Molecular Plant Breeding 2024, Vol.15, No.6, 417-428 http://genbreedpublisher.com/index.php/mpb 421 demonstrating the potential of multigene resistance strategies (Blanco et al., 2001). The integration of novel alleles from wild relatives and landraces into elite cultivars has also contributed to the development of multigene resistant germplasm. For instance, the identification of new SNP variations in landraces adapted to drought and heat stress environments has opened new avenues for pre-breeding and the development of disease-resistant wheat varieties (Sehgal et al., 2015). 4 Innovation and Utilization of Wheat Stress Resistant Germplasm Resources 4.1 Exploration and application of drought- and salt-tolerant wheat germplasm The exploration and application of drought- and salt-tolerant wheat germplasm are crucial for developing wheat varieties that can thrive in harsh environments. Recent studies have highlighted the importance of utilizing diverse germplasm collections to identify and develop drought-tolerant wheat varieties. For instance, extensive collections of genetic resources conserved in national and international genebanks have been pivotal in identifying useful genes for drought tolerance in wheat. These collections have been evaluated using advanced molecular techniques such as genotype by sequencing to identify quantitative trait loci (QTLs) associated with drought tolerance traits, which are essential for genome- and marker-assisted selection approaches (Khadka et al., 2020a). Additionally, local wheat cultivars have been screened for drought tolerance, revealing that certain cultivars, such as Barani-83 and Blue Silver, exhibit significant drought tolerance due to their ability to maintain higher shoot and root weights under stress conditions (Ghaffar et al., 2023). Similarly, the identification and characterization of wheat germplasm for salt tolerance have been a focus of recent research. A study involving 334 internationally derived wheat genotypes identified 12 genotypes with significant salt tolerance. These genotypes demonstrated better growth under salt stress due to their ability to maintain stable osmotic potential, ion homeostasis, and efficient use of soluble sugars (Quan et al., 2021). The exploration of such germplasm resources is essential for breeding new wheat cultivars that can withstand salinity and drought, thereby ensuring food security in regions affected by these stresses. 4.2 Molecular breeding for stress tolerance traits Molecular breeding has played a significant role in the discovery and application of key stress tolerance genes in wheat. The identification of over 100 genes associated with drought and salt tolerance has provided valuable insights into the mechanisms of stress tolerance. These genes are involved in various functions such as osmotic adjustment, ionic and redox homeostasis, and are crucial for the efficient selection of new tolerant genotypes through marker-assisted selection (MAS) (Urbanavičiūtė et al., 2021). The use of advanced molecular techniques, including CRISPR-Cas9 and other gene-editing technologies, has further enhanced the ability to fine-tune the expression of genes controlling drought adaptive traits, thereby improving drought tolerance in wheat (Khadka et al., 2020a). Moreover, the genetic characterization and agronomic evaluation of wheat cultivars have identified specific genotypes with high drought tolerance. For example, Egyptian wheat cultivars such as Giza 171 and Misr 2 have been identified as valuable germplasm for breeding high-yielding, drought-tolerant wheat. These cultivars exhibited significant positive correlations between yield under drought conditions and indices such as mean productivity (MP) and geometric mean productivity (GMP), highlighting their potential for use in breeding programs (Emam et al., 2022). The integration of molecular breeding techniques with traditional breeding approaches is essential for developing wheat varieties with enhanced stress tolerance. 4.3 Environmental adaptability of stress tolerance traits The performance and resource development of stress-tolerant wheat under different climate conditions are critical for ensuring the adaptability of these traits. Studies have shown that wheat germplasm with drought tolerance can maintain yield stability and performance under varying environmental conditions. For instance, the evaluation of 152 spring wheat cultivars under non-stress and drought-stress conditions revealed that certain germplasm accessions could sustain grain yield and improve drought tolerance simultaneously (Figure 3). These findings provide a theoretical basis for developing new wheat cultivars with excellent drought tolerance and high yields in diverse environments (Xu et al., 2023).
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