Wheat production and productivity are challenged by recurrent droughts associated with climate change globally. Drought and heat stress resilient cultivars can alleviate yield loss in marginal production agro-ecologies. The ability of some crop genotypes to thrive and yield in drought conditions is attributable to the inherent genetic variation and environmental adaptation, presenting opportunities to develop drought-tolerant varieties. Understanding the underlying genetic, physiological, biochemical, and environmental mechanisms and their interactions is key critical opportunity for drought tolerance improvement. Therefore, the objective of this review is to document the progress, challenges, and opportunities in breeding for drought tolerance in wheat. The paper outlines the following key aspects: (1) challenges associated with breeding for adaptation to drought-prone environments, (2) opportunities such as genetic variation in wheat for drought tolerance, selection methods, the interplay between above-ground phenotypic traits and root attributes in drought adaptation and drought-responsive attributes and (3) approaches, technologies and innovations in drought tolerance breeding. In the end, the paper summarises genetic gains and perspectives in drought tolerance breeding in wheat. The review will serve as baseline information for wheat breeders and agronomists to guide the development and deployment of drought-adapted and high-performing new-generation wheat varieties.

Powdery mildew (PM) of wheat caused by Blumeria graminis f. sp. tritici is among the most important wheat diseases, causing significant yield and quality losses in many countries worldwide. Considerable progress has been made in resistance breeding to mitigate powdery mildew. Genetic host resistance employs either race-specific (qualitative) resistance, race-non-specific (quantitative), or a combination of both. Over recent decades, efforts to identify host resistance traits to powdery mildew have led to the discovery of over 240 genes and quantitative trait loci (QTLs) across all 21 wheat chromosomes. Sources of PM resistance in wheat include landraces, synthetic, cultivated, and wild species. The resistance identified in various genetic resources is transferred to the elite genetic background of a well-adapted cultivar with minimum linkage drag using advanced breeding and selection approaches. In this effort, wheat landraces have emerged as an important source of allelic and genetic diversity, which is highly valuable for developing new PM-resistant cultivars. However, most landraces have not been characterized for PM resistance, limiting their use in breeding programs. PM resistance is a polygenic trait; therefore, the degree of such resistance is mostly influenced by environmental conditions. Another challenge in breeding for PM resistance has been the lack of consistent disease pressure in multi-environment trials, which compromises phenotypic selection efficiency. It is therefore imperative to complement conventional breeding technologies with molecular breeding to improve selection efficiency. High-throughput genotyping techniques, based on chip array or sequencing, have increased the capacity to identify the genetic basis of PM resistance. However, developing PM-resistant cultivars is still challenging, and there is a need to harness the potential of new approaches to accelerate breeding progress. The main objective of this review is to describe the status of breeding for powdery mildew resistance, as well as the latest discoveries that offer novel ways to achieve durable PM resistance. Major topics discussed in the review include the genetic basis of PM resistance in wheat, available genetic resources for race-specific and adult-plant resistance to PM, important gene banks, and conventional and complimentary molecular breeding approaches, with an emphasis on marker-assisted selection (MAS).

Russian wheat aphid (RWA) Diuraphis noxia is a global pest of small grains, such as wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena L.), and rye (Secale L.). Though laborious and time‐consuming in terms of efforts required to eliminate the unwanted traits, wheat landraces have been widely used in breeding programs to deliver resistance sources and genes responsive to RWA among other stresses. Continuous exploitation of resistance traits/alleles in the landraces should be prioritized as a RWA intervention strategy to minimize its devastating impacts on wheat. Eighty donor lines were evaluated for their resistance to four South African RWA biotypes, namely RWASA1, RWASA2, RWASA3, and RWASA4. The collection was composed of 74 donor lines and six breeding lines collected from Afghanistan (38), Iran (22), Pakistan (11), United States (4), South Africa (2), Turkey (1), Georgia (1), and Egypt (1). Majority of the accessions were susceptible to RWASA3. Of the 80 accessions evaluated, 14 were uniformly resistant to moderately resistant to RWASA1, 9 to RWASA2, 7 to RWASA3, and 9 to RWASA4. A heterogeneous resistance (resistant–moderately resistant: ≥ 50%) was recorded in 18 accessions for RWASA1, 28 for RWASA2, 13 for RWASA3, and 17 for RWASA4. In addition, 25 genotypes performed comparably to the check genotype CItr 2401, with resistance to all four RWA biotypes. Selection of resistant lines for genetic improvement of RWA resistance is of paramount importance. The use of genotypes conferring both high levels and moderate resistance could offer scope for effective resistance to RWA in wheat. The merits of their exclusive resistance should be emphasized in prebreeding programs.

Drought‐adapted new‐generation wheat genotypes enhance production and productivity in water‐limited agroecologies, including South Africa. Therefore, drought‐tolerant wheat ideotypes need to be bred and deployed using economic traits and tolerance indices. The aim of this study was to evaluate genetically diverse wheat genotypes and select drought‐adapted lines based on yield response, tolerance indices and genetic groups using biplot analyses for breeding and production. Ninety‐eight wheat genotypes were assessed in five environments, that is, two seasons and three sites under drought‐stressed (DS) and non‐stressed (NS) growing conditions using an alpha lattice design with two replications. Grain yield (GY) was recorded, and yield‐based 10 drought‐tolerance indices were computed for genotype selection and comparison of test environments using the genotype plus genotype by environment interaction (GGE) biplot model. The mean GY values of the test genotypes in descending order across the five environments (E) were 1.59 t ha ⁻¹ (Bethlehem site in 2022, designated as BHM‐E2), 1.57 t ha ⁻¹ (Kransfontein in 2021, KRANS‐E4), 1.03 t ha ⁻¹ (Ficksburg in 2021, FICKS‐E3), 0.63 t ha ⁻¹ (Bethlehemin 2021, BHM‐E1) and 0.58 t ha ⁻¹ (Kransfontein in 2022, KRANS‐E5). The following genotypes were the best yielders: LM29, LM9 and at BHM‐E1, BHM‐E2, FICKS‐E3 and KRANS‐E4; LM59, LM63, LM66 and LM67 at BHM‐E2, FICKS‐E3 and KRANS‐E4; and LM83 at BHM‐E1, BHM‐E2 and FICKS‐E3. The genotypes LM59, LM25, LM84, LM96, LM23 and LM39 exhibited low tolerance (TOL), susceptibility index (SSI) and high mean productivity (MP), geometric mean productivity (GMP), drought index (DI), yield index (YI), yield stability index (YSI) and relative drought index (RDI) values in a desirable trend. Correlation analysis revealed a strong association ( p < 0.001) between mean GY in non‐stressed conditions ( Y _p ) and drought tolerance indices such as TOL ( r = 0.87), MP ( r = 0.77), SSI ( r = 0.72), SDI ( r = 0.72), GMP ( r = 0.65) and STI ( r = 0.54). In contrast, the mean GY in stressed conditions ( Y _s ) positively and significantly ( p < 0.001) correlated with YI ( r = 1.00), DI ( r = 0.97), RDI ( r = 0.73), YSI ( r = 0.73), GMP ( r = 0.51) and MP ( r = 0.41). The indices were invaluable in identifying relatively high‐yielding and drought‐tolerant wheat genotypes, and their combined use could be effective for screening drought tolerance in wheat breeding programmes. Based on GGE biplot analysis, genotypes LM6, LM9, LM30, LM64, LM83 and LM95 were discerned to be stable and high‐yielding in the test environments. Developing new breeding populations is recommended using the above complementary selections through combining ability tests and progeny selection for yield and agronomic traits performance for variety registration and release.