Sorghum grain with a waxy endosperm is more digestible and has a higher feeding efficiency compared to sorghum grain with a non-waxy (or normal) endosperm. However, waxy sorghums (Sorghum bicolor (L.) Moench) yield 10-15% less than normal sorghum and the cause of the yield reduction is unclear. The objective of this research is to determine if the yield decrease could be due to the waxy phenotype itself. The waxy phenotype is an example of a xenia effect, where the pollen not only contributes to the genotype of the resulting hybrid, but also immediately influences the phenotype of the resulting seed. Sterile hybrids under different pollination types, and different genotypes of fertile hybrids, both resulted in hybrids that produced different ratios of waxy phenotype seed. The effects on yield and 500 kernel weight were investigated in Weslaco, College Station, and Halfway, Texas over two years. Yields of sterile heterozygous waxy hybrids under waxy pollination, which produced an average 27% waxy seed over all environments, were nearly identical to homozygous nonwaxy hybrids that produced 0% waxy seed. Average 500 kernel weights for the same hybrids were not different. Grain yields for the fertile hybrid genotypes were significantlydifferent. Hybrids which produced 100% waxy seed yielded significantly less than hybrids which produced 25% waxy seed. Upon further examination, hybrids that were produced from waxy F1 endosperm seed (wxwxwx) had significantly worse stand and panicle number per plot means than did hybrids from nonwaxy F1 endosperm seed (Wxwxwx). Grain yields adjusted for panicle number showed no significant differences. The average 500 kernel weights between hybrids with different amounts of waxy phenotype grain did not significantly differ. The yield effect seen in this population was the result of waxy endosperm hybrid seed displaying significantly poorer stand establishment than nonwaxy endosperm hybrid seed. These data do not support a xenia yield effect due to the waxy gene.

In sorghum, a single recessive gene Wx conditions waxy endosperm type. While parental inbred lines and hybrids with waxy endosperm have been developed, there has been little to no adoption of these hybrids by producers, primarily because waxy hybrids consistently yield 5-10% less than non-waxy hybrids and end-use buyers will not pay for the utilization benefits. While current waxy germplasm does not yield competitively at this time, there is a question as to whether the yield reduction is due to a negative relationship between waxy per se or due to the lack of effort to develop high yielding waxy germplasm. The purpose of this study is to determine the relationship between the waxy endosperm phenotype and grain yield in sorghum. From each of two F2 breeding populations segregating for waxy endosperm, 50 inbred lines were derived, selected only for homozygosity of endosperm type. No selection for yield was practiced during the development of these lines. Approximately 25 waxy and 25 non-waxy lines were selected for further evaluation from each population. These lines and a set of testcross hybrids were evaluated in four environments. When combined across environments and populations, waxy inbred lines and hybrids yielded 17% less than non-waxy inbred lines and hybrids. However, analysis of the individual inbred lines and hybrids indicated that several waxy inbred lines were competitive in yield with the best non-waxy genotypes. The results indicate that it should be possible to develop waxy hybrids that are competitive in yield, but that this will require additional breeding efforts to identify the correct inbred lines and hybrids.

In sorghum, a single recessive gene Wx conditions waxy endosperm type. While parental inbred lines and hybrids with waxy endosperm have been developed, there has been little to no adoption of these hybrids by producers, primarily because waxy hybrids consistently yield 5-10% less than non-waxy hybrids and end-use buyers will not pay for the utilization benefits. While current waxy germplasm does not yield competitively at this time, there is a question as to whether the yield reduction is due to a negative relationship between waxy per se or due to the lack of effort to develop high yielding waxy germplasm. The purpose of this study is to determine the relationship between the waxy endosperm phenotype and grain yield in sorghum. From each of two F2 breeding populations segregating for waxy endosperm, 50 inbred lines were derived, selected only for homozygosity of endosperm type. No selection for yield was practiced during the development of these lines. Approximately 25 waxy and 25 non-waxy lines were selected for further evaluation from each population. These lines and a set of testcross hybrids were evaluated in four environments. When combined across environments and populations, waxy inbred lines and hybrids yielded 17% less than non-waxy inbred lines and hybrids. However, analysis of the individual inbred lines and hybrids indicated that several waxy inbred lines were competitive in yield with the best non-waxy genotypes. The results indicate that it should be possible to develop waxy hybrids that are competitive in yield, but that this will require additional breeding efforts to identify the correct inbred lines and hybrids.

Amylose content is generally the most important factor determining rice eating and cooking quality. Commercial rice varieties are, in fact, placed into market classes based on having “zero” (0-7%), low (10-20), intermediate (20-25%), or high (>25%) apparent amylose. This study demonstrates that the single-nucleotide polymorphisms (SNP) in the exon 1 (G->T) and in exon 6 (A->C) of GBSS can be used as markers to efficiently distinguish the amylose classes. These two SNPs accounted for 89.2% of the variation in apparent amylose content in a pedigree of 89 US rice varieties and 93.8% of the variation among 279 accessions in a European germplasm collection. All low amylose varieties had the T allele of exon 1. All intermediate amylose varieties had the G allele of exon 1 and the C allele of exon 6. All high amylose varieties had the G allele of exon 1 and the A allele of exon 6. In contrast to previous reports, the amylose content of rice varieties in West Africa was also largely determined by GBSS alleles, which accounted for 93.3% of the variation among 77 samples from West Africa Rice Development Association. GBSS gene from O. glaberrima was found to lack a transposon in exon 10 and have an additional polymorphism (G->A) in exon 12, but these do not significantly alter amylose content. The study also shows that some GBSS genes from high amylose varieties contain an additional C->T polymorphism in exon 10. This SNP does not significantly alter amylose content, but alters rice starch pasting properties. Traditional RVA analysis of starch pasting properties is complicated by differences in the shear forces between samples. However a simple method was developed to overcome this problem and it was shown that starch granules from rice varieties with the T allele of exon 10 are notably more shear resistant. Amylose and the SNP in exons 1, 6 and 10 of GBSS also played a key role in starch re-association. They accounted for 81 and 71.5%, respectively, of the variation in “gel hardness” of RVA samples which have been allowed to incubate at room temperature for 24 hours.

No description available.

Molecular genetic analyses focused on selected aspects of technological quality were carried out on 25 wheat genotypes with non-standard coloured caryopses. Occurrence of null alleles was observed for the GBSSI gene responsible for amylose synthesis, the so-called waxy gene. Null allele Wx-B1 was found in 20 % of the genotypes, other null alleles were not observed. Allelic state of Pina and Pinb genes affecting caryopsis hardness was analysed too. Allele identification of three genotypes was not successful. In the Pina case, only the wild-type allele Pina-D1a was present, in the Pinb wider variability was observed, 36 % of the genotypes carried wild-type Pinb-D1a allele, 40 % carried Pinb-D1b allele and 12 % Pinb-D1d allele. Instrumental hardness was measured and it correlated with the detected allelic state. Caryopses texture was determined based on the laser beam transmission through the caryopsis. Occurrence of mealy caryopses ranged from 0 % to 100 %. Caryopsis texture and hard-ness do not correlate neither on the instrumental nor on the genetic basis. Null allele Wx-B1 occurrence did not influence the caryopsis hardness nor their texture. Partial sequences of F3H a DFR structural genes of the anthocyanin biosynthetic pathway were obtained at five genotypes with blue, purple and white caryopses. Single nucleotide polymorphisms among individual gene copies were observed.

A major problem faced by the petroleum industry is the deposition of wax during the pumping of waxy crude oils. This precipitation occurs at “normal” temperature, typically 20-30°C in Libya. It could occur during the journey from well to terminal through hundreds of miles of pipelines. This kind of transportation is expensive in terms of pumping costs. The pumping has to be continuous; otherwise wax can build up in the pipeline, reducing the pumping or even stopping it. The property that defines this characteristic is the yield stress which depends on wax concentration and cooling rate. The build-up of paraffin and asphaltenes can lead to serious problems in formation, tanks, and pipelines. Blockages can be expensive and time-consuming to deal with; this is precisely the topic of this research. For this research, model and real waxy crude oils are formulated and their rheology systematically measured under various cooling rates to determine the yield stress. A pipeline loop has been designed to measure the start-up pressure of stagnant oil which has been allowed to precipitate wax. The start-up pressure and the thickness of deposited wax are used in a simple mathematical model to calculate the yield stress. This research thus provides two independent means of predicting the yield stress. This research studied three different waxy crude oils. An MCR-301 Anton Paar rheometer was used to measure the rheology of the oils, and a pipeline rig was used to obtain the start-up pressure to calculate the yield stress of each type of oil after different stoppage times. Also, the thickness of the precipitated wax is measured to calculate the yield stress precisely. The data show that the layer thickness has significant effect on the yield stress and start-up pressures and corresponding yield flow stresses have been found to underpin the crystallisation process of the wax and slow cooling rate produce stronger structures requiring higher stresses to fracture and induce flow. Also, longer shutdown times make these structures even stronger and therefore require even larger stresses for flow to commence.

Master of Science / Department of Grain Science and Industry / Yong-Cheng Shi / Jon Faubion / The rheological properties of two waxy and two normal wheat flours were investigated and the observed differences between them were explained by biochemical analysis. Protein analysis showed that waxy flour had lower polymeric to monomeric ratio (0.70 and 0.58 for waxy flour compared to 0.75 and 0.76 for normal flour) and higher gliadin content in waxy wheat dough (43.9 and 47.3 for waxy wheat dough compared to 41.0 and 41.7 for normal wheat dough). Waxy flour had high amounts of insoluble (IPP) and unextractable (UPP) polymeric protein despite the poor dough forming properties of the waxy flours, contrary to previous correlations made between IPP, UPP and dough strength. Gluten index determination showed a clear difference between waxy and normal flour; there was no gluten aggregation when the waxy samples were tested. The determination of gluten index done on a variety of water washed flour samples indicated that the water-extractable fraction may contain compounds that affect gluten aggregation. HPLC analysis coupled with arabinose/xylose ratio and viscosity determination of the water extractable portion of the flour indicated that water extractable arabinoxylans (WEAX) in waxy wheat flour were different in composition and conformation. Further research is needed to determine if they could be responsible for the lack of gluten aggregation in waxy flour.

Dans le but d’identifier des critères de sélection du blé (T. aestivum L.) destiné à la production de bioéthanol, les objectifs de cette thèse étaient (1) de mettre en évidence les caractéristiques physico-chimiques du grain associées aux rendements en glucose et éthanol, et (2), d’étudier par approche protéomique l’effet de variants génétiques affectant la quantité d’amylose sur le métabolisme des sucres et de l’amidon. L’analyse de trente variétés implantées dans un essai multilocal pluriannuel a mis en évidence l’importance du taux de protéines, de la dureté et de la distribution des granules d’amidon sur les rendements en glucose et éthanol. Dans une moindre mesure, la composition allélique des protéines de réserves et la viscosité des arabinoxylanes ont également un effet lors de l’étape de transformation de l’amidon en sucres fermentescibles. Huit lignées isogéniques waxy de trois variétés françaises ont été implantées dans un essai multilocal. Les lignées dépourvues d’amylose ont produit moins de glucose et d’éthanol que les variétés normales. Les analyses protéomiques des protéines de l’albumen (albumines, globulines et amphiphiles) ainsi que des protéines associées aux granules d’amidon des grains matures des lignées isogéniques de la variété Trémie ont mis en évidence : (1) une relation entre le volume spécifique des GBSS et la quantité d’amylose et (2) une modification de l’expression d’enzymes impliquées dans le métabolisme des sucres et de l’amidon (Susy, AGPase, fructose biphosphate aldolase) mais aussi de protéines de stress et de défense (serpines et HSP). Ces observations suggèrent un développement du grain incomplet pour la lignée dépourvue d’amylose. / To identify selection criteria for wheat (T. aestivum L.) used for bioethanol production, our objectives were (1) to identify the physicochemical grain characteristics associated with glucose and ethanol yields and (2) using a proteomic approach, to study the impact on sugar and starch metabolism of genetic variants that influence the quantity of amylose. The analysis of 30 wheat varieties grown in a 3-year multi-local field trial underlined the importance of protein content, grain hardness and starch granule size distribution for glucose and ethanol yields. A minor effect of the allelic composition of the storage proteins and of viscosity on the transformation of starch in fermentable sugars was also revealed. Eight waxy isogenic lines of three French varieties were grown in a multi-local field trial. The amylose-free lines produced less glucose and ethanol than normal varieties. Proteomic analyses of endosperm proteins (albumins, globulins and amphiphilic proteins) and of proteins associated with starch granules in mature grains of isogenic lines of the Tremie variety revealed : (1) a relation between the specific volume of the GBSS and amylose quantity and (2) a modification of the expression of enzymes involved in starch and sugar metabolism (Susy, AGPase, Fructose biphosphate aldolase) and also in stress and defence proteins (serpins and HSP). These observations suggest incomplete grain development in the line without amylose.

Master of Science / Department of Grain Science and Industry / Paul A. Seib / Yong Cheng Shi / Waxy wheat starch contains almost all amylopectin and is relatively new. Currently, advanced lines of hard winter waxy wheats are being bred through genetic elimination of waxy proteins. To realize the full potential of waxy wheat, the wet-milling of waxy wheat flour to produce gluten and waxy wheat starch was investigated. Flours of six advanced lines of waxy hard wheats and two normal hard wheats cultivars, Karl '92 and Trego, were fractioned by the dough-washing method. Doughs prepared from the waxy flours were found to be weaker than those of from normal wheats. All the waxy wheat and normal wheat flours were wet-milled by the dough-washing (Martin) process and the yield and recovery of starch and gluten were compared. One waxy wheat flour, NWX02Y2459, was sticky during the early stages of dough washing, and it gave relatively poor gluten and starch recoveries with low purity. By mixing the dough with 2% NaCl solution or by adding hemicellulase, the stickiness of the dough subsided during the washing step, and thereby recoveries of the gluten and starch fractions were improved. Waxy wheat starch offers unique functional properties. Waxy wheat starches gelatinize and cook at a relatively low temperature compared to maize starches, and their pastes retrograde more slowly and to a lower extent than waxy maize starch. Pasting curves showed that waxy wheat starch generated a much higher viscosity at a lower temperature, and a lower setback viscosity than normal wheat starch and waxy maize starch. Changes in the morphology of waxy and normal wheat starch granules were determined by using a hot-stage microscope, and those changes were related to their pasting properties. After waxy wheat starch was cross-linked in an aqueous slurry at about 37% starch solids with 0.01% phosphoryl chloride (starch basis), visco-amylograms showed that viscosity breakdown was eliminated and that the cooked paste became non-cohesive (less "stringy"). Increasing levels of phosphoryl chloride at 0.03% and 0.06% caused a steady decline in the peak and final paste consistencies of cross-linked waxy wheat starch, whereas the consistencies of waxy maize starch proceeded through an optimum. Waxy maize starch cross-linked with 0.03% phosphoryl chloride had a higher peak and final consistency at 7% solids than when cross-linked with 0.01% and 0.06% phosphoryl chloride.