Key messageOver 140 QTLs for resistance to stripe rust in wheat have been published and through mapping flanking markers on consensus maps, 49 chromosomal regions are identified.AbstractOver thirty publications during the last 10 years have identified more than 140 QTLs for stripe rust resistance in wheat. It is likely that many of these QTLs are identical genes that have been spread through plant breeding into diverse backgrounds through phenotypic selection under stripe rust epidemics. Allelism testing can be used to differentiate genes in similar locations but in different genetic backgrounds; however, this is problematic for QTL studies where multiple loci segregate from any one parent. This review utilizes consensus maps to illustrate important genomic regions that have had effects against stripe rust in wheat, and although this methodology cannot distinguish alleles from closely linked genes, it does highlight the extent of genetic diversity for this trait and identifies the most valuable loci and the parents possessing them for utilization in breeding programs. With the advent of cheaper, high throughput genotyping technologies, it is envisioned that there will be many more publications in the near future describing ever more QTLs. This review sets the scene for the coming influx of data and will quickly enable researchers to identify new loci in their given populations.

In this study, we defined the target population of environments (TPE) for wheat breeding in India, the largest wheat producer in South Asia, and estimated the correlated response to the selection and prediction ability of five selection environments (SEs) in Mexico. We also estimated grain yield (GY) gains in each TPE. Our analysis used meteorological, soil, and GY data from the international Elite Spring Wheat Yield Trials (ESWYT) distributed by the International Maize and Wheat Improvement Center (CIMMYT) from 2001 to 2016. We identified three TPEs: TPE 1, the optimally irrigated Northwestern Plain Zone; TPE 2, the optimally irrigated, heat-stressed North Eastern Plains Zone; and TPE 3, the drought-stressed Central-Peninsular Zone. The correlated response to selection ranged from 0.4 to 0.9 within each TPE. The highest prediction accuracies for GY per TPE were derived using models that included genotype-by-environment interaction and/or meteorological information and their interaction with the lines. The highest prediction accuracies for TPEs 1, 2, and 3 were 0.37, 0.46, and 0.51, respectively, and the respective GY gains were 118, 46, and 123 kg/ha/year. These results can help fine-tune the breeding of elite wheat germplasm with stable yields to reduce farmers’ risk from year-to-year environmental variation in India’s wheat lands, which cover 30 million ha, account for 100 million tons of grain or more each year, and provide food and livelihoods for hundreds of millions of farmers and consumers in South Asia.

Micronutrient malnutrition, resulting from dietary deficiency of important minerals such as zinc (Zn) and iron (Fe), is a widespread food-related health problem. Genetic enhancement of crops with elevated levels of these micronutrients is one of the most cost effective ways of solving global micronutrient malnutrition problem. Development and dissemination of high Zn and Fe containing high-yielding, disease-resistant wheat varieties by International Maize and Wheat Improvement Center (CIMMYT) is initially targeted for the Indo-Gangetic plains of South Asia, a region with high population density and high micronutrient malnutrition. The most promising sources for grain Zn and Fe concentrations are wild relatives, primitive wheats and landraces. Synthetic hexaploids were developed at CIMMYT by crossing Aegilops taushii and high Zn and Fe containing accessions of T. dicoccon. Current breeding efforts at CIMMYT have focused on transferring genes governing increased Zn and Fe from T. spelta, T. dicoccon based synthetics, land races and other reported high Zn and Fe sources to high yielding elite wheat backgrounds.

Leaf rust, caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici, is an important disease of wheat (Triticum aestivum L.) worldwide. The Lr34 gene is known to confer durable resistance. We evaluated the effect of Lr34 on grain yield and other traits in the absence and presence of leaf rust. ‘Jupateco 73R’ and ‘Jupateco 73S’ (near‐isogenic reselections from the Mexican spring wheat cultivar ‘Jupateco 73’ for the presence and absence of Lr34, respectively) and 22 random inbred F6 lines, 11 with and 11 without Lr34 (derived from the cross ‘Jupateco 73R/Jupateco 73S’), were planted in replicated field trials during the 1992–1993 and 1993–1994 seasons in northwestern Mexico. The mean grain yield of Jupateco 73R was 5.9% lower (P < 0.05) than that of Jupateco 73S in protected plots in the 1992–1993 experiment. Significant reductions (P < 0.05) were also observed for biomass, kernels per spike and kernels m‐2. Significant (P < 0.01) reductions of 5% in mean grain yield and 3.7% in mean kernel weight were again evident in one of the two experiments sown during the 1993–1994 season. Comparison of grain yield in protected and non‐protected treatments indicated that though leaf rust could significantly (P < 0.01) reduce grain yield by approximately 15% in the presence of Lr34, the reductions in the absence of Lr34 were substantially higher and ranged between 42.5 to 84% depending on planting date and year. Reductions in all other traits were also significantly higher in the absence of Lr34. We conclude that although the presence of Lr34, which is linked with leaf tip necrosis of adult plants, may carry a slight yield penalty in some disease free environments, its use in leaf rust prone areas could provide substantial protection to grain yield and other traits.

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