Plant Gene and Trait 2024, Vol.15, No.6, 295-304 http://genbreedpublisher.com/index.php/pgt 299 under polyethylene glycol (PEG)-induced drought stress revealed that about 180 genes are differentially regulated in response to drought stress, with a significant number being up-regulated in drought-resistant genotypes. These genes include transcription factors, signaling proteins, and stress-related proteins, many of which are novel and uncharacterized (Abdel-Ghany et al., 2020). Additionally, multi-environment field trials of Ethiopian sorghum germplasm identified high phenotypic variation in traits related to drought tolerance, such as chlorophyll content and stay-green, which are crucial for breeding drought-tolerant varieties (Figure 2) (Enyew et al., 2022). Quantitative trait locus (QTL) mapping has also been instrumental in identifying genomic regions associated with drought resistance traits, such as the stay-green trait, which helps in maintaining photosynthetic activity under drought conditions (Sanchez et al., 2002). Figure 2 Geographical map, constructed using geographic information system (ArcGIS), showing the three testing environments: Mehoni, Mieso and Melkassa in Ethiopia (Adopted from Enyew et al., 2022) 5.3 Application of drought resistance genes in breeding The application of drought resistance genes in sorghum breeding has shown promising results. For example, the stay-green QTLs identified in sorghum have been consistently associated with drought resistance across multiple field trials, accounting for a significant portion of phenotypic variance. These QTLs have been incorporated into breeding programs to develop drought-resistant sorghum hybrids (Sanchez et al., 2002). Furthermore, the identification of novel drought tolerance traits, such as restricted transpiration and root architecture, has expanded the genetic base for breeding drought-tolerant sorghum varieties. The integration of high-throughput phenomics and genomics in breeding programs has also facilitated the development of genotypes that can withstand both drought and high-temperature stresses, thereby improving yield and resilience (Prasad et al., 2021). 5.4 Inspiration from the case and future application prospects The case studies provide valuable insights into the complex genetic and physiological mechanisms underlying drought resistance in sorghum. The discovery of novel genes and QTLs associated with drought tolerance not only enhances our understanding of plant stress responses but also offers new avenues for breeding resilient crop varieties. The successful application of these genes in breeding programs underscores the potential of integrating advanced genomic tools with traditional breeding techniques to achieve sustainable agricultural production. Future prospects include the exploration of gene editing technologies, such as CRISPR/Cas9, to precisely modify drought resistance genes and the development of climate-resilient sorghum varieties tailored to specific agro-ecological zones. Additionally, expanding the genetic diversity of breeding populations by incorporating wild relatives and landraces could further enhance the drought tolerance of sorghum (Fracasso et al., 2016; Harris-Shultz et al., 2019; Varoquaux et al., 2019).
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