Molecular Plant Breeding 2025, Vol.16, No.3, 165-179 http://genbreedpublisher.com/index.php/mpb 170 5.2 QTL mapping QTL mapping is another genomic approach that has been extensively used to identify regions of the genome associated with drought resistance traits in rice. QTL mapping involves the use of molecular markers to link phenotypic traits with specific genomic regions. Price and Courtois (1999) highlighted the importance of QTL mapping in revealing the complex genetic architecture of drought tolerance traits. Using mapping populations like recombinant inbred lines (RILs) and doubled haploids, researchers can identify QTLs associated with specific drought-related phenotypes, such as root depth, leaf water retention, and osmotic adjustment. Babu et al. (2003) identified 47 QTLs associated with plant water stress indicators, phenology, and production traits under both irrigated and drought stress conditions. Another study mapped QTLs for various drought-related traits in a panel of Vietnamese rice landraces, identifying 17 different QTLs with potential pleiotropic effects on drought tolerance (Figure 2) (Hoang et al., 2019). Figure 2 Manhattan plots and Linkage Disequilibrium (LD) heatmaps for some strong QTLs (Adopted from Hoang et al., 2019) Another study conducted on rice at the germination stage identified multiple QTLs linked to germination percentage (GP), mean germination time (MGT), and seedling percentage (SP). These QTLs are associated with drought tolerance, with genes such as LOC_Os03g14990 and LOC_Os03g16050 playing critical roles in
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