R. P. Ellis

Starch production and industrial use

This review of starch is concerned with its industrial uses, origins and structure. The current demand for starch is met by a restricted range of crops, the most important of which are potatoes, maize, wheat and tapioca. Improvements in the properties of starches for industrial uses can be achieved through chemical and physical modification of extracted starch and through the manipulation of starch biosynthesis in the plant itself. We examine starch structure and composition in relation to its use and exploitation by industry. The current understanding of physiological and biochemical mechanisms influencing starch formation in higher plants is described. This information is set in the context of the need to know the physical/chemical specification for each individual starch and to understand the genetic control of these characteristics in order to identify target genes for manipulation.

Detection of quantitative trait loci for agronomic, yield, grain and disease characters in spring barley (Hordeum vulgare L.)

Quantitative trait loci (QTLs) have been revealed for characters in a segregating population from a spring barley cross between genotypes adapted to North-West Europe. Transgressive segregation was found for all the characters, which was confirmed by the regular detection of positive and negative QTLs from both parents. A QTL for all the agronomic, yield and grain characters measured except thousand grain weight was found in the region of the denso dwarfing gene locus. There were considerable differences between the location of QTLs found in the present study and those found in previous studies of North American germ plasm, revealing the diversity between the two gene pools. Thirty-one QTLs were detected in more than one environment for the 13 characters studied, although many more were detected in just one environment. Whilst biometrical analyses suggested the presence of epistasis in the genetic control of some characters, there was little evidence of interactions between the QTLs apart from those associated with yield. QTLs of large effect sometimes masked the presence of QTLs of smaller effect.

The use of AFLPs to examine genetic relatedness in barley

The generation of AFLPs in spring barley cultivars provided genetic information relating to the development of the crop in the UK since 1953. Principal co-ordinate (PCO) analysis of genetic similarities (gs) confirmed the marked contrast in the cultivars used in the 1970s and 1980s. The earliest cultivars, many derived from Proctor, were succeeded by tall-strawed, disease-resistant types with high yield but poor malting potential. In the 1980s they were in turn replaced by short-strawed cultivars with excellent yield and good malting quality, which originated from Triumph. A PCO plot of gs provided insight into the effects of selection for disease resistance and the antagonism between malting quality and particular resistance genes. The analysis of gs was more useful than pedigrees and estimates of kinship in revealing the genetic relationship between cultivars. Theoretical considerations for maximising the efficiency of an AFLP genotyping programme are discussed in the context of the number of primer pairs required to distinguish genotypes at varying levels of similarity.

Shoot δ15N correlates with genotype and salt stress in barley

Given a uniform N source, the δ15N of barley shoots provided a genotypic range within treatments and a separation between control and salt-stress treatments as great as did δ13C*. Plant δ15N has been represented in the literature as a bioassay of external source δ15N and used to infer soil N sources, thus precluding consideration of the plant as a major cause in determining its own 815N. We believe this to be the first report of plant δ15N as a genetic trait. No mechanistic model is needed for use of δ15N as a trait in controlled studies; however, a qualitative model is suggested for further testing.

Patterns of Barley grain development in spain and Scotland and their implications for malting quality

ABSTRACT To determine whether patterns of grain filling were consistent between seasons and different between sites in northern and southern Europe, the cultivar Troubadour and TR49, a mutant derived from it, were grown, over two seasons, at sites in Scotland and northern Spain. Differences in sowing date and climate were reflected in different patterns of grain filling. Ear emergence in Scottish grown barley occurred around the time when daylight hours were maximal; optimal photosynthesis was the likely explanation for the rapid increase in grain size observed at the Scottish site. Differences between the sites in temperature and rainfall were most evident during the last month of the growing season. In Scotland, where ripening occurred in cooler, more humid conditions, synthesis of hordein and β-glucan followed the pattern of grain filling, reaching a peak at ~600 degree days after anthesis (the product of days after anthesis and average temperature). Levels then remained fairly constant until harvest r...

Statistical analysis of a linkage experiment in barley involving quantitative trait loci for height and ear-emergence time and two genetic markers on chromosome 4.

SummaryThe quantitative traits height and ear-emergence date were analyzed in the F2 progeny of a cross between a tall winter barley cultivar (Gerbel) and a short spring barley cultivar (Heriot). The trait distributions were found to be related to the genotypes at two biochemical loci, β-amylase (Bmy1) and water-soluble protein (Wsp3), which are known to lie on the long arm of chromosome 4. Linkages between each trait and the markers were investigated using normal mixture models. The two parental phenotypes and the heterozygote phenotype of Bmy1 were distinguishable so the model could be used directly to estimate linkage between Bmy1 and a quantitative trait locus (QTL) for height (Height). The Gerbel homozygote and heterozygote phenotype of Wsp3 could not be distinguished and the model was adapted accordingly. The proportion of plants requiring vernalization was consistent with control by two independent genes acting epistatically, and a normal mixture model based on a two-gene hypothesis was fitted to the distribution of ear-emergence date to estimate linkage between the marker loci and a QTL for ear-emergence date (Vrn1). The parameters of each model were the recombination fraction between the marker locus and the QTL and the means and standard deviations associated with each QTL genotype; these were estimated by maximum likelihood. The fitted distributions correspond well to those observed and the order of the loci along the chromosome is inferred to be Height — Vrn1 — Bmy1 — Wsp3, with Wsp3 being the most distal.

The effects of major genes on quantitatively varying characters in barley. III. The two row/six row locus (V-v).

Inbred lines have been extracted from a barley cross between Dissa (six-row ear type) and Sabarlis (two-row ear type) by single seed descent (SSD) and by the H. bulbosum doubled haploid (DH) technique. Estimates of the additive genetic variation from DH and SSD have been compared and demonstrate association between the V-v locus, which conditions ear type, and agronomically important characters. Characters contributing to plant height and biomass production are located near the V-v locus on barley chromosome 2I. The significance of the behaviour of such quantitative trait loci (QTL) and possible applications to plant breeding are discussed.

The effect of selection for protein and isozyme loci on quantitative traits in a doubled haploid population of barley.

Doubled haploid families extracted from the F1 hybrid of the spring barley cross (Dissa × Sabarlis) by the Hordeum bulbosum technique were scored for the segregation of alleles at isozyme loci. Isozyme and protein loci on all seven pairs of barley chromosomes were examined and five out of the seven pairs of barley chromosomes (2I, 3I, 4I, 6I and 7I) were shown to possess polymorphic isozyme and protein loci. The systems tested did not deviate significantly from the expected 1:1 ratio and esterase loci on chromosome 3 were mapped intra-chromosomally. The relationship between marker loci and quantitative trait loci (QTL) was examined. A comparison of the mean scores for each allelic class revealed significant differences in the expression of a range of quantitative traits. Thus, by selecting for isozyme and protein phenotypes one can significantly affect the expression of certain QTL in barley. For example, allelic variation at the α-Amy-1 locus makes a large contribution to the genetic variation available for selection in the case of single plant yield. The advantage of using DH families for gene mapping and in dissecting QTL are discussed.

Potato starches: variation in composition and properties between three genotypes grown at two different sites and in two different years

Starch granules were isolated from three distinct potato (Solanum tuberosum L) genotypes, cvs Glamis and Record and line 86Q35(8), grown at two different sites in 1996 and 1997. Differences in the chemical compositions of the granules were investigated using blue values of the starch–iodine complexes as indicators of amylose contents and from phosphorus contents. The physical properties determined were starch damage, swelling power, turbidity, granule size distribution, viscosity data and profile, and gelatinisation temperatures as well as enthalpy of gelatinisation. The differences in the blue values of the starch–iodine complexes were significant for genotype (P < 0.001) but not for site or year. Highly significant differences in starch granule phosphorus contents were found both between genotypes (P < 0.001) and between sites (P < 0.001), but the differences between years were less significant (P < 0.01). Genotype 86Q35(8) had nearly twice the starch phosphorus content of the other two genotypes. Significant differences were also found between genotypes in terms of granule size distributions (P < 0.01), with 86Q35(8) having a modal granule size smaller than that of the other two genotypes. The viscosity data and profiles, measured at 48 g l−1, showed that samples of starch granules isolated from genotype 86Q35(8), irrespective of the site or year, behaved similarly to each other. However, the profiles obtained from starch granules derived from Glamis and Record depended on the site and year and were distinctly different from the profiles obtained from starch granules isolated from 86Q35(8). On the other hand, the differential scanning calorimetric data recorded no consistent differences in the gelatinisation temperatures and enthalpy of gelatinisation between genotype, site and year. The prospects of using specific potato genotypes as sources of starch for particular uses are discussed. © 2000 Society of Chemical Industry

An investigation of two-dimensional yield variability in breeders' small plot barley trials

This paper describes an investigation into yield variability and spatial correlations in 129 spring barley trials using small plots between 2·4 and 6·0 m 2 in area. We report on the efficiencies of the generalized lattice designs used, and discuss the effects of plot size and year-to-year variations. Results indicate that the recommendations of Patterson & Hunter (1983) on choice of block size apply equally well to small-plot trials. The observed variability and correlations are then discussed and so is the potential for improvement by using alternative designs. Patterns of variability were not at all consistent from year to year, or even between trials in the same year, but it appears important to take account of column effects as well as row effects.