Jointed goatgrass (Aegilops cylindrica Host; 2n=4x=28; CCDD) is an agriculturally important species both as a weed and as a genetic resource for wheat (Triticum aestivum L.; 2n=6x=42; AABBDD) improvement. In order to better understand the evolution of this species, the diversity of Ae. cylindrica was evaluated along with its progenitors, Ae. markgrafii (Greuter) Hammer (2n=2x=14; CC) and Ae. tauschii Coss. (2n=2x=14; DD), using chloroplast and nuclear microsatellite markers. Ae. cylindrica had lower levels of plastome and nuclear diversity than its progenitors. The plastome diversity of Ae. cylindrica was lower than its nuclear diversity. Ae. cylindrica was found to have either C-or D-type plastomes, derived from Ae. markgrafii or Ae. tauschii, respectively, where the C-type plastome was found to occur at a lower frequency than the D-type plastome. The nuclear genomes of Ae. cylindrica accessions with C-or D-type plastome were found to be very closely related, suggesting a monotypic origin. Furthermore, analyses suggests that Ae. tauschii ssp. tauschii contributed its D genome and D-type plastome to Ae. cylindrica. Ae. cylindrica accessions collected near Van Lake in southeastern Turkey, an area where Ae. tauschii ssp. tauschii and Ae. markgrafii overlap, showed high allelic diversity and may represent the site where Ae. cylindrica formed. Population structure analyses suggested a lack of regional genetic structure in Ae. cylindrica and evidence of migration of Ae. cylindrica among various regions. Finally, Ae. cylindrica accessions in the USA were found to be closely related to accessions from at least three regions of its native range central Anatolia, central East Turkey and western Armenia, and Caucasia. Wheat and jointed goatgrass are closely related and both have the D-genome. These two species can hybridize and produce backcross derivatives under natural conditions, a situation that may allow gene flow between these two species. In order to better understand mating patterns between these two species, a total of 413 first-generation backcross (BC₁) seeds obtained from 127 wheat-jointed goatgrass F₁ hybrids, produced under natural conditions, were evaluated for their parentage using chloroplast and nuclear microsatellite markers. Of the 127 F₁ hybrids evaluated, 109 had jointed goatgrass as the female parent, while the remaining 18 F₁ plants had wheat as the female parent. Of the 413 BC₁ plants analyzed, 358 had wheat and 24 had jointed goatgrass as the recurrent male parent. The male parentage of 31 BC₁ plants could not be determined. Although the majority of hybrids were pollinated by wheat, backcrossing of hybrids to jointed goatgrass would enable gene flow from wheat to jointed goatgrass. Though the observed frequency of jointed goatgrass-backcrossed hybrids (F₁ X jointed goatgrass) was low under field conditions, their absolute number is dependent on frequency of hybrids, which in turn, depends on the density of jointed goatgrass in wheat fields. Therefore, the recommendations to control jointed goatgrass in wheat fields and adjacent areas and to plant jointed goatgrass free wheat seed should be followed in order to avoid gene flow from wheat to jointed goatgrass. / Graduation date: 2006

Graduation date: 2002

The lack of information regarding the inheritance of the duration and rate of grain filling, and the possible relationship between grain fill and grain protein content in wheat prompted this study. Early maturing Chinese cultivars, 'AI Feng 2' and 'CB 83-52', and late maturing cultivars adapted to Oregon, 'Stephens' and 'Yamhill Dwarf', were examined for vernalization and photoperiod responses. Progeny from a diallel cross of the genotypes was evaluated for grain filling parameters, grain protein content and other agronomic traits for two years. 'Yamhill Dwarf' required six weeks of vernalization, while other cultivars needed only four weeks. The two Oregon developed genotypes were more sensitive to photoperiod than Chinese genotypes. Variation in developmental patterns among genotypes was related to differences in leaf number, spikelet number, rate of spikelet initiation, and rate of grain fill. Compared to solid planting, space-planting reduced the grain filling period. Significant genotypic variation for grain filling rate, duration, and kernel weight was observed in both seasons. Genotype X year interaction was not significant for any of the grain filling traits. General combining ability effects for grain filling rate, duration, and kernel weight were much larger than specific combining ability effects. Additive gene action made the major contribution to the inheritance of the grain filling traits. However, dominance effects appeared also to be involved in the genetic control of grain filling duration and kernel weight. Narrow sense heritability estimates were high for all three grain filling traits. Results indicated that early generation selection for both duration and rate of grain fill should be effective in these populations. Rate, but not duration of grain fill was closely associated with kernel weight. There was an inverse relationship between duration and rate of grain filling. Kernel protein percentage was positively associated with duration, but negatively related to rate of the grain filling. Results suggest that starch and protein accumulations in the kernel are two highly independent processes and may not necessarily compete for assimilates or energy. It may be necessary under the environments of this study to increase the duration of the grain fill to obtain high protein content with acceptable grain yield. / Graduation date: 1993

Septoria leaf blotch of wheat is a major biotic factor limiting the grain yield. To determine the nature of inheritance involving selected genotypes, three resistant semidwarf spring wheat lines exhibiting durable global resistance and one susceptible cultivar were crossed in all possible combinations, excluding reciprocals. Parents, Fl, F2, and F3 generations were inoculated with one pathogenic strain of Septoria tritici and evaluated under field conditions. Data were collected on an individual plant basis. F2 and F3 frequency distributions were computed to determine the nature of inheritance. Combining ability analysis of the 4x4 diallel cross and narrow-sense heritability were employed to estimate the nature of gene action. Phenotypic correlations were obtained to examined the possible association between disease severity traits and their relationship with heading date and plant height. The continuous distribution of the F2 and F3 populations among crosses made it impossible to classify plants into discrete classes in crosses between resistant x susceptible genotypes. Mean values of the disease traits Septoria progress coefficient, Relative coefficient of infection, and Septoria severity of flag leaf among the segregating populations were similar to the midparent values. Transgressive segregation was also observed in the F2 and F3 suggesting that parents had different resistance genes. Additive gene effects were found to be the major component of variation although nonadditive gene action played an important role in the expression of all three disease traits. The resistant parents Bobwhite"S" and Kavkaz /K4500 L.A.4 were found to have the largest negative general combining ability effects for the disease traits suggesting that these parents would be the best source for resistance to Septoria leaf blotch. High general combining ability and high narrow sense heritability estimates in the F3 population, indicated that substantial progress for resistance to Septoria tritici would be effective selecting in this generation. Of the three disease measures it would appear that selection for the lowest percentage of Septoria infection on the flag leaf would provide the most progress in developing resistant cultivars. Moderate and low negative phenotypic correlations were found among generations for the disease traits with heading date and plant height. From the results of this study the selection of early maturing short stature progeny would be possible within the genetic materials employed in this study. / Graduation date: 1993

Salinity stress limits the growth and productivity of agricultural crops in many regions of the world. Whole plant tolerance to soil salinity involves numerous processes in many different tissues and cell types. For many cereals, sensitivity to salinity is due to the accumulation of sodium (Na⁺) to toxic concentrations in the leaves. This thesis investigates a mechanism of control of Na⁺ accumulation in leaves of wheat. Bread wheat excludes sodium from the leaves better than durum wheat. Bread wheat is hexaploid (AABBDD) whereas durum wheat is tetraploid (AABB). The D-genome in bread wheat carries a major locus for sodium exclusion, Kna1, which may contribute to the differences in sodium exclusion between bread wheat and durum wheat. An unusual durum wheat, Line 149, excludes sodium to a similar degree as bread wheat. Line 149 was derived from a cross between a Triticum monococcum (accession C68-101; AA) and a durum wheat (T. turgidum ssp. durum cv. Marrocos; AABB). Line 149 had been found to contain two major genes for sodium exclusion, named Nax1 and Nax2, which appeared to retrieve sodium from the xylem sap in the roots and so prevent it reaching the leaves. Line 149 had been crossed with the durum wheat cv. Tamaroi, which accumulates high concentrations of Na⁺ in the leaves, and near-isogenic single-gene mapping populations had been developed for Nax1 and Nax2. Nax1 had been located on chromosome 2A. The objective of this thesis was to map Nax2 and identify a candidate gene. Nax2 mapped to chromosome 5AL based on linkage to microsatellite markers. A high-affinity potassium (K⁺) transporter (HKT)-like gene, HKT1;5 was considered as a candidate gene for Nax2, based on similarity of the phenotype to a rice orthologue. Sequence information from a wheat HKT1;5-like expressed sequence tag in the public database was used to develop a probe for use in Southern hybridsation. A HKT1;5-like fragment was identified in Line 149 and T. monococcum C68-101, but was absent in Tamaroi. The HKT1;5-like gene, named TmHKT1;5-A, co-segregated with Nax2 in the Nax2 single-gene mapping population. The HKT1;5 probe identified three putative HKT1;5-like genes on the long arm of chromosome 4B, and one HKT1;5-like gene on the long arm of chromosome 4D, in Langdon (T. turgidum ssp. durum) substitution lines, and in Chinese Spring (T. aestivum) ditelomeric lines. No A-genome HKT1;5 like gene was identified in Langdon or Chinese Spring. The D-genome HKT1;5 gene, named TaHKT1;5-D, was found to co-locate with Kna1, the gene for sodium exclusion in bread wheat, in Chinese Spring chromosome 4D deletion lines. Nax2 (TmHKT1;5-A) was found to be homoeologous with the gene for sodium exclusion in bread wheat, Kna1 (TaHKT1;5-D). TmHKT1;5-A and TaHKT1;5-D, and their promoters, were 94% identical, and both were expressed in the roots of wheat plants. This is consistent with the genes being located in the stele of the roots and retrieving Na⁺ from the xylem sap as it flows towards the shoot, and so excluding Na⁺ from the leaves. A marker for TmHKT1;5-A was developed to track this gene in durum wheat breeding programs. A study of the HKT1;5 gene in diploid ancestors of wheat indicated that this gene is present in most Triticum monococcum accessions, some T. boeoticum accessions, but not present in any T. urartu accessions. T. urartu is the likely A genome ancestor of modern wheat. This may explain the absence of HKT1;5 in the A genome of modern wheat. The protein encoded by TaHKT1;5-D transported sodium when expressed in Xenopus laevis oocytes. The inward currents were specific to Na⁺, but at particular mole fractions of Na⁺ and K⁺ outward currents were observed that were consistent with outward K⁺ transport. These data were consistent with the putative physiological function, of retrieving Na⁺ from the xylem sap as it flows to the leaves, and resulting in a net exchange with K⁺. A construct designed to silence the expression of TaHKT1;5-D was introduced to bread wheat cv. Bob White. Nineteen putative transgenic plants were developed. The leaf Na⁺ concentrations and genotype of the T1 individuals were assayed. The data from two of the transgenic plants indicated that TaHKT1;5-D may have been silenced and that this may have lead to the increase in Na⁺ accumulation in the leaves. However, this data is not conclusive at this time. The information gained from this study will assist the introduction of the Na⁺ exclusion trait into current durum cultivars, which are poor at excluding Na⁺ and are salt sensitive. This information will also contribute to the body of knowledge of ion transport in plants and salinity tolerance in wheat. / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Bibliography: leaves [129]-146 / v, 146, [50] leaves, [50] 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 Agronomy, Waite Agricultural Research Institute, 1985

Bibliography: leaves [129]-146 / v, 146, [50] leaves, [50] 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 Agronomy, Waite Agricultural Research Institute, 1985

Salinity stress limits the growth and productivity of agricultural crops in many regions of the world. Whole plant tolerance to soil salinity involves numerous processes in many different tissues and cell types. For many cereals, sensitivity to salinity is due to the accumulation of sodium (Na⁺) to toxic concentrations in the leaves. This thesis investigates a mechanism of control of Na⁺ accumulation in leaves of wheat. Bread wheat excludes sodium from the leaves better than durum wheat. Bread wheat is hexaploid (AABBDD) whereas durum wheat is tetraploid (AABB). The D-genome in bread wheat carries a major locus for sodium exclusion, Kna1, which may contribute to the differences in sodium exclusion between bread wheat and durum wheat. An unusual durum wheat, Line 149, excludes sodium to a similar degree as bread wheat. Line 149 was derived from a cross between a Triticum monococcum (accession C68-101; AA) and a durum wheat (T. turgidum ssp. durum cv. Marrocos; AABB). Line 149 had been found to contain two major genes for sodium exclusion, named Nax1 and Nax2, which appeared to retrieve sodium from the xylem sap in the roots and so prevent it reaching the leaves. Line 149 had been crossed with the durum wheat cv. Tamaroi, which accumulates high concentrations of Na⁺ in the leaves, and near-isogenic single-gene mapping populations had been developed for Nax1 and Nax2. Nax1 had been located on chromosome 2A. The objective of this thesis was to map Nax2 and identify a candidate gene. Nax2 mapped to chromosome 5AL based on linkage to microsatellite markers. A high-affinity potassium (K⁺) transporter (HKT)-like gene, HKT1;5 was considered as a candidate gene for Nax2, based on similarity of the phenotype to a rice orthologue. Sequence information from a wheat HKT1;5-like expressed sequence tag in the public database was used to develop a probe for use in Southern hybridsation. A HKT1;5-like fragment was identified in Line 149 and T. monococcum C68-101, but was absent in Tamaroi. The HKT1;5-like gene, named TmHKT1;5-A, co-segregated with Nax2 in the Nax2 single-gene mapping population. The HKT1;5 probe identified three putative HKT1;5-like genes on the long arm of chromosome 4B, and one HKT1;5-like gene on the long arm of chromosome 4D, in Langdon (T. turgidum ssp. durum) substitution lines, and in Chinese Spring (T. aestivum) ditelomeric lines. No A-genome HKT1;5 like gene was identified in Langdon or Chinese Spring. The D-genome HKT1;5 gene, named TaHKT1;5-D, was found to co-locate with Kna1, the gene for sodium exclusion in bread wheat, in Chinese Spring chromosome 4D deletion lines. Nax2 (TmHKT1;5-A) was found to be homoeologous with the gene for sodium exclusion in bread wheat, Kna1 (TaHKT1;5-D). TmHKT1;5-A and TaHKT1;5-D, and their promoters, were 94% identical, and both were expressed in the roots of wheat plants. This is consistent with the genes being located in the stele of the roots and retrieving Na⁺ from the xylem sap as it flows towards the shoot, and so excluding Na⁺ from the leaves. A marker for TmHKT1;5-A was developed to track this gene in durum wheat breeding programs. A study of the HKT1;5 gene in diploid ancestors of wheat indicated that this gene is present in most Triticum monococcum accessions, some T. boeoticum accessions, but not present in any T. urartu accessions. T. urartu is the likely A genome ancestor of modern wheat. This may explain the absence of HKT1;5 in the A genome of modern wheat. The protein encoded by TaHKT1;5-D transported sodium when expressed in Xenopus laevis oocytes. The inward currents were specific to Na⁺, but at particular mole fractions of Na⁺ and K⁺ outward currents were observed that were consistent with outward K⁺ transport. These data were consistent with the putative physiological function, of retrieving Na⁺ from the xylem sap as it flows to the leaves, and resulting in a net exchange with K⁺. A construct designed to silence the expression of TaHKT1;5-D was introduced to bread wheat cv. Bob White. Nineteen putative transgenic plants were developed. The leaf Na⁺ concentrations and genotype of the T1 individuals were assayed. The data from two of the transgenic plants indicated that TaHKT1;5-D may have been silenced and that this may have lead to the increase in Na⁺ accumulation in the leaves. However, this data is not conclusive at this time. The information gained from this study will assist the introduction of the Na⁺ exclusion trait into current durum cultivars, which are poor at excluding Na⁺ and are salt sensitive. This information will also contribute to the body of knowledge of ion transport in plants and salinity tolerance in wheat. / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Salinity stress limits the growth and productivity of agricultural crops in many regions of the world. Whole plant tolerance to soil salinity involves numerous processes in many different tissues and cell types. For many cereals, sensitivity to salinity is due to the accumulation of sodium (Na⁺) to toxic concentrations in the leaves. This thesis investigates a mechanism of control of Na⁺ accumulation in leaves of wheat. Bread wheat excludes sodium from the leaves better than durum wheat. Bread wheat is hexaploid (AABBDD) whereas durum wheat is tetraploid (AABB). The D-genome in bread wheat carries a major locus for sodium exclusion, Kna1, which may contribute to the differences in sodium exclusion between bread wheat and durum wheat. An unusual durum wheat, Line 149, excludes sodium to a similar degree as bread wheat. Line 149 was derived from a cross between a Triticum monococcum (accession C68-101; AA) and a durum wheat (T. turgidum ssp. durum cv. Marrocos; AABB). Line 149 had been found to contain two major genes for sodium exclusion, named Nax1 and Nax2, which appeared to retrieve sodium from the xylem sap in the roots and so prevent it reaching the leaves. Line 149 had been crossed with the durum wheat cv. Tamaroi, which accumulates high concentrations of Na⁺ in the leaves, and near-isogenic single-gene mapping populations had been developed for Nax1 and Nax2. Nax1 had been located on chromosome 2A. The objective of this thesis was to map Nax2 and identify a candidate gene. Nax2 mapped to chromosome 5AL based on linkage to microsatellite markers. A high-affinity potassium (K⁺) transporter (HKT)-like gene, HKT1;5 was considered as a candidate gene for Nax2, based on similarity of the phenotype to a rice orthologue. Sequence information from a wheat HKT1;5-like expressed sequence tag in the public database was used to develop a probe for use in Southern hybridsation. A HKT1;5-like fragment was identified in Line 149 and T. monococcum C68-101, but was absent in Tamaroi. The HKT1;5-like gene, named TmHKT1;5-A, co-segregated with Nax2 in the Nax2 single-gene mapping population. The HKT1;5 probe identified three putative HKT1;5-like genes on the long arm of chromosome 4B, and one HKT1;5-like gene on the long arm of chromosome 4D, in Langdon (T. turgidum ssp. durum) substitution lines, and in Chinese Spring (T. aestivum) ditelomeric lines. No A-genome HKT1;5 like gene was identified in Langdon or Chinese Spring. The D-genome HKT1;5 gene, named TaHKT1;5-D, was found to co-locate with Kna1, the gene for sodium exclusion in bread wheat, in Chinese Spring chromosome 4D deletion lines. Nax2 (TmHKT1;5-A) was found to be homoeologous with the gene for sodium exclusion in bread wheat, Kna1 (TaHKT1;5-D). TmHKT1;5-A and TaHKT1;5-D, and their promoters, were 94% identical, and both were expressed in the roots of wheat plants. This is consistent with the genes being located in the stele of the roots and retrieving Na⁺ from the xylem sap as it flows towards the shoot, and so excluding Na⁺ from the leaves. A marker for TmHKT1;5-A was developed to track this gene in durum wheat breeding programs. A study of the HKT1;5 gene in diploid ancestors of wheat indicated that this gene is present in most Triticum monococcum accessions, some T. boeoticum accessions, but not present in any T. urartu accessions. T. urartu is the likely A genome ancestor of modern wheat. This may explain the absence of HKT1;5 in the A genome of modern wheat. The protein encoded by TaHKT1;5-D transported sodium when expressed in Xenopus laevis oocytes. The inward currents were specific to Na⁺, but at particular mole fractions of Na⁺ and K⁺ outward currents were observed that were consistent with outward K⁺ transport. These data were consistent with the putative physiological function, of retrieving Na⁺ from the xylem sap as it flows to the leaves, and resulting in a net exchange with K⁺. A construct designed to silence the expression of TaHKT1;5-D was introduced to bread wheat cv. Bob White. Nineteen putative transgenic plants were developed. The leaf Na⁺ concentrations and genotype of the T1 individuals were assayed. The data from two of the transgenic plants indicated that TaHKT1;5-D may have been silenced and that this may have lead to the increase in Na⁺ accumulation in the leaves. However, this data is not conclusive at this time. The information gained from this study will assist the introduction of the Na⁺ exclusion trait into current durum cultivars, which are poor at excluding Na⁺ and are salt sensitive. This information will also contribute to the body of knowledge of ion transport in plants and salinity tolerance in wheat. / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008

Experiments were undertaken to examine the extent of variation for potassium and nitrogen uptake and utilization in wheat and also to address some issues of relevance to the improvement of these traits. These issues included the inheritance of these traits and the difficulties that could arise due to (1) the methodology that is used to measure ion fluxes and utilization, (2) ontogenetic variation in the expression of these traits, and (3) the growth stage at which nutrient utilization is evaluated. To compare varieties developed during different periods in the history of wheat breeding, the varieties were assigned to five groups on the basis of height and origin. Nutrient fluxes were measured either as average net fluxes or short-term net fluxes. Nutrient utilization was expressed as shoot fresh weight per plant, efficiency ratio or utilization efficiency. Substantial variation was observed for all traits except potassium and nitrogen efficiency ratios. Although short-term net potassium fluxes were negatively correlated with root potassium concentration, some of the differences in flux were not associated with differences in root potassium concentration. These differences must therefore be heritable. Due to the complexity of the regulation of nitrate uptake, genotypic differences in short-term net nitrate flux were not examined in relation to root nitrate concentration. Therefore, some of the variation in nitrate flux could be due to differences in root nitrate concentration or some other factor(s) which regulates nitrate uptake. Significant differences between groups were also observed. The tall varieties had the highest potassium and nitrate fluxes but were not significantly different from the triple dwarfs. The double dwarfs were the poorest performers for both nutrient uptake and utilization. In general, the tall traditional varieties were more vigorous and hence showed the highest shoot weight per plant and utilization efficiencies. These findings are examined in relation to the contention that plant breeding under high fertility conditions may have resulted in a decline in the ability of plants to acquire and utilize mineral nutrients. The inheritance of short-term net potassium flux, shoot weight per plant, potassium efficiency ratio and potassium utilization efficiency was studied in four crosses. Complex modes of inheritance were observed for all the traits. For one of the crosses significant reciprocal effects were observed for shoot weight per plant, efficiency ratio and utilization efficiency. Narrow sense heritabilities for the two traits most likely to be selected for, namely short-term net potassium flux and shoot weight per plant, indicated that selection for these traits should be carried out amongst families rather than amongst single plants. Diallel analysis for nitrate uptake and utilization indicated that both additive and dominance gene effects are important in the determination of these traits. The effect of developmental changes in potassium uptake and utilization on varietal comparisons and genetic studies was investigated by comparing the performance of six varieties at different stages of growth over a five-week period. The rankings of the varieties for short-term net potassium flux and shoot weight per plant were found to be fairly consistent. Correlations between average net fluxes for different time periods as well between short-term and average net fluxes were poor. These findings indicate that selection for differences in uptake should be based on fluxes obtained from solutions identical in concentration to the growth solution rather than on perturbation fluxes obtained by depletion of a solution much more concentrated than the growth solution. All measures of potassium utilization based on vegetative growth were poorly correlated with performance at the adult stage. Significant negative rank correlations between shoot fresh weight per plant and grain weight per plant were obtained most likely due to differences in harvest index. This finding casts some doubt on the usefulness of vegetative measures of nutrient utilization as indicators of nutrient-use efficiency for a crop in which the economic product consists of grain. / Science, Faculty of / Botany, Department of / Graduate