|dc.contributor.author||Thistlethwaite, Rebecca Janette||-|
|dc.description.abstract||Increasing global climatic variability will most likely increase temperatures and reduce annual rainfall in many cropping regions in the coming years. Changes in seasonal conditions are likely to have a significant impact on all food crops including wheat. This thesis aims to (1) identify genetic diversity for high temperature tolerance in bread wheat by evaluating a large number of genotypes across years and sowing dates, (2) evaluate a subset of germplasm was using different screening methods for heat tolerance (in-field controlled environment chambers and glasshouses) and (3) compare different screening methods, Field experiments were conducted between 2012 and 2015 to identify superior genotypes with tolerance to high temperature from Australian and international wheat germplasm. Yield and yield components and phenological and physiological traits were assessed each season. Mean maximum temperature between heading and maturity demonstrated that for every 1 °C rise in mean maximum temperature, grain yield decreased by approximately 230kg/ha. A subset of twenty genotypes was maintained across all years and times of sowing to assess trait stability under heat stress. A
significant genotype x environment interaction was observed for yield and yield components and the size of the interaction differed by trait.
In-field controlled environment chambers were designed to implement a heat shock at anthesis on normally sown materials to assess the validity of late sowing as a method for heat tolerance screening. The heat shock applied at anthesis using chambers consistently reduced grain number more than TKW, largely due to negative impacts on pollen viability. A glasshouse experiment was conducted to impose a heat shock to the same subset of twenty genotypes. Plants were heated for three days at pollen formation (meiosis) and anthesis. Heat shock at meiosis had a greater impact on yield components than heat shock at anthesis.
An ideotype for the warmer conditions in northwestern NSW was developed from the trait responses and relationships with productivity traits such as yield, kernel weight and screenings. Such an ideotype would be short-statured, maintain and prolong greenness at booting and anthesis, maintain and produce larger grain, extend the vegetative period and produce a 1:1 ratio of grain to biomass.||en_AU|
|dc.publisher||University of Sydney||en_AU|
|dc.publisher||School of Life and Environmental Sciences||en_AU|
|dc.rights||The author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission.||en_AU|
|dc.title||Identification of genetic variation in heat stress, genotype screening for and mechanisms of tolerance in wheat||en_AU|
|dc.type.pubtype||Doctor of Philosophy Ph.D.||en_AU|
|dc.description.disclaimer||Access is restricted to staff and students of the University of Sydney . UniKey credentials are required. Non university access may be obtained by visiting the University of Sydney Library.||en_AU|
|Appears in Collections:||Sydney Digital Theses (University of Sydney Access only)|