximum yield still has not been attained. Attempts to unravel the genetics of flour yield are made especially difficult by the number and complexity of linkages between gene expression and grain processing. Our approach was to improve the understanding of the role of grain endosperm microstructure in determining high flour yield.

A lack of vitreousness in hard wheat causes microstructural weaknesses characterised by low endosperm strength and stiffness that result in fracture through cell contents with a consequent high first break release and low overall flour yield. The SKCS provides a method for stress-strain analysis of wheat grain in which better milling quality is characterised by increased endosperm strength and stiffness. These properties were used to discriminate wheat samples according to their milling yield so that the differences in microstructure between contrasting groups, within each of the two hardness genotypes present in Australian wheat germplasm, could be examined.

The Pina-D1a, Pinb-D1b set was characterised by a higher average flour yield than the Pina-D1b, Pinb-D1a, although the ranges of flour yields showed considerable overlap between the genotypes. For the Pina-D1b, Pinb-D1a genotype, which does not express starch bound puroindoline protein, starch granule type accounted for up to 47% of the variation in flour yield between varieties. For the Pina-D1a, Pinb-D1b genotype, starch granule type accounted for no more than 24% of the variation in flour yield between varieties, with 31-35% accounted for by starch bound puroindoline protein content. The combined effect of starch granule type and starch bound puroindoline accounted for 68% of the variation in flour yield in the Pina-D1a, Pinb-D1b set.

]]> Mark A. Edwards et al. Investigation of the effect of conditioning on the fracture of hard and soft wheat grain by the single-kernel characterization system: a comparison with roller milling http://works.bepress.com/markedwards/2 http://works.bepress.com/markedwards/2 Tue, 09 Feb 2010 22:14:10 PST A study has been carried out on selected hard and soft Australian wheats to determine the effect of conditioning on the crush-response profiles (CRPs) measured using the single-kernel characterization system (SKCS 4100). In addition, the fragmentation patterns that resulted from crushing in the SKCS have been compared with those that resulted from the first break stage of roller milling. It was found that the CRPs were changed significantly (P<0.05) as a result of conditioning. In particular, the rheological parameters shell stiffness and strength and endosperm strength all decreased following conditioning. The fragmentation patterns, assessed using low-resolution microscopy and particle size analysis, that resulted from the crushing of unconditioned wheat in the SKCS were the closest match with those that resulted from first break milling of conditioned wheat. These results show how the SKCS may be used to monitor the progress of wheat conditioning prior to milling. They also provide support for the use of SKCS measurements on unconditioned wheat for the prediction of milling performance.

]]> Mark A. Edwards et al. Is SKCS analysis relevant to commercial wheat milling? http://works.bepress.com/markedwards/1 http://works.bepress.com/markedwards/1 Tue, 09 Feb 2010 22:14:10 PST Mark A. Edwards et al.