Bibliography: leaves 187-216.

The major objectives of this study were to analyze the spatial and temporal distribution of starch branching enzyme (SBE) activity in wheat (Triticum aestivum L. cv. Fielder), to clone and characterize Sbe cDNA and to analyze the expression of genes encoding the SBE isoforms. An assay based on SBE-mediated unprimed synthesis of á-1,4 glucan by phosphorylase a was standardized to detect SBE activity in the protein extracts of wheat tissues. Analysis of SBE activity in the various parts of a wheat plant revealed highest activity in developing kernels. Within a kernel, the embryo axis exhibited higher SBE activity than either the endosperm or scutellum. During kernel development, SBE activity was highest in kernels 10 days post-anthesis (DPA). As the kernels matured beyond 10 DPA SBE activity decreased. Kernel dry weight, starch and amylose concentration increased rapidly until 20 DPA whereas the moisture concentration decreased during this period. Quantitative image analysis of starch granules suggested two distinct granule types (type A and type B that varied in size and shape) were present in kernels after 15 DPA. Image analysis of starch granules isolated at the different stages of kernel development suggested that granules formed immediately after anthesis developed as type A granules while the type B granules were initiated at 12 to 15 DPA. The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to isolate partial cDNA that corresponded to Sbe1 and Sbe2 transcripts expressed in wheat kernels. Northern blot analysis, using the isolated Sbe1 and Sbe2 cDNA detected two transcripts of 4.9 and 2.8 kb in kernels and a single transcript of 2.8 kb in leaves and roots. The 2.8 kb Sbe transcript detected in kernels corresponded in size to that of Sbe transcripts reported from other plants. However, the 4.9 kb transcript detected in wheat kernels seems to represent a unique Sbe transcript. During kernel development, Sbe1 and Sbe2 genes were differentially expressed. Northern blot analysis also revealed that 4.9 and 2.8 kb Sbe1 transcripts were expressed in kernels of three hexaploid wheat cultivars, two tetraploid wheat cultivars and in a barley cultivar. A cDNA library constructed from 12 day old kernels was screened to isolate full length Sbe1 and Sbe2 cDNA clones. The longest clone isolated using the Sbe1 cDNA probe contained a truncated cDNA that represented the 4.9 kb transcript expressed in wheat kernels. RT-PCR analysis suggested that the 4.9 kb transcript was formed as a result of duplication of Sbe1 mRNA sequences. A full-length cDNA (2970 bp) that corresponded to the 2.8 kb Sbe2 transcript expressed in wheat kernels was also isolated. The translated region of the cDNA predicted a 823 amino acid primary product with a molecular mass of 91.4 kDa. The isolated cDNA clones were able to restore BE activity in BE deficient E. coli indicating that the isolated cDNA coded for a functional BE. Southern blot analysis suggested that the Sbe1 and Sbe2 transcripts were encoded by more than one gene.

No description available.

Agronomic and physiological traits associated with drought adaptation were assessed within the Seri/Babax recombinant inbred line population, derived from parents similar in height and maturity but divergent in their sensitivity to drought. Field trials under different water regimes were conducted over three years in Mexico and under rainfed conditions in Australia. Under drought, canopy temperature (CT) was the single-most drought-adaptive trait contributing to a higher performance (R2= 0.71, p<0.0001), highly heritable (h2= 0.65, p<0.0001) and consistently associated with yield phenotypically (r= -0.75, p<0.0001) and genetically [R(g)= -0.95, p<0.0001]. CT epitomises a mechanism of dehydration avoidance expressed throughout the growing season and across latitudes, which can be utilised as a selection criteria to identify high-yielding wheat genotypes or as an important predictor of yield performance under drought. Early response under drought, suggested by a high association of CT with estimates of biomass at booting (r= -0.44, p<0.0001), leaf chlorophyll (r= -0.22,p<0.0001) and plant height (r= -0.64, p<0.0001), contrast with the small relationships with anthesis and maturity (averaged, r= -0.10, p<0.0001), and with osmotic potential (r= -0.20, p<0.0001). Results suggest that the ability to extract water from the soil under increasing soil water deficit is a major attribute of drought adaptation. Ample genetic variation and significant transgressive segregation under drought suggested a polygenic governance feasible of dissection via molecular markers of CT and associated physiological and agronomic traits. Bulked segregant analysis of selected secondary traits was utilised as an alternative to complete genome mapping, due to a low polymorphism (27%) within the cross and limited chromosomic linkage of loci. The assessment of the extremes of expression in a genotypic subset with a composite molecular database of 127 markers (PCR-based and AFLPs) allowed evaluation of the three hexaploid wheat genomes and coverage of all chromosomic groups, except 3D. One-way analysis of variance indicated significant associations of loci explaining phenotypic variance under drought and rainfed conditions, of 20-70% in Mexico and 20-45% in Australia (F>5.00, p<0.05). Significant loci were established in both latitudes for all physiological and agronomic traits assessed via BSA, with CT being the trait with the most numerous associations (in Mexico, 34 loci; in Australia, 24). Results demonstrate an efficient development of molecular markers associated to physiological traits under specific soil water conditions in Mexico and Australia, and suggest further genomic and transcriptomic studies be conducted for unravelling the complex relationship between drought adaptation and performance under drought. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1284279 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Bibliography: leaves 187-216 / xxi, 216 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1987

Bibliography: leaves 245-271 / xiv, 271 leaves, [47] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Physiology, 1985

Agronomic and physiological traits associated with drought adaptation were assessed within the Seri/Babax recombinant inbred line population, derived from parents similar in height and maturity but divergent in their sensitivity to drought. Field trials under different water regimes were conducted over three years in Mexico and under rainfed conditions in Australia. Under drought, canopy temperature (CT) was the single-most drought-adaptive trait contributing to a higher performance (R2= 0.71, p<0.0001), highly heritable (h2= 0.65, p<0.0001) and consistently associated with yield phenotypically (r= -0.75, p<0.0001) and genetically [R(g)= -0.95, p<0.0001]. CT epitomises a mechanism of dehydration avoidance expressed throughout the growing season and across latitudes, which can be utilised as a selection criteria to identify high-yielding wheat genotypes or as an important predictor of yield performance under drought. Early response under drought, suggested by a high association of CT with estimates of biomass at booting (r= -0.44, p<0.0001), leaf chlorophyll (r= -0.22,p<0.0001) and plant height (r= -0.64, p<0.0001), contrast with the small relationships with anthesis and maturity (averaged, r= -0.10, p<0.0001), and with osmotic potential (r= -0.20, p<0.0001). Results suggest that the ability to extract water from the soil under increasing soil water deficit is a major attribute of drought adaptation. Ample genetic variation and significant transgressive segregation under drought suggested a polygenic governance feasible of dissection via molecular markers of CT and associated physiological and agronomic traits. Bulked segregant analysis of selected secondary traits was utilised as an alternative to complete genome mapping, due to a low polymorphism (27%) within the cross and limited chromosomic linkage of loci. The assessment of the extremes of expression in a genotypic subset with a composite molecular database of 127 markers (PCR-based and AFLPs) allowed evaluation of the three hexaploid wheat genomes and coverage of all chromosomic groups, except 3D. One-way analysis of variance indicated significant associations of loci explaining phenotypic variance under drought and rainfed conditions, of 20-70% in Mexico and 20-45% in Australia (F>5.00, p<0.05). Significant loci were established in both latitudes for all physiological and agronomic traits assessed via BSA, with CT being the trait with the most numerous associations (in Mexico, 34 loci; in Australia, 24). Results demonstrate an efficient development of molecular markers associated to physiological traits under specific soil water conditions in Mexico and Australia, and suggest further genomic and transcriptomic studies be conducted for unravelling the complex relationship between drought adaptation and performance under drought. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1284279 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Thesis (PhD(Agric) (Agronomy))--Stellenbosch University, 2008. / The adoption of the no-till planting method brought about changes to the way the wheat crop is established in the Mediterranean climate of the Western Cape. Row widths have to increase from the normal narrow rows (170-180 mm) to at least 250 mm to allow for sufficient stubble handling. Furthermore, planters are designed to place seed accurately in the soil at uniform depth, which may increase seedling survival rates. The main objective of this study was to determine the influence of the use of wide row widths on yield, the components of yield and grain quality parameters and to revisit planting density recommendations to be used with the notill planting method. On-farm, producer managed trials which included cultivars, row widths and planting density treatments were planted at Riversdale, Swellendam and Caledon in the Southern Cape region and at Moorreesburg and Hopefield in the Swartland during the 2004 to 2006 production seasons. All trials were factorial RCB designs with split-split plot arrangements. Grain yield, grain protein, hectolitre mass (HLM) and the yield components, seedlings m-2, seedling survival (%), number of heads m-2, number of heads plant-1, number of kernels head-1 and thousand kernel mass (TKM) were determined at all sites in 2005 and 2006. Seedling survival rates of 80% were easily achieved in all trials with the exception of Caledon and Swellendam in 2005. The no-till planting method may be efficient to improve on survival rates of 50-70% found with the conventional planting methods. The yield component response that raised the most concern was the clear trend of the reduction in the number of heads m-2 as row widths increased, which was significant in eight out of the nine experiments. The number of heads plant-1 decreased significantly as planting density increased in all experiments. Cultivars differed in the grain quality parameters grain protein (%) and HLM but were influenced minimally by the other treatments. Reductions in grain yield occurred in three out of eight trials in the Southern Cape and in three out of six trials in the Swartland, with reductions of between 6.8% and 33% in some seasons. The risk of yield loss due to wide row widths could not be excluded by this study and therefore the row widths used by producers should remain as narrow as practically possible. Grain yield response to increasing planting density differed between the two regions. No significant yield benefits were found in any of these trials if planting densities were increased above 175 target plants m-2. Planting densities may be reduced to between 70 and 87.5 kg seed ha-1 to achieve this target if the crop is planted in time and seedling survival rates of at least 80% can be achieved.

ABSTRACT Triticum sphaerococcum (AABBDD, 2n = 6x = 42) is a land race of wheat known from the Indian subcontinent. It has several favourable characters including short and strong culms, hemispherical grains with a shallow crease (that may increase the yield of white flour), higher protein content compared to bread wheat (T. aestivum), and resistance to drought, and yellow rust caused by Puccinia striiformis. However, an unfavourable characteristic of T. sphaerococcum is its lower yield compared to bread wheat. Being a land race, the sphaerococcum wheat is poorly studied. This study was undertaken to increase knowledge of the physiology and genetics of this land race and determine if it may be possible to separate the favourable characters of T. sphaerococcum from its unfavourable characters. Plant height in bread wheat is controlled by many genes. ‘Reduced Height’ (Rht) genes which differ in their response to externally applied gibberellic acid (GA3) are responsible for the short stature of modern bread wheat varieties. Therefore, GA3 was used to probe the relationship between the semidwarf sphaerococcum phenotype and the Rht gene. T. sphaerococcum variety Sp5 showed a unique “seedling response” to externally applied GA3 when compared with T. aestivum varieties harbouring Rht1, Rht2, Rht8, Rht12, Rht13 or Rht18 alleles. A mapping population of doubled haploids was generated through wide hybridisation of F1 (Sp5 x Otane) with Zea mays. A genome-wide scan of Sp5 and Otane (parents) using 348 microsatellite (SSR) markers showed that only 169 of these markers (49%) were polymorphic between the parents. A DArT profiling yielded 348 markers that were polymorphic between the parents. Microsatellite markers and DArT markers were used to create a genetic map. The mapping population was phenotyped and a quantitative trait loci (QTL) analysis was performed for component traits of the complex sphaerococcum trait including plant height, spike length, awn length, yield, grain shape and crease size. Results of the QTL analysis indicated that it may be difficult to separate the favourable characters of T. sphaerococcum from its unfavourable characters through mutation because the component traits of the complex sphaerococcum trait may be under pleiotropic control of the Sp gene. The hypothesis that T. sphaerococcum originated through a mutation in T. aestivum was tested through induced mutation using gamma rays. Mutants from sphaerococcum-type to aestivum-type were isolated and phenotyped. Sphaerococcum-type mutants also were isolated and characterised from mutated aestivum-type wheat suggesting a possible origin of T. sphaerococcum through a mutation in T. aestivum.

ABSTRACT Triticum sphaerococcum (AABBDD, 2n = 6x = 42) is a land race of wheat known from the Indian subcontinent. It has several favourable characters including short and strong culms, hemispherical grains with a shallow crease (that may increase the yield of white flour), higher protein content compared to bread wheat (T. aestivum), and resistance to drought, and yellow rust caused by Puccinia striiformis. However, an unfavourable characteristic of T. sphaerococcum is its lower yield compared to bread wheat. Being a land race, the sphaerococcum wheat is poorly studied. This study was undertaken to increase knowledge of the physiology and genetics of this land race and determine if it may be possible to separate the favourable characters of T. sphaerococcum from its unfavourable characters. Plant height in bread wheat is controlled by many genes. ‘Reduced Height’ (Rht) genes which differ in their response to externally applied gibberellic acid (GA3) are responsible for the short stature of modern bread wheat varieties. Therefore, GA3 was used to probe the relationship between the semidwarf sphaerococcum phenotype and the Rht gene. T. sphaerococcum variety Sp5 showed a unique “seedling response” to externally applied GA3 when compared with T. aestivum varieties harbouring Rht1, Rht2, Rht8, Rht12, Rht13 or Rht18 alleles. A mapping population of doubled haploids was generated through wide hybridisation of F1 (Sp5 x Otane) with Zea mays. A genome-wide scan of Sp5 and Otane (parents) using 348 microsatellite (SSR) markers showed that only 169 of these markers (49%) were polymorphic between the parents. A DArT profiling yielded 348 markers that were polymorphic between the parents. Microsatellite markers and DArT markers were used to create a genetic map. The mapping population was phenotyped and a quantitative trait loci (QTL) analysis was performed for component traits of the complex sphaerococcum trait including plant height, spike length, awn length, yield, grain shape and crease size. Results of the QTL analysis indicated that it may be difficult to separate the favourable characters of T. sphaerococcum from its unfavourable characters through mutation because the component traits of the complex sphaerococcum trait may be under pleiotropic control of the Sp gene. The hypothesis that T. sphaerococcum originated through a mutation in T. aestivum was tested through induced mutation using gamma rays. Mutants from sphaerococcum-type to aestivum-type were isolated and phenotyped. Sphaerococcum-type mutants also were isolated and characterised from mutated aestivum-type wheat suggesting a possible origin of T. sphaerococcum through a mutation in T. aestivum.