This study was conducted with the aim of improving our understanding of the genetic basis of the superior grain yield of an elite bread wheat breeding line, RAC875, under drought and heat stressed Mediterranean-type climates in southern Australia. Here, these abiotic stresses present a significant barrier to production. Kukri is a locally adapted variety which achieves acceptable grain yield under more favourable conditions, but relatively low grain yields under severe stress. A cross between the two lines resulted in an F1 derived doubled haploid population consisting of 368 individuals. The population was initially used for the genetic dissection of time to ear emergence and flag leaf glaucousness, with the latter trait hypothesised to explain a significant proportion of RAC875's relative drought and heat tolerance. Whilst parents of the population achieved similar time to ear emergence, segregation for Ppd-B1 and Ppd-D1a created large variation for this trait within the population. Two novel minor loci were detected for time to ear emergence (Q.Eet.aww-1A and Q.Zad.aww-4A), in addition to another eight known, minor loci. Five novel loci were detected for flag leaf glaucousness (Q.W.aww-3A, Q.W.aww-3B, Q.W.aww-3D, Q.W.aww-4D and Q.W.aww-5B), with one in particular (Q.W.aww-3A) accounting for up to 52 percent of the genetic variance for this trait. Sixteen field experiments were sown across southern Australia between 2006 and 2010, where average site grain yields ranged from 314 to 5275 kg ha−1. Kernels per square metre was the trait most correlated with grain yield, while spikelet fertility, which had a significant positive correlation with grains per square metre in all experiments and the subsequently derived environment clusters, was also related to grain yield. Nine loci were detected for grain yield independent of time to ear emergence and plant height. Five of these loci co-located with loci for kernels per square metre and only one of these nine loci were associated with any of the loci for flag leaf glaucousness and this genetic effect was opposite (i.e. Kukri allele resulting in large glaucousness value and lower grain yield). The RAC875 allele at QTL on chromosomes 1B and 7A (Q.Yld.aww-1B and Q.Yld.aww-7A-2) was associated with greater grain yield, kernels per spikelet and kernels per square metre. These two loci were detected in environment clusters where heat stress was a differentiating factor and it was concluded that these may therefore be associated with heat stress tolerance. Another QTL of large effect was consistently detected on chromosome 6A (Q.Tkw.aww-6A), with the RAC875 allele positively affecting grain size, flag leaf width and stem water soluble carbohydrate content but resulting in lower kernels per spikelet and therefore kernels per square metre. Experiments were also sown to assess the performance of the population in north-west Mexico under well watered, high yield potential conditions, as well as drip irrigated drought treatment and late planted but well watered conditions to expose the experiments to heat stress. This resulted in three very distinctive treatments and subsequently detected different genetic regions controlling grain yield. Two distinct QTL were detected for grain yield and canopy temperature on chromosome 3B, under irrigated (Q.Yld.aww-3B-1) and irrigated, drought and heat stressed treatments (Q.Yld.aww-3B-2). The latter QTL accounted for up to 22 percent of the genetic variance for grain yield and 20 percent of the genetic variance for canopy temperature under the heat stress treatment. However, all three treatments failed to detect any major QTL of common effect to southern Australia. This study highlighted the complex genetic basis of grain yield and physical grain quality in drought and heat stressed conditions, as well as the importance of conducting QTL dissection in the target environment. However, key loci detected offer potential for marker development and deployment of marker assisted selection within wheat breeding programmes targeting southern Australia. In the longer term, this should help improve the rate of genetic gain for grain yield, increasing production by growers in the Mediterranean type climate of southern Australia.

A stagnation of wheat yield was reported in France and other countries worldwide since the 1990's, which incriminated mainly drought and heat stress. Improving the European wheat tolerance to them is of first importance. This study aimed to investigate the genetic determinism of the tolerance to such stresses. Three CIMMYT bread wheat populations combining complementary heat and drought adaptive habits were grown in Northern Mexico under irrigated, drought and heat-irrigated treatments from 2011 to 2013. The trial network comprised 15 trials and both physiological and agronomic traits were scored. First, an environmental characterization methodology was developed and resulted in the identification of six main environmental scenarios in the network. A representative environmental covariate was extracted from each of them. Then, a factorial regression model leaded to the dissection of the genotype-by-environment interaction and highlighted differential stress sensitivity of the germplasm. Finally, a multi-environmental QTL detection resulted in the discovery of genomic regions involved in the control of both physiological and agronomic traits and the study of their sensitivity to the environment. From the environmental characterization to the QTL detection, this study resulted in the development of a tool for breeders which may enable the evaluation of the potential of any genotypes in front of a range of environment, but also the identification of genomic regions involved in the control of the tolerance to drought and heat stress in bread wheat. This may help in improving the tolerance of the European bread wheat germplasm to drought and heat stress.

Abiotic Stresses in Wheat: Unfolding the Challenges presents the current challenges, possibilities, and advancements in research-based management strategies for the adaptation of wheat crops under abiotic-stressed growth conditions. This book comprehensively discusses different abiotic stress conditions in wheat, and also covers current trends in their mitigation using advanced tools to develop resilience in wheat crops. Chapters provide insight into the genetic, biochemical, physiological, molecular, and transgenic advances and emerging frontiers for mitigating the effects of wheat abiotic stresses. This text is the first resource to include all abiotic stresses in one volume, providing important translational insights and efficient comparison. Describes advances in conventional and modern breeding approaches in countering the effect of wheat abiotic stresses Highlights the role of physiological, biochemical and OMICS strategies Includes coverage of biotechnological tools such as whole genome sequencing, nanotechnology, and genome editing

The global population is projected to reach almost 10 billion by 2050, and food and feed production will need to increase by 70%. Wheat, maize and sorghum are three key cereals which provide nutrition for the majority of the world's population. Their production is affected by various abiotic stresses which cause significant yield losses. The effects of climate change also increase the frequency and severity of such abiotic stresses. Molecular breeding technologies offer real hope for improving crop yields. Although significant progress has been made over the last few years, there is still a need to bridge the large gap between yields in the most favorable and most stressful conditions.

QTL Mapping in Crop Improvement: Present Progress and Future Perspectives presents advancements in QTL breeding for biotic and abiotic stresses and nutritional improvement in a range of crop plants. The book presents a roadmap for future breeding for resilience to various stresses and improvement in nutritional quality. Crops such as rice, wheat, maize, soybeans, common bean, and pigeon pea are the major staple crops consumed globally, hence fulfilling the nutritional requirements of global populations, particularly in the under-developed world, is extremely important. Sections cover the challenges facing maximized production of these crops, including diseases, insect damage, drought, heat, salinity and mineral toxicity. Covering globally important crops including maize, wheat, rice, barley, soybean, common bean and pigeon pea, this book will be an important reference for those working in agriculture and crop improvement. Uses the latest molecular markers to identify QTLs/genes responsible for biotic and abiotic stress tolerance in plants Includes multiple core crops for efficient comparison and translational learning Provides a ready reference for improving quality traits through the use of the latest technologies