Introduction: Cereals are among the most important sources of food for the world’s growing population and play a crucial role in global food security. Barley (Hordeum vulgare L.), owing to its broad ecological adaptation and high genetic diversity, is considered an important strategic crop in Iran. However, environmental stresses, particularly drought stress during the reproductive stage, are among the major factors limiting barley yield and quality. Understanding the genetic control of traits associated with drought tolerance and identifying the genomic regions controlling these traits are essential for improving yield stability under stress conditions. Quantitative trait locus (QTL) mapping using molecular markers provides an effective approach for investigating the genetic architecture of complex and polygenic traits. Therefore, the objective of this study was to identify QTLs associated with drought tolerance-related traits during the reproductive stage and to improve the existing genetic map using a barley population derived from the cross between Badia and Kavir. The identification of effective genomic regions and evaluation of their phenotypic effects may facilitate the application of marker-assisted selection (MAS) and the development of drought-tolerant barley cultivars.
Materials and methods: To identify QTLs associated with traits related to drought tolerance, an experiment was conducted using 103 F3 families derived from the cross between Badia and Kavir at the reproductive stage in Kordkuy, Iran. The experiment was carried out in a completely randomized design with two replications under two water regimes: normal conditions and drought stress corresponding to 70% of field capacity. The traits evaluated included plant height, stem length, spike length, peduncle length, awn length, flag leaf length, internode length, peduncle diameter, grain diameter, awn diameter, stem diameter, total plant weight, stem weight, spike weight, grain weight per spike, peduncle weight, awn weight, leaf weight, flag leaf weight, number of grains per spike, number of spikelets, number of nodes, number of leaves, flag leaf width, total tiller number, fertile tiller number, and grain yield. Genomic DNA was extracted from leaf samples using the CTAB method. A genetic linkage map was constructed using 29 SSR and 10 ISSR markers. QTLs controlling the studied traits were identified using composite interval mapping implemented in Qgene software.
Results: A total of 36 QTLs associated with 20 traits were identified under normal conditions, whereas 25 QTLs associated with 15 traits were detected under drought stress. The identified QTLs were associated with various morphological and agronomic traits, including plant height, stem length, spike length, peduncle length, awn length, peduncle diameter, stem diameter, total plant weight, leaf weight, tiller number, and grain yield. Differences in the number, genomic position, and effects of QTLs between normal and drought conditions indicated that environmental conditions influenced the expression and effects of genomic regions controlling the studied traits.
Conclusion: The results demonstrated that the studied traits were controlled by multiple genomic regions, confirming their quantitative and polygenic inheritance. Differences in the number and effects of QTLs detected under normal and drought conditions further indicated that environmental conditions influence the expression of genes controlling these traits. The identified QTLs and their associated molecular markers may provide useful genetic resources for marker-assisted selection and the development of drought-tolerant barley cultivars. |
